Tuesday, 24 May 2005 - 9:00 AM
This presentation is part of: Physical Organic
Efficient Acylation of Benzimidazoles with Esters and Identification of a Tetrahedral Hemiacetal Alkoxide IntermediateKenneth J. Fitch, Merck Research Labs, Rahway, NJ
Substituted benzimidazoles are important intermediates for the synthesis of various drugs and natural products. Substituents at the 2-position are generally introduced by the reaction of the 2-litio derivative of N-protected benzimidazoles with electrophiles. In some cases when esters were used as acylating agents, the yields were low and bis addition products predominated. Here we describe a general method for the efficient acylation of 2-lithio benzimidazoles with esters, lactones and lactams and present evidence of a tetrahedral hemiacetal alkoxide interemediate responsible for the selective reaction.
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