Synthesis and reactivity of 2-(6,7-diethoxy-3,4-dihydroisoquinolin-1-yl) acetonitrile towards hydrazonoyl halides

The synthesis of 2-(6,7-diethoxy-3,4-dihydroisoquinolin-1-yl)acetonitrile ( 1) has been performed by ring closure of the corresponding amide according to the Bischler-Napieralski method (Scheme 1). Based on spectroscopic data, the tautomeric 2-(tetrahydroisoquinolin-1-ylidene)acetonitrile is the actu al compound. The reactions of 1 with alpha -oxohydrazonoyl halides 4 in the presence of Et3N led to 2-(aryldiazenyl)pyrrolo[2,1-a]-isoquinoline deriva tives 8 (Scheme 2), whereas with C-(ethoxycarbonyl)hydrazonoyl chlorides 14 , 2-(arylhydrazono)pyrrolo[2,1-a]isoquinoline-l-car 16 were formed (Scheme 4). The structures of the products were established from their analytical a nd spectroscopic data and, in the case of 8b, by X-ray crystallography.