Next Article in Journal
Synthesis of High Molecular Weight Stereo-Di-Block Copolymers Driven by a Co-Initiator Free Catalyst
Previous Article in Journal
Denture Acrylic Resin Material with Antibacterial and Protein-Repelling Properties for the Prevention of Denture Stomatitis
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Polymers
Volume 14
Issue 2
10.3390/polym14020231
polymers-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles thumb_up
...
Endorse textsms
...
Comment
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Construction of a (NNN)Ru-Incorporated Porous Organic Polymer with High Catalytic Activity for β-Alkylation of Secondary Alcohols with Primary Alcohols

by
Yao Cui
1,
Jixian Wang
1,
Lei Yu
2,
Ying Xu
2,
David J. Young
3,
Haiyan Li
2 and
Hongxi Li
1,*
1
College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, China
2
Analysis and Testing Center, Soochow University, Suzhou 215123, China
3
College of Engineering, Information Technology and Environment, Charles Darwin University, Brinkin 0909, Australia
*
Author to whom correspondence should be addressed.
Polymers 2022, 14(2), 231; https://doi.org/10.3390/polym14020231
Submission received: 16 December 2021 / Revised: 29 December 2021 / Accepted: 4 January 2022 / Published: 7 January 2022
(This article belongs to the Special Issue High Performance Porous Polymers)
Browse Figures
Versions Notes

Abstract

:
Solid supports functionalized with molecular metal catalysts combine many of the advantages of heterogeneous and homogeneous catalysis. A (NNN)Ru-incorporated porous organic polymer (POP-bp/bbpRuCl3) exhibited high catalytic efficiency and broad functional group tolerance in the C–C cross-coupling of secondary and primary alcohols to give β-alkylated secondary alcohols. This catalyst demonstrated excellent durability during successive recycling without leaching of Ru which is ascribed to the strong binding of the pincer ligands to the metal ions.

1. Introduction

The construction of carbon–carbon bonds is fundamental to organic synthesis [1,2]. Alkyl halides were the workhorse of this transformation last century, but replacing these relatively toxic and wasteful electrophiles has been an imperative in recent years [3,4,5]. Transition-metal-catalyzed α- or β-alkylation of carboxyl complexes, nitriles and secondary alcohols using alcohols as alkylating agents generates only hydrogen and/or water as waste [6,7,8]. Metal-catalyzed heterocoupling reactions of secondary and primary alcohols proceeds through controllable dehydrogenation–condensation–hydrogenation steps, selectively affording α,β-unsaturated ketones, α-alkylated ketones or β-alkylated secondary alcohols [9,10,11,12,13]. Various molecular complexes based on Ru [14,15,16,17], Ir [18,19,20,21], Co [22,23,24,25], Ni [26,27,28,29,30], and Mn [31,32,33,34,35,36] have been developed for these transformations. However, these are homogeneous catalysts and separation and recycling is an impediment to their large-scale industrial use. Some heterogeneous catalysts, including IrO2/Fe3O4 [37], Ni/CaxMgyO [38], SBA-15-supported Ir/NHC complex [39], Pt–Sn/γ-Al2O3 [40], DMF-stabilized Ir nanoclusters [41] have been developed for the cross-alkylation of alcohols to give β-alkylated secondary alcohols. However, these systems suffer from the need for relatively high temperatures, and/or long catalytic reaction time, intricate formulations.
Porous organic polymers (POPs) with high stability, low skeleton density, tunable porous structures and easy synthesis are an intriguing platform for incorporating homogeneous metal/ligand molecular catalysts into heterogeneous supports [42,43,44,45]. One particular advantage of POPs is the range of possible chemical functionality within the porous framework. Phosphines, pyridines, bipyridyl/phenanthroline derivatives, porphyrins, carbenes, and salen have been introduced into the skeleton of POPs [46,47,48,49]. Functionalized POPs with metal ions or nanoparticles have demonstrated excellent catalytic performance for the Suzuki-Miyaura coupling reaction [50], Heck reaction [51], Ullmann coupling reaction [52], CO2 conversion into cyclic carbonates [53,54], alkyne carboxylation [55,56,57], photocatalytic hydrogen evolution [58], the reduction of nitroarenes [59,60,61] and the hydroformylation of higher olefins [62]. In the present work, we have incorporated 2,6-bis(benzimidazo-1-yl)pyridine (bbp) into a POP through a simple one-pot Scholl co-coupling polymerization with biphenyl to give NNN pincer based POP (POP-bp/bbp). RuCl3-incorporated POP-bp/bbp (POP-bp/bbpRuCl3) displayed high catalytic performance, selectivity and recyclability for the β-alkylation of secondary alcohols with primary alcohols.

2. Materials and Methods

2.1. Materials

2,6-Bis(benzimidazo-1-yl)pyridine (bbp) was prepared according to a published procedure [63]. All chemicals were commercially available and used as received without further purification. Biphenyl, 2,6-pyridinedicarboxylic acid, o-phenylenediamine, phenylmethanol, (4-chlorophenyl)methanol, (4-(trifluoromethyl)phenyl)methanol, p-tolylmethanol, (4-methoxyphenyl)methanol, (4-(tert-butyl)phenyl)methanol, o-tolylmethanol, (2-methoxyphenyl)methanol, (3-methoxyphenyl)methanol, m-tolylmethanol, (3-chlorophenyl)methanol, naphthalen-1-ylmethanol, benzo[d][1,3]dioxol-5-ylmethanol, thiophen-2-ylmethanol, 1-phenylethan-1-ol, 1-(4-chlorophenyl)ethan-1-ol, 1-(4-bromophenyl)ethan-1-ol, 1-(p-tolyl)ethan-1-ol, 1-(4-methoxyphenyl)ethan-1-ol, 1-(2-chlorophenyl)ethan-1-ol, 1-(2-methoxyphenyl)ethan-1-ol, 1-(o-tolyl)ethan-1-ol, 1-(3-methoxyphenyl)ethan-1-ol, 1-(m-tolyl)ethan-1-ol, 1-(naphthalen-2-yl)ethan-1-ol, RuCl3·xH2O, CDCl3 were purchased from J&K. Toluene, chloroform, methanol, tetrahydrofuran, N,N-dimethylformamide, dimethyl sulfoxide, petroleum ether, and ethyl acetate were from Shanghai Titan Technology Co., Ltd. (Shanghai, China). Orthophosphoric acid, hydrochloric acid, aluminum chloride, potassium hydroxide, potassium tert-butoxide, cesium carbonate, sodium hydroxide, cesium hydroxide got from Sinopharm Chemical Reagent Co. Ltd. (Shanghai, China).

2.2. Synthesis of Porous Organic Polymer (POP)-bp/bbp

Under a N2 atmosphere, 2,6-bis(benzimidazo-1-yl)pyridine (bbp) (0.311 g, 1 mmol) and biphenyl (0.154 g, 1 mmol) were dissolved in anhydrous chloroform (20 mL), followed by the addition of anhydrous aluminum chloride (10 mmol, 1.33 g) with vigorous stirring at 58 °C. After 24 h, the reaction mixture was cooled to ambient temperature, filtered and the solid product was washed with methanol, HCl-H2O (v/v = 1:1), H2O, CH2Cl2 and EtOH, followed by washing with methanol in a Soxhlet thimble for 72 h. The polymer was then dried in a vacuum oven at 100 °C for 24 h to give a brown solid. Yield: 0.418 g (90%). Elemental analysis: calculated: C, 82.66; H, 4.95; N, 15.05. Found: C, 73.86; H, 4.19; N, 13.42.

2.3. Synthesis of POP-bp/bbpRuCl3

Under a N2 atmosphere, a mixture of POP-bp/bbp (0.2 g), RuCl3·xH2O (0.017 g), and anhydrous ethanol (25 mL) was introduced into a round-bottom flask (100 mL). The resulting mixture was refluxed for 12 h. After this period, the brown solid POP-bp/bbpRuCl3 was separated by centrifugation, washed sequentially with ethanol and ethyl ether, and then dried under vacuum.

2.4. Typical Procedure for Syntheses of β-Alkylated Secondary Alcohols

Under an N2 atmosphere, a mixture of secondary alcohol (1 mmol), primary alcohol (1.2 mmol), POP-bp/bbpRuCl3 (20 mg, 0.6 mol% Ru), KOH (0.5 mmol) and toluene (2 mL) was added into a 15 mL sealed tube equipped with a stirring bar. The reaction mixture was heated to 130 °C for 12 h. After cooling to ambient temperature, the catalyst was separated by centrifugation and washed with ethanol and diethyl ether. The catalyst was then dried in a vacuum at 60 °C for 2 h to give recycled catalyst for the next run. The organic layers were combined and dried over anhydrous Na2SO4 and concentrated under reduced pressure. The crude product was purified by flash column chromatography using petroleum ether and ethyl acetate as the eluent.

2.5. Characterizations

The analytical instruments employed in this work are as described in our previous article [57,64,65], unless otherwise noted. 1H and 13C NMR spectra were recorded at ambient temperature on a Varian UNITY plus-400 spectrometer. Solid-state cross-polarization magic angle spinning 13C NMR measurements were carried out on Bruker Avance III/WB solid-state NMR spectrometer operating at 400 MHz equipped with a standard 4 mm magic angle spinning double resonance probe head. Powder X-ray diffraction patterns were collected on a PANalytical Aeris diffractometer (Cu-Ka). Infrared spectra were recorded on a Varian Scamiter-1000 spectrometer. The thermal stability of materials was evaluated using thermogravimetric analysis (Perkin-Elmer Pyrisl) under a nitrogen atmosphere. Scanning electron microscopy (SEM) images and energy dispersive X-ray spectroscopy spectra were obtained using a HITACHI S-4700 cold field-emission SEM. Transmission electron microscopy (TEM) was performed on a FEI Tecnai G20 electron microscope operating at 200 kV. Annular dark-field scanning TEM (ADF-STEM) was performed on a FEI Tecnai F20 electron microscope operating at 200 kV, equipped with Genesis EDS detector. X-ray photoelectron spectra were recorded on an X-ray photoelectron spectrometer (AXIS Ultra DLD) and binding energies were referenced to C 1s at 284.7 eV from hydrocarbon to compensate for possible charging effects.

3. Results and Discussion

3.1. Subsection Synthesis and Characterization of POP-bp/bbpRuCl3

POP-bp/bbp was synthesized by the AlCl3-promoted Scholl reaction of bbp and biphenyl (bp) in CHCl3 at 58 °C (Scheme 1). The resulting brown polymer was insoluble in common organic solvents such as tetrahydrofuran (THF), methanol (MeOH), N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO). Thermogravimetric analysis (TGA) showed that POP-bp/bbp was stable at temperatures up to 300 °C (Figure S1). The 13C NMR solid-state spectrum of POP-bp/bbp contained signals at δ = 148, 140 and 138 ppm ascribed to the carbons on pyridine and imidazole rings, and a broad signal at δ = 125 ppm assigned to the other aromatic carbons (Figure S2). Scanning electron microscopy (SEM) (Figure S3) and transmission electron microscopy (TEM) (Figure S4) images showed that the as-prepared polymer POP-bp/bbp was amorphous with particles of irregular shape and size. The energy-dispersive X-ray (EDX) elemental mapping images (Figure S5) indicated the homogenous distribution of C and N, indicating homogeneous distribution of bbp monomer. The FT-IR spectrum (Figure 1a) contained absorptions at 1600, 1573, and 1460 cm−1 attributed to the C−C, C=N and C−N stretching vibrations, respectively. In addition, the band at 3185 cm−1 were assigned to the −NH, originating from the imidazole moiety.
POP-bp/bbp bearing NNN pincer groups was treated with RuCl3·xH2O in refluxing EtOH under N2 for 12 h to give Ru-metalated POP-bp/bbp (POP-bp/bbpRuCl3). The porosity of POP-bp/bbp and POP-bp/bbpRuCl3 was assessed by N2 adsorption and desorption analyses at 77.3 K. Absorption isotherms (Figure 1b) exhibited a type I adsorption isotherm with steep N2 uptake at low relative pressure (P/P0 < 0.1), indicating abundant micropores in the polymer structure. A slight hysteresis loop with a small rise in N2 uptake at higher pressures was attributed to the presence of mesopores. The Brunauer−Emmett−Teller (BET) surface areas of POP-bp/bbp and POP-bp/bbpRuCl3 were calculated to be 632 and 602 m2 g−1, respectively. The pore-size distribution of POP-bp/bbp and POP-bp/bbpRuCl3 were estimated with the aid of non-local density functional theory modeling to be centered around 6−10 Å (Figure S7). Inductively coupled plasma optical emission spectrometry (ICP-OES) of POP-bp/bbpRuCl3 indicated 3.11 wt % Ru loading. The powder X-ray diffraction (PXRD) patterns confirmed that both the polymer and POP-bp/bbpRuCl3 were amorphous (Figure S8).
Ruthenium ion interaction with the NNN pincer moieties were observed by XPS (Figures S9 and S10). Coordination of Ru(III) ions with POP-bp/bbp significantly changes the electron density at the pyridinic N sites and thus the binding energies of their N 1s electrons. The N 1s XPS profile of POP-bp/bbp was deconvoluted into two peaks centered at 398.84 and 400.47 eV, which are assigned to pyridinic N and imidazolic N, respectively (Figure 1c). After the loading of RuCl3, a new N 1s XPS peak was observed at 399.71 eV, corresponding to Ru-bound N species [66]. The binding energy of Ru 3p3/2 was 463.35 eV, indicating that the Ru species maintained its original oxidation state of Ru3+ in POP-bp/bbpRuCl3 [67]. Compared with the reported binding energy of Ru 3p3/2 of RuCl3 (464.1 eV), the down-shift (0.75 eV) of coordinated Ru3+ can be attributed to additional electron density from the strongly electron-donating ligands [68]. High-resolution transmission electron microscopy (HR-TEM) (Figure 1e) did not reveal the presence of Ru nanoparticles. EDX elemental mapping confirmed that the Ru was distributed evenly throughout the POP-bp/bbpRuCl3 (Figure 1f). The C, N and Ru contents of the as-synthesized POP-bp/bbpRuCl3 were 80.5 wt %, 14.6 wt %, and 4.8 wt %, respectively (Figure S11). The Ru content obtained by EDX element mapping analysis is higher than that calculated by the ICP-OES analysis, which is attributed to the fact that Ru is mainly loaded on the surface of bp/bbp material.

3.2. Catalytic β-Alkylation of Secondary Alcohols

We next determined the performance of as-prepared POP-bp/bbpRuCl3 as a catalyst for the catalytic acceptorless dehydrogenation coupling of alcohols. The reaction of 1-phenylethanol (mol %) with benzyl alcohol (2a) was conducted in toluene with KOH under a nitrogen atmosphere (Table 1). A standard workup produced 1-([1,1′-biphenyl]-4-yl)ethan-1-one (3aa) in 68% yield with a trace of 1,3-diphenylpropan-1-one (4aa) as determined by high-performance liquid chromatography (HPLC). The screening of different bases (entries 1–5) revealed that CsOH was more selective than KOBut, Cs2CO3 or NaOH, but that KOH facilitated the highest yield. Lowering the reaction temperature to 100 °C or 120 °C reduced the yield of 3aa significantly, while raising it slightly (140 °C) had a modest impact (entries 6–9). The optimal amount of KOH was 0.5 equivalents (entries 10–13). The yield of 3aa could be increased up to 93% by extending the reaction time to 12 h (entries 15). Interestingly, neither of the individual components of the catalyst (i.e., POP-bp/bbp or RuCl3) facilitated more than a very modest amount of product under these conditions (entries 16 and 17).
Substrate scope was investigated with a variety of secondary and primary alcohols under the optimized conditions (Table 2). Good to high yields of β-alkylation were obtained with a variety of primary alcohols as the cross-coupling partner. The reaction of 1-phenylethanol with benzyl alcohols bearing both electron-donating and electron-withdrawing groups at the para-position resulted in products 3ab-3af in good yields (73–87%). Substrates bearing ortho- and meta-methoxy, methyl or chloro also delivered the expected products 3ag-3ak in good yields (79–89%). Likewise, 1-naphthylmethanol and 3,4-methylenedioxybenzyl alcohol reacted with 1a to form 3al and 3am in yields of 88% and 80%, respectively. Heterocyclic 2-thiophenemethanol 2n reacted with 1-phenylethanol less efficiently, giving 3an in 59% yield.
Next, the generality of this catalytic alkylation was investigated with various secondary alcohols (Table 3). The reaction of benzyl alcohol with para-substituted 1-phenylethanols bearing either electron withdrawing (-Cl, -Br) or electron-donating (-Me, -OMe) groups afforded the desired β-alkylated secondary alcohols 3ba-3ea in excellent yields (80–89%). No obvious substituent effect was observed. Chloro, methyl and methoxy groups at the ortho position of 1-phenylethanol gave the desired secondary alcohols 3fa-3ga in lower yields (53–79%) probably due to steric hindrance. Substrates with methoxy and methyl groups at the meta-position gave 3ia and 3ja in good yields (85 and 88%). 1-(Naphthalen-2-yl)ethanol was successfully converted to the coupled product 3ka (90%).
The recycling of POP-bp/bbpRuCl3 was examined under optimized reaction conditions. No significant loss of catalytic activity was observed after four cycles (Figure 2a) and ICP analysis indicated that 96% of Ru remained. Ru nanoparticles were not observed in the subsequent TEM images (Figure 2b). EDX analysis revealed the homogeneous distribution of Ru components throughout the polymer POP-bp/bbp (Figure S12). The FT-IR spectrum of the recovered catalyst did not change noticeably (Figure 2c), except for a new peak at 1960 cm−1 which we assign to a Ru-H species [69] generated during the catalytic cycle. XPS measurements indicated that the Cl 2p peak had disappeared in the recovered catalyst indicating ligand substitution (Figure S13). The binding energies of Ru 3p3/2 and Ru 3d5/2 for the catalyst were 463.15 eV and 281.4 eV, respectively (Figure 2d and Figure S14). The slight decrease in binding energies compared to that of fresh catalyst may be due to the substitution of hydride, which has a greater electron donating ability than chloride [69]. To verify whether the observed catalysis was due to the heterogeneous catalyst POP-bp/bbpRuCl3 or due to leached ruthenium species, a reaction was performed between 1a and 2a under standard conditions. The yield of 3aa was 42% accompanied by 7% 4aa after 2h. The reaction was then filtered. No catalytic function was observed in the filtered solution over 24 h and negligible Ru content was detected by ICP. These results indicate that the POP-bp/bbpRuCl3 catalyst is stable, which we ascribe to the strong binding of pincer ligand to metal centers.
A probable mechanism of this reaction was determined by investigating each step individually. The POP-bp/bbpRuCl3-catalysed dehydrogenation of phenylmethanol and 1-phenylethanol for 4 h afforded benzaldehyde in 90% yield and acetophenone in 73% yield, respectively (Scheme 2(a,b)). The condensation of benzaldehyde with acetophenone, facilitated by KOH afforded chalcone in good yield (Scheme 2(c)). reduction of chalcone with 1a under the standard reaction conditions achieved 31% of the corresponding secondary alcohol. as shown in Scheme 2, hydrogenation of chalcone with 2a under the same reaction conditions also gave the same reduced product in a similar 27% yield (Scheme 2(d)).
In light of these results, and of previous literature reports [14,15,16,17], a catalytic mechanism is proposed (Scheme 3). Primary and secondary alcohols are dehydrogenated by the Ru catalyst to form the corresponding aldehyde, ketone and a ruthenium hydride complex. Base-catalysed aldol condensation of the resulting ketone and aldehyde give the α,β-unsaturated ketone intermediate which is reduced by the ruthenium hydride to generate β-alkylated secondary alcohol.

4. Conclusions

A novel porous organic polymer incorporating a NNN pincer ligand possessed excellent thermal durability and high surface area. This acceptorless dehydrogenation, cross-coupling catalyst exhibited good activity, broad substrate scope and good recycling ability. We believe this work provides a green, convenient and scalable method for constructing C–C bonds, combining many of the advantages of homogeneous and heterogeneous catalysis.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/polym14020231/s1, Figure S1: TGA curve. Figure S2: 13C CP-MAS NMR spectrum. Figure S3: SEM image. Figure S4: TEM image. Figure S5: EDS elemental mapping. Figure S6: FT-IR spectrum. Figure S7: Pore-size distribution. Figure S8: PXRD patterns. Figure S9: XPS survey scan spectrum. Figure S10: XPS spectra. Figures S11 and S12: EDX spectroscopy elemental mapping. Figures S13 and S14: XPS survey scan spectra. Figures S15–S38: NMR data of products. References [12,31,70,71,72,73] are cited in the supplementary materials.

Author Contributions

Y.C.: Writing–original draft, Formal analysis, Investigation, Methodology. J.W.: Structural analysis. L.Y., Y.X. and H.L. (Haiyan Li): Characterizations. D.J.Y.: Review & editing. H.L. (Hongxi Li): Conceptualization, Formal analysis, Writing–review and editing, Supervision, Project administration, Funding acquisition. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the National Natural Science Foundation of China (21971182 and 21771131).

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The data presented in this study are available on request from the corresponding author.

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. Irrgang, T.; Kempe, R. 3d-Metal catalyzed N- and C-alkylation reactions via borrowing hydrogen or hydrogen autotransfer. Chem. Rev. 2019, 119, 2524–2549. [Google Scholar] [CrossRef]
  2. Shevick, S.L.; Wilson, C.V.; Kotesova, S.; Kim, D.; Holland, P.L.; Shenvi, R.A. Catalytic hydrogen atom transfer to alkenes: A roadmap for metal hydrides and radicals. Chem. Sci. 2020, 11, 12401–12422. [Google Scholar] [CrossRef]
  3. Zhang, Y.F.; Shi, Z.J. Upgrading cross-coupling reactions for biaryl syntheses. Acc. Chem. Res. 2019, 52, 161–169. [Google Scholar] [CrossRef]
  4. Li, H.; Zheng, B.; Huang, K.-W. A new class of PN3-pincer ligands for metal–ligand cooperative catalysis. Coord. Chem. Rev. 2015, 293–294, 116–138. [Google Scholar] [CrossRef] [Green Version]
  5. Nixon, T.D.; Whittlesey, M.K.; Williams, J.M.J. Transition metal catalysed reactions of alcohols using borrowing hydrogen methodology. Dalton Trans. 2009, 753–762. [Google Scholar] [CrossRef]
  6. Wang, D.; Astruc, D. The golden age of transfer hydrogenation. Chem. Rev. 2015, 115, 6621–6686. [Google Scholar]
  7. Gunanathan, C.; Milstein, D. Bond activation and catalysis by ruthenium pincer complexes. Chem. Rev. 2014, 114, 12024–12087. [Google Scholar] [CrossRef] [PubMed]
  8. Valdés, H.; García-Eleno, M.A.; Canseco-Gonzalez, D.; Morales-Morales, D. Recent advances in catalysis with transition-metal pincer compounds. ChemCatChem 2018, 10, 3136–3172. [Google Scholar] [CrossRef]
  9. Iuchi, Y.; Obora, Y.; Ishii, Y. Iridium-catalyzed α-alkylation of acetates with primary alcohols and diols. J. Am. Chem. Soc. 2010, 132, 2536–2537. [Google Scholar] [CrossRef]
  10. Li, Y.; Li, H.Q.; Junge, H.; Beller, M. Selective ruthenium-catalyzed methylation of 2-arylethanols using methanol as C1 feedstock. Chem. Commun. 2014, 50, 14991–14994. [Google Scholar] [CrossRef] [PubMed]
  11. Cai, Y.; Li, F.; Li, Y.Q.; Zhang, W.B.; Liu, F.H.; Shi, S.L. Base metal-catalyzed alcohol C–C couplings under hydrogen transfer conditions. Tetrahedron Lett. 2018, 59, 1073–1079. [Google Scholar] [CrossRef]
  12. Allen, L.J.; Crabtree, R.H. Green alcohol couplings without transition metal catalysts: Base-mediated β-alkylation of alcohols in aerobic conditions. Green Chem. 2010, 12, 1362–1364. [Google Scholar] [CrossRef]
  13. Xu, Q.; Chen, J.; Liu, Q. Aldehyde-catalyzed transition metal-free dehydrative β-alkylation of methyl carbinols with alcohols. Adv. Synth. Catal. 2013, 355, 697–704. [Google Scholar] [CrossRef]
  14. Bhattacharyya, D.; Sarmah, B.K.; Nandi, S.; Srivastava, H.K.; Das, A. Selective catalytic synthesis of α-alkylated ketones and β-disubstituted ketones via acceptorless dehydrogenative cross-coupling of alcohols. Org. Lett. 2021, 23, 869–875. [Google Scholar] [CrossRef] [PubMed]
  15. Sahoo, A.R.; Lalitha, G.; Murugesh, V.; Bruneau, C.; Sharma, G.V.M.; Suresh, S.; Achard, M. Ruthenium phosphine–pyridone catalyzed cross-coupling of alcohols to form α-alkylated ketones. J. Org. Chem. 2017, 82, 10727–10731. [Google Scholar] [CrossRef] [PubMed]
  16. Cho, C.S.; Kim, B.T.; Kim, H.-S.; Kim, T.-J.; Shim, S.C. Ruthenium-catalyzed one-pot β-alkylation of secondary alcohols with primary alcohols. Organometallics 2003, 22, 3608–3610. [Google Scholar] [CrossRef]
  17. Shee, S.; Paul, B.; Panja, D.; Roy, B.C.; Chakrabarti, K.; Ganguli, K.; Das, A.; Das, G.K.; Kundu, S. Tandem cross coupling reaction of alcohols for sustainable synthesis of β-alkylated secondary alcohols and flavan derivatives. Adv. Synth. Catal. 2017, 359, 3888–3893. [Google Scholar] [CrossRef]
  18. Ng, T.W.; Liao, G.; Lau, K.K.; Pan, H.-J.; Zhao, Y. Room-temperature Guerbet reaction with unprecedented catalytic efficiency and enantioselectivity. Angew. Chem. Int. Ed. 2020, 59, 11384–11389. [Google Scholar] [CrossRef]
  19. Genc, S.; Gulcemal, S.; Gunnaz, S.; Cetinkaya, B.; Gulcemal, D. Iridium-catalyzed alkylation of secondary alcohols with primary alcohols: A route to access branched ketones and alcohols. J. Org. Chem. 2020, 85, 9139–9152. [Google Scholar] [CrossRef]
  20. Fujita, K.; Asai, C.; Yamaguchi, T.; Hanasaka, F.; Yamaguchi, R. Direct β-alkylation of secondary alcohols with primary alcohols catalyzed by a Cp*Ir complex. Org. Lett. 2005, 7, 4017–4019. [Google Scholar] [CrossRef]
  21. Wang, D.; Zhao, K.; Xu, C.; Miao, H.; Ding, Y. Synthesis, structures of benzoxazolyl iridium(III) complexes, and applications on C–C and C–N bond formation reactions under solvent-free conditions: Catalytic activity enhanced by noncoordinating anion without silver effect. ACS Catal. 2014, 4, 3910–3918. [Google Scholar] [CrossRef]
  22. Filonenko, G.A.; van Putten, R.; Hensen, E.J.M.; Pidko, E.A. Catalytic (de)hydrogenation promoted by non-precious metals—Co, Fe and Mn: Recent advances in an emerging field. Chem. Soc. Rev. 2018, 47, 1459–1483. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  23. Mukherjee, A.; Milstein, D. Homogeneous catalysis by cobalt and manganese pincer complexes. ACS Catal. 2018, 8, 11435–11469. [Google Scholar] [CrossRef]
  24. Pandey, B.; Xu, S.; Ding, K. Selective ketone formations via cobalt-catalyzed β-alkylation of secondary alcohols with primary alcohols. Org. Lett. 2019, 21, 7420–7423. [Google Scholar] [CrossRef] [PubMed]
  25. Zhang, L.; Wang, A.; Wang, W.; Huang, Y.; Liu, X. Co–N–C catalyst for C–C coupling reactions: On the catalytic performance and active sites. ACS Catal. 2015, 5, 6563–6572. [Google Scholar] [CrossRef]
  26. Alonso, F.; Riente, P.; Yus, M. Nickel nanoparticles in hydrogen transfer reactions. Acc. Chem. Res. 2011, 44, 379–391. [Google Scholar] [CrossRef]
  27. Tang, G.; Cheng, C.-H. Synthesis of α-hydroxy carboxylic acids via a nickel(II)-catalyzed hydrogen transfer process. Adv. Synth. Catal. 2011, 353, 1918–1922. [Google Scholar] [CrossRef]
  28. Shimura, K.; Kon, K.; Hakim Siddiki, S.M.A.; Shimizu, K.-I. Self-coupling of secondary alcohols by Ni/CeO2 catalyst. Appl. Catal. A-Gen. 2013, 462–463, 137–142. [Google Scholar] [CrossRef]
  29. Babu, R.; Subaramanian, M.; Midya, S.P.; Balaraman, E. Nickel-catalyzed Guerbet type reaction: C-Alkylation of secondary alcohols via double (de)hydrogenation. Org. Lett. 2021, 23, 3320–3325. [Google Scholar] [CrossRef]
  30. Alanthadka, A.; Bera, S.; Vellakkaran, M.; Banerjee, D. Nickel-catalyzed double dehydrogenative coupling of secondary alcohols and β-amino alcohols to access substituted pyrroles. J. Org. Chem. 2019, 84, 13557–13564. [Google Scholar] [CrossRef]
  31. Liu, T.; Wang, L.; Wu, K.; Yu, Z. Manganese-catalyzed β-alkylation of secondary alcohols with primary alcohols under phosphine-free conditions. ACS Catal. 2018, 8, 7201–7207. [Google Scholar] [CrossRef]
  32. Lan, X.-B.; Ye, Z.; Liu, J.; Huang, M.; Shao, Y.; Cai, X.; Liu, Y.; Ke, Z. Sustainable and selective alkylation of deactivated secondary alcohols to ketones by non-bifunctional pincer N-heterocyclic carbene manganese. ChemSusChem 2020, 13, 2557–2563. [Google Scholar] [CrossRef]
  33. El-Sepelgy, O.; Matador, E.; Brzozowska, A.; Rueping, M. C-Alkylation of secondary alcohols by primary alcohols through manganese-catalyzed double hydrogen autotransfer. ChemSusChem 2019, 12, 3099–3102. [Google Scholar] [CrossRef] [PubMed]
  34. Kaithal, A.; van Bonn, P.; Hçlscher, M.; Leitner, W. Manganese(I)-catalyzed β-methylation of alcohols using methanol as C1 source. Angew. Chem. Int. Ed. 2020, 59, 215–220. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  35. Fu, S.; Shao, Z.; Wang, Y.; Liu, Q. Manganese-catalyzed upgrading of ethanol into 1-butanol. J. Am. Chem. Soc. 2017, 139, 11941–11948. [Google Scholar] [CrossRef]
  36. Kulkarni, N.V.; Brennessel, W.W.; Jones, W.D. Catalytic upgrading of ethanol to n-butanol via manganese-mediated Guerbet reaction. ACS Catal. 2018, 8, 997–1002. [Google Scholar] [CrossRef]
  37. Cano, R.; Yus, M.; Ramon, D.J. First practical cross-alkylation of primary alcohols with a new and recyclable impregnated iridium on magnetite catalyst. Chem. Commun. 2012, 48, 7628–7630. [Google Scholar] [CrossRef] [PubMed]
  38. Wang, J.; Yang, W.; Wu, C.; Gong, Y.; Zhang, J.; Shen, C. Upgrading n-butanol to branched alcohols over Ni/CaxMgyO. ACS Sustain. Chem. Eng. 2020, 8, 16960–16967. [Google Scholar] [CrossRef]
  39. Wang, D.; Guo, X.-Q.; Wang, C.-X.; Wang, Y.-N.; Zhong, R.; Zhu, X.-H.; Cai, L.-H.; Gao, Z.-W.; Hou, X.-F. An efficient and recyclable catalyst for N-alkylation of amines and β-alkylation of secondary alcohols with primary alcohols: SBA-15 supported N-heterocyclic carbene iridium complex. Adv. Synth. Catal. 2013, 355, 1117–1125. [Google Scholar] [CrossRef]
  40. Wu, K.; He, W.; Sun, C.; Yu, Z. Bimetallic Pt–Sn/γ-Al2O3 catalyzed β-alkylation of secondary alcohols with primary alcohols under solvent-free conditions. Tetrahedron Lett. 2016, 57, 4017–4020. [Google Scholar] [CrossRef]
  41. Oikawa, K.; Itoh, S.; Yano, H.; Kawasaki, H.; Obora, Y. Preparation and use of DMF-stabilized iridium nanoclusters as methylation catalysts using methanol as the C1 source. Chem. Commun. 2017, 53, 1080–1083. [Google Scholar] [CrossRef]
  42. Zhang, Y.; Riduan, S.N. Functional porous organic polymers for heterogeneous catalysis. Chem. Soc. Rev. 2012, 41, 2083–2094. [Google Scholar] [CrossRef]
  43. Tan, L.; Tan, B. Hypercrosslinked porous polymer materials: Design, synthesis, and applications. Chem. Soc. Rev. 2017, 46, 3322–3356. [Google Scholar] [CrossRef]
  44. Enjamuri, N.; Sarkar, S.; Reddy, B.M.; Mondal, J. Design and catalytic application of functional porous organic polymers: Opportunities and challenges. Chem. Rec. 2019, 19, 1782–1792. [Google Scholar] [CrossRef]
  45. Sun, Q.; Dai, Z.; Meng, X.; Wang, L.; Xiao, F.-S. Task-specific design of porous polymer heterogeneous catalysts beyond homogeneous counterparts. ACS Catal. 2015, 5, 4556–4567. [Google Scholar] [CrossRef]
  46. Giri, A.; Hussain, M.D.W.; Sk, B.; Patra, A. Connecting the dots: Knitting C-phenylresorcin[4]arenes with aromatic linkers for task-specific porous organic polymers. Chem. Mater. 2019, 31, 8440–8450. [Google Scholar] [CrossRef]
  47. Lee, J.M.; Briggs, M.E.; Hasell, T.; Cooper, A.I. Hyperporous carbons from hypercrosslinked polymers. Adv. Mater. 2016, 28, 9804–9810. [Google Scholar] [CrossRef] [PubMed]
  48. Bhunia, S.; Molla, R.A.; Kumari, V.; Islam, S.M.; Bhaumik, A. Zn(ii) assisted synthesis of porous salen as an efficient heterogeneous scaffold for capture and conversion of CO2. Chem. Commun. 2015, 51, 15732–15735. [Google Scholar] [CrossRef]
  49. Li, L.-H.; Feng, X.-L.; Cui, X.-H.; Ma, Y.-X.; Ding, S.-Y.; Wang, W. Salen-based covalent organic framework. J. Am. Chem. Soc. 2017, 139, 6042–6045. [Google Scholar] [CrossRef]
  50. Li, B.; Guan, Z.; Wang, W.; Yang, X.; Hu, J.; Tan, B.; Li, T. Highly dispersed Pd catalyst locked in knitting aryl network polymers for Suzuki–Miyaura coupling reactions of aryl chlorides in aqueous media. Adv. Mater. 2012, 24, 3390–3395. [Google Scholar] [CrossRef]
  51. Song, K.; Liu, P.; Wang, J.; Pang, L.; Chen, J.; Hussain, I.; Tan, B.; Li, T. Controlled synthesis of uniform palladium nanoparticles on novel micro-porous carbon as a recyclable heterogeneous catalyst for the Heck reaction. Dalton Trans. 2015, 44, 13906–13913. [Google Scholar] [CrossRef] [PubMed]
  52. Mondal, J.; Biswas, A.; Chiba, S.; Zhao, Y. Cu0 nanoparticles deposited on nanoporous polymers: A recyclable heterogeneous nanocatalyst for Ullmann coupling of aryl halides with amines in water. Sci. Rep. 2015, 5, 8294. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  53. Bhanja, P.; Modak, A.; Bhaumik, A. Porous organic polymers for CO2 storage and conversion reactions. ChemCatChem 2019, 11, 244–257. [Google Scholar] [CrossRef]
  54. Whiteoak, C.J.; Henseler, A.H.; Ayats, C.; Kleij, A.W.; Pericàs, M.A. Conversion of oxiranes and CO2 to organic cyclic carbonates using a recyclable, bifunctional polystyrene-supported organocatalyst. Green Chem. 2014, 16, 1552–1559. [Google Scholar] [CrossRef]
  55. Lan, L.X.; Du, C.; Cao, L.; She, T.; Li, Y.; Bai, G. Ultrafine Ag nanoparticles encapsulated by covalent triazine framework nanosheets for CO2 conversion. ACS Appl. Mater. Interfaces 2018, 10, 38953–38962. [Google Scholar] [CrossRef]
  56. Dang, Q.Q.; Liu, C.Y.; Wang, X.M.; Zhang, X.M. Novel covalent triazine framework for high-performance CO2 capture and alkyne carboxylation reaction. ACS Appl. Mater. Interfaces 2018, 10, 27972–27978. [Google Scholar] [CrossRef] [PubMed]
  57. Cui, Y.; Xu, Z.; Li, H.-Y.; Young, D.J.; Ren, Z.-G.; Li, H.-X. Synthesis of a pyrazole-based microporous organic polymer for high-performance CO2 capture and alkyne carboxylation. ACS Appl. Polym. Mater. 2020, 2, 4512–4520. [Google Scholar] [CrossRef]
  58. Dhanalaxmi, K.; Yadav, R.; Kundu, S.K.; Reddy, B.M.; Amoli, V.; Sinha, A.K.; Mondal, J. MnFe2O4 nanocrystals wrapped in a porous organic polymer: A designed architecture for water-splitting photocatalysis. Chem. Eur. J. 2016, 22, 15639–15644. [Google Scholar] [CrossRef]
  59. Zhao, H.; Wang, Y.; Wang, R. In situ formation of well-dispersed palladium nanoparticles immobilized in imidazolium-based organic ionic polymers. Chem. Commun. 2014, 50, 10871–10874. [Google Scholar] [CrossRef]
  60. Mondal, J.; Kundu, S.K.; Hung Ng, W.K.; Singuru, R.; Borah, P.; Hirao, H.; Zhao, Y.; Bhaumik, A. Fabrication of ruthenium nanoparticles in porous organic polymers: Towards advanced heterogeneous catalytic nanoreactors. Chem. Eur. J. 2015, 21, 19016–19027. [Google Scholar] [CrossRef]
  61. He, J.; Razzaque, S.; Jin, S.; Hussain, I.; Tan, B. Efficient synthesis of Ultrafine gold nanoparticles with tunable sizes in a hyper-cross-linked polymer for nitrophenolreduction. ACS Appl. Nano Mater. 2019, 2, 546–553. [Google Scholar] [CrossRef]
  62. Jiang, M.; Ding, Y.; Yan, L.; Song, X.; Lin, R. Rh catalysts supported on knitting aryl network polymers for the hydroformylation of higher olefins. Chin. J. Catal. 2014, 35, 1456–1464. [Google Scholar] [CrossRef]
  63. Chetia, B.; Goutam, P.J.; Chipem, F.A.S.; Iyer, P.K. Thiourea recognition by 2,6-bis(2-benzimidazolyl)pyridine using spectroscopic techniques and DFT. J. Mol. Struct. 2013, 1042, 32–36. [Google Scholar] [CrossRef]
  64. Tan, D.-W.; Li, H.-X.; Zhu, D.-L.; Li, H.-Y.; Young, D.J.; Yao, J.-L.; Lang, J.-P. Ligand-controlled copper(I)-catalyzed cross-coupling of secondary and primary alcohols to α-alkylated ketones, pyridines, and quinolines. Org. Lett. 2018, 20, 608–611. [Google Scholar] [CrossRef] [PubMed]
  65. Guo, B.; Li, H.-X.; Zha, C.-H.; Young, D.J.; Li, H.-Y.; Lang, J.-P. Visible-light-enhanced Suzuki–Miyaura reactions of aryl chlorides in water with Pd NPs supported on a conjugated nanoporous polycarbazole. ChemSusChem 2019, 12, 1421–1427. [Google Scholar] [CrossRef] [PubMed]
  66. Padmanaban, S.; Gunasekar, G.H.; Lee, M.; Yoon, S. Recyclable covalent triazine framework-based Ru catalyst for transfer hydrogenation of carbonyl compounds in water. ACS Sustain. Chem. Eng. 2019, 7, 8893–8899. [Google Scholar] [CrossRef]
  67. Wang, S.; Hou, S.; Wu, C.; Zhao, Y.; Ma, X. RuCl3 anchored onto post-synthetic modification MIL-101(Cr)-NH2 as heterogeneous catalyst for hydrogenation of CO2 to formic acid. Chin. Chem. Lett. 2019, 30, 398–402. [Google Scholar] [CrossRef]
  68. Morgan, B.D.J. Resolving ruthenium: XPS studies of common ruthenium materials. Surf. Interface Anal. 2015, 47, 1072–1079. [Google Scholar] [CrossRef]
  69. Park, K.; Padmanaban, S.; Kim, S.-H.; Jung, K.-D.; Yoon, S. NNN Pincer-functionalized porous organic polymer supported Ru(III) as a heterogeneous catalyst for Levulinic acid hydrogenation to γ-valerolactone. ChemCatChem 2021, 13, 695–703. [Google Scholar] [CrossRef]
  70. Genç, S.; Arslan, B.; Gülcemal, S.; Günnaz, S.; Çetinkaya, B.; Gülcemal, D. Iridium(I)-catalyzed C–C and C–N bond formation reactions via the borrowing hydrogen strategy. J. Org. Chem. 2019, 84, 6286–6297. [Google Scholar] [CrossRef]
  71. Wang, Q.F.; Wu, K.K.; Yu, Z.K. Ruthenium(III)-catalyzed β-alkylation of secondary alcohols with primary alcohols. Organometallics 2016, 35, 1251–1256. [Google Scholar] [CrossRef]
  72. Roy, B.C.; Debnath, S.; Chakrabarti, K.; Paul, B.; Maji, M.; Kundu, S. ortho-Amino group functionalized 2,2′-bipyridine based Ru(ii) complex catalysed alkylation of secondary alcohols, nitriles and amines using alcohols. Org. Chem. Front. 2018, 5, 1008–1018. [Google Scholar] [CrossRef]
  73. Zhang, M.-J.; Li, H.-X.; Young, D.J.; Li, H.-Y.; Lang, J.-P. Reaction condition controlled nickel(II)-catalyzed C-C cross coupling of alcohols. Org. Biomol. Chem. 2019, 17, 3567–3574. [Google Scholar] [CrossRef] [PubMed]
Polymers 14 00231 sch001 550
Scheme 1. Synthesis of porous organic polymer (POP)-bp/bbp and POP-bp/bbpRuCl3.
Scheme 1. Synthesis of porous organic polymer (POP)-bp/bbp and POP-bp/bbpRuCl3.
Polymers 14 00231 sch001
Polymers 14 00231 g001 550
Figure 1. (a) Fourier transform infrared (FT-IR) spectra of POP-bp/bbp and POP-bp/bbpRuCl3. (b) N2 sorption isotherm for POP-bp/bbp and POP-bp/bbpRuCl3 at 77 K. (c) N1s X-ray photoelectron spectroscopy (XPS) spectra of POP-bp/bbp and POP-bp/bbpRuCl3. (d) Ru 3p XPS spectra of POP-bp/bbpRuCl3. (e) High-resolution transmission electron microscopy (HR-TEM) image of POP-bp/bbpRuCl3. (f) Energy-dispersive X-ray spectroscopy elemental mapping of POP-bp/bbpRuCl3.
Figure 1. (a) Fourier transform infrared (FT-IR) spectra of POP-bp/bbp and POP-bp/bbpRuCl3. (b) N2 sorption isotherm for POP-bp/bbp and POP-bp/bbpRuCl3 at 77 K. (c) N1s X-ray photoelectron spectroscopy (XPS) spectra of POP-bp/bbp and POP-bp/bbpRuCl3. (d) Ru 3p XPS spectra of POP-bp/bbpRuCl3. (e) High-resolution transmission electron microscopy (HR-TEM) image of POP-bp/bbpRuCl3. (f) Energy-dispersive X-ray spectroscopy elemental mapping of POP-bp/bbpRuCl3.
Polymers 14 00231 g001
Polymers 14 00231 g002 550
Figure 2. (a) Stability of the POP-bp/bbpRuCl3 catalyst. (b) Transmission electron microscopy (TEM) image of the reused POP-bp/bbpRuCl3. (c) FT-IR spectra of fresh and reused POP-bp/bbpRuCl3. (d) Deconvoluted Ru 3p XPS spectrum POP-bp/bbpRuCl3.
Figure 2. (a) Stability of the POP-bp/bbpRuCl3 catalyst. (b) Transmission electron microscopy (TEM) image of the reused POP-bp/bbpRuCl3. (c) FT-IR spectra of fresh and reused POP-bp/bbpRuCl3. (d) Deconvoluted Ru 3p XPS spectrum POP-bp/bbpRuCl3.
Polymers 14 00231 g002
Polymers 14 00231 sch002 550
Scheme 2. Mechanism elucidation experiments.
Scheme 2. Mechanism elucidation experiments.
Polymers 14 00231 sch002
Polymers 14 00231 sch003 550
Scheme 3. Proposed mechanism.
Scheme 3. Proposed mechanism.
Polymers 14 00231 sch003
Table
Table 1. Optimization of the reaction conditions.
Table 1. Optimization of the reaction conditions.
Polymers 14 00231 i001
Entry aCatalystBase (equiv.)Temperature (°C)Time(h)Yield (%) 3aa4aa
1POP-bp/bbpRuCl3KOH/1.0130468<5
2POP-bp/bbpRuCl3KOtBu/1.0130433trace
3POP-bp/bbpRuCl3Cs2CO3/1.0130432<5
4POP-bp/bbpRuCl3NaOH/1.0130411trace
5POP-bp/bbpRuCl3CsOH/1.0130445<5
6POP-bp/bbpRuCl3KOH/1.01004725
7POP-bp/bbpRuCl3KOH/1.011042014
8POP-bp/bbpRuCl3KOH/1.012044920
9POP-bp/bbpRuCl3KOH/1.0140470trace
10POP-bp/bbpRuCl3KOH/0.313046012
11POP-bp/bbpRuCl3KOH/0.51304768
12POP-bp/bbpRuCl3KOH/0.71304756
13POP-bp/bbpRuCl3KOH/1.5130469<5
14POP-bp/bbpRuCl3KOH/1.0130882<5
15POP-bp/bbpRuCl3KOH/0.51301293trace
16POP-bp/bbpKOH/0.5130120trace
17RuCl3KOH/0.51301218trace
a 130 Reaction conditions: 1a (1 mmol), 2a (1.2 mmol), cat. (20 mg, 0.6 mol% Ru), base (eq.), toluene (2 mL) in a 15 mL sealed tube, at 130 °C for 4 h, high-performance liquid chromatography (HPLC) yield using biphenyl as the internal standard.
Table
Table 2. β-Alkylation of 1-phenylethanol with various primary alcohols.
Table 2. β-Alkylation of 1-phenylethanol with various primary alcohols.
Polymers 14 00231 i002
Entry aPrimary AlcoholProductYield (%)
1 Polymers 14 00231 i0032a Polymers 14 00231 i0043aa88
2 Polymers 14 00231 i0052b Polymers 14 00231 i0063ab85
3 Polymers 14 00231 i0072c Polymers 14 00231 i0083ac73
4 Polymers 14 00231 i0092d Polymers 14 00231 i0103ad85
5 Polymers 14 00231 i0112e Polymers 14 00231 i0123ae87
6 Polymers 14 00231 i0132f Polymers 14 00231 i0143af87
7 Polymers 14 00231 i0152g Polymers 14 00231 i0163ag89
8 Polymers 14 00231 i0172h Polymers 14 00231 i0183ah79
9 Polymers 14 00231 i0192i Polymers 14 00231 i0203ai86
10 Polymers 14 00231 i0212j Polymers 14 00231 i0223aj81
11 Polymers 14 00231 i0232k Polymers 14 00231 i0243ak85
12 Polymers 14 00231 i0252l Polymers 14 00231 i0263al88
13 Polymers 14 00231 i0272m Polymers 14 00231 i0283am80
14 Polymers 14 00231 i0292n Polymers 14 00231 i0303an59
a Reaction condition: 1a (1 mmol), primary alcohol (1.2 mmol), POP-bp/bbpRuCl3 (20 mg, 0.6 mol % Ru), KOH (0.5 equiv.), toluene (2 mL), 130 °C, 12 h, isolated yields.
Table
Table 3. β-Alkylation of various secondary alcohols with benzyl alcohol.
Table 3. β-Alkylation of various secondary alcohols with benzyl alcohol.
Polymers 14 00231 i031
Entry aSecondary AlcoholProductYield (%)
1 Polymers 14 00231 i0321a Polymers 14 00231 i0333aa88
2 Polymers 14 00231 i0341b Polymers 14 00231 i0353ba80
3 Polymers 14 00231 i0361c Polymers 14 00231 i0373ca89
4 Polymers 14 00231 i0381d Polymers 14 00231 i0393da81
5 Polymers 14 00231 i0401e Polymers 14 00231 i0413ea88
6 Polymers 14 00231 i0421f Polymers 14 00231 i0433fa53
7 Polymers 14 00231 i0441g Polymers 14 00231 i0453ga76
8 Polymers 14 00231 i0461h Polymers 14 00231 i0473ha79
9 Polymers 14 00231 i0481i Polymers 14 00231 i0493ia88
10 Polymers 14 00231 i0501j Polymers 14 00231 i0513ja85
11 Polymers 14 00231 i0521k Polymers 14 00231 i0533ka90
a Reaction condition: secondary alcohol (1 mmol), 2a (1.2 mmol), POP-bp/bbpRuCl3 (20 mg, 0.6 mol%Ru), KOH (0.5 equiv.), toluene (2 mL), 130 °C, 12 h, isolated yields.
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Share and Cite

MDPI and ACS Style

Cui, Y.; Wang, J.; Yu, L.; Xu, Y.; Young, D.J.; Li, H.; Li, H. Construction of a (NNN)Ru-Incorporated Porous Organic Polymer with High Catalytic Activity for β-Alkylation of Secondary Alcohols with Primary Alcohols. Polymers 2022, 14, 231. https://doi.org/10.3390/polym14020231

AMA Style

Cui Y, Wang J, Yu L, Xu Y, Young DJ, Li H, Li H. Construction of a (NNN)Ru-Incorporated Porous Organic Polymer with High Catalytic Activity for β-Alkylation of Secondary Alcohols with Primary Alcohols. Polymers. 2022; 14(2):231. https://doi.org/10.3390/polym14020231

Chicago/Turabian Style

Cui, Yao, Jixian Wang, Lei Yu, Ying Xu, David J. Young, Haiyan Li, and Hongxi Li. 2022. "Construction of a (NNN)Ru-Incorporated Porous Organic Polymer with High Catalytic Activity for β-Alkylation of Secondary Alcohols with Primary Alcohols" Polymers 14, no. 2: 231. https://doi.org/10.3390/polym14020231

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop