Base-Mediated Radical Borylation of Alkyl Sulfones

A Metal-Free and Operationally Simple Radical Trifluoromethylative Borylation of Unactivated Alkenes

We herein describe a protocol to synthesize trifluoromethylated alkyl boronates from alkenes by the mutual activation of the Togni II and the bis(catecholato)diboron reagents in the absence of any catalyst and additives. This reaction enables synthesizing a series of trifluoromethylated alkyl boronates using unactivated alkenes, including natural products and drug derivatives, in a regioselective manner. Moreover, the synthetic utility of the boronic ester present in the product allows access to a range of trifluoromethyl containing compounds. The radical trapping and gas detection experiments reveal that the more Lewis acidic diboron reagent determines the rapid formation of trifluoromethyl and boron centered radicals.

Photoinduced Dehydrogenative Borylation via Dihydrogen Bond Bridged Electron Donor and Acceptor Complexes

Air-stable amine- and phosphine-boranes are discovered as donors to integrate with pyridinium acceptor for generating photoactive electron-donor-acceptor (EDA) complexes. Experimental results and DFT calculations suggest a dihydrogen bond bridging the donor and acceptor. Irradiating the EDA complex enables an intra-complex single electron transfer to give a boron-centered radical for dehydrogenative borylation with no need of external photosensitizer and radical initiator. The deprotonation of Wheland-like radical intermediate rather than its generation is believed to determine the good ortho-selectivity based on DFT calculations. A variety of α-borylated pyridine derivatives have been readily synthesized with good functional group tolerance.

Adamantane-1-Carbonyl-Directed C-H Borylation and Hydroxylation of Benzenethiols

A novel route has been described for C-H borylation and hydroxylation of benzenethiols directed by adamantane-1-carbonyl using BBr₃. The protocol generates corresponding arylboronic esters and phenols in moderate to excellent yields under metal-free conditions. In addition, the borylated product can be transformed and the directing group can be removed in good yields, which will facilitate the synthesis of structurally diverse benzenethiols.

Redox-active alkylsulfones as precursors for alkyl radicals under photoredox catalysis

Visible-light photoredox catalytic method for the generation of alkyl radicals using redox-active alkylsulfones to form a new C–C bond is reported.

Cu-mediated vs. Cu-free selective borylation of aryl alkyl sulfones

A Cu-catalysed borylation of aryl alkyl sulfones was developed for the high yield synthesis of versatile arylboronic esters using a readily prepared NHC-Cu catalyst. In addition, the selective cleavage of either alkyl(C)-sulfonyl or aryl(C)-sulfonyl bonds of a cyclic sulfone via Cu-free or Cu-mediated processes generates the corresponding sulfinate salts, which can be further derivatised to provide sulfonyl-containing boronate esters, such as sulfones and sulfonyl fluorides.