Synthesis of 2,3-dihydro-1H-pyrrolo[1,2-a]benzimidazoles via the cyclopropyliminium rearrangement of substituted 2-cyclopropylbenzimidazoles
摘要:
2-Cyclopropylbenzimidazole derivatives with various substituents in the small ring undergo cyclopropyliminium rearrangement into 2,3-dihydropyrrolobenzimidazoles substituted at positions 1, 2 or 3. The substrates containing a functional group in position 1 of the cyclopropane ring form products substituted at position 3. Substituents at position 2 in most cases lead to the formation of a mixture of isomers. The reaction can be directed to yield one of the isomers predominantly by varying the solvent polarity. (C) 2013 Elsevier Ltd. All rights reserved.
Herein we report a novel Cu-catalyzed regioselective C2–H alkylation of benzimidazoles with aromatic alkenes. The reaction features exclusive regioselectivity and broad substrate scope in the intermolecular alkylation of benzimidazoles with terminal and internal aromatic alkenes, constituting a modular access toward benzimidazole-containing 1,1-di(hetero)aryl alkanes. The intramolecular C2–H alkylation
Microwave-Assisted C−H Bond Activation: A Rapid Entry into Functionalized Heterocycles
作者:Kian L. Tan、Anil Vasudevan、Robert G. Bergman、Jonathan A. Ellman、Andrew J. Souers
DOI:10.1021/ol030050j
日期:2003.6.1
[GRAPHICS]Microwave irradiation strongly accelerates the rhodium-catalyzed intramolecular coupling of a benzimidazole C-H bond to pendant alkenes. The cyclic products were formed in moderate to excellent yields with reaction times less than 20 min. Additionally, the use of microwave irradiation allowed the reactions to be performed without any solvent purification and with minimal precautions to exclude air.