Selectivities in Reactions of Organolithium Reagents with Unprotected 2-Halobenzoic Acids
作者:Frédéric Gohier、Anne-Sophie Castanet、Jacques Mortier
DOI:10.1021/ol034491e
日期:2003.5.1
[reaction: see text] Exposing 2-fluorobenzoic acid (1a) to 2.2 equiv of LTMP at ca. -78 degrees C leads to deprotonation at the 3-position whereas 2-chloro/bromobenzoic acids (1b,c) are lithiated adjacent to the carboxylate. The resulting dianions 3Li-1a and 6Li-1b,c are trapped as such by chlorotrimethylsilane. In the absence of internal quench, 6Li-1b,c isomerize to the more stable 3Li-1b,c. The
[反应:见正文]将2-氟苯甲酸(1a)暴露于2.2当量的LTMP中。-78℃导致3位去质子化,而2-氯/溴苯甲酸(1b,c)在羧酸盐附近被锂化。所得的二价阴离子3Li-1a和6Li-1b,c本身被三甲基氯硅烷捕获。在没有内部淬灭的情况下,6Li-1b,c异构化为更稳定的3Li-1b,c。后者除去卤化锂并释放出游离的3-羧酸苄酯(2),后者与LTMP区域选择性反应生成3-四甲基哌啶子基苯甲酸(3)。