4,4′-Bipyridyl worked as an organocatalyst for the reduction of nitroarenes by bis­(neopentylglycolato)­diboron (B2nep2), followed by hydrolysis to give the corresponding anilines. This reduction proceeded under aerobic conditions without any prepurification of substrates and reagents. We found broad functional group tolerance and compatibility for O- and N-protecting groups under the reaction conditions. The key in this catalytic system was the addition of B2nep2 to 4,4′-bipyridyl to form N,N′-bis­[(neopentylglycolato)­boryl]-4,4′-bipyridinylidene as a deoxygenating reagent of nitroarenes.

A metal-free deoxygenation and reductive disilylation of nitroarenes was achieved using N,N'-bis(trimethylsilyl)-4,4'-bipyridinylidene (1) under mild and neutral reaction conditions, and a broad functional group tolerance was possible in this reaction. Mono-deoxygenation, giving a synthetically valuable N,O-bis(trimethylsilyl)phenylhydroxylamine (7 a) as a readily available and safe phenylnitrene source from nitrobenzene, and double-deoxygenation, giving N,N-bis(trimethylsilyl)anilines 8, were easily controlled by varying the amounts of 1 and reaction temperature as well as adding dibenzothiophene (DBTP). Reaction of 2-arylnitrobenzenes with 1 resulted in the formation of the corresponding carbazoles 14 via in situ-generated phenylnitrene species derived by thermolysis of N,O-bis(trimethylsilyl)phenylhydroxylamines 7, followed by their subsequent intramolecular C-H insertion. In addition, the intramolecular N-N coupling reaction proceeded in the reduction of 2,2'-dinitrobiphenyl derivatives by 1, giving the corresponding benzo[c]cinnolines.

We have developed a hydrodehalogenation reaction of haloalkanes using PhSiH3. The α-diimine ligand on the niobium center plays an important role in releasing one electron from the dianionic ligand to the alkyl halides to a generate carbon radical as the initial step of the catalytic reaction.

Molecular oxygen is kinetically inert and rarely used as a primary oxidant for low temperature selective oxygenation reactions. Here, we show that O2 is converted into H2O2 in almost quantitative yields (98 %) at ambient temperature and atmospheric pressure in the presence of bis(trimethylsilyl)‐1,4‐cyclohexadiene 1. Similarly, the reaction of O2 with dihydro‐bis(trimethylsilyl) viologen 2 and pyrazine 3 yields bis(trimethylsilyl) peroxide (BTSP) in excellent yields (up to 99 %) at low temperature. Both processes demonstrate that readily available organosilicon reagents enable chemistry typically observed with mono‐oxygenase co‐enzymes, such as FADH2 and FMNH2, in biological systems, or at higher pressure via the industrial anthraquinone process. This efficient synthesis of H2O2 and BTSP directly from O2 is particularly attractive for the preparation of the corresponding O‐17 and O‐18 labeled reagents without the need of large excess amounts of O2. These are showcased in O‐atom transfer reactions to various organic or inorganic substrates, in a two‐step one‐pot process, making the rapid and on‐demand synthesis of large libraries of O‐labeled compounds readily possible.

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