Yasuo Gama

An effective synthesis of N-substituted 2-sulfenamoylbenzoates and 1,2-benzisothiazolin-3-ones that uses 1,2-benzisothiazolin-3-one as a leaving group

N-Substituted 2-sulfenamoylbenzoates and 1,2-benzisothiazolin-3-ones were effectively synthesized by the substitution reaction between S-[2-(3-oxo-1,2-benzisothiazolinyl)]-2-mercaptobenzoates (2) and primary amines. The substitution reaction occurred on the sulfur atom of the 2-sulfenamoyl group of 2, and 1,2-benzisothiazolin-3-one behaved as a leaving group. The eliminated 1,2-benzisothiazolin-3-one could be reused as a starting material for the synthesis of 2. N,N-Disubstituted 2-sulfenamoylbenzoates were prepared by the reaction of 2 with secondary amines.

Silver ion-mediated desulfurization-condensation of thiocarbonyl compounds

The title reaction of N-hydroxybenzamide with aryl isothiocyanates at ambient temperature gave 5-(arylimino)-3-phenyl-1,4,2-dioxazoles (1, 2) with elimination of Ag 2 S. The structure of 1 was determined by X-Ray crystal structure analysis. N-Hydroxybenzamide also reacted with diary thioketones to afford condensation products, 5,5-diaryl-3-phenyl-1,4,2-dioxazdes( 3, 4). Desulfurizations of diaryl thioketones with α-hydroxy adds and with salicylic add gave in the same way 2,2-diaryl-5-phenyl-1,3-dioxolan-4-ones (5-8) and 2,2-diaryl-1,3-benzodioxan-4-ones (9-11), respectively. N-Phenylglycine and N-methylanthranilic add gave similar types of condensation products (12, 13).

Synthesis Of Glucosylamino Heterocycles By Desulfurization-Condensation Of Glucosyl Isothiocyanates With Jv-Substituted Amino Acids

Abstract Desulfurisation-condensation of glucosyl isothiocyanates with various N-substituted amino acids in the presence of silver trifluoroacetate and triethylamine gave glucosylamino heterocycles in good yields.

SYNTHESIS OF 6-SUBSTITUTED 5-AZAURIDINES AND THEIR PYRANOSE-TYPE NUCLEOSIDES BY CYCLODESULFURIZATION OF GLYCOSYL THIOUREAS

Cyclodesulfurization of N,N,N′-trisubstituted glycosyl thioureas with silver cyanate in acetonitrile for 5 h at 50 °C gave 1-glycosyl 5-azauracil derivatives as nucleoside analogues in good yields. The structures were determined by spectroscopic and X-Ray analyses and the reaction mechanism is discussed.

Silver Ion Mediated Desulfurization-Condensation of Glucosyl Isothiocyanate With Hydroxy Acids

ABSTRACT Desulfurization-condensation of 2,3,4,6-tetra-O-acetyl-β-D-glucopyranosyl isothiocyanate with α-hydroxy acids and salicylic acid in the presence of silver trifluoroacetate and triethylamine gave glucosylamino heterocycles in good yields, while the reaction with β-hydroxy acids afforded N-glucosyl olefinic amides with the evolution of carbon dioxide.

Silver Ion-mediated Desulfurization of N,N-Disubstituted 2-Hydroxythiobenzamides

Silver ion-mediated desulfurization of N-(2-hydroxythiobenzoyl)morpholine (1a) or -piperidine (1b) was used to develop a new synthetic method for heterocycles such as 1,3-benzoxazin-1-ium salts. 2-Amino-4-morpholino- and 2-amino-4-piperidino-1,3-benzoxazin-1-ium perchlorate (2a, 2b) or 2-(N,N-dimethylamino)-4-morpholino- and 2-(N,N-dimethylamino)-4-piperidino-1,3-benzoxazin-1-ium perchlorate (3a, 3b) were obtained by treatment of 1a and 1b, respectively, with silver perchlorate in the presence of excess cyanamide or N,N-dimethylcyanamide, and the structure of 3a was confirmed by X-Ray crystallography. Desulfurization of 1 with AgOCN afforded 1,3-benzoxazin-2-ones (4). In addition, treatment of 1 with methyl cyanoacetate in the presence of silver trifluoroacetate and triethylamine gave 3-cyanochromen-2-ones (5).

Silver ion-mediated desulfurization of N, N-disubstituted dithiocarbamate derivatives

Silver ion-mediated desulfurization of N-aroyl-S- (disubstituted thiocarbamoyl) -thio-hydroxylamines (1) and disubstituted dithiocarbamic acid phenacyl esters (4) in aqueous solution gives the corresponding their carbamoyl derivatives. On the other hand, the reaction of 4 in acetic acid leads to formation of 2- (N, N-disubstituted amino) -5-phenyl-1, 3-oxathiolium salts in one pot.

A Practical Synthesis of N-Substituted 1,2-Benzisothiazolin-3-ones from N,N′-Disubstituted 2,2′-Dithiodibenzamides

A variety of N-substituted l,2-benzisothiazolin-3-ones were easily synthesized from N,N-disubstituted 2,2-dithiodibenzamides in the presence of O-methylhydroxylamine hydrochloride. Derivatives with a primary, secondary,or tertiary alkyl group or an aryl group on the N-1 nitrogen of the l,2-benzisothiazolin-3-one were obtained.

New and Efficient Glycosylation of Glucosylsulfoxide under High Pressure

Glycosylation reactions of methyl 2, 3, 4, 6-tetra-O-benzyl-D-glucopyranosylsulfoxide with various alcohols under high pressure in toluene using O-mesityrenesulfonylhydroxylamine as the activator gave the corresponding glucosides each in good yield and selectivity.