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.     

1,2-Epoxycarotinoide. 3. Mitteilung. Isolierun von 1,2-Epoxy-1,2-dihydrolycopin aus Tomaten

1,2-Epoxycarotenoids: Isolation of 1,2-Epoxy-1,2-dihydrolycopene from Tomatoes The optically active, 1,2-epoxy-1,2-dihydrolycopene was isolated from tomatoes. Its constitution was established by comparison with the racemic synthetic compound.     

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.     

Nucleophilic aromatic substitution reactions of 1,2-dihydro-1,2-azaborine

Could go either way: The addition of nucleophiles to the parent 1,2-dihydro-1,2-azaborine and subsequent quenching with an electrophile generates novel substituted 1,2-azaborine derivatives. Mechanistic studies are consistent with two distinct nucleophilic aromatic substitution pathways depending on the nature of the nucleophile.     

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.     

1，2－联烯亚砚和1，2－联烯砜的反应

1，2－联烯亚砜和1，2－联烯砜是重要的含硫联烯化合物，综述了1，2－联烯 亚砜和1，2－联烯砜的亲核加成、亲电加成、Diels-Alder反应、1，3－偶极加成 、[2+2]环加成等反应以及在天然产物中的应用。     

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.

     

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.     

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.     

Synthesis of optically pure 1,2-diaryl- and 1,2-alkylaryl-1,2-amino sulfides

[reaction: see text] The reactions of the lithium (S)-alpha-(methylthio)-2-(p-toluenesulfinyl)benzyl carbanion with (S)-N-p-tolylsulfinyl aldimines evolve in a completely stereoselective manner providing a one-step synthesis of enantiomerically pure anti-1,2-disubstituted 1,2-amino sulfide derivatives.     

Electrophilic aromatic substitution reactions of 1,2-dihydro-1,2-azaborines

The aromatic boron-nitrogen heterocycle 1,2-dihydro-1,2-azaborine undergoes classical electrophilic substitution. These reactions allow easy functionalization to provide a variety of 3- and 5-substituted derivatives. [reaction: see text].     

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.     

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.     

Crystal clear structural evidence for electron delocalization in 1,2-dihydro-1,2-azaborines

The first examples of "pre-aromatic" 1,2-dihydro-1,2-azaborine heterocycles have been structurally characterized, enabling the direct comparison of delocalized bonds of 1,2-dihydro-1,2-azaborines to their corresponding formal double and single bonds in nonaromatic systems. The crystallographic data provide an unprecedented look into the structural changes that occur in six-membered BN-heterocycles on their road to aromaticity, and they establish with little ambiguity that 1,2-dihydro-1,2-azaborines possess delocalized structures consistent with aromaticity.     

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.     

Diversity through isosterism: the case of boron-substituted 1,2-dihydro-1,2-azaborines

The first general synthesis of boron-substituted 1,2-dihydro-1,2-azaborines is described. The versatile 1,2-dihydro-1,2-azaborine precursor 4 is synthesized through a ring-closing metathesis-oxidation sequence. Treatment of 4 with a wide range of anionic nucleophiles furnishes the desired adducts 5 in good yields. The scope includes hydrogen- and a variety of carbon- and heteroatom-based nucleophiles. Furthermore, the boron-containing isostere (7) of the potent hypolipidemic agent, methyl 2-ethylphenoxyacetate (8), is readily prepared through our method.     

INDO study of 1,2-fluorine atom migration in 1,2-difluoroethyl and 1,1,2-trifluoroethyl radicals

INDO molecular orbital calculations have been carried out to estimate the barrier heights to the 1,2-migration of fluorine and hydrogen atoms in 1,2-difluoroethyl and 1,1,2-trifluoroethyl radicals. The calculated results suggest that (1) the 1,2-fluorine atom migration through a fluorine atom bridging intermediate will occur more readily than the 1,2-hydrogen atom migration through a hydrogen atom bridging intermediate in both radicals, (2) a fluorine atom will undergo 1,2-migration in 1,1,2-trifluoroethyl radical more readily than in 1,2-difluoroethyl radical. The enthalpy change accompanied by the 1,2-fluorine atom migration in 1,1,2-trifluoroethyl radical was estimated to be 1.7 kcal/mol, which was in good agreement with the value(1.6 kcal/mol) obtained experimentally.     

Catalytic monoalkylation of 1,2-diols

A catalytic monoalkylation of 1,2-diols by using a weak base has been developed. Copper(II) dichloride and boronic acids are effective catalysts for activating 1,2-diols in the presence of potassium carbonate as a base. Various 1,2-diols were selectively monoalkylated with allyl-, benzyl- and alkyl- halides in DMF by choosing a suitable catalyst for each 1,2-diols.     

Indole-tolerant Oxidation of 1,2-Diarylalkynes to 1,2-Diketone Derivatives

A new indole-tolerant oxidation condition for the synthesis of 1,2-diketone derivatives from the corresponding 1,2-diarylalkynes was described. By screening a series of oxidation systems on alkynes linked with indole and different substituted aromatic ring, the DMSO/PdCl₂/CuCl₂ system afforded moderate to good yields despite the existence of electron-rich indole ring.