Photocascade chemoselective controlling of ambident thio(seleno)cyanates with alkenes via catalyst modulation.

Controlling the ambident reactivity of thiocyanates in reaction manifolds has been a long-standing and formidable challenge. We report herein a photoredox strategy for installing thiocyanates and isothiocyanates in a controlled chemoselective fashion by manipulating the ambident-SCN through catalyst modulation. The methodology allows redox-, and pot-economical 'on-demand' direct access to both hydrothiophene and pyrrolidine heterocycles from the same feedstock alkenes and bifunctional thiocyanomalonates in a photocascade sequence. Its excellent chemoselectivity profile was further expanded to access Se- and N-heterocycles by harnessing selenonitriles. Redox capability of the catalysts, which dictates the substrates to participate in a single or cascade catalytic cycle, was proposed as the key to the present chemodivergency of this process. In addition, detailed mechanistic insights are provided by a conjugation of extensive control experiments and dispersion-corrected density functional theory (DFT) calculations.

Organic Dye-Catalyzed Intermolecular Radical Coupling of α-Bromocarbonyls with Olefins: Photocatalytic Synthesis of 1,4-Ketocarbonyls Using Air as an Oxidant.

An organic dye-catalyzed visible light-promoted ketocarbonylation protocol of vinyl arenes has been disclosed with the help of α-bromocarbonyls where aerial oxygen played a role of an oxidant to install the keto-oxygen functionality. This unique process is compatible with both internal and terminal olefins and tolerates a diverse array of functional groups (ketone, ester, amide, diketones, ketoester, and malonate). This process is mild and environmentally friendly and deals with greener oxidants like oxygen, affording 1,4-ketocarbonyls as a value-added end product.

Photoredox-Catalyzed Intermolecular Radical Arylthiocyanation/Arylselenocyanation of Alkenes: Access to Aryl-Substituted Alkylthiocyanates/Alkylselenocyanates.

An efficient and highly selective approach for intermolecular arylthiocyanation/arylselenocyanation of alkenes has been reported under mild conditions. Using diazonium salts as the arylating agent and ammonium thiocyanate as the thiocyanate source, chemoselective difunctionalization of alkenes has been done under irradiation of visible light. Both styrenes and acrylates work well to deliver various aryl-substituted alkylthiocyanates in good to excellent yields. In addition, hitherto unknown ß-aryl alkylselenocyanates were also synthesized using the developed protocol with potassium selenocyanate.

TBAI/TBHP-Promoted Generation of Malonyl Radicals: Oxidative Coupling with Styrenes Leads to γ-Keto Diesters.

A metal-free protocol for oxidative coupling of malonic esters with styrenes to form γ-keto diesters has been developed. Key to the success of this process is the generation of malonyl radicals from unfunctionalized malonic esters under organo-catalysis conditions with TBAI and TBHP. This process tolerates both terminal and internal olefins with diverse malonic esters. It provides a new green metal-free alternative to traditional metal mediated process for generation of malonyl radicals and there by γ-keto diesters.