Radical C(sp3)–H functionalization and cross-coupling reactions

Thiol is known to act as a hydrogen atom transfer catalyst working in synergy with a photocatalyst in photoredox catalysis, but we report herein that an arene thiolate with an appropriate substituent can be photoactivated under visible light to function as both a strongly reducing electron-donating redox catalyst and a HAT catalyst to enable catalytic C–F activation of trifluoromethyl substrates for selective hydrodefluorination and coupling with various alkenes in the presence of formate salts. These reactions demonstrate the promising utility of arenethiolates as dual function photocatalysts. The synthetic utility of this method is demonstrated by the broad scope of amenable trifluoromethyl substrates, including trifluoromethylated (hetero)arenes, trifluoroacetates, and trifluoroacetamides, which exhibited high levels of chemoselectivity. The reaction efficacy allows site-selective late-stage functionalization of multitrifluoromethylated bioactive compounds and pharmaceuticals 

Arenethiolate as a Dual Function Catalyst for Photocatalytic Defluoroalkylation and Hydrodefluorination of Trifluoromethyls

Recent Advances in Mono‐ and Difunctionalization of Unactivated Olefins

Selenium-substituted heteroarenes are biologically active compounds and useful building blocks. In this study, we have developed a metal- and oxidant-free, environmentally friendly protocol for the regioselective selenylation of 2H-indazole derivatives by an electrochemical strategy. A number of selenylated 2H-indazoles with a wide range of functional groups have been synthesized in moderate to good yields under mild and environment-friendly reaction conditions. 

Electrochemical regioselective C–H selenylation of 2<i>H</i>-indazole derivatives

Deuterated organic compounds have become increasingly important in many areas; however, it remains challenging to install deuterium site-selectively to unactivated aliphatic positions with control of the degree of deuteration. Here, we report a Cu-catalyzed degree-controlled deacylative deuteration of diverse alkyl groups with the methylketone (acetyl) moiety as a traceless activating group. The use of N-methylpicolino-hydrazonamide (MPHA) promotes efficient aromatization-driven C-C cleavage. Mono-, di-, and trideuteration at specific sites can be selectively achieved. The reaction is redox-neutral with broad functional group tolerance. The utility of this method has been demonstrated in forming a complete set of deuterated ethyl groups, merging with the Diels-Alder reaction, a net devinylative deuteration, and the synthesis of the d2-analogue of Austedo.

Site-Specific and Degree-Controlled Alkyl Deuteration via Cu-Catalyzed Redox-Neutral Deacylation.

Radical hydroalkylation of olefins enabled by hydrogen atom transfer (HAT) catalysis represents a straightforward means to access C(sp3)-rich molecules from abundant feedstock chemicals without the need for prefunctionalization. While Giese-type hydroalkylation of activated olefins initiated by HAT of hydridic carbon-hydrogen bonds is well-precedented, hydroalkylation of unactivated olefins in a similar fashion remains elusive, primarily owing to a lack of general methods to overcome the inherent polarity-mismatch in this scenario. Here, we report the use of visible-light-driven dual HAT catalysis to achieve this goal, where catalytic amounts of an amine-borane and an in situ generated thiol were utilized as the hydrogen atom abstractor and donor, respectively. The reaction is completely atom-economical and exhibits a broad scope. Experimental and computational studies support the proposed mechanism and suggest that hydrogen-bonding between the amine-borane and substrates is beneficial to improving the reaction efficiency.

Guangyue Lei

Papers

Hydroalkylation of Unactivated Olefins via Visible-Light-Driven Dual Hydrogen Atom Transfer Catalysis.