Inhibition of radiation-chemical oxidation of n-octane by stable iminoxyl biradicals

Conclusions The biradicals are effective inhibitors, their inhibiting action increasing with an increase in the distance between the fragments.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 45–48, January, 1977.     

Fluorinated azines and benzazines containing oxygen or sulfur atoms

In the frames of this review article the recently obtained data on synthetic approaches to fluorinated oxa(thia)azines and benzazines, their chemical properties, structure, and biological activity have been analyzed.     

新型含硫化合物的合成及其晶体结构研究

通过简单的一步亲核取代反应合成了一新型含硫化合物(4-羧基甲硫醇基-2,3,5,6-四氯-苯硫醇基)乙酸(1),产物经乙酸乙酯重结晶分离纯化,并在适当的条件下培养得到单晶,测定了该化合物的晶体结构,以及其DMSO加合物的晶体结构.其中该化合物晶体属于单斜晶系,空间群为P21/c,a=0.508 93(4)nm,b=0.969 81(7)nm,c=1.439 1(1)nm,β=91.036(4)°,V=0.710 20(9)nm3,Z=2,Dc=1.843 g/cm3,F(000)=392,μ=1.133,R1[I2σ(I)]=0.097 3,wR2[I2σ(I)]=0.193 1.其DMSO加合物的晶体结构属于正交晶系,空间群为Pnma,a=1.372 48(2)nm,b=2.883 6(4)nm,c=0.461 48(6)nm,V=1.826 4(4)nm3,Z=4,Dc=1.703 g/cm3,F(000)=936,μ=1.010,R1[I2σ(I)]=0.088 8,wR2[I2σ(I)]=0.203 9.晶体结构分析表明,分子间氢键是这一化合物的一大特点.     

Quantum-chemical calculations of the spectroscopic parameters of heteroaromatic compounds containing sulfur and selenium atoms

Conclusions A new single set of spectroscopic parameters of the CNDO method for compounds containing sulfur and selenium atoms, which permits the simultaneous calculation of the ionization potentials and energies of the electronic transitions on a semiquantitative level, has been proposed.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2251–2253, October, 1986.     

A scent of therapy: pharmacological implications of natural products containing redox-active sulfur atoms

A range of sulfur-containing natural products from plants, fungi, bacteria and animals have recently been investigated to determine their therapeutic potential. Preliminary in vitro and in vivo studies of compounds such as ergothioneine, ovothiols, allicin, leinamycin, varacin, lenthionine and diallyltetrasulfide have provided evidence for antioxidant, antibacterial, antimicrobial, antifungal and anticancer properties. The biological activity of these compounds is the result of specific chemical properties which converge in chemotypes such as thiols, disulfides, sulfenic and sulfinic acids,thiosulfinates, sulfoxides, sulfones and polysulfides. Redox-activity, catalysis, metal binding, enzyme inhibition and radical generation allow reactive sulfur species to interact with oxidative stressors, to affect the function of redox-sensitive cysteine proteins and to disrupt the integrity of DNA and cellular membranes. In some cases, the biological activity of sulfur-containing plant products depends on initial enzymatic activation, which allows thiosulfinates and isothiocyanates to be generated with high target selectivity. Not surprisingly, research into the biochemical and pharmacological properties of the lesser known sulfur chemotypes is rapidly gathering momentum.     

Novel sulfur containing polymers

Sulfur containing polymers were synthesized by the addition of thiols to alkenes and alkynes. Although the polymer formation is explained on the basis of a radical intermediate these processes show typical characteristics of step growth polymerizations. These reactions have been applied for the syntheses of telechelics.     

Tetrahydrofuran analogues with silicon and sulphur atoms

Quantum-mechanical calculations at the self-consistent-field–M?ller–Plesset level have been performed for various compounds obtained by substituting two or four CH₂ groups of the tetrahydrofuran molecule with SiH₂ groups, as well as the oxygen with a sulphur atom. Cyclic tetrasilane oxide, (SiH₂)₄O, and sulphide, (SiH₂)₄S, are suggested as possible alternatives to the carbon ring of natural sugars for the design of exobiological molecules because of certain similarities with tetrahydrofuran, (CH₂)₄O, especially the relatively small energy differences between different conformers and the subsequent ability to cross the energy barriers between them by puckering on the pseudorotation wheel. Received: 16 September 1999 / Accepted: 3 February 2000 / Published online: 21 June 2000     

A novel flame retardant containing phosphorus,nitrogen, and sulfur

In this article, a novel intumescent flame retardant (IFR) PNSFR containing three flame-retardant elements, phosphorus, nitrogen, and sulfur was designed and synthesized. Then a series of flame-retardant thermoplastic polyurethanes (TPU) were prepared using the PNSFR. The effects of the flame retardant on the flammability of TPU/PNSFR composites were investigated by limited oxygen index (LOI) and UL-94 vertical burning. The results showed that TPU containing 10 mass% PNSFR had the highest LOI value (36) and could reach the V-0 rating. The flame-retardant mechanism of PNSFR in TPU was also disclosed using thermogravimetric analysis (TG), scanning electron micrograph, TG-infared spectrometry, and Fourier transform infrared spectroscopy. The sulfur and phosphorus elements of PNSFR can be kept in residual char. Moreover, an optimal loading amount of the IFR in TPU is in favor of forming dense and continuous char layer to prevent heat transfer and the spread of flammable gases. The IFR PNSFR may find potential use for various flame-retardant polyurethanes.     

Synthesis of nitrogen and sulfur macrocycles with cis exogenous oxygen and sulfur donor atoms

A series of new N4 and N8 macrocycles has been prepared, that includes cis-exogenous O2, S2 and S/O atoms to allow chelation to a metal external to the macrocyclic ring. We found that thioamide units within the macrocycles were unstable to attack by secondary amines and thus alkylated precursors containing only tertiary amines could lead to exogenous-S2 macrocycles. Cyclisation of alkylated tetraamine precursors with dimethyloxalate or dithiooxamide led to both N4 and N8 macrocycles via 1 + 1 and 2 + 2 cyclisation reactions with exogenous-O2 or S2 respectively. Alkylation of preformed exogenous-O2 macrocycles was explored and led to alkyl substitution at the secondary amine nitrogens in the ring, however synthesis of these species was overall lower yielding than cyclisation using alkylated tetraamine precursors. Thionation of an exo-O2 macrocycle using an analogue of Lawesson's Reagent led to formation of the analogous exogenous-S2 and exogenous-O,S macrocycles. Related S2N2 macrocycles with exogenous-O2 were prepared by a cyclisation route but could not be isolated free of larger ring analogues.