Regioselective Ortho Palladation of Stabilized Iminophosphoranes in Exo Positions: Scope, Limitations, and Mechanistic Insights
摘要:
The reactivity of the stabilized iminophosphoranes R3P = NC(O)Ph (R = p-tolyl, m-tolyl), Ph3P = NC(O)CH2Ph, and Ph2P(CH2)(n)PPh2 = NC(O)Ph (n = 1, 2) toward Pd(OAc)(2) has been examined. These substrates undergo palladation at the ortho C(sp(2))-H bond of the benzamide ring, giving exo complexes with complete regioselectivity. The mechanism of this reaction has been studied using DFT calculations and the regioselectivity explained on a kinetic basis, since the activation barrier is lower for the exo pathway than for the endo. The origin of this lower energy for the exo barrier seems to reside mainly on the interaction energy between the metal center and the ligand at the transition state. On the other hand, the palladation of the related keto-stabilized systems Ph3P = NC(O)FG (FG = NC4H8, NC4H8O) gives selectively the endo isomers through C-H bond activation at the Ph ring of the PPh3 unit.
Interweaving Visible‐Light and Iron Catalysis for Nitrene Formation and Transformation with Dioxazolones
作者:Jing‐Jing Tang、Xiaoqiang Yu、Yi Wang、Yoshinori Yamamoto、Ming Bao
DOI:10.1002/anie.202016234
日期:2021.7.19
transfer reactions with dioxazolones for intermolecular C(sp3)-N, N=S, and N=P bond formation are described. These reactions occur with exogenous-ligand-free process and feature satisfactory to excellent yields (up to 99 %), an ample substrate scope (109 examples) under mild reaction conditions. In contrast to intramolecular C−H amidations strategies, an intermolecular regioselective C−H amidation via