Synthesis of some N-methyl-1,2,3,4-tetrahydroisoquinolines by Friedel–Crafts cyclisation using benzotriazole auxiliary
作者:Cornelia Locher、Naseem Peerzada
DOI:10.1039/a807543c
日期:——
1-Hydroxymethylbenzotriazole reacts with phenylethylamines to give the respective N,N-bis(benzotriazol-1-ylmethyl)phenylethylamines, which are then subject to an intramolecular FriedelâCrafts cyclisation at room temperature to yield N-benzotriazol-1-ylmethyl-1,2,3,4-tetrahydroisoquinolines. These crystalline UV- and oxygen-stable products can be reduced at room temperature to the corresponding N-methyl-1,2,3,4-tetrahydroisoquinolines using NaBH4. The method offers an elegant approach to a wide range of N-methylated 1,2,3,4-tetrahydroisoquinolines since it can be applied not only for the synthesis of 1,2,3,4-tetrahydroisoquinolines with electron-donating substituents on the aromatic moiety, but also for deactivated derivatives. All steps involved work under very mild conditions in high to excellent yields.
1-羟甲基苯并三氮唑与苯乙胺反应生成相应的N,N-双(苯并三氮唑-1-甲基)苯乙胺,然后在室温下进行分子内Friedel-Crafts环化反应,生成N-苯并三氮唑-1-甲基-1,2,3,4-四氢异喹啉。这些结晶的紫外光和氧气稳定产物可以在室温下用NaBH4还原成相应的N-甲基-1,2,3,4-四氢异喹啉。这种方法为合成广泛范围的N-甲基化的1,2,3,4-四氢异喹啉提供了一种优雅的途径,因为它不仅可以应用于具有电子供体取代基的芳香部分的1,2,3,4-四氢异喹啉的合成,还可以应用于去活化的衍生物。所有步骤均在非常温和的条件下进行,收率高至优秀。