ZnBr2-Mediated oxidative spiro-bromocyclization of propiolamide for the synthesis of 3-bromo-1-azaspiro[4.5]deca-3,6,9-triene-2,8-dione

Abstract

ZnBr₂-Mediated oxidative spiro-bromocyclization of N-arylpropiolamide has been described herein for the synthesis of 3-bromo-1-azaspiro[4.5]deca-3,6,9-triene-2,8-dione with high efficiency. One equivalent of water was introduced into the final product. The reaction efficiently proceeded at room temperature, and an excellent tolerance of functional groups was demonstrated. Under standard conditions, 3-bromo-1-oxaspiro[4.5]deca-3,6,9-triene-2,8-dione and 3-bromo-1-azaspiro[4.5]deca-3,6,9-trien-8-one were synthesized.