The underlying factors controlling the Pd-catalyzed site-selective alkenylation of aliphatic amines
Yang-Yang Xing1, Jian-Biao Liu1, Chuan-Zhi Sun1
1College of Chemistry, Chemical Engineering and Materials Science, Collaborative Innovation Center of Functionalized Probes for Chemical Imaging in Universities of Shandong, Institute of Molecular and Nano Science, Shandong Normal University, Jinan 250014, P. R. China. jianbiaoliu.thu@gmail.com chendzh@sdnu.edu.cn.
Abstract:
The Pd(ii)-catalyzed site-selective δ-C(sp3)-H alkenylation in the presence of more accessible γ-C(sp3)-H bonds is investigated by DFT calculations. Migratory insertion is found to be both the rate-limiting and the selectivity-determining step. The origin of the unusual site-selectivity is originally attributed to the different steric repulsion between the alkyne and palladacycle; however, our theoretical results reveal that the inherent electronic effect instead of steric repulsion determines the site-selectivity. The proposal is further validated by model calculations involving the less sterically hindered 1,2-dimethyl acetylene and acetylene. In addition, a novel HCO3--assisted N-H activation mechanism is reported, and the origin of the regioselectivity of an unsymmetrical alkyne is also studied.
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