Solid-phase synthesis of 3,4-dihydroquinazoline

A novel, facile and efficient method for the synthesis of aryl iminophosphorane has been developed by treating a series of Ar-NH2 (1) attached to a solid support with Ph3P and diethyl azodicarboxylate at room temperature. The resulting solid-supported cinnamyl iminophosphorane (4) was treated with an aryl isocyanate to generate the corresponding solid-supported carbodiimide (5), which upon exposure to a secondary amine underwent 1,2-addition followed by an intramolecular Michael addition to afford the desired 3,4-dihydroquinazoline (7). (C) 1997 Elsevier Science Ltd.