1,3-Dipolare Cycloadditionen von Nitrilium-Betainen mit 4,4-Dimethyl-2-phenyl-2-thiazolin-5-thion

Abstract

1,3-Dipolar Cycloadditions of Nitrilium Betaines with 4,4-Dimethyl-2-phenyl-2-thiazolin-5-thione
Benzonitrile ylides, imines, and oxides undergo smooth 1.3-dipolar cycloaddition reactions with the exocyclic C,S-double bond of 4,4-dimethyli-2-phenyl-2-thiazolin-5- thione (1), yielding heterocyclic spiro-compounds. The structure of the cycloadducts 5c, 5c', and 3f (Fig.) have been established by X-ray structure analysis.
With the benzonitrile ylides, the two regioisomeric cycloaddition modes have been observed, depending on the substituents of the ylide-C-atom. It is questionable, whether the reaction of 1 and the oxazaphosphol 8 (Schemes 8 and 13) proceeds via the corresponding nitrile ylide as an intermediate.