Photooxidation of substituted indenes at low temperature

1,2-, 1,4- and ene products were obtained on photooxidation of 2,3-dimethylindene and 3-tert-butylindene at low temperature. The product distribution depends on solvent.     

Palladium-catalyzed synthesis of substituted cyclopentadienes and indenes from allylic esters

Various mono- and di-substituted cyclopentadienes have been prepared by palladium-catalyzed alkylation of allylic esters with cyclopentadienide and t-butyl-cyclopentadienide anions. The same procedure has been applied to the preparation of substituted indenes.     

On the mechanism of the photoisomerization reaction of aryl substituted indenes

The mechanism of the phototransposition reaction of a number arylalkyl substituted indenes has been found to be markedly dependent on the nature and location of the substituent groups.     

Mechanism of electrochemical reduction of vanadium oxides

We specify the different electrochemical processes occurring when V₂O₅ is electrochemically reduced, yielding insertion products with lithium. Under low current density, V₂O₅ is of a ternary phase of approximate stoichiometry, V₂O₅Li_0.5. During the second step a further reversible insertion of Li⁺ occurs, yielding V₂O₅Li without any important modification of the crystalline structure, thus making the reduction reversible. During the two last steps, Li⁺ incorporation is much more difficult and rapidly causes an important and irreversible modification of the crystalline structure, thus making the reduction irreversible.V₂O₃, has nearly the same faradaic capacity as V₂O₅ but, unlike V₂O₅, it can be hardly be used in batteries since its discharge occurs in a wide potential range.     

Mechanism of electrochemical reduction of oxamide analytical applications

Oxamide is electrochemically reduced at mercury electrodes between pH 5.6 and 11.6. The overall mechanism proceeds by an initial 2e reduction of the 1,2-carbonyl groups of oxamide to give a dianion. This then protonates, rearranges, and loses ammonia to glyoxylamide, which is reduced in a further 2e/2H⁺ reaction giving glycolamide as the ultimate product. The reaction thus proceeds by a typical e.c.e. mechanism. The overall homogeneous rate contant for the chemical reaction(s) interposed between the two charge-transfer steps was measured by peak voltammetric, potentiostatic and d.c. polarographic methods. The d.c. polarographic wave of oxamide between pH 5.6 and 11 provides the basis for a very simple analytical method for the determination of oxamide.     

The electrochemical reduction of some substituted π-cyclopentadienylnickel(II) complexes

The electrochemical reduction of the complexes [CpNi(PR₃)₂]⁺, where R = C₂H₅, C₃H₇, C₄H₉ or [C₆Ni,(diphos)]⁺ and [CpNi(diars)⁺ in acetonitrile is described and the data are compared with those for the complexes Cp₂Ni, [Ni(PR₃)₄]²⁺ and Ni(diphos)²⁺₂.     

One-pot two step synthesis of unsymmetrically substituted indenes from 3,4-diarylbutadiene sulfones

A new one-pot two step synthesis of unsymmetrically substituted indenes from available 3,4-diarylbutadiene sulfones involves SO₂ thermal extrusion followed by acid- catalyzed cyclization of the diene formed, the cyclization proceeding selectively at the more electron-rich aryl rings. The procedure is efficient for substrates bearing donor, acceptor, as well as bulky substituents.     

Mechanism of the electrochemical reduction of 2-halo-5-nitrothiophenes in dimethylformamide

The reduction of 2-bromo-5-nitrothiophene and 2-iodo-5-nitrothiophene in dimethylformamide (DMF) was studied by means of classical and commutated polarography, EPR spectroscopy, a rotating platinum disk electrode with a ring, and preparative electrolysis. It was established that, depending on the nature of the halogen, their anion radicals may undergo further reduction to 2-nitrothiophene anion radicals or decomposition with splitting out of a halide anion and conversion to nitrothienyl radicals, which were identified on the ring electrode. The latter are capable of undergoing dimerization to 2,2-dinitro-5,5-dithienyl. The spectra of the anion radicals of 2-nitrothiophene and 2,2-dinitro-5,5-dithienyl were recorded by means of EPR. A mechanism for the reduction of halonitrothiophenes is proposed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 195–198, February, 1981.     

Synthesis of various arylated trifluoromethyl substituted indanes and indenes,and study of their biological activity

A series of 1-trifluoromethyl substituted indanes and indenes bearing aryl groups in positions 1 and/or 3 of the indane core have been synthesized mainly by electrophilic cyclization and arylation of the corresponding trifluoromethylated allyl and propargyl alcohols. The distinctly lipophilic compounds thus obtained were tested against various components of human endocannabinoid system. None of the compounds displayed affinity toward CB₁ or CB₂ receptors. Two compounds inhibited monoacylglycerol lipase (MAGL) and three compounds showed inhibition of anandamide (AEA) uptake. The latter can be related to the low-micromolar inhibition of fatty acid amide hydrolase (FAAH) inhibition displayed by one of these compounds.     

A combined mechanistic and computational study of the gold(I)-catalyzed formation of substituted indenes

Substituted indenes can be prepared after a sequence [1,3] O-acyl shift-hydroarylation-[1,3] O-acyl shift. Each step is catalyzed by a cationic NHC-Gold(I) species generated in situ after reaction between [(IPr)AuOH] and HBF(4)·OEt(2). This interesting silver-free way is fully supported by a computational study justifying the formation of each intermediate.     

Mechanism of halogen substitution in the electrochemical reduction of halonitrofurans in dimet hylformamide

The polarographic reduction of 2-halo-5-nitrofurans in dimethylformamide, which leads ultimately to replacement of the halogen by hydrogen to give a nitrofuran, was studied. The ESR spectra of halonitrofuran anion radicals (Hal=Cl, Br) were recorded. Only the spectrum of the nitrofuran anion radical can be observed in the reduction of 2-I-5-nitrofuran. It is shown that the stabilities of the anion radicals of the halonitrofurans and the mechanism of their subsequent transformations depend to a considerable degree on the nature of the halogen.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 23–26, January, 1977.     

A computer study of borohydride reduction kinetics and stereochemistry

A computer simulation of the sodium borohydride reduction of an alkyl-substituted cyclohexanone in isopropanol has shown the following two apparently contradictory experimental observations to be compatible: (1) The kinetics are experimentally indistinguishable from second-order, with the first hydride transfer rate determining. (2) The cis : trans product ratio changes significantly during the course of reduction. The calculations suggest that the fourth hydride transfer is the second-slowest, with a rate constant approximately eight times that of the first.