Abstract

The cyclization products from the photolysis of 3-arylamino-4-ethoxycarbonyl-2-heteroarylisoxazol-5(2H)-ones are interpreted as arising from intramolecular cyclization of carbenes. The mode of cyclization appears to be controlled by hydrogen bonding of the 3-NH group with either the 2-heteroaryl group or the 4-ethoxycarbonyl group.