Visible-light-induced cascade chromone cyclization/chalcogenation to access 3-chalcogenyl-chromones using elemental sulfur/selenium

A mild and efficient visible-light-induced cascade undergoing a chromone cyclization/chalcogenation at room temperature has been developed. This three-component reaction employs user-friendly elemental S8 and Se as the chalcogenide source, providing an attractive route for the convenient synthesis of 3-chalcogenyl-chromones with a wide substrate scope and good functional group tolerance.

Metal-free radical selenothiocyanation of terminal and internal alkynes

We report herein a synthetic strategy for the generation of direct selenothiocyanation from both terminal and internal alkynes via a radical process. Alkynes derived from bioactive molecules, such as L(-)-borneol and L-menthol, are suitable for selenothiocyanation reaction. This method features metal-free conditions and readily available reagents.

Visible photons as ideal reagents for the activation of coloured organic compounds

In recent decades, the traceless nature of visible photons has been exploited for the development of efficient synthetic strategies for the photoconversion of colourless compounds, namely, photocatalysis, chromophore activation, and the formation of an electron donor/acceptor (EDA) complex. However, the use of photoreactive coloured organic compounds is the optimal strategy to boost visible photons as ideal reagents in synthetic protocols. In view of such premises, the present review aims to provide its readership with a collection of recent photochemical strategies facilitated via direct light absorption by coloured molecules. The protocols have been classified and presented according to the nature of the intermediate/excited state achieved during the transformation.

Copper-catalyzed thiocyanation of cyclobutanone oxime esters using ammonium thiocyanate

A copper-catalyzed thiocyanation of cycloketone oxime esters with ammonium thiocyanate has been developed for the first time. This innovative approach allows access to cyano and thiocyano bifunctionally substituted alkanes, which can be further transformed into their respective trifluoromethylthiol-substituted or difluoromethylthiol-substituted alkylnitriles, alkynyl sulfides, and phosphorothioate esters. The readily available nature of ammonium thiocyanate and the cost-effectiveness of the copper catalyst make this method a promising strategy for the synthesis of sulfur-containing alkylnitriles.

Copper-Catalyzed Three-Component Tandem Reaction of Alkynes, α-Diazo Esters, and TMSN3 to Access N-Substituted 1,2,3-Triazoles

An efficient copper-catalyzed three-component tandem reaction of alkynes, α-diazo esters, and TMSN3 to construct triazoles has been developed. Through this strategy, a number of diverse N-substituted 1,2,3-triazoles were conveniently obtained in moderate to good yields from simple and readily available starting materials using K2CO3 as the base. The mechanism of the tandem Cu-catalyzed azide-alkyne cycloaddition (CuAAC) and Cu-carbenoid-participated C-N coupling reaction has been investigated.

Visible-light-promoted N-H functionalization of O-substituted hydroxamic acid with diazo esters

Herein we report an N-H functionalization of O-substituted hydroxamic acid with diazo esters under blue LED irradiation conditions. The present transformations could be performed efficiently under mild conditions without use of catalyst, additive and N₂ atmosphere. Interestingly, when THF and 1,4-dioxane were employed as the reaction solvents, an active oxonium ylide involved three-component reaction and an N-H insertion of carbene species into hydroxamate occurred, respectively.

Visible-Light-Initiated Multicomponent Reactions of α-Diazoesters to Access Organophosphorus Compounds

A simple visible-light-initiated strategy has been established for the construction of organophosphorus compounds via aerobic multicomponent reaction of α-diazoesters, cyclic ethers, and P(O)H compounds under air. A number of phosphonates and phosphinates could be efficiently isolated in moderate to good yields without the use of photosensitizers and metal reagents. This multicomponent reaction has advantages of mild condition, simple operation, eco-friendly energy, good functional-group tolerance, and gram-scale synthesis.

Visible-light-mediated multi-component carbene transfer reactions of α-diazoesters to construct multisubstituted pyrazoles and 1,3-dicarbonyl derivatives

A visible-light-promoted strategy has been developed for the assembly of multisubstituted pyrazoles and 1,3-dicarbonyl derivatives via a multi-component carbene transfer reaction of α-diazoesters.