Transition-Metal-Free Synthesis of Benzimidazoles Mediated by KOH/DMSO
作者:Hannah Baars、Astrid Beyer、Stefanie V. Kohlhepp、Carsten Bolm
DOI:10.1021/ol403414v
日期:2014.1.17
Benzimidazoles are prepared by intramolecular N-arylations of amidines mediated by potassium hydroxide in DMSO at 120 degrees C. In this manner, diversely substituted products have been obtained in moderate to very good yields.
Synthesis of annulated benzimidazoles via amidine cyclization
Structurally diverse annulated benzimidazoles were synthesized via two copper(I)-catalyzed cyclocondensation reactions. In the first case the title compounds were prepared from lactams and o-bromoaniline. An alternative route consisted of an intramolecular cyclization of o-bromoarylamidines.
The irdium-catalyzed intramolecular arylcarbon-hetero cross-coupling reactions with o-haloarylamides or o-haloarylamidine have been effectively achieved using KOAc and just 1 mol% catalyst. The [Ir(cod)Cl]2 was proved to be more potential for smoothly assembling functional structures benzimidazoles, benzoxazoles and benzothiazoles, which was superior to Cu- and Pd-catalyzed systems. Simultaneously