Dative Directing Group Effects in Ti-Catalyzed [2+2+1] Pyrrole Synthesis: Chemo- and Regioselective Alkyne Heterocoupling
作者:Hsin-Chun Chiu、Xin Yi See、Ian A. Tonks
DOI:10.1021/acscatal.8b04669
日期:2019.1.4
found to play a key role in controlling the regioselectivity of alkyne insertion and [2+2] cycloaddition in Ti-catalyzed [2+2+1] pyrrole synthesis and Ti-catalyzed alkyne hydroamination. TMS-protected alkynes with pendent Lewis basic groups can invert the regioselectivity of TMS-protected alkyne insertion, leading to the selective formation of highly substituted 3-TMS pyrroles. The competency of various
研究发现,在Ti催化的[2 + 2 + 1]吡咯合成和Ti催化的炔烃加氢胺化反应中,过渡性的基质-Ti相互作用在控制炔烃插入的区域选择性和[2 + 2]环加成中起关键作用。具有悬垂的Lewis碱性基团的TMS保护的炔烃可以逆转TMS保护的炔烃插入的区域选择性,从而导致选择性形成高度取代的3-TMS吡咯。研究了各种潜在的导向基团的能力,发现可以通过改变催化剂路易斯酸度,导向基团的碱度或导向基团的链长来调节导向基团的作用。Ti催化剂没有探索出直接的导向基团效应,这项研究证明了在调节选择性方面,潜在的底物与Ti相互作用的潜在能力。