Synthesis and Reactivity of 2-(6,7-Diethoxy-3,4-dihydroisoquinolin-1-yl)acetonitrile towards Hydrazonoyl Halides

Abstract

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 actual compound. The reactions of 1 with alpha-oxohydrazonoyl halides 4 in the presence of Et3N led to 2-(aryldiazenyl)pyrrolo[2,1-a]isoquinoline derivatives 8 (Scheme 2), whereas with C-(ethoxycarbonyl)hydrazonoyl chlorides 14, 2-(arylhydrazono)pyrrolo[2,1-a]isoquinoline-1-carbonitriles 16 were formed (Scheme 4). The structures of the products were established from their analytical and spectroscopic data and, in the case of 8b, by X-ray crystallography