199Hg and13C NMR spectra of bromine-substituted benzyl derivatives of mercury

Conclusions ¹⁹⁹Hg chemical shifts indicate that in dibenzyl derivatives of mercury and in benzylmercury bromides, there is, conjugation of the C-Hg bond with the orbitals of the aromatic ring, and also intramolecular coordination of the Hg atom with the Br atoms located in the o-position relative to the CH₂HgBr group, leading to the formation of a five-membered chelate ring. Such coordination interaction does not have an appreciable effect on the¹³C chemical shifts or the J_C-Hg constants.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 793–799, April, 1985.     

Redox troponization as a novel method for the synthesis of stereoisomeric Eschenmoser's oximes and related non-benzenoid aromatic systems

A novel method for the synthesis of the oxime of 4-methyl-2,4,6-cycloheptatrien-1-one (Eschenmoser's oxime) is proposed. The method involves redox enlargement of the ring of 4-dibromomethyl-4-methyl-2,5-cyclohexadien-1-one oxime through the action of Ni(PPh₃)₄ in DMF (in the presence of Zn). The product is formed as a mixture ofsyn- andanti-forms readily interconverting in solutions. A similar reaction of 4-methyl-4-trichloromethyl-2,5-cyclohexadien-1-one oxime afforded the dimer of agem--centered semiquinoid carbene (1,2-bis-(1-methyl-4-oxyimino-2,5-cyclohexadienyl)-1,2-dichloroethylene), together withsyn- andanti-isomers of 4-chloro-5-methyl-2,4,6-cycloheptatrien-1-one oxime, which are readily separable but also quickly interconverting in solutions. For the latter compounds, the complete¹H NMR assignment of the stereoisomeric structures has been carried out.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 519–523, March, 1995.The authors are grateful to the International Science Foundation (Grant MHW000) as well as the Russian Foundation for Basic Research (Project No. 94-03-08873) for the financial support of the work.     

X-ray study of the molecular structure of α-mercury and α-platinummercury derivatives of l-menthyl phenylacetate

The molecular structures of the L-menthyl ester of S-α-bromomercuriphenyl-acetic acid, diastereomer II, [α]²⁰_D ?18°, and of the related L-menthyl ester of α-bromobis(triphenylphosphine)platinummeruriphenylacetic acid, VI, have been investigated by the X-ray method. Insertion of L₂Pt carbenoid appears to occur into the HgBr bond in II and two phosphine ligands in the product VI occupy cis positions in a planar square around the platinum atom. The HgPt distance is 2.50 Å; there is intermolecular HgBr coordination in II, the distance being 3.23 Å.     

Isotope exchange study of the e lectrophilic replacement reaction in a saturated carbon atom

Summary A study of the isotope exchange of the ethyl esters of -brommercuryarylacetic acids with²⁰³Hg Br₂ and 70% aqueous dioxane at 60°, made it possible to arrange the substituents in the following series in order of decreasing reaction rate: p-I, Br, Cl > p-F >H > o-CH₃ > p-CH₃> p-typet. C₄H₉.     

Reaction of 2,6-dibenzylidenecyclohexanone with phosphorus pentachloride: Triple functionalization of the isosemiquinoid system

The reaction of 2,6-dibenzylidenecyclohexanone with PCl₅ occursvia the sequential stages of desoxychlorination and substitutional phosphorylation to form (after oxidation, methoxylation, and hydrolysis on the surface of the chromatographic SiO₂ adsorbent) organophosphorus products of the 1-(a-chloro-, a-hydroxy-, or -alkoxy)benzyl-2-chloro-3-(-(dimethylphosphoryl)benzylidene)cyclobex-1-ene series.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 441–443, February, 1996.     

Electrochemical disk generation and ring identification of carbanions from organomercurials in acetonitrile

A rotating disk-ring electrode was used for study of a series of organomercury compounds R₂Hg, where R = CN, CF(NO₂)₂, C₆F₅, PhCC, p-NO₂C₆H₄OCC, PhSCH₂CC, PhCOCH₂, CH₂CN, CCl₂CCl, 2-phenyl-o-carboranyl. Reduction of these compounds at a Pt-disk in acetonitrile is a two-electron process and results in generation of the carbanion R^?. The carbanions generated at the disk interact with the solvent during their convective diffusion to the ring electrode where there may be oxidized. The main reaction in solution, shown using chromatography-mass spectrometry techniques, is acid-base interaction of carbanions with the solvent acetonitrile, which acts as a Brönsted acid. Reaching the ring, the carbanions may be oxidized at anodic potentials of the ring; oxidation potentials depend significantly on carbanion structure (e.g.+0.28 V (vs. SCE), for PhCC^? and +2.20 V for CN^?. It is shown that PK_a value of the carbanions do not correlate with the oxidation potentials, however, a linear correlation is observed between pK_a values and a special parameter called the efficiency coefficient.