Quaternization at the picolinic carbon. Application to the synthesis of pyridylalkanecarboxylic acids

摘要

The paper describes two different methodologies for the construction of a quaternary center at the picolinic site, and their application to the synthesis of pyridylalkanecarboxylic acids. The first one involves a one-pot acetylation-Michael addition procedure followed by an alkylative quaternization of the picolinic carbon. The second one is based on the deprotonation at the picolinic carbon of 2-(alpha,alpha-dialkyl)pyridines using the superbasic mixture BuLi-diisopropylamine-(BuOK)-O-t ("KDA"). Both routes give very good yields. [References: 33]