Wen-Jie Wei

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.

Density functional theory calculations are employed to investigate the detailed reaction mechanism and origins of selectivity of the diphenyl selenide-catalyzed sulfenofunctionalization of chiral α-CF ₃ allylboronic acids.

The synthesis of strained carbocyclic building blocks is relevant for Medicinal Chemistry, and methylenecyclobutanes are particularly challenging with current synthetic technology. Careful inspection of the reactivity of [1.1.1]propellane and diboron reagents has revealed that bis(catecholato)diboron (B₂cat₂) can produce a bis(borylated) methylenecyclobutane in a few minutes at room temperature. This reaction constitutes the first example of B−B bond activation by a special apolar hydrocarbon and also the first time that propellane is electrophilically activated by boron. Mechanistic studies including in situ NMR kinetics and DFT calculations demonstrate that the diboron moiety can be directly activated through coordination with the inverted sigma bond of propellane, and reveal that DMF is involved in the stabilization of diboronate ylide intermediates rather than the activation of the B−B bond. These results enable new possibilities for both diboron and propellane chemistry, and for further developments in the synthesis of methylenecyclobutanes based on propellane strain release.

The reaction mechanism of N ₂ reduction for V-nitrogenase has been studied by hybrid DFT with a cluster model. The calculations show that, after four reduction steps, a sulfide is released and in E ₁ the carbide is protonated. After a Jahn–Teller distortion of V ³⁺ , one hydride is bound to vanadium.

The present study concerns the technical aspects of obtaining the energetics for the E4 state of nitrogenase, the enzyme that fixes N₂ in nature. EPR experiments have shown that the critical E4 structure that activates N₂ should contain two bridging hydrides in the FeMo‐cofactor. It is furthermore in equilibrium with a structure where the two hydrides have been released and N₂ binds. These observations led to the suggestion that E4 should have two bridging hydrides and two protonated sulfides. It is important to note that the structure for E4 has not been determined, but only suggested. For a long time, no DFT study led to the suggested structure, independent of which functional was used. However, in two recent DFT studies a good agreement with the experimental suggestion was claimed to have been obtained. In one of them the TPSS functional was used. That was the first out of 11 functionals tried that led to the experimentally suggested structure. In the second of the recent DFT studies, a similar conclusion was reached using the TPSSh functional. The conclusions in the recent studies have here been studied in detail, by calculating a critical energetic value strongly implied by the same EPR experiments. Both the TPSS and TPSSh functionals have been used. The present calculations suggest that those DFT functionals would not lead to agreement with the experimental EPR results either.