Kikuhiko Koyama

Free radical reactions in organic electrode processes—IV : Anodic oxidation of cyanide ions in the presence of aromatic hydrocarbons

Abstract Anodix oxidation of sodium cyanide in methanol has been carried out at a Pt anode in the presence of 1,2,3,4-tetrahydronaphthalene, naphthalene or anthracene. 1,2,3,4-Tetrahydronaphthalene added as organic substrate afforded 6-cyano-1,2,3,4-tetrahydronaphthalene and 1-methoxy-1,2,3,4-tetrahydronaphthalene. In the electrolysis between a Pt anode and a Hg-pool cathode in the presence of naphthalene and anthracene, yielded 1-cyanonaphthalene and 9-cyanoanthracene, respectively. The possible pathways are discussed.

Free radical reactions in organic electrode processes—III : The reaction of aromatic hydrocarbons at platinum anode in acetonitrile solutions containing perchlorate supporting electrolytes☆☆☆

Abstract The electrolysis of certain perchlorates in acetonitrile solutions has been carried out both in the absence and presence of aromatic hydrocarbons, such as toluene and cumene. The products formed indicate that the reactions involve oxidation of the hydrocarbons by perchlorate ions (or radicals). Oxygen-free coupling products of the hydrocarbons were detected, but the extent of these reactions is generally small. Possible reaction paths for the formation of these products are discussed.

Cyclisation of 2-azidodiphenylmethane and 2-azidobiphenyls by regiospecific N-attack of arylnitrenium–aluminium chloride complexes

Decomposition of 2-azidodiphenylmethane and 2-azidobiphenyls in CH2Cl2 in the presence of AlCl3 gave 9,10-dihydroacridine and carbazoles, respectively, in reasonable yields by regiospecific N-attack of an arylnitrenium–AlCl3 complex.

Thermolysis and photolysis of 1-anilino-2-methyl-4,6-diphenylpyridinium tetrafluoroborate in arene–trifluoroacetic acid mixtures: a novel route to singlet and triplet phenylnitrenium ions

Thermolysis of 1-anilino-2-methyl-4,6-diphenylpyridinium tetrafluoroborate (1) in trifluoroacetic acidbenzene or–toluene yielded 2-methyl-4,6-diphenylpyridine (2) and the N-substitution products 2-(2-anilinophenyl)-6-methyl-4-phenyl pyridine (3) and diphenylamine (4a)[or 2- and 4-methyldiphenylamine (4b) and (5b)], via a singlet phenylnitrenium ion formed in the unimolecular decomposition of the salt (1). The mechanism was inferred from the kinetics of decomposition of the salt (1), the o-/p-direction in the formation of (4b) and (5b), the large partial rate factors for ortho- and para-substitution of toluene, and analysis of the products of the reaction of (1) with diethyl sulphide. The preferred production of the 2-anilinophenyl derivative (3) rather than the corresponding 4-anilinophenyl compounds, and the relative formation rates of (2) and (3) suggest that the product (3) is formed by an intimate contact reaction between pyridine and phenylnitrenium ion formed initially; the results give relative reactivities of the nitrenium ion with benzene, toluene, naphthalene, and dimethyl sulphide. Photolysis of the salt (1), however, gave the pyridine (2), aniline (9), and hydrogen abstraction products [biphenyl (10) or the bitolyls (11)]via a triplet phenylnitrenium ion, without contamination by compounds (3)–(5). The triplet mechanism was proved by observation of inter- and intra-molecular heavy atom effects.

Reactions of β-azidostyrenes with halogenoacetic acid. A novel formation of oxazoles

The reaction of β-azidostyrene with trifluoro-, trichloro-, dichloro-, or monochloro-acetic acid gave 2-halogenomethyl-5-phenyloxazole via attack of halogenoacetate anion on a benzylic carbocation or a conjugate acid of the azide.

A novel ring-opening reaction of an aziridinium-AlCl3 complex. Reaction of phenyl azide with alkenes in the presence of AlCl3

Reaction of phenyl azide with alkenes in the presence of AlCl3 gives an aziridinium–AlCl3 complex viaan azide–AlCl3 complex; this reaction is followed by ring-opening reactions of the aziridinium–AlCl3 complex to give N-allylanilines and/or N-phenyl-β-chloroamines after work-up with aqueous Na2CO3, but the reaction with cis-cyclo-octene yields a novel aziridine, 9-phenyl-9-azabicyclo[6.1.0]nonane after the work-up.

Reaction of phenylnitrenium ion with sulphides. A novel synthetic method for aminophenyl sulphide derivatives

The reaction of phenyl azide with sulphides in the presence of both trifluoroacetic acid and trifluoromethanesulphonic acid to produce 2- and 4-aminophenyl sulphides (2) and (3) was investigated in order to obtain information on the following points: the kinetics of decomposition of phenyl azide, the effect of addition of benzene to reaction systems, the replacement of phenyl azide by 1-phenyl-2-methyl-4,6-diphenylpyridinium salt, and the steric and electronic effect of substituents in the sulphides. The products are formed through an azasulphonium ion by reaction of phenylnitrenium ion with sulphide, followed by rearrangement of the alkyl group in the azasulphonium ion. Sulphides with primary alkyl groups larger than propyl result in selective formation of ortho-products (2), the mechanism of which is discussed in detail.

Synthesis of cyclopropane derivatives from electron-deficient olefins and dichloromethane via copper(I) catalysed photochemical addition followed by an electroreductive dehalogenation reaction

The CuCl-catalysed photochemical reaction of electron-deficient olefins with dichloromethane gave 1,3-dichloro compounds, which then afforded cyclopropane derivatives by electrochemical reduction.

Photolysis and thermolysis of phenyl azide in acetic acid. Trapping of 1-azacyclohepta-1,2,4,6-tetraene and nucleophilic aromatic substitution

Photolysis and thermolysis of phenyl azide in acetic acid yielded 1H-azepin-2(3H)-one (4), 2-methylbenzoxazole (15), 2- and 4-acetamidophenyl acetates (16) and (12), 2- and 4-acetamidophenols (14) and (13), acetanilide, and azobenzene. Addition of ethanol to the system caused a linear decrease in the yield of (4) and a more remarkable decrease in total yield for the para-products than that for the ortho-products to give 2- and 4-acetamidophenyl ethyl ethers (9) and (8). Photolysis of the azide in ethanol in the presence of phenol afforded 2-phenoxy-3H-azepine (5) and aniline, but no 2- and 4-phenetidines. The yield of compounds (4) and (12)–(16) was independent of the presence of penta-1,3-diene (0.01 M), and somewhat decreased by an addition of bromobenzene. The rate of decomposition of azide in acetic acid was not accelerated as compared with that in 1,4-dioxan, and the activation parameters varied little in the two solvents. The results suggest that 1-azacyclohepta-1,2,4,6-tetraene (1) formed via singles phenylnitrene or via singles excited phenyl azide is trapped by acetic acid or phenol to give (4) or (5), and that a resonance-stabilized ion (3) neighbouring acetate anion is formed by an attack of the singlet nitrene on acetic acid to give aromatic nucleophilic substitution.

Aromatic N-substitution by phenylnitrenium ion. Reaction of phenyl azide with aromatics in the presence of trifluoroacetic acid

Reaction of phenyl azide with aromatics in the presence of trifluroacetic acid gave diarylamines by an electrophilic N-substitution of the phenylnnitrenium ion onto aromatics.