Oxidation of the [Rh(CO)2Cl2] anion in aqueous solution

The reaction of rhodium(I) carbonyl chloride, [Rh(CO)₂Cl]₂, with dichromate, cerium(IV) sulfate, hexachloroplatinic acid or p-benzoquinone in aqueous hydrochloric acid proceeds by consumption of 4 equivalents of oxidizing agent per mole or rhodium(I) in accordance with the equation Rh^I(CO)₂  4e + H₂O → Rh^III(CO) + 2H⁺ + CO₂A “cyclic” oxidation mechanism is suggested.     

Hydrogenation without a transition-metal catalyst: on the mechanism of the base-catalyzed hydrogenation of ketones

The hydrogenation of unsaturated organic substrates such as olefins and ketones is usually effected by homogeneous or heterogeneous transition-metal catalysts. On the other hand, a single case of a transition-metal-free and purely base-catalyzed hydrogenation of ketones was reported by Walling and Bollyky some 40 years ago. Unfortunately, the harsh reaction conditions (ca. 200 degrees C, >100 bar H(2), potassium tert-butoxide as base) limit the substrate spectrum of this reaction to robust, nonenolizable ketones such as benzophenone. We herein present a mechanistic study of this process as a basis for future rational improvement. The base-catalyzed hydrogenation of ketones was found to be irreversible, and it shows first-order kinetics with respect to the substrate ketone, hydrogen, and catalytic base. The rate of the reaction depends on the type of alkali ion present (Cs > Rb - K > Na > Li). Using D(2) instead of H(2) revealed a rapid base-catalyzed isotope exchange/equilibration between the gas phase and the solvent as a concomitant reaction. The degree of deuteration of the product alcohols did not indicate a significant kinetic isotope effect. It is proposed that both ketone reduction and isotope exchange proceed via similar six-membered cyclic transition states involving the H(2)(D(2))-molecule, the alkoxide base, and the ketone (solvent alcohol in the case of isotope exchange). Mechanistic analogies are pointed out which apparently exist between the base-catalyzed hydrogenation of ketones studied here and the Ru-catalyzed asymmetric ketone hydrogenation developed by Noyori. In both cases, heterolysis of the hydrogen molecule appears to be assisted by a Br?nsted-base (i.e., alkoxide), the latter being bound to the substrate ketone or the catalyst ligand, respectively, by a bridging Lewis-acidic alkali ion.     

Preparation of isomeric 1,3- and 1,5- (o-phenylene)-hexamethylcyclotetrasiloxanes and investigation of their spectral characteristics

Workup of the mixture of products of pyrolysis of cyclotetrasiloxane (Me₂SiO)₂(MePhSiO)₂ yielded 1,3- (I) and 1,5-(o-phenylene)cyclosiloxane (II), the structures of which were established on the basis of data from their IR, PMR, and mass spectra.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 24–25, January, 1978.     

Imidazopyeidine derivatives as polymethine dyes

Several new polymethine dyes of the cyanine and merocyanine series with 1-methyl-1H-imidazo [4,5-b]pyridine residues were synthesized, and their colors were studied. Replacement of the benzimidazole residue in the cyanine dyes by a l-methyl-1H-imidazo[4,5-b]-pyridine residue leads to deepening of the dye color.See [1] for communication II.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1561–1565, November, 1971.     

Trivalent phosphorus thiocyanides

Conclusions The acid chlorides of thiophosphorous and thiophosphonous acids react with trimethylsilyi cyanide to give the corresponding trivalent phosphorus thiocyanides, which give the-cyanoalkyl esters of phosphorus thioacids when reacted with carbonyl compounds.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 939–940, April, 1982.     

Spectrophotometric investigation of the reaction of eriochrome cyanin RC and magnesium and aluminium

The reaction of magnesium or aluminium ions with Eriochrome Cyanin RC in alkaline medium leads to formation of a complex of type ML. The molar absorptivities of the complexes are 1.90 +/- 0.14 x 10(3)1. mole(-1).cm(-1) at 570 nm for the magnesium complex and 3.87 +/- 0.04 x 10(4) at 555 nm for the aluminium complex. The conditional stability constants of the complexes were determined at various pH values, and hence the overall formation constants, which were found to be log beta(111) = 8.65 +/- 0.06 for MgOHL, log beta(121) = 22.29 +/- 0.05 for AlH(2)L, log beta(111) = 18.25 +/- 0.14 for AlHL, and log beta(101) = 13.66 +/- 0.01 for AlL.     

Pyridylethylation of some heterocyclic thioamides and potential mercaptans

2-Pyridylethylation of benzazothiones-2 which are potential mercapto compounds (benzothiazolethione-2, benzoxazolethione-2, 1-methylbenzoimidazolethione-2, benzoimidazolethione-2, 5, 6-dimethylbenzoimidazolethione-2), is described, as well as preparation of 5, 6-dimethylbenzoimidazolethione-2 by direct oxidation of 5, 6-dimethylbenzoimidazole.     

Unusual dealkylations and rearrangements in aromatic nucleophilic substitution

The reaction of 2,4-dinitrohalobenzenes with di-isopropylamine produces mainly N-(2,4-dinitrophenyl)-isopropylamine and N-(2,4-dinitrophenyl)-n-propylamine instead of the expected straightforward substitution product. Dealkylations are also observed in the reactions with isopropylcyclohexylamine and dicyclohexylamine. A carbanionic mechanism is proposed.