3-bromopyridine, followed by Li/Zn transmetalation and Pd-mediated coupling processes, provides a flexible entry to 4-substituted and 3,4-disubstituted pyridines. Application of a similar sequence to 2-bromopyridine (with LDA as base) provides 2,3-disubstituted pyridines, but using lithium 2,2,6,6-tetramethylpiperidide (LiTMP) provides access to both the 2,3- and 2,4-disubstituted isomers.
3-
溴吡啶的区域选择性C-4脱质子化,然后进行Li / Zn过渡
金属化和Pd介导的偶联过程,可灵活进入4-取代和3,4-二取代的
吡啶。对2-
溴吡啶(以
LDA为碱基)施加类似的序列可提供2,3-二取代的
吡啶,但使用
2,2,6,6-四甲基哌啶锂(Li
TMP)可同时获得2,3-和2, 4-二取代的异构体。