Catalytic 1,3-Proton Transfer in Alkenes Enabled by Fe═NR Bond Cooperativity: A Strategy for p<i>K</i><sub>a</sub>-Dictated Regioselective Transposition of C═C Double Bonds
作者:Yafei Gao、Xuelian Li、Jeremiah E. Stevens、Hao Tang、Jeremy M. Smith
DOI:10.1021/jacs.2c13350
日期:2023.6.7
(1-K(18-C-6)) catalyzes 1,3-proton transfer from 1-alkene substrates to afford 2-alkene transposition products. Mechanistic investigations involving kinetics, competition, and isotope labeling studies, supported by experimentally calibrated DFT computations, strongly support an unusual nonhydridic mechanism for alkene transposition that is enabled by the cooperative action of the iron center and basic imido ligand
过渡金属催化的烯烃双键转位通常涉及金属氢化物中间体。尽管在决定产品选择性的催化剂设计方面取得了重大进展,但对底物选择性的控制却不太先进,而且在含有多个 1-烯烃官能团的底物中选择性转位双键的过渡金属催化剂很少见。在此,我们报道了三坐标高自旋 ( S = 2) Fe(II) 亚胺络合物 [Ph 2 B( t BuIm) 2 Fe═NDipp][K(18-C-6)THF 2 ] ( 1- K(18-C-6)) 催化 1,3-质子从 1-烯烃底物转移,得到 2-烯烃转座产物。由实验校准的 DFT 计算支持的涉及动力学、竞争和同位素标记研究的机理研究强烈支持一种不寻常的烯烃转座非氢化机制,这种机制是由铁中心和碱性亚氨基配体的协同作用实现的。正如烯丙基质子的 p K a所指示的,该催化剂能够在含有多个 1-烯烃的底物中实现 C=C 双键的区域选择性转座。配合物的高自旋 ( S = 2) 状态允许广泛