Chemistry of 1,2-diphospholide anions and 1,2-diphospholes

The main trends in the chemistry of 1,2-diphosphacyclopentadienes (1,2-diphospholes) and their derivatives 1,2-diphosphacyclopentadienide anions (1,2-diphospholide anions) were systematized, analyzed, and generalized. Methods for the generation of 1,2-diphospholide anions and their reactions with organic and organoelement electrophiles, as well as with transition metal complexes, were considered. Particular attention was paid to the cycloaddition reactions of 1-alkyl-1,2-diphospholes to obtain polycyclic chiral phosphines. A comparative analysis of the reactivity of 1,2-diphospholes and 1,2-diphospholide anions with respect to other representatives of phosphacyclopentadienes and phosphacyclopentadienide anions was carried out. The potential of application of 1,2-diphosphacyclopentadiene derivatives for the design of materials with magnetic, catalytic, and optical properties was shown.

     

Reactions of azoles with tetrachloro-1,2-difluoroethane and 1,2-dichlorodifluoroethylene

Tetrachloro-1,2-difluoroethane reacted with pyrazole and imidazole sodium salts to give mixtures of the corresponding N-(1,2,2-trichloro-1,2-difluoroethyl) derivatives and (E)-1,2-difluoro-1,2-dihetarylethenes. (E)-1,2-Difluoro-1,2-di(3,5-dimethyl-1H-pyrazol-1yl)ethene was also obtained as a result of replacement of chlorine atoms in 1,2-dichloro-1,2-difluoroethene. Analogous reaction with more nucleophilic imidazole involved replacement of not only chlorine but also fluorine atoms in 1,2-dichloro-1,2-difluoroethene, yielding tetraimidazolyl-substituted ethylene.     

Synthesis of disubstituted 1,2-dioxolanes, 1,2-dioxanes, and 1,2-dioxepanes

A route to cyclic peroxides containing 1,2-dioxolane, 1,2-dioxane or 1,2-dioxepane rings is described. These compounds present simpler structures related to the bicyclic core of stolonoxides, metabolites with marked cytotoxicity against several mammalian tumor cell lines, isolated from the marine tunicate Stolonica socialis. The key synthetic step consists in the intramolecular Michael addition of a secondary hydroperoxide group to an α,β-unsaturated ester.     

The synthesis of 1,2-diacetyl- and 1,2-diethylferrocenes

A method is described for the preparation of 1,2-diacetylferrocene, in which ferrocene is acetylated with acetyl chloride in the presence of AlCl₃ in methylene chloride. Addition of the ferrocene to an excess of the acetylation mixture over a prolonged period was found to be most favourable. The 1,2-diacetylferrocene formed proved to be free of the 1,3-isomer. It was reduced with LiAlH₄/AlCl₃ to 1,2-diethylferrocene.     

Acidity constants of 1,2-cycloheptane- and 1,2-cyclo-octanedione dioximes

Summary The acidity constants of 1,2-cycloheptanedione dioxime and 1,2-cyclo-octanedione dioxime have been determined potentiometrically and spectrophotometrically. Derivation of the acidity constants and molar absorptivities from the spectrophotometric data is discussed.

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Zusammenfassung Die sauren Dissoziationskonstanten des 1,2-Cykloheptandiondioxims und des 1,2-Cyklooctandiondioxims wurden potentiometrisch bzw. spektrophotometrisch bestimmt. Die Ableitung der sauren Dissoziationskonstanten und der molaren Absorptionskoeffizienten aus spektrophotometrischen Daten wurde diskutiert.

     

Reduction of 1,2-diaroyl-1,2-diazetidines by lithium aluminum hydride

Reaction of a series of four-membered ring hydrazides (1,2-diaroyl-1,2-diazetidines) with lithium aluminum hydride at 80° results in reductive saturation of both carbonyl groups affording 1,2-diaryl-1,2-diazetidines in modest yield. Reactions at 22° result in reductive fragmentation at one carbonyl moiety, producing a monoaroyl-1,2-diazetidine as the exclusive product. A mechanism similar to that postulated for the temperature-dependent reduction of amides by lithium aluminum hydride is proposed for the reduction of these 1,2-diazetidines.     

Halogen-metal exchange in 1,2-dibromobenzene and the possible intermediacy of 1,2-dilithiobenzene

The one-step high-yield synthesis of 1,2-bis(trimethylsilyl)benzene from 1,2-dibromobenzene using tert-butyllithium and trimethylsilyltriflate is reported. A mechanistic investigation shows that 1,2-dilithiobenzene is not an intermediate in this reaction; the coexistence of trimethylsilyltriflate and tert-butyllithium at very low temperatures allows a sequence of bromine-lithium exchange and subsequent derivatization reactions to operate.     

Reducing properties of 1,2-diaryl-1,2-disodiumethanes

1,2-Diphenyl- and 1-phenyl-2-(2-pyridyl)-1,2-disodiumethane efficiently dehalogenate vic-dibromoderivatives, affording the corresponding alkenes. The reaction proceeds rapidly, under mild conditions and is tolerant of a variety of functional groups (alcohol, carboxylic acid, ester and amide). This procedure was successfully extended to similar vic-disubstituted compounds.     

Synthesis of 1,2-disubstituted naphth [1,2-d]imidazole-4,5-diones

A convenient synthesis of 3-acylamino-1,2-naphthoquinones (I) is presented. The addition of aromatic and aliphatic amines to I followed by exposure to oxygen gives the corresponding 4-arylamino- or 4-alkylamino-3-acylamino-1,2-naphthoquinones (II). The addition of 4-cyclo-hexylbutylamine to 3-trichloroacetamino-1,2-naphthoquinone took an anomalous course and 1-(4′-cyclohexylbutyl)-3(H)-naphth[1,2-d]imidazoline-2,4,5-trione (VII) was obtained. Treatment of II with refluxing acetic acid gave 1,2-disubstituted naphth[1,2-d]imidazole-4,5-diones (III). The reaction was successful with a variety of 4-substituted amino-3-acylamino-1,2-naphthoquinones (II) and usually occurred in excellent yield. However, the cyclization of II to III is subject to steric limitation and attempts to cyclize 4-tert-butylamino-3-acetamino-1,2-naphthoquinone to the corresponding imidazole derivative was unsuccessful. The infrared, ultraviolet and nuclear magnetic resonance spectra of I, II, and III are discussed in relation to their structures.     

Stereoelectronic effects in the reactions of conformationally restricted,substituted cyclohexane-1,2-diones with 1,2-diols

The asymmetric synthesis of a C₂-symmetric cyclic 1,2-diketone is reported along with investigations into its properties as a potential asymmetric protecting group for 1,2-diols as the corresponding 1,2-diacetal.     

Synthesis of 1,2 difluoro-1,2-bis(pentafluorophenyl)dichlorane

1,2-Difluoro-1,2-bis(pentafluorophenyl)dichlorane is a new class of organic polyvalent chlorine compound. The closeness of the retention time of this compound and that of chloropentafluoro- benzene made its purification difficult. All attempts to obtain this compound in high yield have failed. 1,2-Difluoro-1,2-bis- (pentafluorophenyl)dichlorane is prepared by fluorination of chloropentafluorobenzene at 128°C with elemental fluorine. It has been characterized by ¹⁹F n.m.r., i.r., mass spectroscopy and elemental analysis.     

Substituent effects of 1,2-dithiole groups on the electrochemical oxidation of some ferrocenyl-1,2-dithiole compounds

New ferrocenyl compounds substituted by sulfur containing groups were synthesized leading to ferrocenyl-3H-1,2-dithiole-3-thiones and related compounds. The substituent of the ferrocene was a [3-thioxo-3H-1,2-dithiol]-4 or 5-yl, a [3-oxo-3H-1,2-dithiol]-4 or 5- yl or a [3-methylsulfanyl-3H-1,2-dithiolium]-4 or 5-yl cation group. Their anodic behavior was studied by cyclic voltammetry at a Pt electrode in aprotic solvent. All synthesized ferrocenes exhibited a one-electron reversible oxidation leading to the corresponding ferricinium cation. At low potential scan, the irreversible oxidation of 5-ferrocenyl-3H-1,2-dithiole-3-thione was observed and attributed to a dimerization involving the dithiolethione group. Redox potential of the reversible oxidation allowed the determination of the electronic effect of the 1,2-dithiole groups. The Hammett σ_p constants of the dithiole substituents were obtained from linear correlation between oxidation potentials and electronic effects. The results showed that the [3-thioxo-3H-1,2-dithiol]-5-yl and the [3-methylsulfanyl-3H-1,2-dithiolium]-5-yl cation groups were strong inductive electron withdrawing substituents characterized by σ_p values of 0.55 and 0.97, respectively.     

1,2-Dimethyl-1,2-diphenyidisilane-1,2-diol and its K,Na, and FeII derivatives. Molecular structure of the all-trans-isomer, 2,3,5,6-tetra-methyl-2,3,5,6-tetraphenyl-1,4-dioxa-2,3,5,6-tetrasilacyclohexane

Hydrolysis of 1,2-dimethyl-1,2-diphenyl-1,2-dichlorodisilane yields 1,2-dimethyl-1,2diphenyldisilane-1,2-diol, which undergoes dimerization into stereoisomeric 2,3,5,6-tetramethyl-2,3,5,6-tetraphenyl-1,4-dioxa-2,3,5,6-tetrasilacyclohexanes under the action of H₂SO₄. Pure all-trans-isomer has been isolated and characterized by¹H NMR and IR spectroscopy and X-ray analysis. The reaction of sodium disilanediolate with FeBr₂ results in the formation of 1,2-dimethyl-1,2-diphenyl-4-ferra(ii)-3,5-dioxa-1,2-disilacyclopentane.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2550–2556, October, 1996.     

Mild template synthesis of copper(II)-containing macrocyclic compounds in the CuII–1,2-diaminoethanedithione-1,2–ethanedione-1,2 and CuII–1,2-diamino-ethanedithione-1,2–butanedione-2,3 triple systems into Cu2[Fe(CN)6]-gelatin-immobilized matrix implantates

The complexing processes in the Cu^II–1,2-diaminoethanedithione-1,2–ethanedione-1,2 and Cu^II–1,2-diaminoethanedithione-1,2–butanedione-2,3 triple systems occuring in the copper(II)hexacyanoferrate(II) gelatin-immobilized matrix in contact with aqueous alkaline solutions (pH~12) containing 1,2-diaminoethanedithione-1,2 and ethanedione-1,2 or butanedione-1,2 under room temperature, and between MCl₂, 1,2-diaminoethanedithione-1,2 and ethanedione-1,2 or butanedione-1,2 in the ethanol solutions, upon heating up to ~80 °C, have been studied. In both systems indicated, template synthesis occurs in the gelatin-immobililized matrix but does not occur in the ethanol solution. As a result of template synthesis, macrocyclic Cu^II chelates with 2,7-dithio-3,6-diazaoctadien-3,5-dithioamide-1,8 and its 4,5-dimethylsubstituted derivative are formed in the gelatin-immobililized matrix. 1,2-diaminoethanedithione-1,2 and ethanedione-1,2 or butanedione-2,3 are the ligand synthons in the processes indicated.     

New transformations of Si-methoxy-substituted 1,2-disilylethylenes and 1,2-disilylacetylenes

Conclusions Some transformations of 1,2-disilylethylenes and 1,2-disilylacetylenes that involve the methoxyl groups on the silicon atom were described.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2145–2147, September, 1978.     

Phenolic proton transfer to the 1,2 double bond in the molecular ion of trans-1,2-tetrahydrocannabinol

It is known that the molecular ion of trans-1,6-tetrahydrocannabinol (1,6-THC) with m/e 314 decomposes via a retro Diels-Alder reaction to fragment m/e 246, which then loses a Me radical to give the ion m/e 231 (cf Scheme 1).¹A similar breakdown is found for trans-1,2-tetrahydrocannabinol (1,2-THC), suggesting a shift of the double bond from the 1,2 to the 1,6 position in its molecular ion.Methylation of the phenolic OH group in trans-1,2-tetrahydrocannabinol however, shows that the phenolic proton transfer to the 1,2 double bond (cf Scheme 2) is much more important (～ 35–80%) than simple double bond migration (～ 20%; Scheme 3) in the formation of fragment m/e 231.     

Heterogeneous platinum catalytic aerobic oxidation of cyclopentane-1,2-diols to cyclopentane-1,2-diones

A method for the aerobic oxidation of cyclopentane-1,2-diols to the corresponding diketones over a commercial heterogeneous Pt/C catalyst is described. Unsubstituted and 3- or 4-substituted cyclopentane-1,2-diols are oxidized to 1,2-dicarbonyl compounds in good yields under the reported optimized reaction conditions (atmospheric air, 1 mol % of catalyst, 1 equiv of LiOH, aqueous solvents and 60 °C temperature). The method is applicable for producing cyclopentane-1,2-diketones in a scalable manner.     

Synthesis of vinyl 1,2-diketones

A new route is outlined for preparation of vinyl 1,2-diketones via a three-step sequence. First, allylic alcohols are photooxidized by ¹O₂ to hydroperoxides, which are reduced to vinyl 1,2-diols. These vinyl 1,2-diols are oxidized to vinyl 1,2-diketones with oxoammonium salts, which are prepared in situ from organic nitroxyl radicals. The new route is short, avoids the use of protecting groups, and is generally applicable to obtain aliphatic or aromatic vinyl 1,2-diketones.     

Building block synthesis of predominantly (E) symmetrical and unsymmetrical 1,2-difluorostilbenes from 1,2-dibromo-1,2-difluoroethene

An efficient synthesis of predominantly (E) symmetrical or unsymmetrical 1,2-difluorostilbenes based on the Suzuki–Miyaura palladium-catalyzed cross-coupling reaction of arylboronic acids with predominantly (E)-1,2-dibromo-1,2-difluoroethene in the presence of Cs₂CO₃ in toluene is described. The reaction preserved the stereochemistry of the building block and performed in good yield independently of the electron-withdrawing or electron-donating character of the substituents.     

1,2-Dichalcogenins: Simple Syntheses of 1,2-Diselenins, 1,2-Dithiins,and 2-Selenathiin

Ring opening of titanacyclopentadienes 1 with (SCN)₂ or (SeCN)₂ followed by bis(thiocyanate) or bis(selenocyanate) cyclization affords 1,2-dithiin ( 2 a ) or 1,2-diselenin ( 2 b ), respectively. Compound 1 gives 2 a directly on reaction with S₂Cl₂. Unsubstituted 1,2-diselenin is prepared by reaction of PhCH₂SeNa with 1,4-bis(trimethylsilyl)-1,3-butadiyne followed by reductive cleavage of the benzyl group and oxidation. The unsubstituted 2-selenathiin is prepared in an analogous manner, but from a mixture of PhCH₂SeNa and PhCH₂SNa.