Iterative Stereospecific Reagent-Controlled Homologation Using a Functionalized α-Chloroalkyllithium: Synthesis of Cyclic Targets Related to Epibatidine
作者:Christopher R. Emerson、Lev N. Zakharov、Paul R. Blakemore
DOI:10.1021/ol103170y
日期:2011.3.18
Enantioenriched 1-chloro-2-(1,3-dioxolan-2-yl)ethyllithium was generated by PhLi initiated sulfoxide-ligand exchange and deployed in situ for sequential double stereospecific reagent-controlled homologation (StReCH) of B-(2-chloro-pyrid-5-yl) pinacol boronate. This process afforded highly functionalized contiguous stereodiad motifs (typically, % ee >= 98%, dr >= 85:15) amenable to subsequent annulative transformations as demonstrated by the concise synthesis (5-7 steps) of cyclic adducts related to the analgesic alkaloid epibatidine.