Ikuzo Nishiguchi

Facile synthesis of S-alkyl thiocarbamates through reaction of carbamoyl lithium with elemental sulfur

Abstract Efficient synthesis of S-alkyl thiocarbamates was developed. The key step of this synthetic method is a conversion of carbamoyl lithium, generated from lithium dialkylamide and carbon monoxide, to lithium thiocarbamate by addition of elemental sulfur.

Novel synthesis of S-alkyl thiocarbamates from amines, carbon monoxide, elemental sulfur, and alkyl halides in the presence of a selenium catalyst

Abstract Carbonyl selenide easily reacted with elemental sulfur at low temperature to form carbonyl sulfide in a good yield, and reaction of ammonium salts of selenocarbamates with elemental sulfur brought about ready transformation to those of thiocarbamates. On the basis of the high catalytic activity of selenium for carbonylation of amines with carbon monoxide in addition to these important findings, a convenient new method for synthesis of S-alkyl thiocarbamates was developed through the carbonylation of amines with carbon monoxide and elemental sulfur in the presence of a selenium catalyst under mild conditions followed by alkylation of ammonium salts of the thiocarbamates with alkyl halides.

Selective and one-pot formation of phenols by anodic oxidation☆

Abstract Direct monohydroxylation of benzene and substituted benzenes was successfully performed by anodic oxidation to form the corresponding phenol derivatives in good yields. The anodic oxidation was generally carried out in a mixed solvent of trifluoroacetic acid and dichloromethane containing triethylamine using a divided cell equipped with a platinum plate as the anode, a carbon rod as the cathode. Benzene derivatives having electron withdrawing groups were suitable for the present electrochemical oxidation. It was clarified that aryltrifluoroacetates were formed as the initial products from the reaction of the radical cations, generated by one electron transfer from the substrates, with trifluoroacetic acid, followed by hydrolysis during work-up to give the corresponding phenols.

CARBON-CARBON BOND FORMATION USING MANGANESE(III) ACETATE AS AN ELECTROCHEMICAL MEDIATOR

Abstract Anodic oxidation in a solution containing a variety of olefins and a small amount of Mn(OAc)2·4H2O brought about Mn+3-mediated carbon—carbon bond formation, such as efficient carboxymethylation of styrene derivatives to the corresponding γ-aryl-γ-butyrolactones, and selective coupling of active methylene compounds with non-activated monoolefins, unconjugated dienes or 5-arylpent-1-enes.

Electroreductive silylation of activated olefins using a reactive metal anode

Abstract Electroreductive acylation of 3-aryl substituted α,β-unsaturated esters and nitriles in the presence of aliphatic carboxylic anhydrides using areactive metal anode (Mg, Al, Zn) in an undivided cell afforded the corresponding β-acyl compounds in moderate to good yields. It was found that anionic species formed by electron transfer from a cathode may be stabilized by metal ions freshly formed from an anode and undergo electrophilic attack of carboxylic anhydrides to give the β-acyl products in high yields as compared with the previously reported method using a divided cell.

Sulfur-assisted O-carbonylation of alcohols with carbon monoxide in the presence of dbu

Abstract The first example of sulfur-assisted O-carbonylation is described. Alcohols react with carbon monoxide, elemental sulfur, and alkyl halides in the presence of DBU to give S-alkyl carbonothioates selectively in good to excellent yields.

Highly selective and facile synthesis of dihydro- and tetrahydropyridine dicarboxylic acid derivatives using electroreduction as a key step

Abstract Electroreduction of pyridinedicarboxylic acid derivatives 1a – g in methanol containing ammonium chloride using a divided cell brought about highly selective hydrogenation to give the corresponding dihydropyridines in good yields. From the electrolysis of dimethyl 2,3- and 2,5-pyridinedicarboxylates 1a , c , only the corresponding 1,2-dihydropyridine derivatives 2a , c were obtained in a regioselective manner while that of 2,4-, 2,6-, and 3,4- disubstituted pyridines 1b , d , e afforded the corresponding 1,4-dihydropyridines 2b , d , e selectively in good yields. Further hydrogenation of the resultant dihydropyridines by several methods led to the selective and facile formation of the corresponding tetrahydropyridines 6 . Furthermore, Mg-promoted hydrosilylation of the N-acetylated product 5a gave C-silylated tetrahydropyridines in a stereoselective manner.

Reactions of unstable dialkylcarbamoyl lithiums with sulfur compounds

Abstract Unstable dialkylcarbamoyl lithiums, generated from the reaction of lithium dialkylamides with carbon monoxide, were successfully trapped by sulfur compounds (elemental sulfur, disulfides, carbon disulfide, and carbonyl sulfide) at low temperature, through their potent affinity with a sulfur atom. These efficient reactions were also applied to development of a facile synthetic method for thiocarbamates, useful herbicides, and thiooxamates.

Facile synthesis of silyl enol ethers by Mg-promoted coupling of aliphatic carbonyl compounds with trimethylsilyl chloride

Abstract Treatment of aliphatic carbonyl compounds with trimethylsilyl chloride with Mg turning for Grignard reaction without any pre-treatment in N,N-dimethylformamide at room temperature brought about highly facile, effective and stereoselective coupling to give the corresponding silyl enol ethers in good yields.

Electroreductive acylation of activated olefins using a reactive metal anode

Abstract Electroreductive acylation of 3-aryl substituted α,β-unsaturated esters and nitriles in the presence of aliphatic carboxylic anhydrides using areactive metal anode (Mg, Al, Zn) in an undivided cell afforded the corresponding β-acyl compounds in moderate to good yields. It was found that anionic species formed by electron transfer from a cathode may be stabilized by metal ions freshly formed from an anode and undergo electrophilic attack of carboxylic anhydrides to give the β-acyl products in high yields as compared with the previously reported method using a divided cell.