An Accessible Method for DFT Calculation of B NMR Shifts of Organoboron Compounds.

The study of boron-mediated reactions in organic synthesis and reactions of organoboron compounds is greatly facilitated by the use of B NMR. However, the identification and characterization of reaction intermediates in often complex systems is far from trivial, as B NMR does not provide any detailed structural information. Greater insight into the structures present in such systems can be obtained by using DFT chemical shift calculations to support or exclude proposed reaction intermediates.

Mechanistic insights into boron-catalysed direct amidation reactions.

The generally accepted monoacyloxyboron mechanism of boron-catalysed direct amidation is brought into question in this study, and new alternatives are proposed. We have carried out a detailed investigation of boron-catalysed amidation reactions, through study of the interaction between amines/carboxylic acids and borinic acids, boronic acids and boric acid, and have isolated and characterised by NMR/X-ray crystallography many of the likely intermediates present in catalytic amidation reactions. Rapid reaction between amines and boron compounds was observed in all cases, and it is proposed that such boron-nitrogen interactions are highly likely to take place in catalytic amidation reactions.