Gold catalyzed intramolecular cyclization of (2-aminophenyl)-cyclopropyl methanols as an expedient route to 2,3-dihydro-1h-benzazepines and indolines.

Abstract

We reported herein an efficient synthetic route of 2,3-dihydro-1H-benzazepines and indolines that relies on (4-CF3Ph)3PAuCl/AgOTf catalyzed intramolecular hydroamination of cyclopropyl methanols containing an aniline moiety. The methodology is applicable to a wide range of electron-donating, electron-withdrawing, and sterically demanding substituted (2-aminophenyl)-cyclopropyl methanol substrates that gave the corresponding 2,3-dihydro-1H-benzazepine and indoline products in yields of 23-92%. The mechanism is suggested to involve activation of hydroxyl group of the substrate by (4-CF3Ph)3PAuCl/AgOTf followed by ring opening of the cyclopropane moiety. Intramolecular cyclization in a 7-endo-trig manner of intermediates derived from unactivated cyclopropyl methanols furnished the 2,3-dihydro-1H-benzazepine. On the other hand, intramolecular hydroamination of intermediates derived from activated cyclopropyl methanols underwent 5-endo-trig cyclization to give the indoline products.