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Synthesis of an Enantiomerically Pure 1,3-Thiazole-5(4H)-thione and Its Stereoselective 1,3-Dipolar Cycloaddition with an Azomethine Ylide


Gebert, Andreas; Heimgartner, Heinz (2002). Synthesis of an Enantiomerically Pure 1,3-Thiazole-5(4H)-thione and Its Stereoselective 1,3-Dipolar Cycloaddition with an Azomethine Ylide. Helvetica Chimica Acta, 85:2073-2081.

Abstract

Starting from the enantiomerically pure 2H-azirin-3-amines (R,S)-4 and (S,S)-4, the enantiomeric, optically active 4-benzyl-4-methyl-2-phenyl-1,3-thiazole-5(4H)-thiones (R)-1 and (S)-1, respectively, have been prepared (Schemes 2 and 3). In each case, the reaction of 1 with N-(benzylidene)[(trimethylsilyl)methyl]amine (2) in HMPA in the presence of CsF and trimethylsilyl triflate gave a mixture of four optically active spirocyclic cycloadducts (Scheme 4). Separation by preparative HPLC yielded two pure diastereoisomers, e.g., (4R,5R,9S)-10 and (4R,5R,9R)-10. The regioisomeric compounds 11 were obtained as a mixture of diastereoisomers. The products were formed by a 1,3-dipolar cycloaddition of 1 with in situ generated azomethine ylide 3, which attacks 1 stereoselectively from the sterically less-hindered side, i.e., with (R)-1 the attack occurs from the re-side and in the case of (S)-1 from the si-side.

Starting from the enantiomerically pure 2H-azirin-3-amines (R,S)-4 and (S,S)-4, the enantiomeric, optically active 4-benzyl-4-methyl-2-phenyl-1,3-thiazole-5(4H)-thiones (R)-1 and (S)-1, respectively, have been prepared (Schemes 2 and 3). In each case, the reaction of 1 with N-(benzylidene)[(trimethylsilyl)methyl]amine (2) in HMPA in the presence of CsF and trimethylsilyl triflate gave a mixture of four optically active spirocyclic cycloadducts (Scheme 4). Separation by preparative HPLC yielded two pure diastereoisomers, e.g., (4R,5R,9S)-10 and (4R,5R,9R)-10. The regioisomeric compounds 11 were obtained as a mixture of diastereoisomers. The products were formed by a 1,3-dipolar cycloaddition of 1 with in situ generated azomethine ylide 3, which attacks 1 stereoselectively from the sterically less-hindered side, i.e., with (R)-1 the attack occurs from the re-side and in the case of (S)-1 from the si-side.

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Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Department of Chemistry
Dewey Decimal Classification:540 Chemistry
Language:English
Date:2002
Deposited On:25 Sep 2013 12:47
Last Modified:05 Apr 2016 17:00
Publisher:Wiley-Blackwell
ISSN:0018-019X
Funders:Swiss National Science Foundation, F. Hoffmann-La Roche AG, Basel
Publisher DOI:https://doi.org/10.1002/1522-2675(200207)85:7<2073::AID-HLCA2073>3.0.CO;2-1
Permanent URL: https://doi.org/10.5167/uzh-81318

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