Tetra- and hexa-dehydroyohimbane synthesis by an intermolecular cycloaddition of o-quinodimethane

Abstract

The thermolytic intermolecular cycloaddition reaction of 3,4-dihydro-β-carboline (9) with 1,2-dihydro-5-methoxy-benzocyclobutene-1-carbonitrile (6) gave 15,16,17,18,19,20-hexahydro-17-methoxy-yohimbane-14-carbonitrile (3) which was converted into the decyano-derivative (2) and tetradehydroyohimbane (12) by Birch reduction. Xylopinine (8) has been synthesised by a novel decyanation reaction, and 18-methoxyhexadehydro-yohimbane (4) has been obtained from 1-(1,2-dihydro-5-methoxybenzocyclobuten-1-yl)-3,4-dihydro-β-carboline (1).