An Improved Synthesis of 1,2,3,4-Tetrahydroisoquinolines via Intramolecular Cyclization of N-Acyl-N-(aryl)methyl-2-(phenylsulfinyl)ethylamine by Pummerer Reaction.
作者:Tatsumi SHINOHARA、Jun TODA、Takehiro SANO
DOI:10.1248/cpb.45.813
日期:——
Pummerer reaction of the sulfoxides 5 of N-acyl-N-(aryl)methyl-2-(phenylthio)ethylamines (4) on treatment with trifluoroacetic anhydride (TFAA) effectively caused intramolecular cyclization under a mild condition to give N-acyl-4-phenylthio-1, 2, 3, 4-tetrahydroisoquinolines (TIQs) (7). The reaction of the N-formyl sulfoxide 5c without a methoxy group in the benzene ring using a formyl group for N-protection is particularly efficient. Treatment of the N-formyl sulfoxide 5f with TFAA did not give any TIQ, but a sequential treatment using TFAA and BF3·Et2O afforded N-formyl-4-phenylthio-TIQ (7f) in quantitative yield. The efficiency of this method of preparing TIQs was demonstrated in the synthesis of 1, 4-dideuterio-TIQ (10D) and its N-methyl derivative (11D).
N-酰基-N-(芳基)甲基-2-(硫苯基)乙胺(4)中的亚砜化合物5与三氟醋酸酐(TFAA)反应后,能有效引发分子内环化,生成N-酰基-4-硫苯基-1, 2, 3, 4-四氢异喹啉(TIQs)(7),该反应在温和条件下进行。对于没有甲氧基的N-甲酰亚砜5c,使用甲酰基进行N-保护特别高效。N-甲酰亚砜5f与TFAA反应时未能生成任何TIQ,但使用TFAA和BF3·Et2O进行顺序处理则定量产出N-甲酰基-4-硫苯基-TIQ(7f)。这种制备TIQs的方法在合成1, 4-二氘-TIQ(10D)及其N-甲基衍生物(11D)中展示了其高效性。