Rate Dependence on Inductive and Resonance Effects for the Organocatalyzed Enantioselective Conjugate Addition of Alkenyl and Alkynyl Boronic Acids to β-Indolyl Enones and β-Pyrrolyl Enones
作者:Amy Boylan、Thien S. Nguyen、Brian J. Lundy、Jian-Yuan Li、Ravikrishna Vallakati、Sasha Sundstrom、Jeremy A. May
DOI:10.3390/molecules26061615
日期:——
Two key factors bear on reaction rates for the conjugate addition of alkenyl boronic acids to heteroaryl-appended enones: the proximity of inductively electron-withdrawing heteroatoms to the site of bond formation and the resonance contribution of available heteroatom lone pairs to stabilize the developing positive charge at the enone β-position. For the former, the closer the heteroatom is to the
影响烯基硼酸与杂芳基连接的烯酮共轭加成反应速率的两个关键因素:感应吸电子杂原子与成键位点的接近度以及可用杂原子孤对对稳定产生的正电荷的共振贡献在烯酮β-位。对于前者,杂原子距离烯酮β-碳越近,反应越快。对于后者,苄基阳离子电荷的共振稳定性更强,可加速反应。因此,反应速率通过感应吸电子元件的更接近而增加,但如果涉及共振效应,则观察到具有给电子能力的速率增加。提出了异构底物这些趋势的证据,并且这些见解的应用允许反应条件改善与以前有问题的底物的反应性。