Chemoselective annulation of 1,3-dithiin, -thiazine and -oxathiin rings on thiazoles using a green protocol

Tandem Knoevenagel and Michael reactions of 3-arylrhodanines, aromatic aldehydes and ammonium N-aryldithiocarbamates diastereoselectively yield dithioesters, thiazol-5-ylmethyl N-aryldithiocarbamates, under solvent-free microwave irradiation conditions in a one-pot procedure. Under the same conditions, the dithioesters are chemoselectively and expeditiously annulated with montmorillonite K-10 clay, Li+-montmorillonite clay and I-2 to give thiazolo-1,3-dithiins, -thiazines and -oxathiins, respectively. (c) 2006 Elsevier Ltd. All rights reserved.