Larisa A. Baeva

The reaction of 3-[(alkylsulfanyl)methyl]pentane-2,4-diones with naphthalen-1-amine in the presence of a catalytic amount of acetic acid afforded 1-(2-methylbenzo[h]quinolin-3-yl)ethanone. This transformation was presumed to proceed as a consecutive process including the formation of β-enamino ketone, elimination of alkanethiol from the latter, Friedel–Crafts intramolecular cyclization with the participation of the new double bond, and oxidative aromatization. 1-(Benzo[h]quinolin-3-yl)ethanone was also obtained by the three-component condensation of pentane-2,4-dione, formaldehyde, and naphthalen-1-amine in the presence of acetic acid. In this case, the precursor of 1-(benzo[h]quinolin-3-yl)ethanone is 4-(naphthalen-1-ylamino)pent-3-en-2-one.

A method for the synthesis of 1,1,1-(6-methyl-1-aryl-1,2,3,4-tetrahydropyridine-3,3,5-triyl)triethanones by the reaction of 3-[(propan-2-ylsulfanyl)methyl]pentane-2,4-dione with anilines in the presence of catalytic amounts of acetic acid was developed. It was found that the reactivity of substituted anilines in the studied reaction depends on the nature and position of the substituent, decreasing in the series: 2,4-Me₂-С₆H₃NH₂ > С₆H₅NH₂ 4-Me-С₆H₄NH₂ 2-Me-С₆H₄NH₂ > 3-Me-С₆H₄NH₂ 2-MeO-С₆H₄NH₂ > 4-MeC(O)-С₆H₄NH₂ 4-Br-С₆H₄NH₂.

A three-component condensation of 4,4,4-trifluoro-1-phenylbutane-1,3-dione with formaldehyde and alkanethiols led to 2-[(alkylsulfanyl)methyl]-4,4,4-trifluoro-1-phenylbutane-1,3-diones, the heterocyclization of which with hydrazine, phenylhydrazine, or benzylhydrazine under heating or microwave irradiation afforded the corresponding 4-(alkylsulfanylmethyl)-substituted 3-(trifluoromethyl)-1H-pyrazoles. The reaction of sulfur-containing 4,4,4-trifluoro-1-phenylbutane-1,3-diones with phenyl- and benzylhydrazine was characterized by high regioselectivity and resulted in the predominant formation of 1-aryl-5-phenyl-3-(trifluoromethyl)-1H-pyrazoles. 2-[(Alkylsulfanyl)methyl]-4,4,4-trifluoro-1-phenylbutane-1,3-diones were unstable and underwent detrifluoroacetylation upon isolation by chromatography to form 3-(alkylsulfanyl)-1-phenylpropan-1-ones.

A method for the synthesis of 1,1,1-(6-methyl-1-aryl-1,2,3,4-tetrahydropyridine-3,3,5-triyl)triethanolines was developed by the reaction of 3-[(propan-2-ylsulfanyl)methyl]pentane-2,4-dione with anilines in the presence of catalytic amounts of acetic acid. The reactivity of substituted anilines in the studied reaction, depending on the nature and position of the substituent, decreases in the series: 2,4-Me-CHNH > CHNH = 4-Me-CHNH = 2-Me-CHNH > 3-Me-CHNH = 2-MeO-CHNH > 4-MeC(O)-CHNH = 4-Br-CHNH.

Palladium(II) extraction from hydrochloric acid solutions with 2,6-bis[(methylsulfanyl)methyl]cyclohexan-1-one, obtained from natural methanethiol, was studied using chloroform as a diluent. Palladium(II) is recovered rapidly and with high efficiency by the extractant from solutions of 0.1–10 mol/L HCl and can be separated with high selectivity from Pt(IV), Cu(II), Ni(II), Zn(II) and Fe(III). A coordination mechanism of the palladium(II) extraction from 1 M HCl solutions was established. The extraction agent is coordinated to the Pd(II) ion through donor sulfur atoms in an extracted compound of the [PdCl2L] type. Stripping of Pd(II) is effectively carried out with a 1 M NH4OH solution or an acidic (0.1 mol/L HCl) thiourea solution.

Heterocyclization of 3-[(alkylsulfanyl)methyl]pentane-2,4-diols with formaldehyde or propionaldehyde in boiling benzene in the presence of hydrochloric acid afforded new 5-[(alkylsulfanyl)methyl]-4,6-dimethyl-1,3-dioxanes. 1,3-Dioxanes are formed as a mixture of 4,6-cis- and 4,6-trans-isomers at a ratio of 1:0.3–0.9. In both isomers, the preferred chair conformation is realized. In the 4,6-cis-isomers of all 1,3-dioxanes, the methyl groups occupy a diequatorial position, and the alkylsulfanylmethyl substituent is in an axial orientation. In the 4,6-cis-isomer of 5-[(pentylsulfanyl)methyl]-2-ethyl-1,3-dioxane, the ethyl group is oriented equatorially. The 4,6-trans-isomers of 5-[(alkylsulfanyl)methyl]-1,3-dioxanes are characterized by a rapid conformational inversion chair–chair.