Catalyst-free photooxidation of triarylphosphines under aerobic conditions

AbstractA new method for the photooxidation of triarylphosphines into the corresponding oxides is developed. In this new protocol, neither a catalyst nor an additive is required. The greenest oxidant, oxygen in air atmosphere, is used. After a short period of photo irradiation at rt, stoichiometric amounts of the oxides can be easily afforded by simply recycling the solvent under vacuum. No waste is formed in the whole process of this reaction. The substrate scope of this reaction is broad, showing very good application prospects in both organic chemistry and industrial processes

Bromo-catalyzed photo esterification of benzylsilanes with alcohols under aerobic conditions

A photoinduced esterification reaction has been developed. In this reaction, benzylsilane shows very nice reactivity and selectivity, affording the corresponding esters as the only products. Under photo irradiation, the highly active bromo radical can be generated from the pre-catalyst CBr4, which would promote the initial CSi bond cleavage of benzylsilane via single electron transfer and the final transformation of acetal into ester via proton transfer. The existence of oxygen can not only oxidize the in situ generated benzyl radical into aldehyde intermediate, but also assist to regenerate bromo radical from bromine anion

Visible light sensitizer-catalyzed highly selective photo oxidation from thioethers into sulfoxides under aerobic condition

Abstract We report herein a visible light sensitizer-catalyzed aerobic oxidation of thioethers, affording sulfoxides in good to excellent yields. The loading of the catalyst was as low as 0.1 mol%. The selectivity was excellent. Mechanism studies showed both singlet oxygen and superoxide radical anion were likely involved in this transformation

New developments in the enantioselective synthesis of spiro compounds

The enantioselective synthesis of spirocycles has long been pursued by organic chemists. Despite their unique 3D properties and presence in several natural products, the difficulty in their enantioselective synthesis makes them underrepresented in pharmaceutical libraries. Since the first pioneering reports of the enantioselective construction of spirosilanes by Tamao et al., significant effort has been devoted towards the development of new promising asymmetric methodologies. Remarkably, with the advent of organocatalysis, particularly over six years, the reported methodologies for the synthesis of spirocycles have increased exponentially. The aim of this review is to summarize the latest trends and developments in the enantioselective synthesis of spirocompounds during these last six years

Visible light induced oxidative hydroxylation of boronic acids

We report herein a visible light-induced aerobic oxidative hydroxylation of boronic acids. The reaction employed 7H-benzo[c]thioxanthen-7-one as metal-free catalyst and dimethyl carbonate as green solvent. Scale-up experiment was achieved using 0.1 mol% catalyst in a good yield with column-free purification. This reaction showed great green chemistry features and potential in synthetic applications.</p

Catalyst-free photocyclopropanation of dibromomalonates with alkenes: an approach to multisubstituted cyclopropanes

We report herein a novel photocyclopropanation of dibromomalonates with alkenes in the presence of Hünig base. This protocol provides an environmentally benign approach for the synthesis of multisubstituted cyclopropanes, since no catalyst is required. The Photo-induced Electron Transfer (PET) from Hünig base to dibromomalonate is the key process during this transformation