The Chemistry of 5-Oxodihydroisoxazoles. II. Photolysis and Pyrolysis of 2-(Isoquinolin-1-yl)-3-methyl-5-oxo-2,5-dihydroisoxazole-4-carboxylate

Abstract

Photolysis of ethyl 2-( isoquinolin-1-yl )-3-methyl-5-oxo-2,5-dihydroisoxazole-4-carbolate occurs by two pathways. The major pathway involves the loss of CO₂ to form an imino carbene which may cyclize to form the expected (6) or rearranged (8) imidazo[2,1-a] isoquinolines or react with nucleophiles and recyclize to form the 4-oxopyrimido[2,1-a]isoquinolines. The minor pathway involves electrocyclic ring opening of the isoxazolone and ring closure with or without loss of CO. Pyrolysis leads predominantly to an imino carbene which reacts intramolecularly to give (6) or undergoes insertion into CH bonds.