A cascade reaction of cinnamyl azides with vinyl sulfones directly generates dihydro-pyrrolo-pyrazole heterocycles.

Abstract

This report describes the direct synthesis of dihydro-pyrrolo-pyrazole heterocycles from allylic azides and methyl vinyl sulfone. The product results from a complex cascade reaction that is operationally straightforward, with aromatization being the result of a concomitant elimination step. A variety of azides could participate in this reaction (12 examples) and the isolated yields of the desired product ranged from 51%-72%. Lastly the ethylene sulfone group could be removed by heating the product in pyrrolidine.