1,3-Dipolar cycloadditions of alkyl azides with picryl isothiocyanate:Isolation of stable monoadducts

Picryl isothiocyanate ( 4 ), prepared in a two-step sequence from picryl chloride ( 2 ), reacts smoothly with alkyl azides to yield 4-alkyl-5-picrylimino-1,2,3,4-thiatriazolines 5 which are stable below 100°. These adducts combine with isocyanates in a bimolecular process with loss of nitrogen, similar to the formation of phenylimino derivatives but different from that of sulfonyliminothiatriazolines.