Photocatalyzed oxidative cleavage of CC bond to carbonyl compounds by a recyclable homogeneous carbon nitride semiconductor/aqueous system.

The development of methods based on direct oxidative cleavage of alkynes to carbonyls is an extremely challenging task. In this work, we describe a UV light-driven, potassium/sodium poly(heptazine imide) (K,Na-PHI)-catalyzed protocol for the selective oxidative cleavage of alkynes to acids under an O2 atmosphere using water as a solvent. Various aromatic alkynes can be selectively cleaved to afford aromatic acids in good to high yield under clean, mild conditions. Mechanistic investigation indicates that the photogenerated hydroxyl radicals in situ act as green oxidation active species. Moreover, this protocol could be further developed as a sequential oxidative cleavage/esterification process for the preparation of aryl esters. Notably, the KNaPHI-II/water catalyst system could be used several times without significant loss of activity.

Heterogeneous Carbon Nitrides Photocatalysis Multicomponent Hydrosulfonylation of Alkynes To Access ß-Keto Sulfones with the Insertion of Sulfur Dioxide in Aerobic Aqueous Medium.

Although hydrosulfonylation of alkynes is an ideal process to generate ß-keto sulfones, such an approach is rarely implemented. Here we reported a facile and efficient graphitic carbon nitride (p-g-C3N4) photocatalyzed hydrosulfonylation of alkynes with the insertion of sulfur dioxide in aerobic conditions. Controlled experiments and ESR results indicated both the superoxide radicals and valence band holes played an important role in the reaction. Further isotope experiments confirmed the oxygen atom of the products comes from H2O, while the O2 plays an important role in the reaction by quenching the DABCO radical cation. The metal-free heterogeneous semiconductor is fully recyclable at least 6 times without significant reducing activity. Furthermore, this reaction could be carried out under solar light irradiation and was applicable for a large-scale reaction with conserved results.

A visible-light-induced chemoselective radical/oxidative addition domino process to access α-chloro and α-alkoxy aryl ketones.

A visible-light-induced radical-triggered chemoselective domino process to access α,α-di-functionalized ketones under mild conditions has been developed. This protocol provides a direct approach to synthesize α-chloro or α-alkoxy aryl ketones based on the electronic properties of the substrates. The reaction can tolerate a variety of functional groups to afford the corresponding products in moderate to good yields.