抄録
A synthesis of 1, 2, 3, 4-tetrahydroisoquinolines (TIQs)(23) with one and two methoxyl groups at various positions of the benzene ring was achieved via the intramolecular cyclization of N-(aryl)methyl-2-(phenylsulfinyl)ethylamines (9) using the Pummerer reaction as a key step. The reaction was carried out by using trifluoroacetic anhydride (TFAA)(method A) of TFAA-BF3·Et2O (method B). The cyclization to 4-SPhTIQs (11) proceeded effectively when the reaction center at the benzene ring was electronically activated by a methoxyl group. In the reaction of the sulfoxide (9e) having two OMe groups at ortho- and para-positions a different cyclization reaction leading to a benzothiazepine (12) was observed, indicating that the high nucleophilicity of the benzene ring caused the unexpected reaction prior to the cyclization to 4-SPhTIQ (11e). The route starting from methoxylated benzaldehydes (5) was proved to provide an efficient and convenient method of TIQ synthesis which should be complementary to the well known Pictet-Spengler method.
