An unusual base-mediated ring contraction reaction of benzopyrans to benzofurans
摘要:
The reaction of electron deficient pyrroles and pyrazoles with trans 3-bromo-6-cyano-3,4-dihydro-2,2-dimethyl-2H-1-benzopyran-4-ol under basic conditions results in the formation of 2-isopropylbenzofurans by a mechanism which appears to be dependent on the rate of the competitive dehydration reaction leading to the corresponding benzopyrans.