1,7-Dithioxo Systems. Synthetic Routes to Bis(5,5-dimethyl-3-thioxo-1-cyclohexenyl) Sulfide

Synthetic routes to bis(5,5-dimethyl-3-thioxo-1-cyclohexenyl) sulfide have been studied. The title compound can be obtained by reaction of 3-chloro-5,5-dimethyl-2-cyclohexenethione with sodium thiosulfate and by condensation of 3-mercapto-5,5-dimethyl-2-cyclohexenethione. The reaction of bis(5,5-dimethyl-3-oxo-1-cyclohexenyl) sulfide with hydrogen sulfide and hydrogen chloride yields 3-oxo-3'-thioxobis(5,5-dimethyl-1-cyclohexenyl) sulfide.     

Steric Structure of Bis(5,5-dimethyl-3-thioxo-1-cyclohexenyl) Sulfide

Two-dimensional NMR spectroscopy, dipole moment measurements, and quantum-chemical calculations (basis 6-31G^*) were used to show that in the gas phase and in solutions bis(5,5-dimethyl-3-thioxo-1-cyclohexenyl) sulfide prefers a nonplanar cis-trans conformation.     

Reaction of α,β-unsaturated carbodiimides with enamines leading to fused pyridine derivatives

The treatment of (5,5-dimethyl-3-oxo-1-cyclohexenyl)iminotriphenylphosphorane ( 2 ) with phenyl isocyanate ( 3a ) gave N-(5,5-dimethyl-3-oxo-1-cyclohexenyl)-N'-phenylcarbodiimide ( 4a ) in situ. The reaction of 4a with enamines proceeded smoothly to afford the pyridine ring formation with the elimination of amine. This means that 4a is regarded as a new class of 2-aza-1,3-butadiene. The scopes and limitation of this reaction are also discussed.     

Synthesis of 2,3,4,6,7,8-Hexahydro-5H-1-benzopyran-5-ones and 3-(6-Oxo-1-cyclohexenyl)alkanoic Acids by Reduction of 4,6,7,8-Tetrahydro-2H-1-benzopyran-2,5(3H)-diones

Comparative results on the reduction of 4,6,7,8-tetrahydro-7,7-dimethyl-2H-1-benzopyran-2,5(3H)-diones 1 are reported. Hydride reduction (LiAlH₄ in Et₂O or NaBH₄ in i-PrOH) affords 2,3,4,6,7,8-hexahydro-5H-1-benzopyran-5-ones 5 in 30-60% isolated yield. Photochemical reduction of 1b and 1d (direct irradiation at λ = 300 or 254 nm in i-PrOH, or sensitized irradiation in acetone/i-PrOH or benzene/i-PrOH) gives 3-(6-oxo-1-cyclohexenyl)alkanoic acids 6 in 50–80%, while 1c affords the isomeric 3-(4,4-dimethyl-6-oxo-1-cyclohexenyl)-4-methyl-4-pentenoic acid ( 9 ) in 73% isolated yield. Electrochemical reduction (Hg, CH₃CN, Bu₄N⁺ClO, ?2.6 V vs. Ag/Ag⁺) requires more than 4 Farad/mol for the consumption of 1 without any major product being detected.     

1,7-Dithioxo systems. Reaction of bis(5,5-dimethyl-3-thioxo-cyclohex-1-en-1-yl) sulfide with amines

Reactions of amines (N,N-dimethylethane-1,2-diamine, benzylamine, aniline) with bis(5,5-dimethyl-3-thioxocyclohex-1-en-1-yl) sulfide result in cleavage of the sulfide bond and formation of the corresponding 3-amino-5,5-dimethylcyclohex-2-ene-1-thiones. Aminolysis of bis(5,5-dimethyl-3-oxocyclohex-1-en-1-yl) sulfide occurs at the carbonyl groups with conservation of the divinyl sulfide fragment.     

Hydrothiolysis of carbofunctional α,β-unsaturated sulfides as an approach to the synthesis of 1,7-dithiocarbonyl compounds

Bis(1-N,N-dimethylimmonio-3-phenylprop-2-en-3-yl) sulfide diperchlorate and (1-N,N-dimethyl-immonio-3-phenylprop-2-en-3-yl) (5,5-dimethyl-1-morpholiniocyclohex-2-en-3-yl) sulfide diperchlorate react with hydrogen sulfide giving rise to the corresponding 1,7-thioxoimmonio sulfides. Treating with the hydrogen sulfide (1-N,N-dimethylimmonio-3-phenylprop-2-en-3-yl) (1-oxo-2-phenyl-inden-3-yl) sulfide perchlorate led to preparation of (1-oxo-2-phenylinden-3-yl) (1-thioxo-3-phenylprop-2-en-3-yl) sulfide. The hydrothiolysis of (5,5-dimethyl-1-morpholiniocyclohex-2-en-3-yl) (1-N,N-dimethylimmonio-2-phenylinden-3-yl) sulfide diperchlorate and (5,5-dimethyl-1-morpholiniocyclohex-2-en-3-yl) (1-oxo-2-phenylinden-3-yl) sulfidea perchlorate resulted in products of the sulfide bond cleavage in the initial immonium salts.     

1,7-Dithioxo-substituted systems. Bis(5,5-dimethyl-3-thioxocyclohex-1-enyl) sulfide in reactions with metals

The transformations of bis(5,5-dimethyl-3-thioxocyclohex-1-enyl) sulfide in the presence of activated copper and zinc powders are studied. The products obtained are analyzed by quantitative ¹³C NMR spectroscopy.     

1,7-dithioxo-substituted systems. Synthesis,structure, and photoconductivity of bis(5,5-dimethyl-3-hydrazonocyclohex-1-enyl) sulfide

Bis(5,5-dimethyl-3-hydrazonocyclohex-1-enyl) sulfide was synthesized by the reaction of bis(5,5-dimethyl-3-thioxocyclohex-1-enyl) sulfide or its oxygen analog with hydrazine. Conformational lability of the molecule of dihydrazone was studied by the DFT(B3LYP) method using expanded basis sets 6–311G and 6–11G(d,p). Analysis of vibration IR and Raman spectra of the most stable conformers of the isolated molecule of dihydrazone was performed at the harmonic approximation. Using the Onsager SCRF solvation model the absence of solvent effect on the relative stability of the conformers was shown. The photoconductivity of dihydrazone was studied. Low value of the ratio of photocurrent to dark current (J _p/J _d = 2.5–3.5) for dyhydrazone was assigned to the lability of its stereoelectronic structure, which was in line with the data of ¹H, ¹³C, and ¹⁵N NMR spectra.     

Synthesis of Alkyl 4-(1-Alkyl-2-aryl-2-oxoethyl)-5,5-dimethyl-2-oxotetrahydrofuran-3-carboxylates

Zinc enolates derived from 1-aryl-2-bromoalkanones react with alkyl 5,5-dimethyl-2-oxo-2,5-dihydrofuran-3-carboxylates to give alkyl 4-(1-alkyl-2-aryl-2-oxoethyl)-5,5-dimethyl-2-oxotetrahydrofuran-3-carboxylates. Reactions of the latter with amines, such as p-toluidine, cyclohexylamine, and piperidine, lead to the corresponding carboxamides.     

Studies on organophosphorus compounds—XXVII: Synthesis of thiono-, thiolo- and dithiolactones

Unsubstituted and alkyl- or cyanosubstituted lactones such as dihydro-2(3 H)-furanone, dihydro-5-methyl-2(3 H)-furanone, dihydro-5,5-dimethyl-4-propyl-2(3 H)-furanone and tetrahydro-2,2-dimethyl-5-oxo-3furan-carbonitrile react with the dimer of p-methoxyphenylthionophosphine sulfide, 1, in anhydrous xylene or toluene to give the corresponding thionolactones, 3a-d, in good yields. Dihydro-2(3 H)-thiophenone and 1 produce dihydro-2(3 H)-thiophenthione. Aromatic lactones such as 2 H-1-benzopyran-2-one give the corresponding 2-thione. 1-Oxa-4-thiaspiro[4,5]decan-2-one, when treated with 1 at 120-125°, gave 1,4-dithiaspiro[4,5]decan-2-one and 1,4-dithias-piro[4,5]decan-2-thione. Tetrahydro-5,5-dimethyl-2-oxo-4-propyl-3-furancarboxylic acid ethyl ester reacted with 1 at 110° giving the corresponding 2-thione and 5,5-dimethyl-4-propyl-4,5-dihydrothieno[2,3-c]-1,2-dithiole-3-thione.     

Phosphorinane and Enol Rings in One Molecule. Evidence for Reciprocal Stabilization of Half-Chair Conformations

Abstract.

The X-ray crystal structure of 2-(2′,4′-dioxo-3′-pentyl)-5,5-dimethyl-2-oxo-1,3,2-dioxaphosphorinane (2) reveals significant half-chair distortion of the axially oriented cisenol ring. The molecule also undergoes in-plane deformations. R(O...O) = 2.410 Å in the enol moiety indicates a very strong hydrogen bonding. The enol content, δ_OH and thermodynamic parameters for the axial-equatorial conformational and keto-enol equilibriums were obtained from ¹H, ³¹P NMR and IR measurements in comparison with the planar 4,6-dimethyl isomer (1) containing equatorially oriented enol ring. The X-ray single crystal structure of 5,5-dimethyl-2-(methoxycarbonyl-3′-oxo-2′-butyl)-2-oxo-1,3,2-dioxaphosphorinane (3) reveals the unusual half-chair conformation of the dioxaphosphorinane cycle disposed a trans-enol ring substituent. ¹H, ³¹P NMR and IR solution data support the same structure displays a strong conformational preference while the minor forms are chair conformers with an axial or equatorial cis-enol ring.     

Synthesis of 4,6-diaryl-1-benzyl-6-hydroxy-5,5-dimethyl-2-oxopiperidine-3-carbonitriles and their analogs via a modified Reformatsky reaction

Organozinc compounds obtained from 1-aryl-2-bromo-2-methylpropanone and zinc react with N-benzyl-3-aryl-2-cyanoacrylamides or N-[6-(2-cyano-1-oxo-3-phenylprop-2-enylamino)hexyl]-2-cyano-3-phenylacrylamide to give 4,6-diaryl-1-benzyl-6-hydroxy-5,5-dimethyl-2-oxopiperidine-3-carbonitriles or 1,6-bis(6-aryl-3-cyano-6-hydroxy-5,5-dimethyl-2-oxo-4-phenylpiperidyl)hexanes as a single isomer with trans-located piperidine hydrogen atoms.     

Mass spectra of isomeric monothiopyrophosphates

The main fragmentation patterns of the phosphorus-containing moiety of bis(5,5-dimethyl-2-oxo-1,3,2-dioxaphosphorinanyl) sulphide, 3, and its isomer P-oxo-P'-thiono-bis(5,5-dimethyl-1,3,2-dioxaphosphorinanyl) oxide, 4, are presented. Isotope studies with ¹⁸O, ³⁶S, ³⁴S and ²H indicate that compound 3 undergoes an extensive isomerization prior to fragmentation. The mechanism of this isomerization must involve interaction of at least two molecules, as shown by isotope scrambling experiments.     

1,7-Dithioxo systems. Photochemical, thermal, and chemical stabilities of bis(5,5-dimethyl-3-thioxo-1-cyclohexenyl) sulfide

Photochemical, thermal, and chemical stabilities of bis(5,5-dimethyl-3-thioxo-1-cyclohexenyl) sulfide in crystal and in solution were studied.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 10, 2004, pp. 1692–1694.Original Russian Text Copyright © 2004 by Timokhina, Panova, Kanitskaya, Sokolnikova, Voronkov.This revised version was published online in April 2005 with a corrected cover date.     

Cyanoacetylene and Its Derivatives: XXVIII. Reactions of 2-Mercaptobenzothiazole with Nitriles of αα,ββ-Acetylene γγ-Hydroxyacids and with 3-Phenyl-2-propynonitrile

Nucleophilic addition of 2-mercaptobenzothiazole to 4-alkyl-4-hydroxy-2-alkynonitriles at 1:1 ratio in the presence of 4-6 wt% of Et₃N occurs regio- and stereospecifically to afford (Z)-4-alkyl-3-(benzothiazolyl-2-thio)-4-hydroxy-2-alkenonitriles (yield 40-51%). In the presence of 1.3 wt% of Dabco the thiazole and 4-hydroxy-4-methyl-2-pentynonitrile (1:1) give rise to a mixture of 2-alkenonitrile and 2-(3,3,6,6-tetramethyl-2-cyanomethyl-5-cyanomethylene-1,4-oxathian-2-yl)thiobenzothiazole. At the use of 4-6 wt% of LiOH arises an intractable mixture containing 1,4-oxathiane, benzothiazol-2-one, 2-[1-(5,5-dimethyl-2-cyanomethyl)-4-cyanomethylene-1,3-oxathiolan-2-yl)-1-methylethyl]thiobenzothiazole, bis(2,2,5,5-tetramethyl-6-cyanomethyl-3-cyanomethylene-1,4-oxathian-6-yl) disulfide, bis[1-(5,5-dimethyl-2-cyanomethyl-4-cyanomethylene-1,3-oxathiolan-2-yl)-1-methylethyl] disulfide, and 3-[1-(5,5-dimethyl-2-cyanomethyl-4-cyanomethylene-1,3-oxathiolan-2-yl)-1-methylethyl]benzothiazol-2-one (according to ¹H and ¹³C NMR data). 2-mercaptobenzothiazole adds to 3-phenyl-2-propynonitrile in the presence of 7 wt% of KOH with regio- and stereospecific formation of (Z)-3-(benzothiazolyl-2-thio)-3-phenyl-2-propenonitrile (88%).     

1,7-dithioxo systems. Reaction of 3-[(5,5-dimethyl-3-thioxocyclohex-1-en-1yl)sulfanyl]-5,5-dimethylcyclohex-2-ene-1-thione with 2-aminoethanol and ethane-1,2-diamine

The reaction of 3-[(5,5-dimethyl-3-thioxocyclohex-1-en-1-yl)sulfanyl]-5,5-dimethylcyclohex-2-ene-1-thione with 2-aminoethanol involves cleavage of the sulfide bond with formation of 3-[(2-hydroxyethyl)-amino]-5,5-dimethylcyclohex-2-ene-1-thione as the major product. The reaction of the same sulfide with ethane-1,2-diamine gave previously unknown 3-({2-[(5,5-dimethyl-3-thioxocyclohex-1-en-1-yl)amino]ethyl}-amino)-5,5-dimethylcyclohex-2-ene-1-thione.     

1-(2-Quinoxalyl)-, 1-[3,5-Di(trifluoromethyl)phenyl]-, 1-(2-Carboxyphenyl)-, and 1-Ethoxycarbonyl-4-oxo-4,5,6,7-tetrahydroindazoles

The corresponding 1-(2-quinoxalyl)-, 1-[3,5-di(trifluoromethyl)phenyl]-, and 1-ethoxycarbonyl-3-methyl-4-oxo-4,5,6,7-tetrahydroindazoles have been obtained from reactions of 2-acetyl-1,3-cyclohexanedione, its 5,5-dimethyl and 5-(2-furyl) derivatives, with 2-hydrazinoquinoxaline, 3,5-di(trifluoromethyl)phenylhydrazine, and ethoxycarbonylhydrazine. On interaction with ethoxycarbonylhydrazine the intermediate 2-[1-(-ethoxycarbonyl)hydrazino]ethylidene-1,3-cyclohexanediones were also isolated. From the potassium salt of 2-formyldimedone and 2-carboxyphenylhydrazine hydrochloride, 2-(2-carboxyphenyl)hydrazinomethylene-5,5-dimethyl-1,3-cyclohexanedione was obtained, the cyclization of which in ethanol in the presence of HCl led to 1-(2-carboxyphenyl)- and 1-(2-ethoxycarbonylphenyl)-6,6-dimethyl-4-oxo-4,5,6,7-tetrahydroindazole.     

Reaction of alkyl 5,5-dimethyl-2-oxo-2,5-dihydrofuran-3-carboxylates with zinc enolates prepared from zinc and 1-arul-2-bromo-2-phenylethanones, 2 bromoindanone, and 2-bromo-6-methyltetralone

Alkyl 5,5-dimethyl-2-oxo-2,5-dihydrofuran-3-carboxylates react with zinc enolates prepared from 1-aryl-2-bromo-2-phenylethanones, 2-bromo indanone, 2-bromo-6-methyltetralone and zinc with formation of ethyl 4-(2-aryl-2-oxo-1-phenyl-ethyl)-5,5-dimethyl-2-oxotetrahydrofuran-3-carboxylates, alkyl 5,5-dimethyl-2-oxo-4-(1-oxoindan-2-yl)tetrahydrofuran-3-carboxylates, and ethyl 5,5-dimethyl-4-(6-methyl-1-oxo-1,2,3,4-tetrahydronaphthalen-2-yl)-2-oxotetrahydrofuran-3-carboxylates respectively, mainly as single diastereomers.     

Die Reaktion von λ5-Diphospheten mit COS und CO2 Dihydro-λ5-Phosphete

Reactions of λ⁵-Diphosphetes with COS and CO₂. Dihydro-λ⁵-Phosphetes 1,1,3,3-Tetrakis(dimethylamino)-1λ⁵,3λ⁵-diphosphete, 1 , reacts with COS to yield the (3-oxo-3,4-dihydro-1λ⁵-phosphete-2-yl)-phosphonothioic bis(dimethylamide) 7 . Reaction of dimethyl substituted 1 , i.e. 1,1,3,3-tetrakis(dimethylamino)-2,4-dimethyl-1λ⁵,3λ⁵-diphosphete 4 , with COS and CO₂ results in (3-oxo-2,3-dihydro-1λ⁵-phosphete-2-yl)-phosphonothioic bis(dimethylamide) 9 , and (3-oxo-2,3-dihydro-1λ⁵-phosphete-2-yl)-phosphonic bis(dimethylamide) 10 , respectively. Reaction mechanisms are suggested. 7, 9 and 10 are characterized by their properties, and their nmr, mass-, and ir-spectra. The results of X-ray structural analyses of 9 and 10 are reported and discussed.     

1- and 2-(4-Hydroxycarbonylphenyl)-4-oxo-4,5,6,7-tetrahydroindazoles

Reactions of 4-hydrazinobenzoic acid with 2-formyl- and 2-acetyldimedones were utilized to synthesize 6,6-dimethyl- and 3,6,6-trimethyl-1-(4-hydroxycarbonylphenyl)-4-oxo-4,5,6,7-tetrahydroindazoles corre-spondingly, and the reaction with 2-cyano-3-ethoxy-5,5-dimethylcyclohex-2-en-1-one gave 2-(4-hydroxy-carbonylphenyl)-3-amino-4-oxo-6,6-dimethyl-4,5,6,7-tetrahydroindazole. Riga Technical University, Riga LV-1658. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 516–519, April, 1997.