One-Pot Decarbonylative Borylation of Aliphatic Aldehydes

We present a mild and direct method for the radical borylation of simple aliphatic aldehydes. By employing an enamine and a photocatalyst under light irradiation, aldehydes can be transformed effectively into alkyl boronic esters via a formal decarbonylative process. This alternative route for radical borylation synthesis can not only be applied to the transformation of primary, secondary, and tertiary aldehydes but also be adapted to other radical conversion reactions through the generated alkyl radical intermediate. Mechanistic studies indicate that 4-alkyl-1,4-dihydropyridines, formed in situ from the aldehyde and enamine, are the key intermediate for the borylation process.

Recent advances in 4CzIPN-mediated functionalizations with acyl precursors: single and dual photocatalytic systems

4CzIPN (1,2,3,5-tetrakis(carbazole-9-yl)-4,6-dicyanobenzene) has emerged as a key metal-free photocatalyst for sustainable organic synthesis. Due to its unique design enabling high photoluminescence quantum yield, thermally activated delayed fluorescence (TADF) and long excited state lifetime, 4CzIPN facilitates diverse reactions, such as C-C and C-X bond formation reactions, under mild reaction conditions. This review highlights its application in decarboxylation, acylation and cyclisation reactions involving α-keto acids, carboxylic acids and aldehydes in a single catalytic system, as well as the combination of a dual catalytic system with transition metals to enhance selectivity and scope. 4CzIPN contributes to the advancement of sustainable chemistry by enabling green, efficient and scalable reactions and this review covers studies published between 2020 and 2024.

Visible-light-mediated radical difunctionalization of alkenes with aromatic aldehydes

We have developed a visible-light-mediated three-component tandem reaction of aromatic aldehydes with acrylates using a Hantzsch ester as the hydrogen atom transfer reagent, generating diethyl pentanedioate products in a one-pot synthesis. The reaction facilitates direct formation of acyl groups from the corresponding aldehydes, which are subsequently coupled successively to two molecules of acrylate in a Giese addition.

Construction of C-S and C-Se Bonds from Unstrained Ketone Precursors under Photoredox Catalysis

A mild photoredox catalyzed construction of sulfides, disulfides, selenides, sulfoxides and sulfones from unstrained ketone precursors is introduced. Combination of this deacylative process with SN 2 or coupling reactions provides novel and convenient modular strategies toward unsymmetrical or symmetric disulfides. Reactivity studies favor a bromine radical that initiates a HAT (Hydrogen Atom Transfer) from the aminal intermediate resulting in expulsion of a C-centered radical that is intercepted to make C-S and C-Se bonds. Gram scale reactions, broad substrate scope and tolerance towards various functional groups render this method appealing for future applications in the synthesis of organosulfur and selenium complexes.

Organophotoredox and Hydrogen Atom Transfer Cocatalyzed C-H Alkylation of Quinoxalin-2(1H)-ones with Aldehydes, Amides, Alcohols, Ethers, or Cycloalkanes

Described is a mild method that merges organophotoredox catalysis with hydrogen atom transfer to enable C-H alkylation of quinoxalin-2(1H)-ones with feedstock aldehydes, amides, alcohols, ethers, or cycloalkanes. This reaction occurred under environmentally benign and external oxidant-free reaction conditions, providing a general and sustainable access to various C3-alkylated quinoxalinone derivatives with broad substituent diversity and good functional group compatibility.