Effect of hydration on polarographic reduction of some carbonyl compounds

Hydration and acid-base equilibria of the hydrated form govern the reduction and oxidation of numerous carbonyl compounds. Aliphatic and aromatic aldehydes are reduced in the free carbonyl form and oxidized as geminal diol anions. In haloacetaldehydes and haloacetones the C?X bond can be reductively cleaved both in the free carbonyl and in the hydrated form, oxidized form is again the geminal diol anion. Schemes (6), (7), (10), (11), (12) and (13) summarize the mechanism of the hydration and its relation to electrooxidation and reduction. Differential pulse of polarographic waves enabled measurement of heights of waves close to the initial or final rise of current and following the variations of their height with changes in activity of the solution.     

The mass spectra of some alkyl and aryl imidazolines

The mass spectra of mono- and di-substituted alkyl and aryl imidazolines have been measured and the spectra analysed with the aid of deuterium labelling and high resolution techiques. In contrast to the fragmentation of thiazolines, all principal fragments of the imidazoline ring contain one nitrogen with or without hydrogen migration. In the case of 2,4-disubstituted imidazolines, the presence of two tautomeric molecular ions are suggested.     

The mass spectra of some alkyl and aryl oxazoles

The mass spectra of a variety of alkyl and aryl oxazoles have been determined and the spectra analyzed with the aid of deuterium labelling and high resolution mass spectrometry. In contrast to the corresponding benzenoid compounds, the mass spectra of isomeric alkyl oxazoles are distinctive and in this respect are akin to those of the corresponding pyridines. Further analogy to the pyridines is suggested by the unfavorable nature of a carbonium ion adjacent to the 2-position and this effect may be used to locate alkyl substituents attached to the oxazole nucleus. The loss of carbon monoxide from the molecular ions of 2,5-disubstituted oxazoles probably occurs with ring opening and migration of the C-5 substituent (e.g.Br) to the C-4 position.     

Nickel-catalyzed cross-coupling of unactivated alkyl halides and tosylate carrying a functional group with alkyl and phenyl Grignard reagents

By the use of catalytic amounts of a nickel salt and a 1,3-butadiene, primary and secondary alkyl Grignard reagents undergo cross-coupling with alkyl bromides, iodide, and tosylate carrying a functional group such as amide, ester, and ketone at 0 °C in THF. The present procedure provides a simple, convenient, and practical method for construction of carbon chains in the presence of various functional groups. PhMgBr also gave the corresponding coupling product in a moderate yield.     

Cr(CO)5(CNCN), a complex in which the coordinated CN group of isocyanogen binds and vibrates like a CO ligand

The IR and Raman spectra have been determined of the products formed by low-temperature (−20°C) replacement of 2-MeTHF (2-methyltetrahydrofuran) in photochemically produced Cr(CO)₅(2-MeTHF) by isocyanogen, CNCN. The IR spectra are interpreted in terms of the formation of an isonitrile and a nitrile complex, Cr(CO)₅(CNCN) and Cr(CO)₅(NCNC). A detailed study of the IR and Raman spectra of Cr(CO)₅(CNCN), which was formed in large excess, reveals that the coordinating CN group of CNCN has coordinating and vibrational properties almost identical to those of the CO ligands in this complex.     

Palladium-catalyzed oxidative carbonylation of alkyl and aryl indium reagents with CO under mild conditions

CO now can react with organoindium reagents. A novel palladium-catalyzed oxidative carbonylation reaction of organoindium reagents by CO gas with desyl chloride as oxidant was developed in supplementation with the classical methods for preparation of carboxylic acid derivatives. Primary, secondary alkyl indium reagents with beta-hydrogens and aryl indium reagents were suitable substrates, and the reaction could be carried out at 60 degrees C under 50 psi CO. Carbonylation of alkyl indium reagents can occur smoothly without additional base. Although the indium reagents were prepared from corresponding Grignard reagents (at low temperature), they displayed full compatibility with various functional groups under the protic reaction conditions. Preliminary mechanistic studies including stoichiometric and catalytic reaction examination provided evidence to support the operation of the mechanism consisted of oxidative addition of deslyl chloride to Pd(0) and quick tautomerization to give a palladium enolate species II (ROPdCl), displacement of the enolate group in II by R(2)OH, followed by CO insertion to give alkoxycarbonyl palladium complex V, which undergoes transmetalation with R(1)(3)In and reductive elimination to afford the product and a Pd(0) species. In this mechanism, the alkoxycarbonyl group was transferred to the palladium center prior to the alkyl group, different from traditional ways initiated from oxidative addition of alkyl halides to a Pd(0) species.     

Polyfluorination of aryl alkyl sulfides by IF5 with concomitant migration of the arylthio group

[reaction: see text] In the reaction of p-chlorophenyl alkyl sulfides with IF(5), polyfluorination reaction took place on the alkyl chain with the migration of the arylthio group. Consequently, p-chlorophenyl polyfluoroalkyl sulfides, having 3-7 fluorine atoms depending on alkyl chain length, could be obtained selectively.     

Hydrogen/deuterium exchange in gas phase reactions of anions with some alkyl phenyl ethers

The gas phase reactions of anions with methyl and ethyl phenyl ether have been studied by Fourier Transform Ion Cyclotron Resonance Mass Spectrometry. ¹⁸O-Labelling has shown that part of the reactions of OH^- with methyl phenyl ether proceed via ipso-substitution, the main reaction channel being S_N2 substitution. Deuterium labelling has shown that extensive inter- and intramolecular hydrogen/deuterium exchange can precede the final substitution reaction. Hydrogen atoms originating from the methoxy substituent are involved in this exchange process. The reactions of anions with ethyl phenyl ether proceed mainly via an elimination mechanism. Deuterium labelling has shown that in some cases hydrogen/deuterium exchange takes place prior to elimination.     

cine-Substitution of the nitro group in 2,4-disubstituted nitroarenes with carbanions of aryl alkyl sulfones

Rapid protonation of short lived σ^H adducts of carbanions of aryl alkyl sulfones to 2,4-disubstituted nitrobenzenes results in elimination of nitrous acid giving 1,3,5-trisubstituted benzenes as products of cine-substitution of the nitro group.     

Effect of structural changes on mesophase stability of some model compounds based on the aryl benzoate group

Compounds based on 4,4'-substituted phenylbenzoate \[ R O-C6H4COO-C6H4- X ] ( I ), where X is a cyano group and R is a terminal alkyl chain ranging from 12 to 30 carbon atoms, and alternatively where R is held at 16 carbons and X is CN, COOH, OH, COOCH2C6H4, OCH2C6H4 and OC16H33 , were prepared and their mesophase stabilities characterized. Similarly, compounds based on symmetric dimers of terminally alkoxy-substituted phenyl esters \[C16H33O-C6H5COO- A -OOCC6H5-OC16H33] ( II ), the central linkage A being 1,2-, 1,3- and 1,4-phenylene, and 4,4'-biphenyl, were synthesized and studied. A partial success was achieved in the synthesis of compounds similar to series II , but where the ester groups were reversed (series III ), in order to assess the influence of this structure variation on the liquid crystallinity.     

Electrochemical reduction of Fe(III), Cr(III), and Mn(III) porphyrin complexes in DMSO

The half-wave potentials are given for the electrochemical reduction of Fe(III), Cr(III), and Mn(III) porphyrin complexes. Cyclic voltamperometry was used to study the reversibility of these reactions. An effect was demonstrated for the structure of the porphyrin ligand on the half-wave potentials for the reduction of the Mn(III) complexes.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1665–1668, July, 1991.