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Umsetzung von Di( tert ‐butyl)‐ und Diphenyldiazomethan mit 1,3‐Thiazol‐5(4 H )‐thionen: Isolierung und Kristallstruktur des primären Cycloadduktes
Author(s) -
Mlostoń Grzegorz,
Petit Mireille,
Linden Anthony,
Heimgartner Heinz
Publication year - 1994
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19940770204
Subject(s) - chemistry , thiazole , adduct , diazomethane , crystal structure , steric effects , medicinal chemistry , phosphorane , diazo , ylide , triphenylphosphine , stereochemistry , crystallography , organic chemistry , catalysis
Reaction of Di( tert ‐butyl)‐ and Diphenyldiazomethane and 1,3‐Thiazole‐5(4 H )‐thiones: Isolation and Crystal Structure of the Primary Cycloadduct Reactions of diazo compounds with CS bonds proceed via the formation of thiocarbonyl ylides, which, under the reaction conditions, undergo either 1,3‐dipolar cycloadditions or electrocyclic ring closer to thiiranes ( Scheme 1 ). With the sterically hindered di( tert ‐butyl)diazomethane ( 2c ), 1,3‐thiazole‐5(4 H )‐thiones 1 react to give spirocyclic 2,5‐dihydro‐1,3,4‐thiadiazoles 3 ( Scheme 2 ). These adducts are stable in solution at −20°, and they could be isolated in crystalline form. The structure of 3c was established by X‐ray crystallography. In CDCl 3 solution at room temperature, a cycloreversion occurs, and the adducts of type 3 are in an equilibrium with 1 and 2c . In contrast, the reaction of 1 with diphenyldiazomethane ( 2d ) gave spirocyclic thiiranes 4 as the only product in high yield ( Scheme 3 ). The crystal structure of 4b was also determined by X‐ray analysis. The desulfurization of compounds 4 to 4,5‐dihydro‐5‐(diphenylmethylidene)‐1,3‐thiazoles 5 was achieved by treating 4 with triphenylphosphine in boiling THF. The crystal structure of 5f is shown.