Reactivity of <i>N</i>-(1,2,4-Triazolyl)-Substituted 1,2,3-Triazoles

Synthetically useful rhodium(II) carbenes were obtained from N-(1,2,4-triazolyl)-substituted 1,2,3-triazoles and Rh(II) carboxylates. The electron-withdrawing 1,2,4-triazolyl group reveals the heretofore unknown reactivity of nonsulfonyl 1,2,3-triazoles, which exhibit the reactivity of diazo compounds. The resulting carbenes provide ready asymmetric access to secondary homoaminocyclopropanes (80–95% ee, dr >20:1) via reactions with olefins and also engage in efficient transannulation reactions with nitriles

Efficient Synthesis of 1-Sulfonyl-1,2,3-triazoles

An efficient room-temperature method for the synthesis of 1-sulfonyl-1,2,3-triazoles from in situ generated copper(I) acetylides and sulfonyl azides is described. The copper(I) thiophene-2-carboxylate (CuTC) catalyst produces the title compounds under both nonbasic anhydrous and aqueous conditions in good yields

Enhanced Reactivity of Dinuclear Copper(I) Acetylides in Dipolar Cycloadditions

Dinuclear alkynyl copper(I) complexes exhibit superior reactivity toward organic azides compared to their monomeric analogues. DFT studies indicate that the second copper center facilitates the formation of the cupracycle in the rate-determining step and stabilizes the metallacycle intermediate itself. These findings support the experimentally determined rate law and shed light on the origin of high reactivity of the in situ generated copper acetylides

Reactivity of <i>N</i>-(1,2,4-Triazolyl)-Substituted 1,2,3-Triazoles

Synthetically useful rhodium(II) carbenes were obtained from N-(1,2,4-triazolyl)-substituted 1,2,3-triazoles and Rh(II) carboxylates. The electron-withdrawing 1,2,4-triazolyl group reveals the heretofore unknown reactivity of nonsulfonyl 1,2,3-triazoles, which exhibit the reactivity of diazo compounds. The resulting carbenes provide ready asymmetric access to secondary homoaminocyclopropanes (80–95% ee, dr >20:1) via reactions with olefins and also engage in efficient transannulation reactions with nitriles

Dual Electrospray Ionization Enhancement of Proteins Enabled by DMSO Supercharging Reagent

Supercharging reagents assist protein ionization by producing higher charge states and increasing signal intensities, thus improving sensitivity. Described here is an approach to employ a dual-spray ionization source with DMSO as a supercharging reagent to expand in-source supercharging. Under denaturing conditions, dual-source supercharging enhances ionization up to an order of magnitude for proteins of various properties and sizes, but the effect is not uniform. Efficient mixing of solutions from two nebulizing plumes was observed, which allowed sufficient transfer of supercharging molecules to a protein. The described method and proposed mechanism require at least 2.5% of DMSO to produce visible enhancement

Synthesis and Reactivity of Sulfamoyl Azides and 1-Sulfamoyl-1,2,3-triazoles

Sulfamoyl azides are readily generated from secondary amines and a novel sulfonyl azide transfer agent, 2,3-dimethyl-1H-imidazolium triflate. They react with alkynes in the presence of a CuTC catalyst forming 1-sulfamoyl-1,2,3-triazoles. The latter are shelf-stable progenitors of rhodium azavinyl carbenes, versatile reactive intermediates that, among other reactions, readily and asymmetrically add to olefins

On-Water Selectivity Switch in Microdroplets in the 1,2,3-Triazole Synthesis from Bromoethenesulfonyl Fluoride

Water profoundly affects many organic reactions by accelerating them or changing their selectivity. Performing reactions “on-water” offers an intriguing opportunity to influence chemical reactivity. A nebulizer plume is an efficient way of generating microdropletsthe uniquely complex reaction environment which opens alternative possibilities that are not readily accessible in bulk emulsions. We describe the on-water switch of chemoselectivity in the formation of triazoles controlled by the on-water environment in dual spray. These conditions facilitate elimination of H–SO2F from the triazoline intermediate, whereas the reaction in organic solvents results in the exclusive HBr elimination. The influence of two-phase conditions was investigated to obtain the best reaction efficiency, and the crucial importance of the water/organic interface interactions was verified by pH variation and D2O use

Rhodium(II)-Catalyzed Asymmetric Sulfur(VI) Reduction of Diazo Sulfonylamidines

Diazo sulfonylamidines readily undergo enantioselective oxygen transfer from sulfur to carbon atom in the presence of chiral rhodium­(II) carboxylates resulting in chiral sulfinylamidines. This unusual asymmetric atom transfer “reduction” occurs rapidly under mild conditions, and sulfinylamidines are obtained in excellent yield

Regioselective Synthesis of Fluorosulfonyl 1,2,3-Triazoles from Bromovinylsulfonyl Fluoride

A regioselective metal-free preparation of 4-fluorosulfonyl 1,2,3-triazoles from organic azides and a hitherto underexplored bromovinylsulfonyl fluoride building block is described. This reaction is very general and was extended to the synthesis of various sulfonates, sulfonamides, and sulfonic acid derivatives of triazoles and other azole heterocycles which would otherwise be difficult to access by existing methods

On-Water Selectivity Switch in Microdroplets in the 1,2,3-Triazole Synthesis from Bromoethenesulfonyl Fluoride

Water profoundly affects many organic reactions by accelerating them or changing their selectivity. Performing reactions “on-water” offers an intriguing opportunity to influence chemical reactivity. A nebulizer plume is an efficient way of generating microdropletsthe uniquely complex reaction environment which opens alternative possibilities that are not readily accessible in bulk emulsions. We describe the on-water switch of chemoselectivity in the formation of triazoles controlled by the on-water environment in dual spray. These conditions facilitate elimination of H–SO2F from the triazoline intermediate, whereas the reaction in organic solvents results in the exclusive HBr elimination. The influence of two-phase conditions was investigated to obtain the best reaction efficiency, and the crucial importance of the water/organic interface interactions was verified by pH variation and D2O use