Unusual<i>t</i>-BuLi Induced Ortholithiation versus Halogen-Lithium Exchange in Bromopyridines: Two Alternative Strategies for Functionalization
作者:Philippe Gros、Yves Fort、Philippe Pierrat
DOI:10.1055/s-2004-831337
日期:——
The reaction of lithiating agents with various 3-bromopyridines has been investigated. An unprecedented selectivity was observed with t-BuLi, which effected a clean lithiation at C-4. With 3-bromo and 2-chloro-3-bromo pyridines, the ortholithiation-exchange ratio was strongly electrophile and addition order dependent while 2-chloro-5-bromopyridine always gave exclusive C-4 substitution.