Synthesis, Characterization and Crystallographic Studies of Three 2-Aryl-3-methyl-4-aryl-1,3-thiazolium-5-thiolates

Abstract

Mesoionic 2,4-diphenyl-3-methyl-1,3-thiazolium-5-thiolate, 2-(4′-chlorophenyl)-3-methyl-4-phenyl-1,3-thiazolium-5-thiolate and 2-(4′-chlorophenyl)-3-methyl-4-(4′-isopropyl-phenyl)-1,3-thiazolium-5-thiolate were synthesized via N-methyl-C-aryl-glycines, involving a one-pot 1,3-dipolar cycloaddition/cycloreversion sequence. The two latter mesoionic compounds are new, as are some of the intermediates. Compounds were fully characterized, while X-ray diffraction studies of the three mesoionic compounds also confirmed their structures and our definition of mesoionic compounds. In particular they showed that the mesoionic ring system has two regions in which there is electron and charge delocalization separated by what are essentially single bonds. The data also suggested a tendency for the 2- and 4-aryl groups to lie in the plane of the mesoionic ring.