Efficient Solvent-Free Synthesis of Benzothiazine-Fused Pyrrolo[3,4-c]coumarins: Cycloaddition Reactions between Coumarin-Based Dihydrobenzothiazoles and Isocyanides

摘要

A new and unusual synthesis of benzothiazine-fused pyrrolo[3,4-c]coumarins, involving the ringopening of coumarin-based dihydrobenzothiazoles and subsequent [4+1] cycloaddition reaction with isocyanides, was described. Thus, simple heating of various 3-(2,3-dihydro-2-methylbenzo[d]thiazol-2- yl)coumarins with isocyanides produced the title compounds in good yields under solvent-free conditions.