Goldilocks Effect of Base Strength on Site Selectivity in Acylation of Amphiphilic Diols
作者:Moshe Portnoy、Reut Fallek、Natali Ashush、Amit Fallek
DOI:10.1055/a-1631-1885
日期:2021.11
shift of the substrate selectivity towards the polar substrate, compared to the base-free acylation, which favors that of the apolar one. The extraordinarily strong change in the substrate selectivity in favor of the polar substrate was induced, however, by aliphatic tertiary amine bases, DIPEA and Et3N, of ‘Goldilocks’ moderate base strength, which strongly accelerate the acylation of the polar substrate
使用极性和非极性醇底物进行的两个系列竞争性酰化实验,模拟两亲性二醇的两部分,研究了不同强度的碱对底物选择性的影响。虽然弱碱性 2,4,6-可力丁仅轻微加速极性底物的酰化而不影响非极性底物的酰化,但强碱性 DBU 大大加速了两种底物的酰化。在这两种情况下,与无碱酰化相比,底物选择性向极性底物发生了显着的但不是压倒性的转变,后者有利于非极性的酰化。然而,由具有中等碱强度的“金发姑娘”的脂肪族叔胺碱 DIPEA 和 Et3N 诱导了底物选择性的异常强烈变化,有利于极性底物,强烈加速极性底物的酰化,同时几乎不影响非极性底物的酰化。碱基对底物选择性的这些影响反映在模型二醇两亲物酰化中观察到的位点选择性趋势中。