CCC pincer Ru complex-catalyzed C-H vinylation/6π-E-cyclization of aldimines for constructing
Heng Cai1, Yong-Qiang Tu1,2, Qiang Niu3
1State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University Lanzhou 730000 P. R. China tuyq@lzu.edu.cn.
Abstract:
An unusual cascade C-H activation, vinylation and 6π-electrocyclization of 2-pyridyl aldimines with vinyl bromides/triflates was achieved using catalysis with a unique CCC pincer NHC-Ru(iii) complex (Cat B). This reaction was found to enable a rapid and diverse synthesis of polycyclic 4H-pyrido[1,2-a]pyrimidine derivatives in mostly good to high yields, and with a broad substrate scope. A mechanistic study suggested the formation of a semi-opened Ru(iii) intermediate chelating/activating the aldimine, and the occurrence of single-electron transfer (SET) to generate a vinyl radical, followed by vinylation and then an intramolecular 6π-electrocyclization of 1N,3N-hexatrene to form the product. This protocol provides a convenient approach for preparing and seeking new drug candidates.
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