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Stereochemical course of the reaction between thiocarbonyl compounds and oxiranes: reaction with cis- and trans-2,3-dimethyloxirane


Blagoev, Milen; Linden, Anthony; Heimgartner, Heinz (2000). Stereochemical course of the reaction between thiocarbonyl compounds and oxiranes: reaction with cis- and trans-2,3-dimethyloxirane. Helvetica Chimica Acta, 83:3163-3178.

Abstract

The reactions of thiocarbonyl compounds with cis-2,3-dimethyloxirane (1a) in CH2Cl2 in the presence of BF3.Et2O or SnCl4 led to trans-4,5-dimethyl-1,3-oxathiolanes, whereas with trans-2,3-dimethyloxirane (1b) cis-4,5-dimethyl-1,3-oxathiolanes were formed. With the stronger Lewis acid SnCl4 , the formation of side-products was also observed. In the case of 1,3-thiazole-5(4H)-thione 2, these side-products are the corresponding 1,3- thiazol-5(4H)-one 5 and the 1:2 adduct 8 (Schemes 2-4). Their formation can be rationalized by the decomposition of the initially formed spirocyclic 1,3-oxathiolane and by a second addition onto the C=N bond of the 1 : 1 adduct, respectively. The secondary epimerization by inversion of the configuration of the spiro-C-atom (Schemes 5 - 7) can be explained by a Lewis-acid-catalyzed ring opening of the 1,3-oxathiolane ring and subsequent ring closure to the thermodynamically more stable isomer (Scheme 12). In the case of 2,2,4,4-tetramethyl-3-thioxocyclobutanone (20), apart from the expected spirocyclic 1,3-oxathiolanes 21 and 23, dispirocyclic 1 : 2 adducts were formed by a secondary addition onto the C=O group of the four-membered ring (Schemes 9 and 10).

The reactions of thiocarbonyl compounds with cis-2,3-dimethyloxirane (1a) in CH2Cl2 in the presence of BF3.Et2O or SnCl4 led to trans-4,5-dimethyl-1,3-oxathiolanes, whereas with trans-2,3-dimethyloxirane (1b) cis-4,5-dimethyl-1,3-oxathiolanes were formed. With the stronger Lewis acid SnCl4 , the formation of side-products was also observed. In the case of 1,3-thiazole-5(4H)-thione 2, these side-products are the corresponding 1,3- thiazol-5(4H)-one 5 and the 1:2 adduct 8 (Schemes 2-4). Their formation can be rationalized by the decomposition of the initially formed spirocyclic 1,3-oxathiolane and by a second addition onto the C=N bond of the 1 : 1 adduct, respectively. The secondary epimerization by inversion of the configuration of the spiro-C-atom (Schemes 5 - 7) can be explained by a Lewis-acid-catalyzed ring opening of the 1,3-oxathiolane ring and subsequent ring closure to the thermodynamically more stable isomer (Scheme 12). In the case of 2,2,4,4-tetramethyl-3-thioxocyclobutanone (20), apart from the expected spirocyclic 1,3-oxathiolanes 21 and 23, dispirocyclic 1 : 2 adducts were formed by a secondary addition onto the C=O group of the four-membered ring (Schemes 9 and 10).

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Department of Chemistry
Dewey Decimal Classification:540 Chemistry
Date:2000
Deposited On:29 Oct 2013 10:52
Last Modified:05 Apr 2016 17:05
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(20001220)83:12<3163::AID-HLCA3163>3.0.CO;2-P
Permanent URL: https://doi.org/10.5167/uzh-83841

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