ABSTRACT
Current methods for constructing amide bonds join amines and carboxylic acids by dehydrative couplings-processes that usually require organic solvents, expensive and often dangerous coupling reagents, and masking other functional groups. Here we describe an amide formation using primary amines and potassium acyltrifluoroborates promoted by simple chlorinating agents that proceeds rapidly in water. The reaction is fast at acidic pH and tolerates alcohols, carboxylic acids, and even secondary amines in the substrates. It is applicable to the functionalization of primary amides, sulfonamides, and other N-functional groups that typically resist classical acylations and can be applied to late-stage functionalizations.
ABSTRACT
Boronic acid is one of the most versatile organic molecules in chemistry. Its uses include organic reactions, molecular recognition, assembly, and even medicine. While boronic acid catalysis, which utilizes an inherent catalytic property, has become an important research objective, it still lags far behind other boronic acid chemistries. Here, we report our discovery of a new boronic acid catalysis that enables the aza-Michael addition of hydroxamic acid to quinone imine ketals. By using 3-borono-BINOL as a chiral boronic acid catalyst, this reaction could be implemented in a highly enantioselective manner, paving the way to densely functionalized cyclohexanes.
ABSTRACT
We developed herein a new chiral Brønsted acid catalyst which is composed of two independent organic molecules, a chiral diol, and 2-boronobenzoic acid. In situ formation of a boronate ester was utilized as a key process to generate an active catalyst. This boronate ester assisted chiral carboxylic acid catalyst was successfully applied to the trans-aziridination of N-Boc and N-benzyl imines with N-phenyldiazoacetamide. This is the first catalyst to achieve high enantioselectivities using N-benzyl imines.