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Review

Enantioselective Transfer Reactions of α-Heteroatom-Substituted Carbenes

by
Mingyao Huang
1,*,†,
Wenjing Shi
2,*,† and
Lu Li
2
1
Frontiers Science Center for New Organic Matter, the State Key Laboratory and Institute of Elemento-Organic Chemistry, College of Chemistry, Nankai University, Tianjin 300071, China
2
Tianjin Baogang Rare Earth Research Institute Co., Ltd., Tianjin 300301, China
*
Authors to whom correspondence should be addressed.
†
These authors contributed equally to this work.
Symmetry 2024, 16(9), 1171; https://doi.org/10.3390/sym16091171
Submission received: 1 August 2024 / Revised: 2 September 2024 / Accepted: 2 September 2024 / Published: 6 September 2024
(This article belongs to the Collection Feature Papers in Chemistry)
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Abstract

:
Metal carbenes are widely acknowledged as a category of highly effective intermediates that facilitate otherwise inaccessible transformations. In recent decades, carbene chemistry has made considerable advances and has demonstrated remarkable abilities in the formation of diverse chemical bonds and the synthesis of structurally distinctive molecules. Nevertheless, the majority of research within this field has concentrated on α-carbon-substituted carbenes, with comparatively little investigation of carbenes that have been functionalized with a wider structural variety, particularly those that have been substituted with heteroatoms (e.g., O, N, P, S, Si, Ge, Sn and B). The objective of this review is to elucidate the advancements in enantioselective transfer reactions involving metal carbenes substituted with these elements, thereby highlighting their contribution to the expansion of the structural diversity and synthetic utility of carbenes in contemporary chemistry.

1. Introduction

Metal carbenes represent a class of paramount and versatile intermediates in organic chemistry, characterized by their rich reactivity profiles. These entities are capable of undergoing a myriad of transformations, including insertion into σ-bonds, addition across π-bonds, alkene metathesis, and various rearrangement reactions [1,2,3,4,5]. The utility of metal carbene intermediates spans across a wide array of applications, encompassing organic synthesis [5], agricultural chemistry [6], medicinal chemistry [5], and materials science [7]. Over recent decades, a diverse set of carbene precursors has been developed, such as diazoalkanes, hydrazones, functionalized alkynes, sulfonium ylides, and cyclopropenes. These precursors facilitate transition-metal-catalyzed enantioselective transfer reactions, offering an efficacious and promising avenue for the establishment of myriad chemical bonds and thus broadening the synthetic landscape of carbene chemistry [8,9,10]. Historically, the focal point within this domain has predominantly been on α-carbon-substituted carbenes, whereas metal carbenes functionalized with a richer structural variety, particularly those substituted with heteroatoms (e.g., O, N, P, S, Si, Ge, Sn and B), have not been thoroughly explored. This review aims to elucidate the advancements in enantioselective transfer reactions involving metal carbenes substituted with these elements, thereby highlighting their contribution to expanding the structural diversity and synthetic utility of carbenes in contemporary chemistry.

2. α-O- and α-N-Substituted Carbenes

Oxo- or amino-substituted carbenes, usually complexed with Group VI metals, belong to the Fischer-type carbene family [11]. These stable metal carbenes have showcased a wide range of reactivities since their discovery over 50 years ago [12]. However, enantioselective transformations of these carbenes remain largely unexplored, likely due to the absence of suitable carbene precursors and efficient asymmetric catalytic systems for their transfer reactions.
In 2022, Davies and coworkers [13] introduced a rhodium-catalyzed enantioselective cyclopropanation reaction involving α-aryloxyl-α-imine carbenes (Scheme 1). These carbenes were transiently generated from the ring-opening/denitrogenation of 4-aryloxy-1-sulfonyl-1,2,3-triazoles, leading to the formation of 1-phenoxycyclopropane-1-carbaldehydes (up to 80% yield, 71% ee and >30:1 dr), followed by the hydrolysis of the imine moiety. Although the results of enantiomeric excess were moderate, this reaction demonstrated that carbenes with electron-donating heteroatoms can participate in asymmetric transformations.
Later in 2023, Hu and Ke’s group [14] described an impressive enantioselective multi-functionalization reaction involving α-alkoxyl or α-amide carbenes (Scheme 2). Using hypervalent iodine diazo compounds as precursors, they generated I(III)-substituted rhodium carbenes, which were intercepted twice by a nucleophile (either alcohol or carbamate). The first interception yielded α-alkoxyl or α-amide carbenes by replacing the I(III) leaving group, while the second captured the resulting Fischer carbenes, forming an ylide or an enolate. The subsequent trapping of the enolate with an electrophilic imine, catalyzed by chiral phosphoric acid, resulted in β-amino esters with high yields and exceptional enantioselectivities (up to 98% yield, 99% ee).
The electron-withdrawing nitro group, alongside the electron-donating amino group, represents another pattern for N-substituted carbenes, which can be generated from corresponding diazo precursors. In 2003, Charette’s group [15] investigated the enantioselective cyclopropanation of α-nitro-α-diazo carbonyl compounds and styrene using chiral rhodium or copper catalysts, yielding cyclopropanyl nitro esters with moderate enantioselectivities (up to 74% yield, E/Z up to 84:16, E type up to 30% ee). They also explored the use of phenyliodonium ylides as safer diazo alternatives, which resulted in significantly lower diastereoselectivity and enantioselectivity under chiral rhodium catalysis [16] (Scheme 3a). However, the use of copper/bisoxazoline (Box) catalysts produced excellent outcomes (up to 84% yield. 95:5 dr, 98% ee), efficiently generating a series of enantioenriched cyclopropanyl nitro esters (Scheme 3b). The reduction of the nitro group yielded the corresponding cyclopropane amino acid esters [17], which serve as functional fragments in bioactive natural product analogues.
In 2011, Charette’s group [18] extended the reaction to α-nitro-α-aroyl-substituted diazocompounds using Rh2(S-TCPTTL)4, demonstrating a broader scope of alkenes. This reaction produced various tri- or tetra-substituted cyclopropanes with remarkable enantioselectivities and diastereoselectivities (up to 91% yield. 99:1 dr, 98% ee) (Scheme 4). Substituents on the phenyl ring significantly impacted both diastereoselectivity and enantioselectivity, with electron-donating groups such as OMe or NMe2 providing better results than the electron-deficient CF3 group, which were attributed to enhanced catalyst–substrate π-stacking interactions for electron-rich aryl ketones.
In 2008, Zhang and coworkers [19] achieved asymmetric cyclopropanation reactions between α-nitro diazoesters and various alkenes using a D2-symmetric chiral porphyrin cobalt(II) catalyst. This method yielded Z-cyclopropanes with up to 97% yield, a 99/1 Z/E ratio, and 95% ee (Scheme 5). Notably, the cobalt carbene formed through the decomposition of the diazo precursor acted as a metalloradical, reacting with the alkene through a radical addition/C-C formation sequence to produce the cyclopropane products.
In 2015, Tang and colleagues [20] reported a copper/bisoxazoline complex-catalyzed highly enantioselective cyclopropanation of α-nitro diazoesters with 1,2-disubstituted alkenes. This method provided the desired products in good to high yields (up to 97%), with excellent diastereoselectivities (up to 99/1 dr) and enantioselectivities (up to 98% ee). (Scheme 6).

3. α-P-Substituted Carbenes

Carbenes substituted with phosphorus are generally generated from their diazo precursors, in which the phosphorus atom adopts a pentavalent form, exhibiting elevated electron deficiency that stabilizes the adjacent diazo’s functionality. These λ5-phosphorus-containing α-diazo compounds constitute a versatile class of reagents in organic chemistry, particularly valuable for synthesizing phosphonate- and phosphinoxide-functionalized molecules [21].
In enantioselective cyclopropanation reactions with olefins, Davies and coworkers [22] reported the highly enantioselective cyclopropanation of alkenes using donor/acceptor α-aryl diazophosphorates in the presence of chiral dirhodium complexes Rh2(S-PTAD)4, resulting in cyclopropanyl phosphorate with an excellent outcome (86% yield, >30:1 dr, 99% ee) (Scheme 7a). They also found that Rh2(S-biTISP)2 performed effectively in the tandem cyclopropanation/Cope rearrangement with phenyl-substituted conjugated dienes, yielding phosphonate-substituted cycloheptadiene as a single diastereoisomer with 65% ee (Scheme 7b).
In 2014, Adly’s group [23] reported that the tert-leucine-derived tratrocarboxylate dirhodium complex exhibited excellent performance in the cyclopropanation of aryl alkenes with α-aryl-α-diazobenzylphosphonate, providing efficient access to cyclopropylphosphonates with high yields (up to 93%), good diastereoselectivity (up to >20:1 dr), and excellent enantioselectivity (up to 99% ee) (Scheme 7c). Recognizing the high potential of acceptor-acceptor cyclopropanes (with two electron-withdrawing groups on the same carbon of the cyclopropane ring) in asymmetric synthesis, Charett and coworkers [24] described the catalytic asymmetric synthesis of cyclopropylphosphonate derivatives in 2013, using α-cyano-α-diazomethylphosphonate as the starting material. The selection of the cyano group as the second electron-withdrawing substituent of the diazo reagent was driven by its steric and electronic properties. Utilizing Rh2(S-IBAZ)4 as the catalyst, the reaction proceeded smoothly, yielding diverse tri- or tetra-substituted α-cyano-α-phosphoryl cyclopropanes with excellent yields and high diastereo- and enantioselectivities (99% yield, >97:3 dr, 99% ee) (Scheme 7d).
Apart from chiral dirhodium catalysts, ruthenium complexes have also been employed in cyclopropanation reactions. In 2004, Simonneaux and coworkers [25] reported the enantioselective synthesis of cyclopropylphosphonates using a chiral ruthenium-porphyrin complex as the catalyst (Scheme 8a). These reactions predominantly yielded the trans-diastereomer with excellent enantioselectivity (up to 92% ee), while the cis-products were few and exhibited low enantiopurity. Subsequently, in 2005, the Charette group [26] investigated the transition metal-catalyzed enantioselective synthesis of cyclopropyl phosphonates. Using a chiral pyridine-bisoxazoline (PyBox)-ruthenium catalyst, they achieved the cyclopropanation of diverse olefins with diazophosphorates, resulting in high diastereoselectivity (>98:2 dr) and excellent enantioselectivity (up to >98:2 dr) (Scheme 8b). Despite there being various methodologies for the cyclopropanation of olefins, particularly styrene derivatives, applications to electron-deficient alkenes, such as α,β-unsaturated carbonyl compounds, remain rare. Iwasa and coworkers [27] reported the stereoselective cyclopropanation of alkenes, including α,β-unsaturated carbonyl compounds, catalyzed by a Ru(II)-Pheox complex (Scheme 8c). This reaction afforded a diversity of trans-1,2-disubstituted phosphorate cyclopropanes, which serve as key intermediates for the synthesis of acyclic nucleoside analogues and glutamic acid analogues.
The intramolecular cyclopropanation of diazophosphates has proven to be an effective tool for synthesizing cyclopropane-containing fused rings. In 2013, the Nakada group [28] achieved the intramolecular cyclopropanation of diphenyl α-diazo-β-keto-phosphinoxide using a chiral copper/Box complex, forming the bicyclic derivative with 91% ee. This compound was a key intermediate in the synthesis of (+)-colletoic acid (Scheme 9).
Donor–acceptor-substituted diazo compounds have also been employed as carbene precursors in the enantioselective synthesis of chiral cyclopropenes using iridium-salen chiral catalysts [29] (Scheme 10a). Beyond diazoesters, dimethyl α-diazobenzylphosphonate has been used to convert terminal alkynes into the corresponding cyclopropenes with good to excellent yields. Another example of cyclopropanation in the literature involves diacceptor diazophosphorates, catalyzed by chiral Rh2(S-IBAZ)4, which exhibit excellent efficiency with both aryl and alkyl terminal alkynes [24] (Scheme 10b).
The enantioselective C-H insertion was first attempted in the intramolecular version using chiral rhodium(II) catalysts, resulting in modest to moderate enantioselectivity (up to 40% ee) [30]. Slightly better results were obtained by Slattery and Maguire with copper complexes, yielding the corresponding α-phosphonocyclopentanone derivative in 71% yield and 52% ee [31] (Scheme 11a). For intermolecular C-H insertion reactions, the steric hindrance and decreased electrophilicity of α-phosphorate-substituted carbenes (relative to α-ester ones) rendered them feasible for insertion into the highly activated C-H bonds of 1,4-cyclohexadiene in the presence of chiral dirhodium(II) catalysts [32] (Scheme 11b).
The Xu group [33] developed a series of chiral C1 symmetric diene ligands and discovered that their complex with rhodium(I) could catalyze highly enantioselective Si-H insertion reactions with α-arylphosphorates, providing efficient access to chiral α-silylphosphorates (up to 63% yield, 99% ee) (Scheme 12a). Recently, Song and coworkers [34] reported a highly enantioselective B-H bond insertion reaction of α-aryl diazophosphates using a copper/Box complex. Notably, this protocol demonstrated excellent tolerance to a broad spectrum of functional groups, offering a straightforward method to synthesize α-borylphosphorates with good enantioselectivities (up to 97% yield, 98% ee) (Scheme 12b).
In 2011, Zhou and coworkers [35] reported the first highly enantioselective O-H insertion reaction of diazophosphorates. Using a spiro bisoxazoline/copper complex as the catalyst, various diazo precursors, and α-aryl-substituted diazophosphorates reacted smoothly with alcohols or phenols, they yielded the corresponding α-oxyl phosphorates with excellent outcomes (up to 89% yield, 98% ee) (Scheme 12c).
In contrast, the enantioselective N-H insertion of diazophosphorates remains an unsolved challenge, despite the extensive investigation of its non-asymmetric versions. This difficulty may be attributed to the poor stereocontrol of the proton-transfer process in the ylide formed by the nucleophilic attack of N-H donors on the carbene intermediate. However, it is possible that the ylide could be captured enantioselectively by an aldehyde. In 2012, Che and coworkers [36] explored the rhodium-catalyzed three-component reaction of dimethyl α-diazobenzylphosphonate, 2-bromoanilines, and 4-nitrobenzaldehyde, resulting in a mixture of the corresponding syn- and anti-α-amino-β-hydroxyethylphosphonates (up to 85% yield, 94:6 dr, 98% ee) (Scheme 13). The syn-diastereoisomer was the major product in each case. The best stereochemical outcome was achieved with a catalyst loading of 2 mol % Rh2(S-PTAD)4. The proposed mechanism involves the initial trapping of the Rh-carbene species by aniline to form a metal-bound ammonium ylide intermediate. The subsequent nucleophilic addition of the ylide to the aldehyde leads to the final compound. The high level of enantiocontrol observed suggests that the reaction proceeds through a metal-bound stabilized ylide rather than a free ylide.

4. α-S-Substituted Carbenes

Akin to α-P carbenes, α-S-substituted carbenes are typically generated from diazo precursors, where sulfur adopts a hexavalent form to stabilize the neighboring diazo moiety. These diazosulfones were first utilized in 1990, when McKervey’s group reported that chiral dirhodium carboxylates could effectively catalyze the intramolecular cyclopropanation of α-diazo-α-keto sulfones, affording bicyclo[3.1.0]hexanyl sulfones in 97% yield, albeit with low ee (ca. 12%) [37]. In 2003, Nakada and coworkers [38] achieved a highly enantioselective version of this reaction using copper/Box catalysts, providing efficient access to bicyclo[3.1.0]hexane frameworks (Scheme 14a). Utilizing substrates with a 1,4-cyclohexadiene group enabled desymmetrizing intramolecular cyclopropanation, forming tricyclo[4.3.0.0]nonene and tricyclo[4.4.0.0]decenyl derivatives with excellent outcomes (Scheme 14b). Furthermore, using a similar copper catalytic system, they extended the intramolecular cyclopropanation reaction for the enantioselective construction of bicyclo[4.1.0]heptanyl and sulfones with moderate to good yields and excellent enantioselectivities (up to 58% yield, 98% ee) [39] (Scheme 14c).
These bicyclic or tricyclic products serve as valuable synthons in natural product synthesis. Nakada and coworkers used bicyclo[3.1.0]hexanyl sulfones as key intermediates to accomplish the enantioselective total synthesis of (-)-erinacine B[40] and cotylenin A [41]. Starting from tricyclo[4.3.0.0]nonenyl or tricyclo[4.4.0.0]decenyl sulfones, they also succeeded in the formal total synthesis of (-)-platensimycin and (-)-platencin [42] as well as constructing an approach towards polycyclic polyprenylated acylphloroglucinols [43] (Scheme 14d).
Beyond intramolecular cyclopropanation reactions, in 2008, Zhang and coworkers [44] established a method for the intermolecular asymmetric cyclopropanation of diazosulfones and terminal alkenes (Scheme 15a). Using D2-symmetrical chiral cobalt/porphyrin catalysts, various aryl alkenes and electron-deficient alkenes were converted into trans-tosyl cyclopropanes with remarkable yields (up to 99% yield), diastereoselectivities (up to >99:1 dr), and enantioselectivities (up to 97% ee). Later, in 2017, Iwasa and coworkers [45] reported a similar highly enantioselective intermolecular cyclopropanation reaction using ruthenium(II)-Phox complexes. The ruthenium(II) system was feasible not only for aryl alkenes but also for vinyl enol ethers and vinyl enamines, affording various chiral 1,2-trans-diheteroatom-substituted cyclopropanes with good outcomes (up to 99% yield, >99:1 dr, 98% ee) (Scheme 15b).
In 2019, Doyle and workers [46] reported the synthesis of enoldiazosulfones, which were employed as carbene precursors for the highly enantioselective [3+3]-cycloaddition with nitrones under copper(I) catalysis with chiral Box ligands. The reaction initiates with the decomposition of enoldiazosulfones to yield α-vinyl-α-sulfone carbene, which acts as a 1,3-dipole and reacts with nitrones to afford oxazine-sulfone derivatives in high yields and enantioselectivities (up to 98% yield, >99% ee) (Scheme 16).

5. α-IV Main Group Element (Si, Ge, Sn)-Substituted Carbenes

Carbenes functionalized with Group IV elements (Si, Ge, Sn) are promising intermediates in the construction of organosilanes, organogermananes, and organotins, leveraging the abundant reactivities of carbene chemistry. In 2017, Nakada and coworkers [47] reported the first highly enantioselective intramolecular cyclopropanation reaction using copper/Box complexes, forming oxabicyclo[3.2.1]hexane derivatives with high yields and enantioselectivities (Scheme 17). Notably, the counteranion of the Cu(I) catalyst played a crucial role in determining both yields and enantioselectivities, with highly anionic counteranions enhancing both.
In 2020, Fürstner et al. [48] synthesized a heteroleptic dirhodium paddlewheel catalyst with a chiral carboxylate/acetamidate ligand and found it highly efficient for catalyzing the enantioselective cyclopropanation of α-IV main group element-substituted (Sn, Ge, Si) carbenes with terminal alkenes, albeit with low diastereoselectivities (up to 78% yield, 84:16 dr, 97% ee) (Scheme 18a). Structural analysis of the heteroleptic dirhodium complex supported the hypothesis that hydrogen bonding between the acetamidate ligand and the carbene residue fixed the configuration, improving both efficiency and enantioselectivity. Later modifications of the chiral carboxylate ligands significantly improved the diastereoselectivities of the cyclopropanation products and broadened the scope and functional group tolerance of alkenes, yielding a diverse array of chiral cyclopropyl silanes, germananes, and tins [49] (Scheme 18b). The organotin products could undergo palladium-catalyzed Migita–Kosugi–Stille cross-coupling with aryl or vinyl halides, affording functionalized cyclopropanes with retained optical purity.
In 2019, the Zhu and Zhou group [50] reported a rhodium-catalyzed asymmetric B-H insertion reaction of α-furyl-α-silyl carbenes generated from the 5-exo-dig cyclization of functionalized alkynes, producing gem-borylsilanes with 34% ee (Scheme 19a). In 2022, using 1-silylcyclopropene as carbene precursors, they achieved a highly enantioselective B-H insertion reaction of α-vinyl-α-silyl carbenes in the presence of a copper(I)/Box complex (Scheme 19b) [51]. Interestingly, the Lewis acidic silyl group was found to polarize the cyclopropenes (int I), rendering the C1 position more negatively charged, which was then attacked by the electrophilic copper, leading to C1-C3 cleavage (TS I, TS III) to form E- or Z-type α-vinyl-α-silyl carbenes. Only the E-carbene could be captured by borane-amine adducts (TS II) to form chiral gem-silylboranes, while the Z-carbene tended to undergo formal intramolecular C-H insertion (TS IV), forming indane byproducts. This protocol provided efficient access to various 3,3-disubstituted allylic chiral gem-silylboranes with excellent optical purity (up to 88% yield, 99% ee).

6. α-B-Substituted Carbenes

Chiral organoborons are widely used in organic synthesis, materials science, and medicinal chemistry. As hybrids of carbene and boryl groups, α-boryl carbenes are promising intermediates for constructing chiral organoborons. However, α-boryl carbene chemistry remains largely underexplored, primarily due to the scarcity of available α-boryl carbene precursors. The strong Lewis acidity of the boryl group tends to decompose diazo groups [52], rendering α-boryl diazo compounds generally unstable. To date, only tetracoordinated BMIDA [53,54] or sterically hindered BN ring-substituted carbenes [55] have been used in transfer reactions, with no enantioselective versions reported. Recently, the Zhu group [56] introduced a new class of α-boryl carbene precursors—1-Bpin cyclopropenes—that can undergo selective ring-opening to form α-vinyl-α-Bpin carbenes. These intermediates can participate in a series of enantioselective carbene transfer reactions, including B-H insertion, Si-H insertion, cyclopropanation, and cyclopropanation/Cope rearrangement reactions (Scheme 20). These processes afford a variety of structurally novel organoborons, specifically chiral gem-diborons, gem-silylborons, tertiary cyclopropyl boronates, and cycloheptadienyl boronates.

7. Conclusions and Outlook

By exploiting the rich reactivity profiles of carbene chemistry, enantioselective transfer reactions of α-heteroatom carbenes present a promising tool for synthesizing chiral organoelemental compounds. Despite the advancements described above, α-heteroatom carbene chemistry remains challenging and underexplored. The discovery of readily available and structurally diverse precursors for the efficient generation of α-heteroatom carbenes is essential for advancing this field. Additionally, expanding the types of transfer reactions based on known α-heteroatom carbenes by developing novel and efficient catalysts and catalytic strategies will greatly enrich carbene chemistry. More importantly, compared to α-carbon-substituted carbenes, the unique properties of heteroatoms attached to the carbene center might introduce new reactive modes, potentially bringing new opportunities and momentum to carbene chemistry.

Author Contributions

Conceptualization, M.H.; literature investigation, M.H. and W.S.; writing—original draft preparation, M.H. and W.S.; writing—review and editing, M.H., W.S. and L.L.; supervision, M.H.; funding acquisition, W.S. and L.L. 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 (22221002), the Fundamental Research Funds for the Central Universities, Natural Science Foundation of Tianjin (63231033), the Research Funds from China Northern Rare Earth (Group) High-tech Co., Ltd.

Conflicts of Interest

Author Wenjing Shi and Lu Li were employed by the company Tianjin Baogang Rare Earth Research Institute Co., Ltd. The authors declare that this study received funding from China Northern Rare Earth (Group) High-tech Co., Ltd. The funder was not involved in the study design, collection, analysis, interpretation of data, the writing of this article or the decision to submit it for publication.

Abbreviations

MeMethyl
EtEthyl
iPrIsopropyl
tBuTert-butyl
PhPhenyl
CbzCarbono benzyl
BnBenzyl
AcAcetyl
DCMDichloromethane
TBDPSDiphenyl-tert-butyl-silyl
BArFTetra(3,5-di-trifluoromethylphenyl)borate
Mes2,4,6-trimethylphenyl
OTfTrifluoromethanesulfonyl
TsTosyl
TBSDimethyl-tert-butylsilyl
BpinPinacolatoboryl

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Symmetry 16 01171 sch001
Scheme 1. Rh (II)-catalyzed enantioselective cyclopropanation reaction involving α-aryloxyl-α-imine carbenes.
Scheme 1. Rh (II)-catalyzed enantioselective cyclopropanation reaction involving α-aryloxyl-α-imine carbenes.
Symmetry 16 01171 sch001
Symmetry 16 01171 sch002
Scheme 2. Rh(II)-catalyzed asymmetric multi-functionalization reaction involving α-alkoxyl or α-amide carbenes.
Scheme 2. Rh(II)-catalyzed asymmetric multi-functionalization reaction involving α-alkoxyl or α-amide carbenes.
Symmetry 16 01171 sch002
Symmetry 16 01171 sch003
Scheme 3. Rh(II)- or Cu(I)-catalyzed enantioselective cyclopropanations of α-nitro carbenes. (a) Catalyzed by Rh2(S-PTPA)4; (b) catalyzed by Cu/Box complex.
Scheme 3. Rh(II)- or Cu(I)-catalyzed enantioselective cyclopropanations of α-nitro carbenes. (a) Catalyzed by Rh2(S-PTPA)4; (b) catalyzed by Cu/Box complex.
Symmetry 16 01171 sch003
Symmetry 16 01171 sch004
Scheme 4. Rh(II)-catalyzed enantioselective cyclopropanations of α-nitro diazo carbonyls-derived carbenes.
Scheme 4. Rh(II)-catalyzed enantioselective cyclopropanations of α-nitro diazo carbonyls-derived carbenes.
Symmetry 16 01171 sch004
Symmetry 16 01171 sch005
Scheme 5. Co(II)-catalyzed asymmetric cyclopropanation reactions of α-nitro carbenes.
Scheme 5. Co(II)-catalyzed asymmetric cyclopropanation reactions of α-nitro carbenes.
Symmetry 16 01171 sch005
Symmetry 16 01171 sch006
Scheme 6. Cu(I)-catalyzed enantioselective cyclopropanation of α-nitro carbenes with internal alkenes.
Scheme 6. Cu(I)-catalyzed enantioselective cyclopropanation of α-nitro carbenes with internal alkenes.
Symmetry 16 01171 sch006
Symmetry 16 01171 sch007
Scheme 7. Rh(II)-catalyzed enantioselective cyclopropanation of α-phosphate carbenes. (a) enantioselective cyclopropanation of styrene; (b) enantioselective cyclopropanation/Cope rearrangement of conjugated dienes; (c) enantioselective cyclopropanation of various aryl substituted alkenes; (d) enantioselective cyclopropanation of α-cyano-α-diazomethylphosphonate.
Scheme 7. Rh(II)-catalyzed enantioselective cyclopropanation of α-phosphate carbenes. (a) enantioselective cyclopropanation of styrene; (b) enantioselective cyclopropanation/Cope rearrangement of conjugated dienes; (c) enantioselective cyclopropanation of various aryl substituted alkenes; (d) enantioselective cyclopropanation of α-cyano-α-diazomethylphosphonate.
Symmetry 16 01171 sch007
Symmetry 16 01171 sch008
Scheme 8. Ru(II)-catalyzed enantioselective cyclopropanation of α-phosphorate carbenes. (a) catalyzed by chiral ruthenium-porphyrin complex; (b) catalyzed by chiral pyridine-bisoxazoline-ruthenium catalyst; (c) catalyzed by Ru(II)-Pheox complex.
Scheme 8. Ru(II)-catalyzed enantioselective cyclopropanation of α-phosphorate carbenes. (a) catalyzed by chiral ruthenium-porphyrin complex; (b) catalyzed by chiral pyridine-bisoxazoline-ruthenium catalyst; (c) catalyzed by Ru(II)-Pheox complex.
Symmetry 16 01171 sch008
Symmetry 16 01171 sch009
Scheme 9. Ru(II)-catalyzed enantioselective intramolecular cyclopropanation of α-P carbenes.
Scheme 9. Ru(II)-catalyzed enantioselective intramolecular cyclopropanation of α-P carbenes.
Symmetry 16 01171 sch009
Symmetry 16 01171 sch010
Scheme 10. Ir(III)- or Rh(II)-catalyzed enantioselective cyclopropanation of α-P carbenes. (a) catalyzed by chiral iridium-salen chiral catalyst; (b) catalyzed by the chiral Rh2(S-IBAZ)4.
Scheme 10. Ir(III)- or Rh(II)-catalyzed enantioselective cyclopropanation of α-P carbenes. (a) catalyzed by chiral iridium-salen chiral catalyst; (b) catalyzed by the chiral Rh2(S-IBAZ)4.
Symmetry 16 01171 sch010
Symmetry 16 01171 sch011
Scheme 11. Cu(I)- or Rh(II)-catalyzed enantioselective C-H insertion reactions of α-P carbenes. (a) Cu(I)-catalyzed intramolecular C-H insertion; (b) Rh(II)-catalyzed intermolecular C-H insertion of 1,4-cyclohexadiene.
Scheme 11. Cu(I)- or Rh(II)-catalyzed enantioselective C-H insertion reactions of α-P carbenes. (a) Cu(I)-catalyzed intramolecular C-H insertion; (b) Rh(II)-catalyzed intermolecular C-H insertion of 1,4-cyclohexadiene.
Symmetry 16 01171 sch011
Symmetry 16 01171 sch012
Scheme 12. Transition-metal-catalyzed enantioselective X-H (X = Si, B, O) insertion reactions of α-P carbenes. (a) Rh(I)-catalyzed enantioselective Si-H insertion reactions; (b) Cu(I)-catalyzed enantioselective B-H insertion reactions; (c) Cu(II)-catalyzed enantioselective O-H insertion reactions.
Scheme 12. Transition-metal-catalyzed enantioselective X-H (X = Si, B, O) insertion reactions of α-P carbenes. (a) Rh(I)-catalyzed enantioselective Si-H insertion reactions; (b) Cu(I)-catalyzed enantioselective B-H insertion reactions; (c) Cu(II)-catalyzed enantioselective O-H insertion reactions.
Symmetry 16 01171 sch012
Symmetry 16 01171 sch013
Scheme 13. Rh(II)-catalyzed enantioselective three-component coupling reaction of α-P carbenes.
Scheme 13. Rh(II)-catalyzed enantioselective three-component coupling reaction of α-P carbenes.
Symmetry 16 01171 sch013
Symmetry 16 01171 sch014
Scheme 14. Cu(I)-catalyzed enantioselective intramolecular cyclopropanation reactions of α-S carbenes and their applications in total synthesis. (a) construction of bicyclo[3.1.0]hexane frameworks; (b) construction of tricyclo[4.3.0.0]nonene and tricyclo[4.4.0.0]decenyl derivatives; (c) construction of bicyclo[4.1.0]heptanyl frameworks; (d) Applications of these compounds in the total synthesis.
Scheme 14. Cu(I)-catalyzed enantioselective intramolecular cyclopropanation reactions of α-S carbenes and their applications in total synthesis. (a) construction of bicyclo[3.1.0]hexane frameworks; (b) construction of tricyclo[4.3.0.0]nonene and tricyclo[4.4.0.0]decenyl derivatives; (c) construction of bicyclo[4.1.0]heptanyl frameworks; (d) Applications of these compounds in the total synthesis.
Symmetry 16 01171 sch014
Symmetry 16 01171 sch015
Scheme 15. Co(II)- or Ru(II)-catalyzed enantioselective intermolecular cyclopropanation reactions of α-S carbenes. (a) catalyzed by chiral cobalt/porphyrin catalysts; (b) catalyzed by ruthenium(II)-Phox complexes.
Scheme 15. Co(II)- or Ru(II)-catalyzed enantioselective intermolecular cyclopropanation reactions of α-S carbenes. (a) catalyzed by chiral cobalt/porphyrin catalysts; (b) catalyzed by ruthenium(II)-Phox complexes.
Symmetry 16 01171 sch015
Symmetry 16 01171 sch016
Scheme 16. Cu(I)-catalyzed enantioselective [3+3]-cycloaddition between nitrones and α-S carbenes.
Scheme 16. Cu(I)-catalyzed enantioselective [3+3]-cycloaddition between nitrones and α-S carbenes.
Symmetry 16 01171 sch016
Symmetry 16 01171 sch017
Scheme 17. Cu(I)-catalyzed enantioselective intramolecular cyclopropanation reactions of α-IV main group carbenes.
Scheme 17. Cu(I)-catalyzed enantioselective intramolecular cyclopropanation reactions of α-IV main group carbenes.
Symmetry 16 01171 sch017
Symmetry 16 01171 sch018
Scheme 18. Rh(II)-catalyzed enantioselective intermolecular cyclopropanation reactions of α-IV main group carbenes. (a) catalyzed by the heteroleptic dirhodium paddlewheel catalyst Rh2(R-TPCP)3(CF3CONH); (b) catalyzed by Rh2(R-TPCP)3(MeCONH).
Scheme 18. Rh(II)-catalyzed enantioselective intermolecular cyclopropanation reactions of α-IV main group carbenes. (a) catalyzed by the heteroleptic dirhodium paddlewheel catalyst Rh2(R-TPCP)3(CF3CONH); (b) catalyzed by Rh2(R-TPCP)3(MeCONH).
Symmetry 16 01171 sch018
Symmetry 16 01171 sch019
Scheme 19. Rh(II)- or Cu(I)-catalyzed enantioselective B-H insertion reactions of α-Si carbenes. (a) rhodium-catalyzed asymmetric B-H insertion reaction of α-furyl-α-silyl carbenes; (b) copper(I)/Box complex catalyzed ring-opening/B-H insertion of 1-silyl cyclopropenes.
Scheme 19. Rh(II)- or Cu(I)-catalyzed enantioselective B-H insertion reactions of α-Si carbenes. (a) rhodium-catalyzed asymmetric B-H insertion reaction of α-furyl-α-silyl carbenes; (b) copper(I)/Box complex catalyzed ring-opening/B-H insertion of 1-silyl cyclopropenes.
Symmetry 16 01171 sch019
Symmetry 16 01171 sch020
Scheme 20. Cu(I)-catalyzed enantioselective transfer reactions of α-Bpin carbenes.
Scheme 20. Cu(I)-catalyzed enantioselective transfer reactions of α-Bpin carbenes.
Symmetry 16 01171 sch020
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Huang, M.; Shi, W.; Li, L. Enantioselective Transfer Reactions of α-Heteroatom-Substituted Carbenes. Symmetry 2024, 16, 1171. https://doi.org/10.3390/sym16091171

AMA Style

Huang M, Shi W, Li L. Enantioselective Transfer Reactions of α-Heteroatom-Substituted Carbenes. Symmetry. 2024; 16(9):1171. https://doi.org/10.3390/sym16091171

Chicago/Turabian Style

Huang, Mingyao, Wenjing Shi, and Lu Li. 2024. "Enantioselective Transfer Reactions of α-Heteroatom-Substituted Carbenes" Symmetry 16, no. 9: 1171. https://doi.org/10.3390/sym16091171

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