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2149 KiB

Open AccessArticle

Chitosan Based Heterogeneous Catalyses: Chitosan-Grafted-Poly(4-Vinylpyridne) as an Efficient Catalyst for Michael Additions and Alkylpyridazinyl Carbonitrile Oxidation

by Khaled D. Khalil and Hamad M. Al-Matar

Molecules 2013, 18(5), 5288-5305; https://doi.org/10.3390/molecules18055288 - 8 May 2013

Cited by 41 | Viewed by 9481

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 methylenes [...] 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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274 KiB

Open AccessArticle

Asymmetric Synthesis of the Carbon-14-Labeled Selective Glucocorticoid Receptor Modulator using Cinchona Alkaloid Catalyzed Addition of 6-Bromoindole to Ethyl Trifluoropyruvate

by Takaaki Sumiyoshi, Daisuke Urabe, Kengo Tojo, Masato Sakamoto, Kazumi Niidome, Norie Tsuboya, Tomoko Nakajima and Masanori Tobe

Molecules 2012, 17(6), 6507-6518; https://doi.org/10.3390/molecules17066507 - 30 May 2012

Cited by 71 | Viewed by 5567

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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375 KiB

Open AccessArticle

H₂TPP Organocatalysis in Mild and Highly Regioselective Ring Opening of Epoxides to Halo Alcohols by Means of Halogen Elements

by Parviz Torabi, Javad Azizian and Shahab Zomorodbakhsh

Molecules 2012, 17(5), 5508-5519; https://doi.org/10.3390/molecules17055508 - 9 May 2012

Cited by 7 | Viewed by 6254

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 opening [...] 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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369 KiB

Open AccessArticle

Organocatalysis in Synthesis: L-Proline as an Enantioselective Catalyst in the Synthesis of Pyrans and Thiopyrans

by Noha M. Hilmy Elnagdi and Noura Saad Al-Hokbany

Molecules 2012, 17(4), 4300-4312; https://doi.org/10.3390/molecules17044300 - 10 Apr 2012

Cited by 79 | Viewed by 12119

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 propiolate [...] 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)

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222 KiB

Open AccessCommunication

4-N,N-Dimethylaminopyridine Promoted Selective Oxidation of Methyl Aromatics with Molecular Oxygen

by Zhan Zhang, Jin Gao, Feng Wang and Jie Xu

Molecules 2012, 17(4), 3957-3968; https://doi.org/10.3390/molecules17043957 - 30 Mar 2012

Cited by 8 | Viewed by 11315

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 (C–H) [...] 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)

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255 KiB

Open AccessArticle

Tandem Three-Component Reactions of Aldehyde, Alkyl Acrylate, and Dialkylmalonate Catalyzed by Ethyl Diphenylphosphine

by Yeong-Jiunn Jang, Siang-En Syu, Yi-Wun Jhang, Yu-Ting Lee, Chia-Jui Lee, Ko-Wei Chen, Utpal Das and Wenwei Lin

Molecules 2012, 17(3), 2529-2541; https://doi.org/10.3390/molecules17032529 - 2 Mar 2012

Cited by 2 | Viewed by 7724

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 to [...] 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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281 KiB

Open AccessArticle

Contribution of Cation-π Interactions in Iminium Catalysis

by Yukie Mori and Shinji Yamada

Molecules 2012, 17(2), 2161-2168; https://doi.org/10.3390/molecules17022161 - 21 Feb 2012

Cited by 13 | Viewed by 6853

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 group [...] 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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79 KiB

Open AccessArticle

Tris(2,4,6-trimethoxyphenyl)phosphine (TTMPP): Efficient Catalysts for the Cyanosilylation and Cyanocarbonation of Aldehydes and Ketones

by Satoru Matsukawa, Izumi Sekine and Ayumi Iitsuka

Molecules 2009, 14(9), 3353-3359; https://doi.org/10.3390/molecules14093353 - 2 Sep 2009

Cited by 22 | Viewed by 8060

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. Full article

(This article belongs to the Special Issue Organocatalysis)

156 KiB

Open AccessArticle

Calixpyrrole Derivatives: “Multi Hydrogen Bond” Catalysts for γ-Butenolide Synthesis

by Grazia Cafeo, Margherita De Rosa, Franz H. Kohnke, Annunziata Soriente, Carmen Talotta and Luca Valenti

Molecules 2009, 14(7), 2594-2601; https://doi.org/10.3390/molecules14072594 - 15 Jul 2009

Cited by 25 | Viewed by 14214

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 and [...] 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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82 KiB

Open AccessArticle

Organocatalytic Oxidative Dehydrogenation of Dihydroarenes by Dioxygen Using 2,3-Dichloro-5,6-dicyano-benzoquinone (DDQ) and NaNO₂

by Wei Zhang, Hong Ma, Lipeng Zhou, Zhiqiang Sun, Zhongtian Du, Hong Miao and Jie Xu

Molecules 2008, 13(12), 3236-3245; https://doi.org/10.3390/molecules13123236 - 18 Dec 2008

Cited by 32 | Viewed by 16775

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 for [...] 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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