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‐dimethyl‐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.