Diastereoselective cycloadditions of 1,3-thiazolium-4-olates with chiral 1,2-diaza-1,3-butadienes

A series of 2-(N-methyl)benzylamino-1,3-thiazolium-4-olates (2-aminothioiso munchnones) react with chiral 1,2-diaza-1,3-butadienes derived from carbohy drates to afford a diastereomeric mixture of (4R,5S)- and (4R,5R)-4,5-dihyd rothiophenes. These substrate-controlled cycloadditions are chemoselective, regiospecific, and proceed with a high facial diastereoselection. A theore tical rationale at semiempirical level does justify the stereochemical outc ome observed in the experiments.