Synthesis of 2-Arylpiperidines by Palladium Couplings of Aryl Bromides with Organozinc Species Derived from Deprotonation of <i>N</i>-Boc-Piperidine
作者:Iain Coldham、Daniele Leonori
DOI:10.1021/ol801579r
日期:2008.9.1
The organolithium species derived from proton abstraction of N-Boc-piperidine with s-BuLi and TMEDA can be transmetalated to the organozinc reagent, and this organometallic species can be coupled directly with aryl bromides in a Negishi-type reaction using palladium catalysis with the ligand tri-tert-butylphosphine (t-Bu3P-HBF4). The chemistry was applied to a very short synthesis of the alkaloid anabasine
electrophiles add α to the nitrogen atom but cyanoformates and chloroformates gave ortho-substituted products. Cyclic carbamates were formed from an aldehyde or ketone electrophile. Kinetic resolution with sparteine was only poorly selective. Removal of the Boc group promoted cyclization to a homoindolizidine or an isoindolinone.