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Mechanistic insight into the regioselectivity of Pd(ii)-catalyzed C-H functionalization of N-methoxy cinnamamide
Weixi Fan1, Chuanzhi Sun, Fang Huang
1College of Chemistry, Chemical Engineering and Materials Science, Collaborative Innovation Center of Functionalized Probes for Chemical Imaging in Universities of Shandong, Key Laboratory of Molecular and Nano Probes, Ministry of Education, Shandong Provincial Key Laboratory of Clean Production of Fine Chemicals, Shandong Normal University, Jinan 250014, P. R. China. suncz@sdnu.edu.cn dchen@sdnu.edu.cn.
Abstract:
Computational studies have been applied to gain insight into the mechanism of Pd(ii) catalyzed α-C-H functionalization of N-methoxy cinnamamide. The results show that the whole catalytic cycle proceeds via sequential six steps, including (i) catalyst Pd(t-BuNC)2 oxidation with O2, (ii) O-H deprotonation, (iii) t-BuNC migratory insertion to the Pd-C bond, (iv) acyl migration, (v) C-H activation and (vi) reductive elimination. The regioselectivity for different C-H activation sites depends on the coordination structures of α-C or β-C to the palladium(ii) center. The coordination of α-C to the palladium(ii) center shows a regular planar quadrilateral structure, which is stable. However, the β-C coordinating to the palladium(ii) center mainly exhibits a distorted quadrilateral structure, which is relatively unstable. Thus, the barrier of α-C-H activation is much lower than that of β-C-H activation. The present results provide a deep understanding of the site-selectivity of C-H activation.