Photoelectron spectra and steric structure of sulfenamides

According to the data from photoelectron and UV spectroscopy, the molecules of N,N-dimethylmethane sulfenamide and N,N-diethylpropane-2-sulfenamide have a conformation with orthogonal orientation of n_N and n_S orbitals, while N,N-dimethylbenzene sulfenamide in the gas phase exists in conformational equilibrium of the planar and skewed conformers.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 77–80, January, 1990.We would like to thank F. G. Nasybullina for conducting the GLC analysis.     

A palladium-catalyzed regio- and stereoselective four-component coupling reaction

Pd(PPh(3))(4) catalytically assembles sulfenamide, alkyne, carbon monoxide, and diphenyl diselenide regio- and stereoselectively in a one-pot four-component coupling reaction to yield (Z)-beta-selenyl acrylamides. The reaction proceeds in good to excellent yields (60-95%) and is tolerant of a range of functional groups on both the nitrogen of the sulfenamide and the alkyne. Moderate selectivities ranging from 4:1 to 7:1 beta-selenyl to beta-sulfenyl acrylamide have been observed despite the initial concentration of 2:1 selenium to sulfur in the reaction. The chalcogeno selectivity was found to depend directly on CO pressure; increased pressure decreased selectivity for selenium over sulfur.     

New class of biodegradable polymers formed from reactions of an inorganic functional group

Although numerous small molecules have been synthesized with sulfenamide bonds (R(2)N-SR), this is the first report of the synthesis of polysulfenamides. These polymers are readily synthesized at room temperature using secondary diamines and dithiosuccinimides. The dithiosuccinimides were readily synthesized in one step by the reaction of dithiols such as HS(CH(2))(6)SH with N-chlorosuccinimide. The resulting dithiosuccinimides were either recrystallized or readily purified by chromatography on silica gel and required no special handling. The conversions of polymerization ranged from 95 to 98%, and the molecular weights of the polymer reached as high as 6,300 g mol(-1). The sulfenamide bond was very stable in organic solvents, and no degradation was observed under atmospheric conditions in C(6)D(6) for 30 days. In contrast, the sulfenamide bond readily decomposed in less than 12 h in D(2)O. Polysulfenamides were fabricated into micron-sized particles loaded with dye and endocytosed into JAWSII immature dendritic and HEK293 cells. Polysulfenamides represent a new class of polymers that are readily synthesized, stable in aprotic solvents, and readily degrade in water.     

Structure,spectral and thermal characteristics of zinc(II) halide complexes with N,N-dimethyl-N′,N′-dimethylthiocarbamoyl sulfenamide

We have studied the spectral (IR, PMR, EAS) and thermal properties of new ZnX₂ complexes (X = Cl, Br, I) with N,N-dimethyl-NN,NN-dimethylthiocarbamoyl sulfenamide (L). We have established that the {[ZnLX₂]}₂ compounds obtained are dimers with Zn—X bridging bonds and monodentate coordination of L through the thione sulfur atom.     

Contrasting thermal reactions of allylic sulfilimines and phosphinimines

Allylic sulfilimines and phosphinimines undergo spontaneous but contrasting rearrangements at low temperatures. Whereas a sulfilimine is converted to an isomeric sulfenamide by (2,3)-sigmatropic rearrangement, a structurally analogous phosphinimine undergoes an unusually facile double bond shift to form an isomeric vinylic structure.     

Barriers to rotation in substituted O-aryl-hydroxylamines.

The effect of substituents on rotational barriers in O-arylhydroxylamines was studied. The results do not support any of the proposed mechanisms for substituent effects in the analogues sulfenamide series.     

超高效液相色谱法测定橡胶中6种橡胶助剂的含量

取条状橡胶样品(厚约2mm,宽约1mm)1.000g,加入体积比为6∶1的乙腈-二氯甲烷混合溶液50mL,超声提取60min,所得溶液经0.45μm滤膜过滤,滤液用于超高效液相色谱法分析。用ZORBAX Eclipse XDB-C18色谱柱(4.6mm×100mm,1.8μm)为固定相,以体积比为40∶60的乙腈-pH 4.0的12.5mmol·L^-1磷酸二氢钠混合溶液为流动相进行等度洗脱,使所测定的6种橡胶助剂得以分离,对6种橡胶助剂在不同波长处进行紫外检测,防老剂6PPD[N-(1,3-二甲基)丁基-N′-苯基对苯二胺]的检测波长为290nm,防焦剂CTP(N-环己基硫代邻苯二甲酰亚胺)和其他4种硫化促进剂[TBBS(N-叔丁基-2-苯并噻唑次磺酰胺)、MBTS(2,2-二硫化二苯并噻唑)、CBS(N-环己基-2-苯并噻唑次磺酰胺)、DCBS(N,N-二环己基-2-苯并噻唑次磺酰胺)]的检测波长均为226nm。6种橡胶助剂的标准曲线的线性范围均为5.0~500.0mg·L^-1,其检出限(3S/N)为0.3~2.5mg·L^-1。按标准加入法进行回收试验,测得回收率为82.8%~107%,测定值的相对标准偏差(n=5)均小于5.0%。     

Reaction of dialkyl trimethylsilyl dithiophosphites with sulfenamides

Dialkyl trimethylsilyl dithiophosphites react with sulfenamides either through involvement of the trimethylsilyl group and the formation of trialkyl trithiophosphates or by isomerization of the starting silylphosphites to give S-alkyl O-trimethylsilyl alkyldithiophosphonates. The direction of the reaction depends on the nature of the substituents at the sulfur atoms of the silylphosphite and sulfenamide.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2146–2147, September, 1990.     

The "Non-Oxidative" pummerer reaction: conclusive evidence for S(N)2-type stereoselectivity, mechanistic insight, and synthesis of enantiopure L-alpha-trifluoromethylthreoninate and D-alpha-trifluoromethyl-allo-threoninate(1)

Enantiopure methyl D-alpha-trifluoromethyl-allo-threoninate 18 and L-alpha-trifluoromethylthreoninate 19 were synthesized using (R)-ethyl p-tolylsulfoxide as chiral alpha-hydroxyethyl anion equivalent. The key step was the S(N)2-type replacement of the sulfinyl auxiliary with a hydroxy group, via trifluoroacetic anhydride promoted "non-oxidative" Pummerer reaction (NOPR) of the diastereomeric intermediate beta-sulfinyl amines 14 and 15, obtained by condensation of (R)-ethyl p-tolylsulfoxide 13 with the N-Cbz imine of methyl trifluoropyruvate 12. The conclusive evidence for S(N)2-type stereoselectivity of the NOPR was achieved by X-ray diffraction of both the starting diastereomer 14 and the p-bromobenzoate 25, obtained from the threoninate 19. NMR monitoring of the NOPR performed on 15 allowed the detection of a transient intermediate, which was identified as the four membered cyclic sigma-sulfurane 27. This intermediate spontaneously rearranged (40 min, rt) into the corresponding sulfenamide 17, probably via an intramolecular displacement of the sulfinyl by a trifluoroacetoxy group, with inversion of configuration at the carbon stereocenter. The same process occurred for the diastereomeric beta-sulfinyl amine 14, but the sulfenamide 16 was formed at a very fast rate, thus precluding NMR detection of the corresponding sigma-sulfurane intermediate 26. One-pot treatment of the diastereomeric sulfenamides 16 and 17 with NaBH(4) afforded very good yields of the corresponding threoninates 18 and 19.     

Mass-spectrometric study of sulfenamide derivatives of 2-substituted benzothiazoles

It is shown that the dissociative ionization of 2-mercaptobenzothiazole derivatives with a sulfenamide bond is accompanied by cleavage of the labile N-S bond and simultaneous migration of the hydrogen atom from the thiol substituent at the site of cleavage to the sulfur atom. Ion peaks with mass 167, 166, R, and (R-H), where R is an N-substituted cycloalkylamine, are maximum peaks and are used for the identification of the compounds.Translated from Khimiya Geterotsiklicheskikh Soedmenii, No. 10, pp. 1330–1336, October, 1975.     

Reaction of bicyclo[2.2.1]hepta-2,5-diene with the arenesulfenamide—phosphorus(v) oxohalide system: chemo-, regio-, and steroselectivity

The chemo-, regio- and stereoselectivities of electrophilic sulfenylation of bicyclo[2.2.1]hepta-2,5-diene with arenesulfenamides activated by phosphorus(v) oxohalides were studied. The ratio of the products of endo- to exo-attack of the diene by the electrophilic species depends on the solvent nature. The proportions of the products formed upon addition to one double bond and upon homoallylic participation of the second double bond depend on solvent polarity, the nature of the halogen, the substituents in the sulfenamide benzene ring, and on the reaction time. In addition, the formation of mixed adducts was proven for the reaction carried out in acetonitrile and the formation of disulfenylation products was found in the reaction with excess sulfenylating reagent. Isomerization of exo-3-arylthio-endo-2-halobicyclo[2.2.1]hept-5-enes to the products formed with homoallylic participation of the second double bond, exo-5-arylthio-endo-3-halotricyclo[2.2.1.0^2,6]heptanes, was shown to be possible.     

Using sulfinamides as high oxidation state sulfur reagent for preparation of sulfenamides

Traditional preparation of sulfenamides require the use of low oxidation state of sulfur reagent such as RSCl, (RS)₂ or RSH, which are toxic, odorous and difficult to deal with due to the harsh reaction conditions. Here high oxidation state of sulfur reagent—aliphatic sulfinamide, were used for preparation of sulfenamide in one step efficiently. Different aromatic amines with all sorts of functional groups, especially amino groups and hydroxyl groups, were transformed to the corresponding sulfenamides in moderate yields, which was difficult to obtain with previous methods.     

Influence of accelerator type on properties of NR/EPDM blends

The effect of accelerator type on processability and mechanical properties of 60/40 natural rubber/ethylene propylene diene monomer (NR/EPDM) blend was investigated. Three groups of commercial accelerators were selected, i.e., sulfenamide group (Santocure-TBBS), thiuram group (Perkacit-TMTD) and mercapto group (Perkacit-MBT and Perkacit-MBTS). The results reveal that the accelerator type not only affects the cure characteristics, but also has great influence on compound viscosity. Among the accelerators studied, TBBS gives the best processing safety together with a relatively high state of cure. In addition, TBBS also provides good cure compatibility between the NR and EPDM phases, giving rise to superior mechanical properties. Although TMTD could give a high state of cure, it causes severe cure incompatibility, leading to poor tensile strength. Due to their lower reactivity, the two mercapto accelerators give a relatively low state of cure. Therefore, the vulcanizates obtained possess low modulus and hardness as well as degree of elasticity. Surprisingly, it is found that the tensile strength of the MBTS-cured blend is relatively high. Good cure compatibility given by MBTS could be used to explain the results.     

Theoretical study of omeprazole behavior: Racemization barrier and decomposition reaction

Omeprazole is a substituted benzimidazole which suppresses gastric‐acid secretion by means of H⁺, K⁺‐ATPase inhibition. It is an optically active drug with the sulfur of the sulfoxide being the chiral center. This pro‐drug can be easily converted into its respective sulfenamide at low pH. In this work, omeprazole has been studied in relation to racemization barrier and decomposition reaction. Quantum chemistry coupled to PCA chemometric method were used to find all minimum energy structures. Conformational analysis and calculation of racemization barriers were carried out by PM3 semiempirical method (Gaussian 98). The average racemization energy barrier for all minimum energy structures (43.56 kcal mol^?1) can be related to the velocity constant in Eyring's equation. The enormous half‐life time at 100°C (9.04 × 10⁴ years) indicates that the process cannot be observed in human time scale. On the other hand, the difference of free energy change (Δ(ΔG) = ?266.78 kcal mol^?1) for the decomposition reaction shows that the process is favorable to the sulfenamide formation. The highly negative Δ(ΔG) obtained for the decomposition reaction shows that this process is extremely exothermic. This result explains why omeprazole decomposes and does not racemize. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008     

Reaction of thiols with N-bonded sulfenamide complexes of cobalt(III): steric effect and reaction pathway

The products and kinetics of the reaction of several thiols (RSH = 2-aminoethanethiol, cysteine, penicillamine, cysteine ethyl ester) with N-bonded sulfenamide complexes ([Co(en)(2)(NH(2)S(CH(2))(2)NH(2)](3+) (IA), [Co(en)(2)(NH(2)SCH(2)CH(CO(2)H)NH(2)](3+) (IC), [Co(en)(2)(NH(2)SC(CH(3))(2)CH(CO(2)H)NH(2)](3+) (IP)) have been studied. The reaction proceeds by nucleophilic attack at sulfur with cleavage of the N-S bond to form a disulfide and leave a coordinated NH(3) ligand. The kinetics (pH 4-10) reveal that the deprotonated thiol, RS(-), is the reactive nucleophile and that the N-deprotonated sulfenamide complex is unreactive. The reactions of IP are approximately 10(4) times slower than those of IA or IC, and the reasons and consequences of this large steric effect are discussed. It is concluded, on the basis of these and other observations from the literature, that there will be substantial steric retardation to nucleophilic attack at two-coordinate sulfur in a R-C(CH(3))(2)-S-X-R' unit because of the regiospecificity of the reaction. The acid dissociation constants of IP and the X-ray structure of its bromide salt also are reported.     

The reaction of benzothiazole sulfenamide with (TMS)3SiH: An example of degenerate-branched chain process

The reaction of sulfenamide 3 with (TMS)₃SiH initiated by the decomposition of AIBN at 76 °C has been studied in some detail. The reaction is a rare example of a radical chain-branching process. The two main products are dialkylamine 4 and the thiosilane 5. It is also established that 2-mercaptobenzothiazole (2) is formed in a substantial yield as one of the by-products. The mechanism of this chain autocatalytic reaction is complex due to a mix of different radical chain reactions and some discussion is provided. The amine obtained in a quantitative yield can arise from two independent routes of attack of (TMS)₃Si radical on sulfenamide 3. The minor route affords thiol 2 that can act as a catalyst for the major route during the reaction course and then gives a salt with secondary amine, which precipitates upon cooling. The origin of autocatalysis is discussed in some detail.     

Absorption, distribution, metabolism and excretion of N-cyclohexyl-2-benzothiazyl sulfenamide (CBS), a vulcanizing accelerator, in rats

Absorption, distribution, metabolism and excretion were studied in rats following a single oral administration of N-cyclohexyl-2-benzothiazyl sulfenamide (CBS) at a dose of 250 mg/kg. About 65% and 24% of the dose were excreted into urine and feces, respectively, for 3 days after administration of labeled CBS (cyclohexyl-14C). Biliary excretion amounted to about 5% of the dose for 3 days. While about 92% of the dose was recovered in urine and feces at a ratio of 1:1 within 3 days when 14C-2CBS was given. No specific organ-affinity was observed in distribution study. Cyclohexylamine and 2-mercaptobenzothiazole were identified as urinary metabolites.     

Formation of a 1,4,2,3-dithiadiazine via dimerization of a transient thione-S-imide (thiocarbonyl imine dipole)

N-(p-Tolyl)trichloromethane sulfenamide when treated with potassium hydroxide in an ether-alcohol mixture resulted in the formation in solution of a red, transient thione-S-imide which underwent a head-to-head dimerization to 2,3-di(p-tolyl)-5,5,6,6-tetrachloro-1,4,2,3-dithiadiazine whose structure was established by a single crystal X-ray determination. A variety of sulfenamides derived from aryl-substituted primary aromatic amines and alcoholic potassium hydroxide undergo this reaction with the formation of analogous structures. This thiocarbonyl imine dipole could not be trapped with alkenic or alkynic dipolarophiles.     

Molecular complexes of cobalt(II) and Zinc(II) chlorides and bromides with 1-piperidinyl dimethylcarbamodithioate (L): Crystal structures of L and [ZnLBr<Subscript>2</Subscript>]

Complexes of MX₂(M = Co, Zn; X = Cl, Br) with 1-piperidinyl dimethylcarbamodithioate (L) of composition [MLX₂] have been synthesized. The compounds have been studied by elemental analysis; X-ray diffraction; thermogravimetry; conductometry; magnetochemistry; and IR, ¹H NMR, and electronic absorption spectroscopy. The ligand molecule is coordinated to the metal atoms in a bidentate chelating mode through the thione sulfur atom and the sulfenamide nitrogen atom to form a five-membered chelate ring. The structures of L and [ZnLBr₂] have been determined by X-ray crystallography.     

An efficient synthesis of 3-aminoisothiazolo[5,4-b] -quinoline from quinoline

Treatment of readily available 3-formylquinoline-2-thiol ( 1 ) with ammoniacal sodium hypochlorite directly afforded isothiazolo[5,4-b]quinoline ( 3 ) in high yield, probably via 3-formylquinoline-2-sulfenamide ( 2 ). Facile conversion of 3 to the corresponding 3-amino derivative ( 7 ) was accomplished by the following sequence: base induced opening of the isothiazole ring to 3-cyanoquinoline-2-thiol ( 5 ), oxidation of 5 to the corresponding stable sulfenamide ( 6 ) and sodium ethoxide catalysed reclosure of the isothiazole ring which provided 3-aminoisothiazolo[5,4-b]quinoline ( 7 ).