Stereoselective 1,3-dipolar cycloaddition of an azomethine ylide with a chiral 1,3-thiazole-5(4H)-thione

The reaction of cis-1-methyl-2,3-diphenylaziridine (2) with racemic 4-benzyl-4-methyl-2-phenyl-1,3-thiazole-5(4H)-thione (rac-1b) in toluene at 100-105degreesC gave a single spirocyclic [2+3] cycloadduct (rac-5). Its structure and relative configuration was established by X-Ray crystallography. Starting with enantiomerically pure (R)-1b and (S)-1b, the enantiomers (4R,5R,7S,9R)-5 and (4S,5S,7R,9S)-5, respectively, were formed in a regio- and stereoselective 1,3-dipolar cycloaddition of the in situ generated (E,Z)-configured N-methyl-1,3-diphenylazomethine ylide (4).