Two Distinct Mechanisms of Alkyne Insertion into the Metal–Sulfur Bond: Combined Experimental and Theoretical Study and Application in Catalysis

The present study reports the evidence for the multiple carbon–carbon bond insertion into the metal–heteroatom bond via a five‐coordinate metal complex. Detailed analysis of the model catalytic reaction of the carbon–sulfur (C? S) bond formation unveiled the mechanism of metal‐mediated alkyne insertion: a new pathway of C? S bond formation without preliminary ligand dissociation was revealed based on experimental and theoretical investigations. According to this pathway alkyne insertion into the metal–sulfur bond led to the formation of intermediate metal complex capable of direct C? S reductive elimination. In contrast, an intermediate metal complex formed through alkyne insertion through the traditional pathway involving preliminary ligand dissociation suffered from “improper” geometry configuration, which may block the whole catalytic cycle. A new catalytic system was developed to solve the problem of stereoselective S? S bond addition to internal alkynes and a cost‐efficient Ni‐catalyzed synthetic procedure is reported to furnish formation of target vinyl sulfides with high yields (up to 99 %) and excellent Z/E selectivity (>99:1).     

A new method for the generation of stable phenoxyl radicals by the reaction of [(Me3Si)2N]2E (E = Ge,Sn) with sterically hindered phenols

An unusual reaction of diaminogermylene and diaminostannylene with sterically hindered phenols which leads to the formation of stable phenoxyl radicals in high concentrations was found. The reaction mechanism was proposed. Amides [(Me₃Si)₂N]₂E (E = Ge, Sn) were investigated electrochemically.     

Reaction of 3-Benzoyl-2,3-dibromopropionic Acid with Substituted ortho-Phenylenediamines

3-Benzoyl-2,3-dibromopropionic acid reacts with 4-substituted o-phenylenediamines to give 3-aryl-2-carboxymethylene-1,2-dihydroquinoxalines.     

Chemical properties of 2,2,4-trisubstituted 2,3-dihydro-1H-1,5-benzodiazepines

Acetylation and nitrosation of 2,4-diaryl-2-methyl-2,3-dihydro-1H-1,5-benzodiazepines take place at the azomethyne nitrogen. Reduction is stereoselective.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1122–1126, August, 1987     

3-Aryl-2-benzyl -1,2-dihydroquinoxalines

The reaction of 1,2-phenylenediamine with 2-bromo-1,3-diaryl-1-propanones led to stable and crystalline 3-(4-R-phenyl)-2-(4-R-benzyl)-1,2-dihydroquinoxalines.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 830–832, June, 1987.     

Effect of free valence on the characteristics of internal rotation in <Emphasis Type="Italic">n</Emphasis>-alkyl radicals

A study of internal rotation in the radicals n-C _n H_2n+1C^·H₂, (2 ≤ n ≤ 7) was carried out for the case of rotation around the bonds not including the radical center. 21 potential functions of internal rotation V(φ) were calculated. The coefficients in V(φ) were shown to depend only on the immediate environment at the bond of rotation. Characteristics of internal rotation in n-alkyl radicals were compared with related parameters of the corresponding alkane molecules. The generalized function V _av(φ) with the coefficients defined only by the position of the bond of rotation in the hydrocarbon chain and possessing the transposition property were proposed. The functions V _av(φ) were recommended for the simulation of the structure and properties of large molecules containing hydrocarbon fragments. This work continues a systematic study on the characteristics of the internal rotation in the n-alkane molecules and the groups containing free valence in n-alkyl radicals.     

Flocculation of synthetic latexes with a quaternary ammonium base derived from resin acids and rosin

The flocculating effect of a quaternary ammonium compound based on resin acids and rosin in the course of rubber recovery from SKMS-30 ARK butadiene-α-methylstyrene latex was studied. The agent shows promise for commercial use.     

Specific properties of hydroxyapatite as a potential transporter of copper ions and its complexes

Russian Chemical Bulletin - Modification of the cocrystallization method for producing hydroxyapatite (HAP) and an HAP-Cu combination to the enzymatic method using alkaline phosphatase leads to a...     

Electrophilic substitution in n-aryl-2-pyrazolines: Reactions with 1,3-dithioles

Dyes that absorb at 525–580 nm were obtained by the reaction of derivatives of 1,3-dithiolium iodide (or perchlorate) with 1-phenyl-3,5-di-R-2-pyrazolines, N,N-dimethylaniline, and benzaldehyde N-methylphenylhydrazone. It was demonstrated by alternative synthesis that the reaction takes place in the para position of the N-phenyl group. Dyes can be obtained in two steps from 2-dimethylamino-1,3-dithioles and activated aromatic compounds with subsequent oxidation of the intermediate leuco compounds with air oxygen.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1245–1250, September, 1981.