Hydroboration, Cyanosilylation, and Sequential Cyanosilylation-Hydroboration of Carbonyl Compounds using Ti(IV) Amido Complex as an Efficient Catalyst

Panda, Tarun K and Harinath, Adimulam and Bhattacharjee, J and Gorantla, Koteswar Rao and Mallik, Bhabani Shankar (2018) Hydroboration, Cyanosilylation, and Sequential Cyanosilylation-Hydroboration of Carbonyl Compounds using Ti(IV) Amido Complex as an Efficient Catalyst. European Journal of Organic Chemistry. ISSN 1434-193X

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Abstract

Catalytic hydroboration using pinacolborane (4,4,5,5‐tetramethyl‐1,3,2‐dioxaborolane) and cyanosilylation using trimethylsilyl cyanide of a wide range of aldehydes and ketones in the presence of titanium (IV) complexes [2‐{(C5H4N)CH2N‐P(=Se)Ph2}Ti(NMe2)3] (1) and [{2‐(C6H4F)NP(=Se)Ph2}Ti(NMe2)3] (2) are reported. The catalytic hydroboration and cyanosilylation processes are high‐yielding, general, and result in efficient conversion of carbonyl compounds to corresponding products under mild conditions. Titanium catalyst 1 exhibits high tolerance toward several functional groups. First‐order kinetics with respect to the catalyst and each of the substrates was observed for the titanium‐catalyzed hydroboration reaction of carbonyl compounds. First principles' calculations were performed to explore the catalytic hydroboration reaction mechanism. In addition, a combination of both reactions and sequential cyanosilylation‐hydroboration was reported. Ti(IV) complexes 1 and 2 were prepared by the aminolysis reaction of [Ti(NMe2)4] with protic ligands [(C5H4N)CH2NHP(=Se)Ph2] (L1H) and [(C6H4F)NHP(=Se)Ph2] (L2H) respectively. The third titanium complex [4‐{(Ph2P(=Se)NCH(C5H4N)CH(C5H4N)‐P(=Se)Ph2}Ti(NMe2)2] (3) was obtained by the reaction of [Ti(NMe2)4] and ligand L1H in a 1:2 molar ratio at room temperature. Molecular structures of complexes 1 and 3 in the solid state are reported.

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