Synthesis of 3, 4-Dihydro- and 1, 2, 3, 4-Tetrahydroisoquinolines

Abstract

N-Alkylthiocarbonyldopa (1a-e) and dopamine (1f-h) derivatives can be converted into the corresponding 3, 4-dihydroisoquinolines (3) by treatment with 4-nitrobenzyl bromide. The NaBH₄ reduction of 1, 3-disubstituted 3, 4-dihydroisoquinolines (3a-e) gave 1, 3-cis-1, 2, 3, 4-tetrahydroisoquinolines (4a-e). Hydrogenation of 3a-e over PtO₂ also gave 4a-e in good yields. The synthesis of optically active 3a, i and 4a, i is also described.