The Preparation of Substituted Isochromans and 1,2,3,4-Tetrahydroisoquinolines by Reduction of Unsaturated Precursors

Abstract

The reduction of 1-acetylamino-3-methylisochromene-4-carbonitrile and an N-butyl-1,2-dihydroisoquinoline analogue with sodium borohydride and sodium cyanoborohydride in ethanol and carboxylic acid media are reported. Ready reduction at the 1-position occurred, followed by further reductive loss of the acetylamino group so formed. The ease of reduction of the 3,4-double bond was different for the O- and N-series but conditions were established for preparation of the fully reduced species. Sodium borohydride with cobalt chloride in methanol was effective at reducing the cyano function.

Manuscript received: 26 February 2001.