Teijiro Kitao

The contribution of singlet oxygen to the photofading of triphenylmethane and related dyes

Abstract The contribution of singlet oxygen (1ΔgO2) to the photofading of Crystal Violet in some solvents is examined. The rates of photofading in dichloromethane or acetone are accelerated in the presence of singlet oxygen sensitizers, e.g. Methylene Blue. The rates are retarded by adding effective singlet oxygen quenchers such as β-carotene or nickel dimethyldithiocarbamate. It seem shtat Crystal Violet is mainly photooxidized to give Michlers ketone and p-dimethylaminophenol via the reaction with singlet oxygen, which can be generated by the dye itself or by an added sensitizer. The effect of various singlet oxygen quenchers on the photostability of coloured materials derived from colour formers, such as Crystal Violet Lactone and 3-diethylamino-6-methyl-7-anilinofluoran, is examined also on silica gel.

Model pathways for enzymatic oxidate demethylation—I : The mechanism of the reaction of dimethyl sulphoxide with acetic anhydride

Abstract The reaction of sulphoxides with at least one methyl or methylene group with carboxylic acid anhydride, called the Pummerer reaction, gives α-acyloxy derivatives of the corresponding sulphide. The mechanism of this reaction was studied by oxygen-18 tracer technique. The reaction between dimethyl sulphoxide and acetic anhydride appears to proceed through an intermolecular rearrangement by nucleophilic attack of acetate anion on methylene carbon atom of the intermediate II. The implications of this reaction and the enzymatic oxidative demethylation are considered in connection with a previous investigation with t-amine N-oxides.

Syntheses and some properties of infrared-absorbing croconium and related dyes

Abstract The correlations between the structure and some properties of croconium and related cyanine dyes are discussed. It is shown by PPP MO calculations that the croconium dyes have the same chromophoric system as cyanines. The λ max of the croconium dyes undergoes a bathochromic shift of about 120 nm compared with the corresponding cyanine dyes. This shift can be calculated by the PPP MO method. Negative solvatochromism is observed for croconium dyes. Croconium dyes generally have better solubility than squarylium dyes in organic solvents and have good lightfastness in solvents, greatly improved by adding nickel complex as a stabilizer.

The mechanisms of the reactions of p-toluenesulfonyl chloride with isoquinoline- and pyridine n-oxides☆

Abstract The mechanisms of the reactions of isoquinoline- and pyridine N-oxides have been studied using oxygen-18 as a tracer. p-Toluenesulfonyl chloride labeled with 18O was reacted with isoquinoline N-oxide, yielding 4-tosyloxyisoquinoline, a portion of which was further hydrolyzed yielding 4-hydroxyisoquinoline. The analytical results suggest that the main path of this reaction proceeds via “intimate ion pair” as depicted by VI. In the reaction of pyridine N-oxide with p-toluenesulfonyl chloride, 18O tracer study suggests that a similar rearrangement via “intimate ion pair” as VI takes place with the formation of 3-tosyloxypyridine.

Novel syntheses of anthraquinonoid near-infrared absorbing dyes

Abstract New series ofanthraquinonoid near-infrared absorbing dyes (hereinafter referred to as infrared dyes) for optical recording media were synthesised by the ring-closure reaction between 2,3-dibromoquinizarins and potassium 2-aminobenzenethiolate. These dyes absorb near-infrared light at 700–810 nm. It was found that substitution of electron-accepting groups, such as tetrahalogeno or the dicarboximide residue, on the quinizarin residue produces a large bathochromic shift of 40–100 nm, and that of the electron-donating alkoxy group at the 5-position of the thiol also produces a bathochromic shift of 25–40 nm.

Synthesis of benzofuran-2-one derivatives by copper(I)-promoted coupling reactions of o-bromophenol with active methylene compounds

Abstract Treatment of o-bromophenoxide anion with sodium salts of active methylene compounds in the presence of copper(I) bromide in dioxane afforded benzofuran-2-one derivatives. The phenoxide group of o- and p-bromophenol activates the coupling reaction.

Oxidation of N21,N22-etheno-bridged 5H-phlorins to the monocationic N21, N22-etheno-bridged 5-alkylporphyrins by Cu(Bf4)2.

Abstract Whereas N 21 ,N 22 -(1,2-diphenyletheno)-octaethyl-5H-phlorin was air-oxidized to the corresponding porphyrin with loss of the 5-exo hydrogen exclusively, the 5-endo hydrogen was lost by the oxidation of the 5-exoalkyl-5H-phlorin derivatives with Cu(BF 4 )2 to give the corresponding 5-alkylporphyrins as monoprotonated forms which could be deprotonated from the 5-meso methylene affording 5-(exomethylene)phlorins.

Photostabilisation of colorants for imaging and data recording systems : effect of metal carboxylates on the lightfastness of colour formers

Abstract Metal complexes of hydroxycarboxylic acids or dicarboxylic acids were prepared and the protecting effect of these compounds towards the photofading of colour materials derived from colour formers was examined on cellulose. It is proposed that nickel or zinc salts of 1-hydroxy-2-naphthoic acid and its derivatives can be applied as effective stabilisers against the photofading of indicator dyes in pressure- (or heat-)sensitive recording systems. These metal carboxylates were also found to improve the image stability of the indicator dyes.

Syntheses and characteristics of infrared absorbing 2:1 nickel complex dyes

Abstract Some 2:1 nickel complex infrared absorbing dyes were synthesized by the reaction of phenylenediamines, 2-aminobenzenethiols and 2-aminobenzene-selenols with nickel(II) chloride. These dyes generally absorbed infrared light over 860 nm, but those from phenylenediamines absorbed at 780–800 nm, which is the most favorable wavelength region for semiconductor laser optical recording dye medium. Introduction of alkyi and/or amino groups into the parent dye greatly improved the solubility in organic solvent and these dyes could be applied by the wet coating method to prepare dye medium.

Reaction of 5-Amino-2,3-dicyano-1,4-naphthoquinone with Arylamines

Abstract The reaction of 5-amino-2,3-dicyano-1,4-naphthoquinone (1) with arylamines gave 5-amino-8-arylamino- (2), 5,8-bis(arylamino)- (3), and 5-hydroxy-8-arylamino-2,3-dicyano-1,4-naphthoquinone (4) together with 5-amino-2-arylamino-3-cyano- (5) and 5-amino-2-cyano-3-aryl-amino-1,4-naphthoquinone (6). It is proposed that the initial quinone-quinoneimine tautomerism of 1 to 4-hydroxy-2,3-dicyano-5-imino-1,5-naphthoquinone 7 facilitates the 8-arylamination. Some derivatives of 2 have good properties as dyes for optical information-recording media for semiconductor lasers.