Theoretical prediction of Ni(I)-catalyst for hydrosilylation of pyridine and quinoline |
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Authors: | Vijay Singh Shigeyoshi Sakaki Milind M Deshmukh |
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Institution: | 1. Department of Chemistry, Dr. Harisingh Gour Vishwavidyalaya (A Central University), Sagar, 470003 India;2. Fukui Institute for Fundamental Chemistry, Kyoto University, Nishihiraki-cho, Takano, Sakyo-ku Kyoto, 606-8103 Japan |
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Abstract: | Catalytic synthesis of dihydropyridine by transition-metal complex is one of the important research targets, recently. Density functional theory calculations here demonstrate that nickel(I) hydride complex (bpy)NiIH (bpy = 2,2′-bipyridine) 1 is a good catalyst for hydrosilylation of both quinoline and pyridine. Two pathways are possible; in path 1, substrate reacts with 1 to form stable intermediate Int1 . After that, N3─C1 bond of substrate inserts into Ni─H bond of 1 via TS1 to afford N-coordinated 1,2-dihydroquinoline Int2 with the Gibbs activation energy (ΔG°?) of 21.8 kcal mol?1. Then, Int2 reacts with hydrosilane to form hydrosilane σ-complex Int3 ; this is named path 1A. In the other route (path 1B), Int1 reacts with phenylsilane in a concerted manner via hydride-shuttle transition state TS2 to afford Int3 . In TS2 , Si atom takes hypervalent trigonal bipyramidal structure. Formation of hypervalent structure is crucial for stabilization of TS2 (ΔG°? = 17.3 kcal mol?1). The final step of path 1 is metathesis between Ni─N3 bond of Int3 and Si─H bond of PhSiH3 to afford N-silylated 1,2-dihydroproduct and regenerate 1 (ΔG°? = 4.5 kcal mol?1). In path 2, 1 reacts with hydrosilane to form Int5 , which then forms adduct Int6 with substrate through Si–N interaction between substrate and PhSiH3. Then, N-silylated 1,2-dihydroproduct is produced via hydride-shuttle transition state TS5 (ΔG°? = 18.8 kcal mol?1). The absence of N-coordination of substrate to NiI in TS5 is the reason why path 2 is less favorable than path 1B. Quinoline hydrosilylation occurs more easily than pyridine because quinoline has the lowest unoccupied molecular orbital at lower energy than that of pyridine. © 2019 Wiley Periodicals, Inc. |
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Keywords: | Ni(I) catalysis DFT calculations hydrosilylation pyridine quinoline |
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