The preparation of substituted isochromans and 1,2,3,4-tetrahydroisoquinolines by reduction of unsaturated precursors

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 r eduction 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 bo nd was different for the O- and N-series but conditions were established fo r preparation of the fully reduced species. Sodium borohydride with cobalt chloride in methanol was effective at reducing the cyano function.