Biorenewable and mercaptoacetylating building blocks in the Biginelli reaction: synthesis of thiosugar-annulated dihydropyrimidines

A novel version of the Biginelli reaction using an unprotected aldose as a biorenewable aldehyde component and 2-methyl-2-phenyl-1,3-oxathiolan-5-one as a mercaptoacetylating active methylene building block with urea/thiourea is reported. The reaction is nanoclay-catalysed, expeditious and effected under solvent-free microwave irradiation conditions in a one-pot procedure to yield diastereoselectively, thiosugar-annulated multifunctionalized dihydropyrimidines via intramolecular domino cyclocondensation reactions of an isolable intermediate.