Enthalpic and entropic contributions to the conformational free energies of methylthio, methylsulfinyl, methylsulfonyl, phenylthio, phenylsulfinyl, and phenylsulfonyl

A variable-temperature NMR study of (cis-4-methylcyclohexyl)methyl sulfide (1), sulfoxide (2), and sulfone (3), as well as (cis-4-methylcyclohexyl)phenyl sulfide (4), sulfoxide (5), and sulfone (6) allowed determination of the thermodynamic parameters, DeltaH degrees and DeltaS degrees, for the title groups. Reproduction of the experimental results with Allinger's MM3 program was successfully accomplished in the case of the sulfoxide and sulfide groups. Nevertheless, modification of the original force field torsional parameters was required in order to adequately reproduce the experimentally observed behavior of the sulfonyl derivatives. Rationalization of the enthalpic and entropic contributions to DeltaG degrees [S(O)(n)()R, n = 0, 1, 2; R = CH(3), Ph] is advanced in terms of the steric characteristics of these sulfur-containing groups and the resulting rotameric populations in the axial and equatorial monosubstituted cyclohexanes.     

The Reaction of Ethyl Bromoacetate with Dimethyl Sulfoxide

The reaction of excess dimethyl sulfoxide with ethyl bromoacetate has been shown to produce ethyl glyoxylate, hydrogen bromide, and dimethyl sulfide. The yield of glyoxylate at first was reduced because the dimethyl sulfide reacted with bromoacetate to form trimethylsulfonium bromide and ethyl (methylmercapto) acetate, presumably via carbethoxymethyldimethylsulfonium bromide. These side reactions were diminished in a thin-film reactor, but the result was not satisfiable, the yield was 51%, and the side reactions were prevented by addition of methyl bromide, which rapidly consumed the dimethyl sulfide with formation of trimethylsulfonium bromide. Addition of 1, 2-epoxy-3-phenoxypropane removed the hydrogen bromide, thereby preventing the deleterious effects casued by its reduction of dimethyl sulfoxide to dimethyl sulfide. In this way has been developed a convenient preparation of ethyl glyoxylate in yields averaging about 70%. Identification and stoichiometry of the reaction products are presented.     

Fe2+-catalyzed heterolytic RO-OH bond cleavage and substrate oxidation: a functional synthetic non-heme iron monooxygenase system

The reaction of [Fe22+(H2Hbamb)2(N-MeIm)2], [1], a binuclear, non-heme iron complex, with 2-methyl-1-phenylprop-2-yl hydroperoxide (MPPH) shows that [1] induces heterolytic cleavage of the peroxy O-O bond. Catalytic atom transfer reactions (1:MPPH:PhSMe 1:596:6011) resulted in the highly efficient (99 +/- 1%), catalytic oxidation of phenyl methyl sulfide to phenyl methyl sulfoxide/sulfone (T.N. = 500/11 respectively) and cyclohexane to cyclohexanol/cyclohexanone (T.N. = 230/5 respectively) showing the highly efficient, catalytic capacity of [1] to carry out oxygen insertion chemistry.     

Chelate ring size variations and their effects on coordination chemistry and catechol dioxygenase reactivity of iron(III) complexes

The catechol dioxygenase reactivity of iron(III) complexes using tripodal ligands was investigated. Increasing, as well as decreasing, chelate ring sizes in the highly active complex [Fe(tmpa)(dbc)]B(C6H5)4 (tmpa = tris[(2-pyridyl)methyl]amine; dbc = 3,5-di-tert-butylcatecholate dianion), using related ligands, only resulted in decreased reactivity of the investigated compounds. A detailed low-temperature stopped-flow investigation of the reaction of dioxygen with [Fe(tmpa)(dbc)]B(C6H5)4 was performed, and activation parameters of DeltaH++ = 23 +/- 1 kJ mol(-1) and DeltaS++ = -199 +/- 4 J mol(-1) K(-1) were obtained. Crystal structures of bromo-(tetrachlorocatecholato-O,O')(bis((2-pyridyl)methyl)-2-pyridylamine-N,N',N')-iron(III), (mu-oxo)-bis(bromo)(bis((2-pyridyl)methyl)-2-pyridylamine-N,N',N' ',N')-diiron(III), dichloro-((2-(2-pyridyl)ethyl)bis((2-pyridyl)methyl)amine-N,N',N' ',N')-iron(III) and (tetrachlorocatecholato-O,O')((2-(2-pyridyl)ethyl)bis((2-pyridyl)methyl)amine-N,N',N' ',N')-iron(III) are reported.     

Thiophene 1-oxides. V. Comparison of the crystal structures and thiophene ring aromaticity of 2,5-diphenylthiophene,its sulfoxide and sulfone

The detailed preparation of 2,5-diphenylthiophene 1-oxide (2) is reported as well as the comparative study of the crystal structures of 2,5-diphenylthiophene, 1 , its sulfoxide 2 and sulfone 3 obtained by X-ray diffraction. This work represents the first experimental study of a complete heterocyclic series, including a thiophene derivative, and the corresponding sulfoxide and sulfone. On the basis of the geometrical parameters, the first unequivocal experimental parameters obtained for a thiophene 1-oxide derivative, we have also examined the evolution of the aromatic character of the thiophene ring when oxidizing the sulfur atom to the sulfoxide and the sulfone. Paolini's bond orders and Julg and Francois's aromaticity indices have also been calculated for the three compounds and compared to those previously calculated for related thiophene derivatives by semi-empirical or ab initio methods [6], [7]. All the data examined showed that, in spite of its non planarity, the thiophene ring of 2,5-diphenylthiophene 1-oxide 2 could still exhibit some de localization of its p electrons indicating a certain degree of aromaticity lower than in thiophene 1 but higher than in the sulfone 3 .     

Chemistry of thienopyridines. VII. Mechanistic studies on the synthesis of thieno[2,3-c] pyridine by thermolytic cyclization

A study was made of the formation of thieno[2,3-c]pyridine (1) from hydrogen sulfide and 4-vinylpyridine in a flow system at 630°. 2-(4-Pyridyl)ethanethiol and bis-2-(4-pyridyl)ethyl sulfide were found to be likely intermediates. Based on these studies, there was devised a two-step practical preparative method for I (optimum overall yield 58%) which consists of preliminary conversion of 4-vinylpyridine to benzyl 2-(4-pyridyl)ethyl sulfide and subsequent thermolysis (at 605°) of this substance.     

Polyesters derived from 1,4-oxathian-2-ones

1,4-Oxathian-2-one ( 1a ) was prepared in high yield by oligomerization of methyl(2-hydroxyethyl)mercaptoacetate ( 3 ) followed by catalytic depolymerization in vacuo. A similar sequence starting with methyl(2-hydroxyethyl)sulfonylacetate ( 5 ) afforded the corresponding sulfone, 1,4-oxathian-2-one-4,4-dioxide ( 1c ), however, 1,4-oxathian-2-one-4-oxide ( 1b ) could not be obtained by this procedure. Ring opening melt polymerization of 1a and 1c afforded low molecular weight crystalline polyesters 2a and 2c . Oxidation of 2a with m-chloroperoxybenzoic acid produced the corresponding polyester 2b containing sulfoxide groups. Thermogravimetric analyses and visual observations indicated 2b to be thermally unstable relative to 2a and 2c .     

The proton and carbon-13 NMR spectra of thioxanthone sulfoxide,thioxanthone sulfone and related ylides - chemical shift assignments

The proton and carbon-13 nmr spectra of thioxanthone sulfoxide, thioxanthone sulfone, thioxanthonium bis(carbomethoxyl)methylide and thioxanthonium bis(carbomethoxyl)methylide S-oxide are assigned using 2-D nmr techniques and compared to those of thioxanthone. The pseudo-equatorial methylide fragment shields C4a/5a by ? 11 ppm relative to the corresponding sulfoxide and by ? 4 ppm relative to thioxanthone. The pseudo-axial methylide fragment in the oxysulfonium ylide has the same effect upon C4a/5a as does the pseudo-axial oxygen of the corresponding sulfone. The sulfoxide and the sulfonium ylide have similar chemical shifts for C2/7 (? 131 ppm) as do the sulfone and oxysulfonium ylide (? 133 ppm).     

Li⁺ selective podand-type fluoroionophore based on a diphenyl sulfoxide derivative bearing two pyrene groups

New podand-type fluoroionophores having two pyrene moieties: 2,2′-bis(1-pyrenylacetyloxy)diphenyl sulfide (3), 2,2′-bis(1-pyrenylacetyloxy)diphenyl sulfoxide (4), and 2,2′-bis(1-pyrenylacetyloxy)diphenyl sulfone (5), have been synthesized by connecting two 1-pyrenecarbonylmethyl groups with the two hydroxy groups of 2,2′-dihydroxydiphenyl sulfide, sulfoxide, and sulfone, respectively. Their complexation behavior toward alkali metal ions was examined by fluorescence spectroscopy. Among these fluoroionophores, compound 4, having a sulfinyl group, showed high selectivity toward Li?.     

A New Route to the Synthesis of 2-Amino-6-(methoxycarbonyl)amino-4-(tetrahydropyridyl)pyrimidine 1-Oxide

A new approach to 2-amino-6-(methoxycarbonyl)amino-4-(1,2,3,6-tetrahydro-1-pyridyl)pyrimidine 1-oxide ( 3 ) is described. Methyl [1-ethoxy-2-(ethoxycarbonyl)-ethylidene]carbamate ( 5 ) reacted with guanidine to the pyrimidinecarbamate 6 , which was successively transformed into methyl 2-amino-6-(p-tolyslulfonyl)oxy-4-pyrimidinecarbamate ( 8 ). Oxidation of 8 led to the corresponding pyrimidine N-oxide 9 , a useful starting material to 3 .     

Indolizine derivatives. VII. indolizines via cyclizations of 2-(2-Pyridyl)methylene-1,3-diketones and −1,3-Keto esters

The reaction of 3-(2-pyridyl)methylene-2,4-pentanedione with acetic anhydride gives at 60° 1-(1-acetoxy-3-methyl-2-indolizinyl)ethanone ( 3a ) or, in the presence of 2,4-pentanedione, 3-(2-acetyl-3-methyl-7-indolizinyI)-2,4-pentanedione ( 7a ) in good yield. In refluxing acetic anhydride, 1-(3-methyl-2-indolizinyl)ethanone ( 4a ) is the main product. In refluxing dimethyl sulfoxide the cycloaddition product, 3-[2-acetyl-3-(2-pyridyl)-l-indolizinyl)]-2,4-pentanedione ( 6 ), is obtained. Ethyl 2-(2-pyridyl)methylene-3-oxobutanoate and ethyl 2-(2-pyridyl)methylene-3-oxo-3-phenylpropanoate behave analogously. The stereochemistry of the keto esters has a marked influence on the course of cyclization. The mechanisms are discussed.     

Reaction of trifluoromethanesulfonamide with heterodienes under oxidation conditions

Reactions of trifluoromethanesulfonamide with divinyl sulfone, divinyl sulfoxide, divinyl sulfide, diphenyl sulfide, vinyl allyl and diallyl ethers was investigated in the presence of oxidation system t-BuOCl + NaI. The reaction with divinyl sulfone afforded a product of 1,5-heterocyclization, 2,6-diiodo-4-[(trifluoromethyl) sulfonyl]thiomorpholine 1,1-dioxide. The same product was obtained in the reaction with divinyl sulfoxide apparently due to its preliminary oxidation to sulfone. In reactions with divinyl sulfide and unsaturated ethers only the oxidation of substrates was observed accompanied with strong tarring; the products of a reaction with trifluoromethanesulfonamide were absent. With diphenyl sulfide a product was formed resulting from the oxidation at the sulfur atom [S(II) → S(IV)], N-(diphenyl-λ⁴-sulfanylidene)trifluoromethanesulfonamide.     

Structure and conformational processes of bis(o-cumyl)sulfide, sulfoxide and sulfone

The NMR solution spectra of the title sulfide and sulfone show decoalescence of the geminal methyl signals of the isopropyl groups at low temperature (−178 °C for the ¹³C signal of sulfide at 150.8 MHz and −147 °C for the ¹H signal of sulfone at 600 MHz). The barriers for the related dynamic processes were measured (4.3 and 7.0 kcal mol⁻¹ for the sulfide and sulfone, respectively). The preferred conformer of sulfide has a propeller shape with a C₁ symmetry, as suggested by Molecular Mechanics (MM) calculations. In the case of sulfone the preferred conformer has a propeller shape with a C₂-anti symmetry, as indicated by calculations and supported by X-ray crystallographic determination. The computed contour map of the potential energy shows that in both cases the dynamic processes take place via correlated rotations (cogwheel mechanism) of the two aromatic substituents about the Ar-S bonds. Dynamic processes could not be observed by NMR in the title sulfoxide, which was also found to adopt a propeller shaped conformation, as indicated by MM calculations and X-ray diffraction.     

ELEMENTAL SULFUR REACTIONS WITH 2-PICOLINE

Abstract

A study of the reaction of the elemental sulfur with 2-picoline is reported. The process was carried out at the boiling point of the 2-picoline under argon. After removing unreacted solids, the reaction products were identified by means of LC. GC and GC-MS. The following products have been identified by mass spectrometry: 1,2-di/2-pyridyl/-ethane. 1,2-di/2-pyridyl/-ethene. 2-methyl-x-[/2-pyridyl/methyl]pyridines, 2-mercapto-methyl-[x/2-pyridyl/methyl]-pyridines, l-mercapto-1,2-di/2-pyridyl/-ethane, 5,6-di/2-pyridyl/-5H-cyclopenta-[b]pyridine, 5,6-di/2-pyridyl/-7H-cyclopenta[b]pyridine, 1,2,3-tri/2-pyridyl/-propane. 1,2-di/2-pyridyl/-1-[x-/2-methyl/-pyridyl]-ethane, 5,6-di/2-pyridyl/-7-[/2-pyridyl/methyl]-7H-cyclopenta[b]pyridine, 5,6-di/2-pyridyl/-5-[/2-pyridyl/-methyl]-5H-cyclopenta-[b]pyridine. Di{7-[5,6-di/2-pyridyl/-7H-cyclopenta[b]pyridyl]} sulfide and di(7-[5,6-di/2-pyridyl/-7H-cyclopentalblpyridyl]} disulfide.     

Studies on tertiary amine oxides. LXVII . Reactions of aromatic N-oxides with 3-arylrhodanines in the presence of acetic anhydride

Quinoline 1-oxides 1 readily react with 3-arylrhodanines 2 in the presence of acetic anhydride to afford 3-aryl-5-(2-quinolyl)rhodanines 3 in high yields. These products resist hydrolysis under both alkaline and acidic conditions, but is oxidized to quinaldinic acid 1-oxide 4 with 30% hydrogen peroxide in hot acetic acid. Besides isoquinoline 2-oxide 5 , pyridine 1-oxide 7a also reacts in the same way to give 3-aryl-5-(2-pyridyl)rhodanines 8 , although the reactivity of γ-picoline 1-oxide 7b is considerably lower. Contrary to 3 , 3-phenyl-5-(2-pyridyl)rhodanine 8a is successfully hydrolyzed with boiling 48% hydrobromic acid to 2-pyridinemethanethiol 10 in 57% yield.     

Tautomeric structure of 1-methyldihydropyridazino-[3,4-b]quinoxalines in solution

The reaction of 6-chloro-2-(1-methylhydrazino)quinoxaline 4-oxide 1 with ethyl 2-ethoxymethylene-2-cyano-acetate or ethoxymethylenemalononitrile gave 6-chloro-2-[2-(2-cyano-2-ethoxycarbonylvinyl)-1-methylhy-drazino]quinoxaline 4-oxide 3a or 6-chloro-2-[2-(2,2-dicyanovinyl)-1-methylhydrazino]quinoxaline 3b , respectively. The reaction of 3a with a base afforded 7-chloro-1-methyl-1,5-dihydropyridazino[3,4-b]quinoxaline 4 . From the NOE spectral data, the 1-methyldihydropyridazino[3,4-b]quinoxalines 2a, 2b and 4 were found to exist as the 1,5-dihydro form in a dimethyl sulfoxide or trifluoroacetic acid/dimethyl sulfoxide solution.     

An EXAFS spectroscopic, large-angle X-ray scattering, and crystallographic study of hexahydrated, dimethyl sulfoxide and pyridine 1-oxide hexasolvated mercury(II) ions

The structure of the solvated mercury(II) ion in water and dimethyl sulfoxide has been studied by means of large-angle X-ray scattering (LAXS) and extended X-ray absorption fine structure (EXAFS) techniques. The distribution of the Hg-O distances is unusually wide and asymmetric in both solvents. In aqueous solution, hexahydrated [Hg(OH(2))(6)](2+) ions in a distorted octahedral configuration, with the centroid of the Hg-O distance at 2.38(1) A, are surrounded by a diffuse second hydration sphere with HgO(II) distances of 4.20(2) A. In dimethyl sulfoxide, the six Hg-O and HgS distances of the hexasolvated [Hg{OS(CH(3))(2)}(6)](2+) complex are centered around 2.38(1) and 3.45(2) A, respectively. The crystal structure of hexakis(pyridine 1-oxide)mercury(II) perchlorate has been redetermined. The space group R(-)3 implies six equal Hg-O distances of 2.3416(7) A for the [Hg(ONC(5)H(5))(6)](2+) complex at 100 K. However, EXAFS studies of this compound, and of the solids hexaaquamercury(II) perchlorate and hexakis(dimethyl sulfoxide)mercury(II) trifluoromethanesulfonate, also with six equidistant Hg-O bonds according to crystallographic results, reveal in all cases strongly asymmetric Hg-O distance distributions. Vibronic coupling of valence states in a so-called pseudo-Jahn-Teller effect probably induces the distorted configurations.     

Asymmetric synthesis of rubiginones A(2) and C(2) and their 11-methoxy regioisomers

Convergent enantioselective syntheses of angucyclinone-type natural products rubiginones A(2) (2) and C(2) (1) and their 11-methoxy regioisomers 3 a and 3 b have been achieved by using two domino processes from a common enantiomerically pure 1-vinylcyclohexene 4. Key steps in the synthesis of this diene were the stereoselective conjugate addition of AlMe(3) on (SS)-[(p-tolylsulfinyl)methyl]-p-quinol (9) and the elimination of the beta-hydroxy sulfoxide fragment, after oxidation to sulfone, to recover a carbonyl group. The first domino sequence comprised Diels-Alder reaction with a sulfinyl naphthoquinone followed by sulfoxide elimination. An efficient opposite regioselection in the cycloaddition step was achieved in the convergent construction of the tetracyclic skeleton using a sulfoxide at C-2 or C-3 of the dienophiles 5 or 6, derived from 5-methoxy-1,4-naphthoquinone. The second domino process, triggered by oxygen and sunlight, allowed the transformation of the initial tetracyclic adducts into the final products after B ring aromatization, silyl deprotection and C-1 oxidation.     

以二氟烷基磺酸修饰的聚降冰片烯为基础的聚合物电解质薄膜的制备

合成了一种新型的二氟烷基磺酰氟单体2-（双环[2.2.1]庚-5-烯-2）-1,1-二氟-2-甲氧基丙基-1-磺酰氟.首先利用二氟甲基2-吡啶基砜和2-乙酰基-5-降冰片烯发生亲核加成反应,在低温下用三氟甲磺酸甲酯保护加成产物中的羟基,之后在KOH/MeOH的条件下脱去吡啶基,得到的二氟亚磺酸盐和Slectfluor试剂反应制得想要的二氟烷基磺酰氟单体.这种新型的二氟烷基磺酰氟单体和不同比例的降冰片烯单体在Grubbs第二代催化剂存在条件下进行开环烯烃复分解聚合（ROMP）,所得的聚合物在碱性条件下水解,再用稀盐酸处理最终制得新型的含有二氟烷基磺酸的聚合物电解质膜.这些新型的聚合物电解质膜具有中等的室温质子电导（12～49mS/cm）.     

The effect of sulfur stereochemistry of l-β,β-dimethylmethionine S-oxide on the physicochemical properties of truncated polytheonamides

l-β,β-Dimethylmethionine S-oxide is a unique amino acid found in polytheonamides. Four designed hexapeptides containing the sulfide, (S_R)-sulfoxide, (S_S)-sulfoxide, and sulfone derivatives of l-dimethylmethionine were synthesized and functionally analyzed. Our results indicate that the sulfoxide stereochemistry of the peptides controls their overall physicochemical properties.