The reductive alkylation of isoquinoline

Abstract

Reductive alkylation of isoquinoline with benzaldehyde in acetic acid gives a mixture of 2-benzyl-, 4-benzyl-, and 2,4-dibenzyl-1,2,3,4-tetrahydroisoquinolines and 4-benzylisoquinoline. Contrary to earlier reports, the major product is 2-benzyl-1,2,3,4-tetrahydroisoquinoline, not the 4-isomer. Similarly, reductive alkylation with cyclohexanone gives good yields of 2-cyclohexyl-1,2,3,4-tetrahydroisoquinoline.