Nobumasa Kamigata

Trifluoromethylation of aromatic compounds with bis(trifluoroacetyl) peroxide

Abstract Bis(trifluoroacety) peroxide was found to be thermally stable, and trifluoromenthylation of aromatic compounds was studied using this peroxide. Thrifluoromethylation of electron-rich benzenes, furan, thiophene, or their benzo derivatives proceeded with the peroxide in moderate to high yields.

Recent progress in perfluoroalkylation by radical species with special reference to the use of bis(perfluoroalkanoyl) peroxides

Abstract Radical species play important roles in perfluoroalkylation, so recent advances in perfluoroalkylation with radical intermediates are reviewed from two aspects; one is thermal and photochemical generations of perfluoroalkyl radicals and the other is via electron transfer. Especially, in this article, perfluoroalkylations with bis(perfluoroalkanoyl) peroxides via electron transfer developed in our laboratory are discussed in detail and compared with methods using other reagents. Organofluorine compounds often show unique properties [1], and are widely used as medicines, pesticides, dyes or surfactants. Especially the substitution by perfluoroalkyl group at particular positions of organic compounds may give rise to unique physical or biological properties which cannot be achieved by incorporating other functional groups. However, the methods for the introduction of perfluoroalkyl groups into organic compounds have not yet been well established. Although nucleophilic substitution via cationic intermediates is the most important and common reaction in hydrocarbon chemistry, the generation of perfluoroalkyl cationic intermediates is very difficult due to the strong electronegativity of fluorine [2] (Scheme 1).

Perfluorophenylation of aromatic and heteroaromatic compounds with pentafluorobenzenesulfonyl chloride catalyzed by a ruthenium (II) phosphine complex

Abstract The reactions of pentafluorobenzenesulfonyl chloride with benzene and thiophene derivatives in the presence of a ruthenium(II) catalyst proceeded at 240°C, with extrusion of sulfur dioxide and hydrogen chloride, to give the corresponding perfluorophenylated compounds.

Crystal structures of optically active diastereomeric telluronium and selenonium salts anion—cation interactions in the crystalline state

Abstract The tellurium atom in optically pure diastereomeric ( R )-ethylmethylphenyltelluronium ( 1S )-camphor-10-sulfonate (( R ) Te - 1 ) was found to interact with two oxygen atoms of the counter anions in the crystalline state, while that in the other diastereomeric isomer ( S ) Te - 1 interacts with three oxygen atoms. This difference in interactions is considered to be caused by steric factors (crystal packing) and not to be caused by electronic effects, since the telluronium cations have the same substituents and counter anions. The crystal packing structure of ( R ) Te - 1 showed M -helix geometry through anion—cation interactions, while that of ( S ) Te - 1 showed a 2D-sheet structure. The corresponding optically active selenonium salt ( R ) Se - 2 showed crystal packing similar to that of ( R ) Te - 1 .

REACTIONS OF PERFLUOROALKANE-SULFONYL CHLORIDES WITH SILYL ENOL ETHERS CATALYZED BY A RUTHENIUM(II) PHOSPHINE COMPLEX

Abstract Reactions of trifluoromethane- and tridecafluorohexanesulfonyl chlorides with silyl enol ethers have been investigated in the presence of a ruthenium(II) phosphine complex. Perfluoroalkylation and chlorination occurred depending on the substituent of silyl enol ether; i.e. perfluoroalkylated compound was selectively obtained in the reactions with silyl enol ether possessing an electron-withdrawing group, on the other hand, chlorinated compounds selectively formed in the reaction with a silyl enol ether possessing electron-donating group.

ISOLATION AND STEREOCHEMISTRY OF OPTICALLY ACTIVE SELENONIUM IMIDES

Optical resolution of racemic diaryl selenonium-N-toluene-4‘-sulfonimides (rac-1a−d) by liquid chromatography using an optically active column yielded optically pure selenonium imides. The absolute configuration around the selenium atom of (−)-2,4,6-tri-tert-butyldiphenylselenonium N-toluene-4‘-sulfonimide [(−)-1a] was determined to be S by X-ray crystallographic analysis, and those of the other optically active selenonium imides were determined on the basis of their specific rotations and CD spectra. The kinetics of racemization by pyramidal inversion of the optically active selenonium imides (+)- and (−)-1b and 1d were studied. The results indicated that the activation energy for the racemization of optically active selenonium imides was greater than those for sulfonium imides.

Synthesis and absolute configuration of optically active selenoxides. X-Ray molecular structure of (–)se-4-menthyloxycarbonylphenyl 2,4,6-tri-isopropylphenyl selenoxide

Enantiomerically pure, stable 4-(methoxycarbonyl)phenyl 2,4,6-tri-isopropylphenyl selenoxide (–)-(3) was isolated by fractional recrystallization of diastereoisomeric 4-[(–)-menthyloxycarbonyl]phenyl 2,4,6-tri-isopropylphenyl selenoxide dia.-(1) followed by removal of the chiral source. The absolute configuration around the selenium atom was determined by X-ray crystallographic analysis of diastereomerically pure selenoxide (–)Se-(1).

Synthesis and stereochemistry of an optically active selenonium ylide. X-Ray molecular structure of (+)Se-{4′-[(–)-menthyloxycarbonyl]phenyl}(methyl)-selenonium 4,4-dimethyl-2,6-dioxocyclohexylide

Fractional recrystallization of diastereoisomeric {4′-[(–)-menthyloxycarbonyl]phenyl}(methyl)-selenonium 4,4-dimethyl-2,6-dioxocyclohexylide from hexane–diethyl ether gave the optically pure (+)-selenonium ylide as stable crystals. The absolute configuration around the selenium atom was determined to be R by X-ray crystallographic analysis. The epimerization of the optically active selenonium ylide by pyramidal inversion was studied.

Novel perfluoroalkylation of alkenes with perfluoroalkanesulphonyl chlorides catalysed by a ruthenium(II) complex

The perfluoroalkylation of acyclic and cyclic alkenes by perfluoroalkanesulphonyl chlorides 1 has been investigated in the presence of a ruthenium(II) catalyst. The addition reactions proceeded smoothly, with extrusion of sulphur dioxide, in alkenes possessing either an electron-donating or an electron-withdrawing group, at 120 °C to give the corresponding chloroperfluoroalkylated compounds in high yield.

ADDITION OF SULFONYL CHLORIDES TO OLEFINS IN THE PRESENCE OF CATALYTIC AMOUNTS OF DICHLOROTRIS-(TRIPHENYLPHOSPHINE)RUTHENIUM(II)

Abstract Reactions of sulfonyl chlorides with olefins catalyzed by dichlorotris(triphenylphosphine)ruthenium(II) have been studied. Methanesulfonyl and arenesulfonyl chlorides added to 1-alkenes to give 1:1 adducts in high yields. Telomer formation is not observed, therefore the present reaction provides a general and convenient method for synthesis of β-chlorosulfones. A radical-chain mechanism is proposed for the reaction.