Motomu Muraoka

Reactions of β-imino-nitriles and -esters with carbon disulphide. A new synthesis and some reactions of 2-cyano-3-imino-dithiocarboxylic acids

Treatment of a series of β-imino-nitriles with carbon disulphide and sodium t-pentyl oxide at room temperature gave the corresponding 2-cyano-3-imino-dithiocarboxylic acids, accompanied in some cases by pyrimidine-2,4-dithiones. β-lmino-β-arylpropiononitriles, when treated with carbon disulphide in dimethylformamide at low temperature, afforded 1,3-thiazine-2,6-dithiones. When an excess of sodium t-pentyl oxide was used in this reaction, β-iminobutyronitrile yielded pyrido[4,3-d][1,3]thiazine-2,4,5,7(1H,8H)-tetrathione. β-lmino-β-phenylpropiononitrile, under the same conditions, gave a 1,5-diazocine-2,6(1H,5H)-dithione. β-lmino-esters in this reaction, afforded 1,3-thiazine-2,6-dithiones. Reactions of 2-cyano-3-imino-dithiocarboxylic acids with methyl and phenyl isocyanates, ethyl and phenyl isothiocyanates, picryl chloride, and hydrazine have also been studied.

Synthesis of β-imino-sulphones. Reaction of the β-imino-sulphones with carbon disulphide

A series of β-imino-sulphones were synthesised by the reaction of alkyl- and aryl-sulphonyl carbanions with nitriles. The β-imino-sulphones, on treatment with carbon disulphide and sodium t-pentyl oxide at room temperature, gave three types of compounds, 1,3-thiazine-2,6-dithiones, 1,2-dithiole-3-thiones, and 1,3-thiazole-2-thiones. In some cases, the formation of 1,3-thiazine-2,6-dithiones were accompanied by the formation of 2-thioxo-1,3-thiazine-6-ones. Ethyl 2-imino-1-methyl-2-phenylethyl sulphone, in this reaction, gave bis-(1,3-dithiol-4-yl) disulphide.

Oxidation and bimolecular condensation reactions of 2-alkyliminocyclopentanedithiocarboxylic acids, 2-oxocyclopentanedithiocarboxylic acids, and 3-methyl-5-oxo-1-phenyl-Δ2-pyrazoline-4-dithiocarboxylic acid

The 2-oxocyclopentanedithiocarboxylic acids (9) and (10) and 3-methyl-5-oxo-1-phenyl-Δ2-pyrazoline-4-dithiocarboxylic acid (13), on oxidation, gave the 3,5-bis-(2-oxocyclopentylidene)-1,2,4-trithioles (11) and (12) and 3,5-bis-(3-methyl-5-oxo-1-phenyl-Δ2-pyrazolin-4-ylidene)-1,2,4-trithiole (14), respectively. The 2-alkyliminocyclopentanedithiocarboxylic acids (1)–(4), under similar conditions, underwent normal oxidation to the bis-(2-alkyliminocyclopentylthiocarbonyl) disulphides (5)–(8). The acid (9) afforded 6,7-dihydro-2-(2-oxocyclopentylidene)cyclopenta[d][1,3]dithiin-4(5H)-thione (15) when treated with dimethylformamide alone, and 2,4-bis-(2-oxocyclopentylidene)-1,3-dithietan (16) when treated with dimethylformamide and an acyl chloride. 2,4-Bis-(3-methyl-5-oxo-1-phenyl-Δ2-pyrazolin-4-ylidene)-1,3-dithietan (17) was likewise obtained from the acid (13).

Some reactions of 2-oxocyclopentanedithiocarboxylic acid and 3-methyl-5-oxo-1-phenyl-Δ2-pyrazoline-4-dithiocarboxylic acid

The title dithiocarboxylic acids, (1) and (6) respectively, were obtained by substitution reactions of the corresponding cyclic ketones with carbon disulphide in the presence of aqueous alkali. The acid (1) reacted with hydrazine to give 1,4,5,6-tetrahydrocyclopenta[c]pyrazole-3(2H)-thione (2); the acid (6) simply afforded the hydrazide (11). Treatment of the acid (6) with aldehydes yielded the 1,3-dithietan-2-ylidenepyrazolines, (7)–(10). The acids (1) and (6) both gave benzodithiol-2-ylidene derivatives [(3), (4), and (12)] when treated with 2,4-dinitrochlorobenzene or similar reagents.

Synthesis of aromatic and heteroaromatic thioaldehydes, aryl-thioenals, and -thiodienals as their η1; complexes with pentacarbonyltungsten(0) by the reaction of aldimines and a new reagent, [PPh4][W(CO)5SH]

A new reagent, [PPh4][W(CO)5SH]1 for the synthesis of pentacarbonyltungsten(0) complexes of thioaldehydes has been synthesised from [PPh4]SH and [W(CO)5(C4H8O)]. The latter was formed conveniently by a nonphotochemical process. Treatment of each imine 2 with [PPh4][W(CO)5SH]1 in the presence of equimolar mixture of BF3·OEt2 and McCO2H (2 equiv.) gave complexes of the thiobenzaldehydes 3a–j, thionaphthaldehydes 4a–b, thioanthraldehydes 5a–b, 5-methyl-2-thioformylfuran 6, 2-thioformylthiophenes 7a–c, 4-substituted thiocinnamaldehydes 8a–c, and 4-substituted thiocinnamylideneacetaldehydes 9a–c with pentacarbonyltungsten(0) in high yields. NMR studies revealed that the above exist as η1 complexes.

Formation of 3-substituted 2-iminocyclopentanedithiocarboxylic acids and N-[amino(dimercapto)methyl]-2-methylcyclopentanimine from 2-substituted cyclopentanones. Some reactions of the imino-dithiocarb-oxylic acids

2-Ethyl, 2-isopropyl. 2-cyclopentyl. and 2-cyclopentylidenecyclopentanones, when treated with carbon disulphide and ammonia, gave the corresponding 3-substituted 2-iminocyclopentanedithiocarboxylic acids (5)–(7) and (9). Under the same conditions, 2-methylcyclopentanone gave 2-imino-3-methylcyclopentanedithiocarboxylic acid (2), and N-[amino(dimercapto)methyl]-2-methylcyclopentanimine (3), and 2-isopropylidenecyclopentanone gave7a-amino-4,4-dimethylperhydrocyclopenta[e][1,3]thiazine-2-thione (8). Reactions of the 2-iminocyclopent-anedithiocarboxylic acids with hydrazine, thiosemicarbazide, picryl chloride, and phenyl isothiocyanate have also been investigated.

Synthesis of thiazolidine-2,5-dithiones: characterisation of 4-substituted thiazolidinedithiones

A general method for the synthesis of a series of 4,4-disubstituted thiazolidine-2,5-dithiones (1)–(6) initially consisted in reactions of α-metallated aralkyl isothiocyanates with carbon disulphide. 4-Monosubstituted thiazolidine-2,5-dithiones (7)–(9) are very susceptible to oxidation, changing rapidly into their oxidative dimers. The reason for the unexpected methylation of thiazolidine dithiones (7)–(9) became evident from the results of MNDO calculations.

Reaction of carbon disulphide with cyclic amides and related compounds. Free N-acyl- and N-carbamoyl-dithiocarbamic acids

2-Pyrrolidone, 2-piperidone, Iµ-caprolactam, imidazolidin-2-one, imidazolidine-2,4-dione, and 2,5-dioxopiperazine, after treatment with sodium hydride or in the presence of alkali, reacted with carbon disulphide to give the respective 1-dithiocarboxylic acid and/or 1,3-bisdithiocarboxylic acid which were readily esterified. The stable crystalline free acids could be easily isolated in the case of the five-membered ring compounds.

Preparation of β-alkylimino-dithiocarboxylic acids

The title compounds were prepared by the reaction of carbon disulphide with the product obtained by refluxing a mixture of a ketone and a primary amine with potassium fluoride. Ketones in which α-position is sterically hindered were reluctant to undergo this reaction.

Synthesis of simple enamino thioaldehydes

Simple enamino thioaldehydes (1)–(5) are synthesised by the thioformylation of alicyclic enamines.