Understanding Internal Chirality Induction of Triarylsilyl Ethers Formed from Enantiopure Alcohols

Chirality transmission from point chirality to helical chirality was explored using triarylsilyl ethers. Circular dichroism (CD) spectroscopy was employed to show that the alcohol stereocenter of silylated, enantiopure secondary alcohols can transmit chirality to the aryl groups on the silicon resulting in a higher population of one helical conformation over another. Cotton effects characteristic of the aryl groups organized into one preferred conformation were observed for all of the compounds examined, which included both triphenyl- and trinaphthylsilyl groups. Alcohols with an R configuration typically induced a PMP helical twist, while an S configuration induced a MPM helical twist. Molecular modeling combined with solid-state structures also gave evidence signifying that point chirality adjacent to triphenylsilyl groups could bias the conformation of the phenyl groups. This work helps in our understanding of the origin of selectivity in our silylation-based kinetic resolutions and a role the phenyl groups play in that selectivity.本研究以三芳基硅醚为研究对象，探究了从点手性到螺旋手性的手性传递过程。采用圆二色 (Circular dichroism，CD) 光谱法证实：经硅基化修饰的对映纯仲醇的醇手性中心，可将手性传递至硅原子连接的芳基，使得某一种螺旋构象的占比高于另一种。在所测试的全部含三苯基硅基与三萘基硅基的化合物中，均观测到了对应单一优势构象芳基的科顿 (Cotton) 效应特征信号。具有R构型的醇通常会诱导产生PMP型螺旋扭转，而具有S构型的醇则会诱导产生MPM型螺旋扭转。分子模拟结合固态结构表征结果同样证实：三苯基硅基邻位的点手性可调控苯基的构象偏好。本研究有助于理解基于硅基化反应的动力学拆分中选择性的起源，以及苯基在该选择性调控过程中所发挥的作用。