Ryutaro Hayashi

The Stabilized Cation Pool Method: Metal- and Oxidant-Free Benzylic C-H/Aromatic C-H Cross-Coupling.

Electrochemical oxidation of toluene derivatives in the presence of a sulfilimine gave benzylaminosulfonium ions as stabilized benzyl cation pools, which reacted with subsequently added aromatic nucleophiles to give the corresponding cross-coupling products. The transformation serves as a powerful metal- and chemical-oxidant-free method for benzylic C-H/aromatic C-H cross-coupling. The method has been successfully applied to synthesis of TP27, an inhibitor of PTPase.

Automated Solution-Phase Synthesis of Oligosaccharides via Iterative Electrochemical Assembly of Thioglycosides

A new iterative one-pot sequential method for the solution-phase synthesis of oligosaccharides has been devised on the basis of the electrochemical oxidation of a propagating thioglycoside terminus to generate the corresponding triflate, followed by the reaction with a thioglycoside building block having a free hydroxyl group. A practical automated synthesizer was developed for the method and was effectively used for assembling up to six thioglycoside building blocks to synthesize partial structures of poly-β-D-(1-6)-N-acetylglucosamine.

Metal-Free Benzylic C-H Amination via Electrochemically Generated Benzylaminosulfonium Ions

Electrochemical oxidation of toluene derivatives in the presence of N-tosyldiphenylsulfilimine gave the corresponding benzylaminosulfonium ions, which were treated with tetrabutylammonium iodide under non-electrolytic conditions to give N-tosylbenzylamines. The transformation serves as a metal- and chemical-oxidant-free method for benzylic C-H amination. Because of high oxidation potential of N-tosyldiphenylsulfilimine the present method can be applied to synthesis of various benzylamines from functionalized toluene derivatives.

Automated Electrochemical Assembly of the Protected Potential TMG-chitotriomycin Precursor Based on Rational Optimization of the Carbohydrate Building Block

The anomeric arylthio group and the hydroxyl-protecting groups of thioglycosides were optimized to construct carbohydrate building blocks for automated electrochemical solution-phase synthesis of oligoglucosamines having 1,4-β-glycosidic linkages. The optimization study included density functional theory calculations, measurements of the oxidation potentials, and the trial synthesis of the chitotriose trisaccharide. The automated synthesis of the protected potential N,N,N-trimethyl-d-glucosaminylchitotriomycin precursor was accomplished by using the optimized building block.

Switching the reaction pathways of electrochemically generated β-haloalkoxysulfonium ions – synthesis of halohydrins and epoxides

Summary β-Haloalkoxysulfonium ions generated by the reaction of electrogenerated Br+ and I+ ions stabilized by dimethyl sulfoxide (DMSO) reacted with sodium hydroxide and sodium methoxide to give the corresponding halohydrins and epoxides, respectively, whereas the treatment with triethylamine gave α-halocarbonyl compounds.

Generation and reactions of thiirenium ions by the cation pool method

Thiirenium ions generated and accumulated by low-temperature electrochemical oxidation of disulfides in the presence of alkynes were successfully observed by low-temperature NMR, Raman, and mass spectroscopies and were found to be stable at temperatures below −40 °C. The thiirenium ions showed ambident reactivity toward subsequently added nucleophiles to give either disubstituted alkenes or alkynes depending on the nature of the nucleophiles. PhSSPh anodic oxidation PhS Nu