Beatriz Meana-Baamonde

The Hypoboric Acid Catecholate (HAC) is a new class of diboron reagent bearing a borylcatecholato and a boronic acid moiety. Herein, we demonstrate that HACs can also be expontaneously formed in situ from collections of catechols and hypoboric acid. These HACs catalyze the decarboxylative borylation of redox-active esters, providing superior reactivity and selectivity. Equilibrium and kinetic NMR experiments indicate that the catalytic turnover is enabled by the high affinity of catechols for hypoboric acid and their low affinity for boronic acids that is uncovered herein. The catalytic system operates in mild conditions and is robust towards air and moisture, demonstrating its utility in the synthesis of important medicinally-relevant boronates. The enhanced selectivity is sourced in the regioselective radical capture by HAC intermediates at their customized borylcatecholato moiety, which can easily be stereoelectronically tailored for specific applications. These features of the catalytic approach with unsymmetrical HACs presented herein contrast with current state-of-the-art methods based on stoichiometric symmetrical diboron reagents.

The decarboxylative borylation of redox‐active esters promoted by bis(catecholato)diboron (B ₂ cat ₂ ) and blue light enables the synthesis of versatile organoboron building blocks from carboxylic acid materials. An LED‐illuminated NMR kinetic study revealed that the reaction is surprisingly accelerated by water, and this hidden catalysis can be attributed to a novel intermediate formed in situ, namely a hypoboric acid catecholate (HAC). This unsymmetrical diboron species can alternatively be formed by hydrolysis of B ₂ cat ₂ or transesterification between B ₂ cat ₂ and hypoboric acid (B ₂ (OH) ₄ ). Experimental and computational studies revealed and rationalized the regioselective capture of alkyl radicals by the HAC species, and the concomitant formation of a more reductive boryl radical chain carrier. The regioselectivity is characteristic of the HAC species studied, and is controlled by electronic rather than steric effects.

(Borylmethyl)trimethylsilanes are important building blocks in organic synthesis displaying a unique reactivity. Yet, the synthesis of more advanced derivatives is limited by the advanced silicon intermediates required for their preparation. Herein, a one-pot synthesis of (borylmethyl)silanes is developed, sourced on available alkyl-, aryl-, alkoxy-, aryloxy-, and silyl-hydrosilane materials. The privileged reactivity of N-hydroxyphthalimidyl diazoacetate (NHPI-DA) in Si-H insertion and α-silyl redox-active esters in different decarboxylative borylation reactions are scrutinized.