[3+2]-cycloadditions of 2-aminothioisomunchnones to alkynes: Synthetic scope and mechanistic insights

This manuscript describes the regiospecific 1,3-dipolar cycloadditions of 2 -aminothioisomunchnones (1-3) with methyl propiolate. The structure of comp ound 4 has been unequivocally determined by X-ray crystallography. Based on these experimental arguments and a theoretical rationale that supports the regiochemistry observed, a mechanistic pathway is discussed to account for the formation of pyridone or thiophene derivatives. The protocol has also been extended to the cycloadditions of aminothioisomunchnones derived from carbohydrates with dimethyl acetylenedicarboxylate to afford interesting gl ycosylaminoheterocycles. (C) 2000 Elsevier Science Ltd. All rights reserved .