Transition-metal-free synthesis of 1,4-benzoxazepines via [4+3]-cycloaddition of para-quinone methides with azaoxyallyl cations

A formal [4+3]-cycloaddition reaction of ortho-hydroxyphenyl-substituted para-quinone methides(p-QMs) with in-situ generated azaoxyallyl cations is reported. The reaction occurs under very mild reaction conditions(transition-metal free, room temperature, cheap inorganic base) and provides a very efficient route to a series of biologically important 1,4-benzoxazepine derivatives in good to excellent yields.