Preparation of 1-methyl-3-phenylisoquinoline derivatives from oximes using polyphosphoric esters

Abstract

We show a beneficial new approach to the preparation of 1-methyl-3-phenylisoquinoline derivatives. This method involves heating polyphosphate ester and the appropriate oximes obtained from 3,4-diphenylbut-3-en-2-one derivatives. The isoquinolines were synthesised in yields mainly ranging from about 50 to 70%, and their structures were confirmed by proton and carbon nuclear magnetic resonance spectroscopy and elemental analysis. This newly developed procedure is particularly suitable for the synthesis of 1-methyl-3-phenylisoquinoline derivatives with chlorine, methyl, and methoxy substituents on the aromatic ring.