Less Is More: N(BOH)₂ Configuration Exhibits Higher Reactivity than the B₃NO₂ Heterocycle in Catalytic Dehydrative Amide Formation

Abstract

Diboron substructures have emerged as a promising scaffold for the catalytic dehydrative amidation of carboxylic acids and amines. This Letter describes the design, synthesis, and evaluation of the first isolable N(BOH)2 compound as an amidation catalyst. The new catalyst outperforms the previously reported B3NO2 heterocycle catalyst, with respect to turnover frequency, albeit the former gradually decomposes upon exposure to amines. This work opens up an avenue for designing a better catalyst for direct amidation.

A Benzophenothiazine/Boronic Acid Hybrid Photocatalyst Enables the Single Electron Transfer (SET) to Carboxy Groups: SET-Initiated Cyclization of α,β-Unsaturated Carboxylic Acids

“…Recently, our group has reported the intramolecular hydroacylation of arenecarboxylic acids with olefins using a dual catalytic system consisting of an iridium photocatalyst and an arylboronic acid. We found that arylboronic acids facilitate SET to the carboxy group via the formation of a complex with the CAs. − Although these results indicate that Lewis acid activation by a boronic acid can facilitate photoredox reactions of CAs, the efficiency of SET from the photocatalyst was not sufficient for the practical application of this catalytic system. Thus, we have designed a new hybrid photocatalyst consisting of a benzophenothiazine moiety and an arylboronic acid.…”

A practical approach for oligopeptide synthesis via synergistic photoredox, cobaloxime and organophosphorus triple catalysis

“…On the other hand, various group IV/V metals and organoboron catalysts have been developed for catalytic amide bond formation directly from nonactivated carboxylic acids and amines. 8,9 However, these catalytic methodologies have not been employed in mainstream peptide synthesis owing to limited reactivity with functionalized substrates and thermodynamic challenges associated with water removal. 10…”

Hydroxy-directed peptide bond formation from α-amino acid-derived inert esters enabled by boronic acid catalysis

“…7–9 However, there is currently no reported utilization of an organoboron catalyst for peptide bond formation from α-amino acid-derived esters, despite the widespread use of various organoboron compounds represented by boronic acids as dehydrative catalysts for amidation or peptide bond formation from carboxylic acids. 10,11…”