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Special Issue "Organocatalysis"

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A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Organic Synthesis".

Deadline for manuscript submissions: closed (30 April 2012)

Special Issue Editor

Guest Editor
Dr. Guofu Zhong

Division of Chemistry and Biological Chemistry, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore

Keywords

  • small molecule catalyst
  • organic catalyst
  • organocatalyst
  • enamine catalysis
  • iminium catalysis
  • N-heterocyclic carbenes
  • phase transfer catalysis
  • H-bond catalysis
  • organocatalysis
  • small molecule catalyzed reactions
  • organocatalytic reactions
  • organocatalytic tandem reactions
  • organocatalytic domino reactions
  • organocatalytic cascade reactions
  • organocatalytic asymmetric reactions

Published Papers (10 papers)

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Research

Open AccessArticle Chitosan Based Heterogeneous Catalyses: Chitosan-Grafted-Poly(4-Vinylpyridne) as an Efficient Catalyst for Michael Additions and Alkylpyridazinyl Carbonitrile Oxidation
Molecules 2013, 18(5), 5288-5305; doi:10.3390/molecules18055288
Received: 10 April 2013 / Revised: 28 April 2013 / Accepted: 28 April 2013 / Published: 8 May 2013
Cited by 9 | PDF Full-text (2149 KB) | HTML Full-text | XML Full-text
Abstract
Chitosan-grafted-poly(4-vinylpyridine) (Cs-PVP) copolymers could be synthesized under heterogeneous conditions in presence of a potassium persulfate and sodium sulfite redox system. The synthesized graft copolymer could be utilized effectively, in the form of beads, as an efficient catalyst for Michael additions of active [...] Read more.
Chitosan-grafted-poly(4-vinylpyridine) (Cs-PVP) copolymers could be synthesized under heterogeneous conditions in presence of a potassium persulfate and sodium sulfite redox system. The synthesized graft copolymer could be utilized effectively, in the form of beads, as an efficient catalyst for Michael additions of active methylenes to functionally substituted alkenes. Moreover, methyl moiety oxidation in methyl pyridazinyl carbonitriles by H2O2 in the presence of chitosan-g-polyvinyl pyridine–supported iron (III) complex, Cs-PVP/Fe, could be affected. A variety of pyrans, naphthopyrans, and thiopyrans could be synthesized efficiently in the presence of these graft copolymer beads by novel catalytic routes. These polymeric catalysts could be used instead of the old toxic commercial organic basic catalysts, piperidine or pyridine, and could be readily isolated from the reaction mixture and recycled several times without significant loss of catalytic activity. Full article
(This article belongs to the Special Issue Organocatalysis)
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Open AccessArticle Asymmetric Synthesis of the Carbon-14-Labeled Selective Glucocorticoid Receptor Modulator using Cinchona Alkaloid Catalyzed Addition of 6-Bromoindole to Ethyl Trifluoropyruvate
Molecules 2012, 17(6), 6507-6518; doi:10.3390/molecules17066507
Received: 27 April 2012 / Revised: 18 May 2012 / Accepted: 21 May 2012 / Published: 30 May 2012
Cited by 2 | PDF Full-text (274 KB)
Abstract
We describe in this study the asymmetric synthesis of radioisotope (RI)-labeled selective glucocorticoid receptor modulator. This synthesis is based on optimization of the cinchona alkaloid catalyzed addition of 6-bromoindole to ethyl trifluoropyruvate and Negishi coupling of zinc cyanide to the 6-bromoindole moiety. [...] Read more.
We describe in this study the asymmetric synthesis of radioisotope (RI)-labeled selective glucocorticoid receptor modulator. This synthesis is based on optimization of the cinchona alkaloid catalyzed addition of 6-bromoindole to ethyl trifluoropyruvate and Negishi coupling of zinc cyanide to the 6-bromoindole moiety. [14C] Labeled (−)-{4-[(1-{2-[6-cyano-1-(cyclohexylmethyl)-1H-indol-3-yl]-3,3,3-trifluoro-2-hydroxypropyl}piperidin-4-yl)oxy]-3-methoxyphenyl}acetic acid (−)-1 was synthesized successfully with high enantioselectivity ( > 99% ee) and sufficient radiochemical purity. Full article
(This article belongs to the Special Issue Organocatalysis)
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Open AccessArticle H2TPP Organocatalysis in Mild and Highly Regioselective Ring Opening of Epoxides to Halo Alcohols by Means of Halogen Elements
Molecules 2012, 17(5), 5508-5519; doi:10.3390/molecules17055508
Received: 10 January 2012 / Revised: 6 April 2012 / Accepted: 12 April 2012 / Published: 9 May 2012
Cited by 1 | PDF Full-text (375 KB)
Abstract
We found that elemental iodine and bromine are converted to trihalide nucleophiles (triiodine and tribromide anion, respectively) in the presence of catalytic amounts of meso-tetraphenylporphyrins (H2TPP). Therefore a highly regioselective method for the synthesis of b-haloalcohols through direct ring [...] Read more.
We found that elemental iodine and bromine are converted to trihalide nucleophiles (triiodine and tribromide anion, respectively) in the presence of catalytic amounts of meso-tetraphenylporphyrins (H2TPP). Therefore a highly regioselective method for the synthesis of b-haloalcohols through direct ring opening of epoxides with elemental iodine and bromine in the presence of H2TPPs as new catalysts is described. At room temperature a series of epoxide derivatives were converted into the corresponding halohydrins resulting from an attack of trihalide species anion atoms at the less substituted carbon atom. This method occurs under neutral and mild conditions with high yields in various aprotic solvents, even when sensitive functional groups are present. Full article
(This article belongs to the Special Issue Organocatalysis)
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Open AccessArticle Organocatalysis in Synthesis: L-Proline as an Enantioselective Catalyst in the Synthesis of Pyrans and Thiopyrans
Molecules 2012, 17(4), 4300-4312; doi:10.3390/molecules17044300
Received: 26 January 2012 / Revised: 19 March 2012 / Accepted: 20 March 2012 / Published: 10 April 2012
Cited by 23 | PDF Full-text (369 KB) | HTML Full-text | XML Full-text
Abstract
The multicomponent reaction (MCR) of aromatic aldehydes 1 and malononitrile (2) with active methylenes 5a–h in the presence of L-proline produced pyrans and thiopyrans 6a–h stereospecifically and in good yields. Moreover a novel MCR of ethyl [...] Read more.
The multicomponent reaction (MCR) of aromatic aldehydes 1 and malononitrile (2) with active methylenes 5a–h in the presence of L-proline produced pyrans and thiopyrans 6a–h stereospecifically and in good yields. Moreover a novel MCR of ethyl propiolate (8) with 1 and 2 in the presence of L-proline to afford (R)-polysubstituted pyran is also reported. X-ray structures, e.e. and optical activity of the synthesized compounds indicated that L-proline as a catalyst is responsible for the observed enantioselectivity in the studied reactions. Full article
(This article belongs to the Special Issue Organocatalysis)
Open AccessCommunication 4-N,N-Dimethylaminopyridine Promoted Selective Oxidation of Methyl Aromatics with Molecular Oxygen
Molecules 2012, 17(4), 3957-3968; doi:10.3390/molecules17043957
Received: 2 March 2012 / Revised: 23 March 2012 / Accepted: 27 March 2012 / Published: 30 March 2012
Cited by 2 | PDF Full-text (222 KB) | HTML Full-text | XML Full-text
Abstract
4-N,N-Dimethylaminopyridine (DMAP) as catalyst in combination with benzyl bromide was developed for the selective oxidation of methyl aromatics. DMAP exhibited higher catalytic activity than other pyridine analogues, such as 4-carboxypyridine, 4-cyanopyridine and pyridine. The sp3 hybrid carbon-hydrogen [...] Read more.
4-N,N-Dimethylaminopyridine (DMAP) as catalyst in combination with benzyl bromide was developed for the selective oxidation of methyl aromatics. DMAP exhibited higher catalytic activity than other pyridine analogues, such as 4-carboxypyridine, 4-cyanopyridine and pyridine. The sp3 hybrid carbon-hydrogen (C–H) bonds of different methyl aromatics were successfully oxygenated with molecular oxygen. The real catalyst is due to the formation of a pyridine onium salt from the bromide and DMAP. The onium salt was well characterized by NMR and the reaction mechanism was discussed. Full article
(This article belongs to the Special Issue Organocatalysis)
Open AccessArticle Tandem Three-Component Reactions of Aldehyde, Alkyl Acrylate, and Dialkylmalonate Catalyzed by Ethyl Diphenylphosphine
Molecules 2012, 17(3), 2529-2541; doi:10.3390/molecules17032529
Received: 19 December 2011 / Revised: 9 February 2012 / Accepted: 17 February 2012 / Published: 2 March 2012
PDF Full-text (255 KB) | Supplementary Files
Abstract
A new highly efficient three-component reaction of alkyl acrylate, aldehyde and dialkyl malonate using ethyl diphenylphosphine as organocatalyst has been described. Various highly functional compounds bearing hydroxyl groups and the ester functions can be easily prepared in moderate to good yields according [...] Read more.
A new highly efficient three-component reaction of alkyl acrylate, aldehyde and dialkyl malonate using ethyl diphenylphosphine as organocatalyst has been described. Various highly functional compounds bearing hydroxyl groups and the ester functions can be easily prepared in moderate to good yields according to our one-step procedure. The reactions are believed to proceed via Morita-Baylis-Hillman reactions of alkyl acrylate and aldehydes, followed by the Michael addition reactions of dialkyl malonates. Our reactions indicated that the intermediate species formed in the phosphine-catalyzed MBH reaction are an effective organic base to catalyze the Michael addition reactions of dialkyl malonates to the preformed MBH adducts. Full article
(This article belongs to the Special Issue Organocatalysis)
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Open AccessArticle Contribution of Cation-π Interactions in Iminium Catalysis
Molecules 2012, 17(2), 2161-2168; doi:10.3390/molecules17022161
Received: 12 January 2012 / Revised: 9 February 2012 / Accepted: 15 February 2012 / Published: 21 February 2012
Cited by 11 | PDF Full-text (281 KB) | Supplementary Files
Abstract
Ab initio calculations were carried out for a benzyl-substituted iminium cation derived from (E)-crotonaldehyde and a chiral imidazolidinone that was developed as an organocatalyst by MacMillan et al. At the MP2 level of theory it is predicted that the phenyl [...] Read more.
Ab initio calculations were carried out for a benzyl-substituted iminium cation derived from (E)-crotonaldehyde and a chiral imidazolidinone that was developed as an organocatalyst by MacMillan et al. At the MP2 level of theory it is predicted that the phenyl group is close to the iminium moiety in the most stable conformer, suggesting that the cation-π interaction contributes to the stabilization of this conformer. Energy decomposition analyses on model systems indicate that the electrostatic and polarization terms make significant contribution to the attractive interactions between the benzene ring and the iminium cation. Full article
(This article belongs to the Special Issue Organocatalysis)
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Open AccessArticle Tris(2,4,6-trimethoxyphenyl)phosphine (TTMPP): Efficient Catalysts for the Cyanosilylation and Cyanocarbonation of Aldehydes and Ketones
Molecules 2009, 14(9), 3353-3359; doi:10.3390/molecules14093353
Received: 6 August 2009 / Revised: 25 August 2009 / Accepted: 31 August 2009 / Published: 2 September 2009
Cited by 13 | PDF Full-text (79 KB)
Abstract
A variety of aldehydes and ketones were transformed to their corresponding cyanohydrin silyl ethers in good to excellent yields in the presence of 1-5 mol% of tris(2,4,6-trimethoxyphenyl)phosphine (TTMPP). Cyanohydrin carbonates were also readily prepared using 5-10 mol% of TTMPP as an organocatalyst. [...] Read more.
A variety of aldehydes and ketones were transformed to their corresponding cyanohydrin silyl ethers in good to excellent yields in the presence of 1-5 mol% of tris(2,4,6-trimethoxyphenyl)phosphine (TTMPP). Cyanohydrin carbonates were also readily prepared using 5-10 mol% of TTMPP as an organocatalyst. Full article
(This article belongs to the Special Issue Organocatalysis)
Open AccessArticle Calixpyrrole Derivatives: “Multi Hydrogen Bond” Catalysts for γ-Butenolide Synthesis
Molecules 2009, 14(7), 2594-2601; doi:10.3390/molecules14072594
Received: 22 May 2009 / Revised: 7 July 2009 / Accepted: 9 July 2009 / Published: 15 July 2009
Cited by 8 | PDF Full-text (156 KB) | HTML Full-text | XML Full-text
Abstract
Calix[4]pyrrole (1), calix[2]m-benzo[4]pyrrole (2), 10α,20β- and 10α,20α- bis(4-nitrophenyl)-calix[4]pyrroles 3 and 4, respectively, were found to exhibit various organocatalytic activities in the diastereoselective vinylogous addition reaction of 2-trimethylsilyloxyfuran (TMSOF, 7) to aldehydes. The γ-hydroxybutenolide products are obtained in fairly good yields [...] Read more.
Calix[4]pyrrole (1), calix[2]m-benzo[4]pyrrole (2), 10α,20β- and 10α,20α- bis(4-nitrophenyl)-calix[4]pyrroles 3 and 4, respectively, were found to exhibit various organocatalytic activities in the diastereoselective vinylogous addition reaction of 2-trimethylsilyloxyfuran (TMSOF, 7) to aldehydes. The γ-hydroxybutenolide products are obtained in fairly good yields and with moderate diastereoselectivity. The structures of the catalysts, as well as the reaction conditions, strongly influence the efficiency of the reaction. Full article
(This article belongs to the Special Issue Organocatalysis)
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Open AccessArticle Organocatalytic Oxidative Dehydrogenation of Dihydroarenes by Dioxygen Using 2,3-Dichloro-5,6-dicyano-benzoquinone (DDQ) and NaNO2
Molecules 2008, 13(12), 3236-3245; doi:10.3390/molecules13123236
Received: 5 November 2008 / Revised: 10 December 2008 / Accepted: 12 December 2008 / Published: 18 December 2008
Cited by 17 | PDF Full-text (82 KB) | HTML Full-text | XML Full-text
Abstract
The oxidative dehydrogenation of dihydroarenes catalyzed by 2,3-dichloro-5,6-dicyano-benzoquinone(DDQ) and NaNO2 with dioxygen is reported. The combination of DDQ and NaNO2 showed high efficiency and high selectivity, compared with other benzoquinones and anthraquinones, e.g., >99% conversion of 9,10-dihydroanthracene with 99% selectivity [...] Read more.
The oxidative dehydrogenation of dihydroarenes catalyzed by 2,3-dichloro-5,6-dicyano-benzoquinone(DDQ) and NaNO2 with dioxygen is reported. The combination of DDQ and NaNO2 showed high efficiency and high selectivity, compared with other benzoquinones and anthraquinones, e.g., >99% conversion of 9,10-dihydroanthracene with 99% selectivity for anthracene can be obtained at 120 °C under 1.3 MPa O2 for 8 h. Excellent results were achieved in the oxidative dehydrogenation of variety of dihydroarenes. Full article
(This article belongs to the Special Issue Organocatalysis)

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