Syntheses and interconversions of some <i>s</i>‐triazolo[3,4‐a]isoquinolines

Abstract

Abstract s ‐Triazolo[3,4‐a]isoquinoline (II) and its 3‐methyl analogue (III) have been synthesized from 1‐isoquinolylhydrazine (I) by cyclisation with formic and acetic acid. The 3‐hydroxy derivative (IV) has been shown to exist in the lactam form. Methylation with methyl iodide gave the N ‐methyl derivative (V). Dimethyl sulphate and diazomethane also led exclusively to the same product. The O ‐methyl derivative (IX) could be obtained only through the 3‐chloro compound (VIII). The chlorine atom in VIII undergoes nucleophilic replacement easily. The 3,6‐dichloro derivative (X) has also been prepared. Several interconversions in the series are described. Aryl hydrazones (XVIII) prepared from (I) have been oxidatively cyclised to give 3‐aryl‐ s ‐triazolo[3,4‐a]isoquinolines (XIX). U.V., I.R. and P.M.R. spectra have been recorded and used for assignment of structures in some cases.