One-Step Transformation of Aryl Diazonium Salts into Aryl Indium(III) Reagents.

A method for the conversion of diazonium salts into intrinsically nucleophilic aryl indium reagents is described. The reaction is performed using indium(I) bromide with the C-In bond being formed by the interaction of aryl radicals with the indium salt. The obtained aryl indium(III) reagents work well in the Liebeskind-Srogl cross-coupling with thioesters, affording a wide variety of aryl ketones. This two-step transformation is a general method for the acylation of diazonium salts.

Photoredox-catalyzed silyldifluoromethylation of silyl enol ethers.

A method for the light-mediated fluoroalkylation of silyl enol ethers with (bromodifluoromethyl)trimethylsilane followed by a reduction of the primary products with sodium borohydride is described. An 18 W, 375 nm LED was used as the light source. The reaction is performed in the presence of a gold photocatalyst, which effects the generation of a (trimethylsilyl)difluoromethyl radical via cleavage of the carbon-bromine bond.

Synthesis of tetrafluorinated piperidines from nitrones via a visible-light-promoted annelation reaction.

A method for the one-step construction of 3,3,4,4-tetrafluorinated piperidines from nitrones and readily accessible tetrafluorinated iodobromobutane is described. The reaction requires an excess amount of ascorbic acid as the terminal reductant and is performed in the presence of an iridium photocatalyst activated by blue light. The annelation is a result of a radical addition at the nitrone, intramolecular nucleophilic substitution, and reduction of the N-O bond.

Radical Addition to N-Tosylimines via C-H Activation Induced by Decatungstate Photocatalyst.

A method for the radical addition toward N-tosylimines based on light promoted C-H activation by tetrabutylammonium decatungstate is described. The reaction proceeds under irradiation using 400 nm light emitting diodes in conventional glassware. The method can be applied for alkylations (cycloalkanes, ethers, dimethylformamide) and acylation (primary aliphatic aldehydes) of both aromatic and aliphatic N-tosylimines.

Visible light-mediated difluoroalkylation of electron-deficient alkenes.

A method for the reductive difluoroalkylation of electron-deficient alkenes using 1,1-difluorinated iodides mediated by irradiation with blue light is described. The reaction involves radical addition of 1,1-difluorinated radicals at the double bond followed by hydrogen atom transfer from sodium cyanoborohydride.

Photocatalytic Reductive Fluoroalkylation of Nitrones.

A method for the addition of fluorinated groups to nitrones using an iridium photocatalyst and ascorbic acid as a stoichiometric reducing agent is described. The reaction proceeds through the generation of fluorinated radicals by single-electron reduction of fluorinated alkyl iodides with an iridium complex mediated by visible light. Besides perfluorinated reagents, partially fluorinated alkyl iodides can also be effectively used leading to the products, which cannot be obtained by conventional nucleophilic addition reactions. The resulting hydroxylamines can be readily converted to valuable fluorinated amines by reduction with zinc.

New approach toward the synthesis of deuterated pyrazolo[1,5-a]pyridines and 1,2,4-triazolo[1,5-a]pyridines.

An efficient and operationally simple synthesis of 7-deuteropyrazolo[1,5-a]pyridine and 7-deutero-1,2,4-triazolo[1,5-a]pyridine derivatives using α-H/D exchange of 1-aminopyridinium cations in basic D2O followed by a 1,3-cycloaddition of acetylenes and nitriles is presented. A high regioselectivity and a high degree of deuterium incorporation were achieved. The procedure was applied for several 4-R-1-aminopyridinium cations (R = H, Me, OMe).

Radical Silyldifluoromethylation of Electron-Deficient Alkenes.

A reaction of bromo- and iododifluoromethyl-substituted silanes with electron-deficient alkenes in the presence of an N-heterocyclic carbene borane complex is described. The reaction is performed under irradiation with light-emitting diodes and proceeds via a radical chain mechanism. The resulting products, the functionalized silicon reagents, can undergo chemoselective transformations involving either the silyldifluoromethyl fragment or the functional group.