A synthesis of isoquinolinones by the photochemical cyclization of 2-azabuta-1,3-dienes in the presence of acids

Abstract

A study of the photochemical reactions of a series of 2-azabuta-1,3-dienes in the presence of perchloric acid or boron trifluoride–diethyl ether is reported. The photochemical reaction affords cyclization of all of the dienes to yield novel isoquinolinone derivatives. The reaction is interpreted as involving protonation, or complexation of the nitrogen lone pair. This prevents an electron transfer reaction which has been reported to yield novel dihydro-oxazole derivatives. Instead a photochemical Mannich reaction results in cyclization with the production of the isoquinolinone skeleton.