The catalytic α-alkylation of amines with alkenes, hydroaminoalkylation, is a promising approach to produce amines. Amidate tantalum complexes were synthesized by Schafer’s research group and were applied for catalytic coupling of various type of amines and alkenes. In the present work, DFT calculations were performed on the proposed catalytic cycle to evaluate free energy barriers and thermodynamics of the different steps in the reaction mechanism. Several levels of theory were examined to find suitable method for the calculations; from these B3PW91-D3/SDD,6-311++G(d,p)/SMD-toluene was thus selected for the subsequent calculations. The catalytic cycle begins with the formation of the tantalaziridine via β-abstraction of a precatalyst (κ2-N, O-Ta(NMe2)4) that is converted to a five-membered metallacycle intermediate through insertion of an alkene into the tantalaziridine Ta-C bond, followed by protonolysis of the intermediate via an amine substrate. Finally, a β-abstraction completes the cycle which results in the alkylated amine product. Protonolysis of the five-membered ring intermediate was found to be the rate-determining step. Since H-transfer is the significant step in three of four transition states, it is worth assessing how pKa is important in the reaction mechanism.

DFT study of hydroaminoalkylation of alkenes with amidate tantalum complexes

256th National Meeting (2018)

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