Deprotonation-Triggered Heavy-Halogen Migrations as a Key to the Structural Elaboration of 2,2-Difluoro-1,3-benzodioxole
作者:Joanna Gorecka、Frédéric Leroux、Manfred Schlosser
DOI:10.1002/ejoc.200300553
日期:2004.1
instantaneously by bromine migration to give 5-bromo-2,2-difluoro-4-lithio-7-SiR3-1,3-benzodioxoles, which were iodinated or carboxylated in 4-position. Upon neutralization and carboxylation, 5-bromo-2,2-difluoro-1,3-benzodioxole (8) and 5-bromo-2,2-difluoro-1,3-benzodioxole-4-carboxylic acid (3) are formed nearly quant. A similar basicity gradient-driven heavy-halogen migration can be accomplished starting
锂化 4-bromo-2,2-difluoro-1,3-benzodioxoles 中的溴迁移是通过用三烷基甲硅烷基保护自行车的 7-位来实现的,从而获得 5-bromo-2,2-difluoro-1, 3-benzodioxole 4-iodo-和4-carboxy-derivs。原脱甲硅烷化后。尽管从 2,2-difluoro-1,3-benzodioxole 的 4-位提取质子非常容易,但只有在没有氧相邻位点未被占据的情况下才能实现更远的 5-位的锂化。因此,与 4-bromo-2,2-difluoro-1,3-benzodioxole (1) 不同,4-bromo-2,2-difluoro-7-SiR3-1,3-benzodioxoles (5a,b; R = Me, Et) 被 LDA 锂化以产生 5-锂硫中间体,该中间体通过溴迁移瞬间异构化,得到 5-溴-2,2-二氟-4-锂-7-SiR3-1