McCarren P R, Liu Peng, Cheong Paul Ha-Yeon, Jamison Timothy F, Houk K N
Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095, USA.
J Am Chem Soc. 2009 May 20;131(19):6654-5. doi: 10.1021/ja900701g.
The mechanism of nickel-catalyzed reductive alkyne-aldehyde coupling reactions has been investigated using density functional theory. The preferred mechanism involves oxidative cyclization to form the nickeladihydrofuran intermediate followed by transmetalation and reductive elimination. The rate- and selectivity-determining oxidative cyclization transition state is analyzed in detail. The d --> pi*(perpendicular) back-donation stabilizes the transition state and leads to higher reactivity for alkynes than alkenes. Strong Lewis acids accelerate the couplings with both alkynes and alkenes by coordinating with the aldehyde oxygen in the transition state.
已使用密度泛函理论研究了镍催化的还原炔烃-醛偶联反应的机理。优选的机理包括氧化环化以形成镍二氢呋喃中间体，随后进行金属转移和还原消除。详细分析了决定速率和选择性的氧化环化过渡态。d→π*(垂直)反馈给电子作用使过渡态稳定，并导致炔烃比烯烃具有更高的反应活性。强路易斯酸通过在过渡态与醛氧配位来加速与炔烃和烯烃的偶联反应。
