Studies on the Lithiation, Borylation, and 1,2‐Metalate Rearrangement of
<i>O</i>
‐Cycloalkyl 2,4,6‐Triisopropylbenzoates
作者:Rory C. Mykura、Pradip Songara、Eugenia Luc、Jack Rogers、Ellie Stammers、Varinder K. Aggarwal
DOI:10.1002/anie.202101374
日期:2021.5.10
have not. We have studied the use of cyclic TIB esters in lithiation‐borylation reactions and looked at the effect of ring size (3‐ → 6‐membered rings) on the three key steps of the lithiation‐borylation protocol: deprotonation, borylation and 1,2‐metalate rearrangement. Although all rings sizes could be deprotonated, the cyclohexyl case was impractically slow, and the cyclopentyl example underwent α‐elimination
锂化-硼化反应中已使用了多种无环的2,4,6-三异丙基苯甲酸伯和仲酯(TIB),而环状TIB酯则没有。我们研究了环状TIB酯在锂化-硼化反应中的用途,并研究了环大小(3元→6元环)对锂化-硼化协议的三个关键步骤的影响:去质子化,硼化和1,2 ‐金属化重排。尽管所有大小的环都可以去质子化,但在环己基的情况下实在不现实地缓慢,并且在-78°C下环戊基实例经历的α-消除速度比去质子化快,因此无法使用。环丁基和环丙基均经历了快速硼化反应,但只有环丁基底物经历了1,2-金属酸盐重排。因此,环丁基TIB酯占据一个“ Goldilocks区”,足够小,可以进行去质子化,并且足够大,可以进行1,2-迁移。用广泛的硼酸酯探索了反应的一般性。