Theoretical Study of the Borono-Mannich Reaction with Pinacol Allenylboronate

SILVINA C. PELLEGRINET; SEBASTIÁN O. SIMONETTI

Innsbruck

Congreso; Young Chemists Summit; 2020

Gessellschaft Österreichiscer Chemiker

The Borono-Mannich reaction (BMR) is a multicomponent transformation that involves analdehyde, an amine and a boronic acid to obtain diversified amines. The reaction can be appliedto a wide range of boronate derivatives, such as, boronic acids, boronate esters and eventrifluoborate salts. Recently, pinacol allenylboronate has been used in the BMR for theobtention of allenylamines and propargylamines. Interestingly, when primary amines asbenzylamine are employed, propargylamine derivatives are obtained, whereas the use ofsecondary amines as piperidine affords the allenylamine derivative. In bothcases, full regioselectivity was observed.To gain understanding about the observed regioselectivity of these reactions, we performed aDensity Functional Theory (DFT) study of the BMR using the M062X/6-311+G** method inMeOH as solvent. For the first system, we analyzed the interaction with imine, derivedfrom benzylamine, and its corresponding iminium ion and salicylaldehyde. Also,we studied the system formed by piperidine.In the first case, it was observed B-O coordination via an eight-membered ring transitionstructure, stabilized by a hydrogen bond between the hydrogen attached to the nitrogenof the iminium ion and the phenolic oxygen to afford the propargylamine(-attack). On the otherhand, exhibits a non-classical hydrogen bond between the hydrogen attached to the iminecarbon and one of the oxygens of the pinacol in the six-membered ring structure toward theallenylamine (α-attack).Herein, we discuss the results of this study, as well as, the possible applications of this work toother systems in the Borono-Mannich Reaction.