Potassamide induced in situ benzylation of 5,6-dihydroisoquinolines: Structure of novel products

Abstract

Potassamide induced in situ benzylation of 1-alkyl-4-cyano-3-methoxy-5,6-dihydroisoquinolines ( 1a-b) with benzyl iodide gave the 5-benzyl-, 5,9-dibenzyl- and 4,4-dibenzyl-5,6-dihydroisoquinolines ( 9a-b, 8a-b & 10a-b), isoquinoline derivatives ( 4a-b) and diastereomeric mixture of 4-benzyl-1,2,3,4-tetrahydroisoquinolin-3(2 H)-ones ( 11a-b & 11′a-b). Structures were assigned on the basis of spectral data [Mass, 1H & 13C NMR, 2D NOESY]. A few reactions carried out to transform the diastereomeric mixture of compounds 11a & 11′a to the spirobenzylisoquinoline system 7a isomeric with naturally occurring ochotensane system 6a are discussed.