Cyclohexene Sulfide Research Articles

Vulcanization of styrene-butadiene rubber with the use of polysulfide sulfur-donors of controlled structure

The sulfide polymers of variable and controlled sulfur content, obtained by anionic copolymerization of elemental sulfur and thiiranes (styrene sulfide and cyclohexene sulfide), were applied as curatives (sulfur donors) in the vulcanization process of styrene-butadiene rubber (SBR). The activity of polysulfides as curatives was investigated on the basis of rheometric measurements of the vulcanization process and calculations of curing parameters using kinetic data. The crosslink density and structure related to the mechanical properties of the vulcanizates under static and dynamic conditions were studied. The overall suitability of polysulfides as crosslinking agents for diene rubbers was investigated.

VULCANIZATION OF STYRENE–BUTADIENE RUBBER WITH THE USE OF POLYSULFIDE SULFUR DONORS OF CONTROLLED STRUCTURE

ABSTRACT The sulfide polymers of variable and controlled sulfur content, obtained by anionic copolymerization of elemental sulfur and thiiranes (styrene sulfide and cyclohexene sulfide), were applied as curatives (sulfur donors) in the vulcanization process of styrene–butadiene rubber. The activity of polysulfides as curatives was investigated based on rheometric measurements of the vulcanization process and calculations of curing parameters using kinetic data. The crosslink density and structure related to the mechanical properties of the vulcanizates under static and dynamic conditions were studied. The overall suitability of polysulfides as crosslinking agents for diene rubbers was investigated.

An efficient ring-opening copolymerization of thiiranes with elemental sulfur in the presence of the fluoride anion

Sulfurization of selected thiiranes such as 2-phenylthiirane (styrene sulfide), 2,3-tetramethylenethiirane (cyclohexene sulfide) and 2-(α-thienyl)thiirane was carried out, leading to sulfur-rich polymers. The activation of the S8 molecule was initiated by the fluoride anion (F−) delivered by tetrabutylammonium fluoride (TBAF) dissolved in tetrahydrofuran (THF). The opening of the thiirane ring, followed by the copolymerization process, was initiated by the fluoropolysulfide anions (FSx−) generated in situ. The anionic copolymerizations were carried out under mild conditions, below the floor temperature of S8 (159 °C), and a variable ratio of monomers (thiirane/sulfur) was applied to obtain polysulfides with a diversified sulfur content. Polysulfides were characterized using analytical (elemental analysis, gel permeation chromatography), spectroscopic (Raman spectroscopy, FTIR), and thermal (thermogravimetry (TGA), differential scanning calorimetry (DSC)) methods. Mechanistic interpretation of sulfur transfer in the anionic copolymerization of thiiranes with S8, in the presence of the fluoride anion, has been discussed.

Coordination Properties of Non-Rigid Phosphinoyldithioformate Complexes of the [Mo2O2(µ-S)2]2+ Cation in Catalytic Sulfur Transfer Reactions with Thiiranes

Two “Mo2O2S2”-based complexes with phosphinoyldithioformate ligands were synthesized from the metathesis reaction of [R2P(O)CS2]− with (Me4N)2[Mo2O2(µ-S)2(Cl)4] to give [Mo2O2(µ-S)2{R2P(O)CS2}2] (1; R = Ph, 2; R = Bn). The complexes were fully characterized, including the X-ray crystal structure for 1. Variable temperatures 31P NMR of 1 and 2 exhibit non-rigid behavior in solution where three and two coordination isomers were present, respectively. The organic substituent on the P atom greatly impacts the complex non-rigid properties and behavior. The catalytic activity of 1 and 2 towards sulfur atom transfer (SAT) using propylene sulfide and cyclohexene sulfide was explored, employing homogeneous reaction conditions at an ambient temperature on the NMR scale. The complexes showed distinctly different properties along with high conversions in short reaction times. A catalytic cycle consistent with the results is proposed.

Synthesis of Sulfur-rich Polymers: Copolymerization of Cyclohexene Sulfide and Carbon Disulfide Using Chromium Complexes

An investigation of the copolymerization of cyclohexene sulfide and carbon disulfide using salphen and salen Cr complexes as catalysts and [PPN]+X– salts as cocatalysts, at different temperatures and reaction times, is reported. Both catalytic systems produce both polymer and cyclic products. For the first time, poly(trithiocyclohexylcarbonates) (PCS) have been synthetized in high yields and high molecular weights. Salphen-based catalysts, in comparison with salen-based ones, show higher productivity and selectivity for polymers with high molecular weight up to 18 kg/mol when the reaction is carried out at 25 °C. At a higher temperature with (salphen)CrCl, the maximum value of selectivity for copolymers (72%) was obtained at a short reaction time (3 h). At long reaction times, great amounts of cyclic by-product are observed, thus evidencing the tendency for cyclohexene sulfide and CS2 to provide cyclic products due to the stability of the trithiocyclohexylcarbonate. PCS possesses high refractive index (n > 1.72), and antimicrobial assays reveal that these materials are active against Escherichia coli and moderately active against Staphylococcus aureus. These properties along with the Tg values of 80 °C make these polymers suitable for interesting applications different from those of poly(trithiopropylencarbonate).

Alternating copolymerization of γ-selenobutyrolactone with episulfides for high refractive index selenium-containing polythioesters

Polythioesters represent a promising functional polymer owing to the ubiquity and uniqueness of thioester bonds, however, to develop new examples of (functionalized) polythioesters for broadening the range of their applications is a grand challenge. Here, we report a convenient synthesis of a polythioester incorporating both thioester and selenide groups in repeating units via the alternating copolymerization of γ-selenobutyrolactone with episulfides including propylene sulfide and cyclohexene sulfide. This process mediated by a relatively mild phosphazene base of P1 exhibits very high activity with turnover of frequency (TOF) values of up to 1200 h−1, in which the nucleophilic attack of a selenol-type anion to episulfides is convinced as the rate-determining step by kinetic investigations. The prepared poly(thioester-alt-selenide)s have rigorously alternating sequences under optimized reaction conditions, molecular weights of 2.5–12.8 kg/mol, glass-transition temperatures of as low as −45.2 °C. Of unique, this copolymer exhibits remarkably high refractive indices of up to 1.74, suggesting a potential application prospect in optical materials.

A Sequential One‐Pot Synthesis of Functionalized Esters and Thioesters through a Ring‐Opening Acylation of Cyclic Ethers and Thioethers

A one‐pot protocol for the synthesis of functionalized esters and thioesters is reported from cyclic ethers/thioethers and carboxylic acids via acyloxyphosphonium salts as key intermediates. The reaction of styrene oxide with acyloxyphosphonium salts gave complete regioselectivity and good yields of the resulting functionalized ester, whereas cyclohexene oxide gave moderate yields. Styrene episulfide, on the other hand, gave good yields with moderate regioselectivity whereas cyclohexene sulfide gave quantitative yields of the corresponding thioesters. We have also shown an alternate procedure for the ring opening of THF to form 4‐bromo butyl esters. All these reactions were carried out in the absence of a catalyst, showing the synthetic versatility of our method.

Partial and Full β-Chlorination of Meso-Tetraphenylporphyrin: Effects on the Catalytic Activity of the Manganese Complexes for Oxidation of Organic Compounds with Periodate

A series of β-chlorinated meso-tetraphenylporphyrins, H2TPPClx (x = 2, 4, 6, or 8) have been prepared and the catalytic activity of their manganese(III) complexes in oxidation of cyclooctene, cyclohexene, and methyl phenyl sulfide with tetra-n-butylammonium periodate was studied. The catalytic activity of the manganese porphyrins in oxidation of cylohexene and cyclooctene decreased in the order MnTPPCl6(OAc) ≥ MnTPP(OAc) ∼ MnTPPCl2(OAc) > MnTPPCl4(OAc) > MnTPPCl8(OAc). The oxidative stability of the manganese porphyrins decreased as MnTPP(OAc) > MnTPPCl6(OAc) > MnTPPCl8(OAc) > MnTPPCl4(OAc) > MnTPPCl2(OAc). Oxidation of methyl phenyl sulfide gave the following order: MnTPP(OAc) ∼ MnTPPCl6(OAc) > MnTPPCl4(OAc) ∼ MnTPPCl2(OAc) > MnTPPCl8(OAc).

Investigations into the coupling of cyclohexene oxide and carbon disulfide catalyzed by (salen)CrCl. Selectivity for the production of copolymers vs. cyclic thiocarbonates

The synthesis of poly(thiocarbonates) has been achieved via the (salen)CrCl/[PPN]Cl (salen = N,N'-bis(3,5-di-tert-butylsalicylidene)-1,2-ethylenediamino) and PPN(+) = bis(triphenyl-phosphoranylidene)ammonium) catalyzed coupling of carbon disulfide and cyclohexene oxide. Optimal catalytic activity was observed at 50 degrees C and a 1:1 carbon disulfide to cyclohexene oxide loading ratio to afford copolymers with molecular weights ranging from 14,000-34,000 g mol(-1) with narrow molecular weight distributions. The exchange of sulfur and oxygen atoms was observed in both the copolymer and cyclic products. In situ infrared monitoring of the coupling reactions revealed an initiation period followed by formation of copolymers enriched in oxygen content, and concomitantly cyclic thiocarbonates enriched in sulfur content. By way of contrast, the copolymerization of cyclohexene sulfide and carbon disulfide was found to be highly selective and effective for producing cyclohexylene trithiocarbonate vs. the all-sulfur copolymer at 30 degrees C. Density functional theory calculations were carried out on the possible cyclic materials from the coupling of cyclohexene oxide and CS(2), which revealed cyclohexylene trithiocarbonate to be the most stable cyclic species.

Oxidative Reactions of the MoIV Dialkyl Complex [{(3‐CF3C6H4NCH2CH2)2NMe}Mo(CH2SiMe3)2

The structure of [(CF3N2NMe)Mo(CH2SiMe3)2] (in which (CF3N2NMe)2- is [(3-CF3C6H4NCH2CH2)2NMe]2-) is approximately trigonal bipyramidal with one axial and one equatorial alkyl ligand. Heating of solutions of [(CF3N2NMe)Mo(CH2SiMe3)2] in [D6]benzene in the presence of five equivalents of 2-butyne led to diamagnetic [(CF3N2NMe)Mo(CHSiMe3)(eta(2)-MeC[triple bond]CMe)], whose structure is approximately square pyramidal with the alkyne occupying the axial site. Addition of one equivalent of cyclohexene sulfide to [(CF3N2NMe)Mo(CH2SiMe3)2] at room temperature produced the diamagnetic, dimeric molybdenum(IV) sulfido complex, [{(CF3N2NMe)MoS}2]. This complex is composed of two approximately trigonal bipyramidal centers, each containing one axial and one equatorial sulfur atom. Oxidation of [(CF3N2NMe)Mo(CH2SiMe3)2] with hexachloroethane resulted in formation of tetramethylsilane, HCl, and the sparingly soluble, red alkylidyne complex, [{(CF3N2NMe)Mo(CSiMe3)Cl}2]. This complex forms a dimer through bridging chlorides. The oxidation reactions of [(CF3N2NMe)Mo(CH2SiMe3)2] with 2-butyne, cyclohexene sulfide, or C2Cl6 are all proposed to proceed by alpha-hydrogen abstraction in the Mo(VI) species to yield (initially) the Mo=CHSiMe3 species and tetramethylsilane.

Terminally Coordinated AsS and PS Ligands

The terminal AsS and PS complexes [(N(3)N)W(ES)] (N(3)N=N(CH(2)CH(2)NSiMe(3))(3); E=P (3), As (4)) were synthesised by reaction of [(N(3)N)W[triple chemical bond]As] and [(N(3)N)W[triple chemical bond]P], respectively, with cyclohexene sulfide. Both complexes present very short W--E and E--S bond lengths. The bonding was investigated by density functional theory (DFT) calculations using the fragment calculation method and natural bond orbital (NBO) analysis. According to the fragment analysis, in which the complexes were separated in an ES and a (N(3)N)W fragment, the bonding in complexes 3, 4 and [(N(3)N)W(SbS)] (5) is realised over a set of two sigma (1 sigma and 2 sigma) and two degenerate pi molecular orbitals (MOs) (1 pi and 2 pi). The 1 sigma MO is a bonding MO extended over the N(ax)-W-E-S core, whereas the 2 sigma MO is localised mainly on the E-S fragment. The 1 pi set is a E-S localised bonding molecular orbital, whereas the 2 pi set is in phase with respect to W-E but in antiphase with respect to E-S. Both methods indicate bond orders around two for both the E--S and the W--E bonds. The polarity of the complexes was examined by Hirshfeld charge analysis. This shows that complexes 3 and 4 are only slightly polarised, whereas 5 is moderately polarised toward the sulphur. As suggested by the computational results, the pi system in complexes 3-5 is best described by two three-centre four-electron bonds.

Kinetics, Mechanism, and Computational Studies of Rhenium-Catalyzed Desulfurization Reactions of Thiiranes (Thioepoxides)

The oxorhenium(V) dimer {MeReO(edt)}2 (1; where edt = 1,2-ethanedithiolate) catalyzes S atom transfer from thiiranes to triarylphosphines and triarylarsines. Despite the fact that phosphines are more nucleophilic than arsines, phosphines are less effective because they rapidly convert the dimer catalyst to the much less reactive catalyst [MeReO(edt)(PAr3)] (2). With AsAr3, which does not yield the monomer, the rate law is given by v = k[thiirane][1], independent of the arsine concentration. The values of k at 25.0 degrees C in CDCl3 are 5.58 +/- 0.08 L mol(-1) s(-1) for cyclohexene sulfide and ca. 2 L mol(-1) s(-1) for propylene sulfide. The activation parameters for cyclohexene sulfide are deltaH(double dagger) = 10.0 +/- 0.9 kcal mol(-1) and deltaS(double dagger) = -21 +/- 3 cal K(-1) mol(-1). Arsine enters the catalytic cycle after the rate-controlling release of alkene, undergoing a reaction with the Re(VII)(O)(S) intermediate that is so rapid in comparison that it cannot be studied directly. The use of a kinetic competition method provided relative rate constants and a Hammett reaction constant, rho = -1.0. Computations showed that there is little thermodynamic selectivity for arsine attack at O or S of the intermediate. There is, however, a large kinetic selectivity in favor of Ar3AsS formation: the calculated values of deltaH(double dagger) for attack of AsAr3 at Re=O vs Re=S in Re(VII)(O)(S) are 23.2 and 1.1 kcal mol(-1), respectively.

X-ray structure and electrophilic reactivity of a cationic, chiral tungsten(II) methylene complex

The structure of a tungsten(II) methylene complex, [Tp′(CO)(PhCCMe)WCH 2 ][BAr′ 4 ] ( 2a ), was obtained by taking advantage of the stabilizing, weakly coordinating counterion, BAr′ 4 − , to form X-ray quality single crystals. The electrophilic reactivity of [Tp′(CO)(PhCCMe)WCH 2 ][PF 6 ] ( 2b ) was surveyed with both neutral nucleophiles (triphenylphosphine and pyridine) and anionic nucleophiles (formed by deprotonation of phthalimide, diethyl malonate, t -butyl acetoacetate, and acetophenone) to give derivatives of the form [Tp′(CO)(PhCCMe)WCH 2 Nu] +,0 . Crystal structures obtained for the phthalimide ( 5 ) and diethyl malonate ( 6 ) adducts are compatible with attack of the nucleophile from along the metal CO axis. The stereochemistry of the t -butyl acetoacetate adduct was determined by 2-D NOESY-NMR. Reaction of methylene carbene 2b with cyclohexene sulfide results in sulfur atom transfer to form a rare π-bound thioformaldehyde complex ( 9 ).

Thiirane Ring Cleavage with Trifluoromethylthiocopper

The thiirane ring cleavage of cyclohexene sulfide with trifluoro-methylthiocopper furnishes seven compounds. Of these, only one compound does not contain the trifluoromethylthio group. This paper presents the probable mechanism of formation of the compounds and their mass spectral characterization.

Novel Sequence-Ordered Polymers by Transformation of Polymer Backbone: Quantitative and Regioselective Insertion of Thiiranes into Poly(S-aryl Thioester)

Novel sequence-ordered poly(S-alkyl thioester)s were synthesized on the basis of transformation of a backbone of the poly(S-aryl thioester) (P-1) using the regioselective insertion of thiiranes. The insertion reaction of 3-butoxypropylene sulfide (BPS) into P-1 using catalysts such as tetrabutylammonium chloride (TBAC), tetrabutylphosphonium chloride, or 18-crown-6-ether/potassium chloride in DMAc at 70 °C for 6 h proceeded completely and regioselectively to provide an ordered poly(S-alkyl thioester) (P-2a) with a new sequence. The molecular weight of P-2a was reasonably higher than that of the starting polymer P-1. The structure of P-2a including a head-to-tail sequence of BPS unit was well-characterized by IR, 1H NMR, 13C NMR spectroscopies, GPC, and elemental analysis. Various sequence-ordered poly(S-alkyl thioester)s were successfully synthesized by the insertion reaction of 3-phenoxypropylene sulfide, BPS, or cyclohexene sulfide using the TBAC catalyst under the same conditions. It was demonstrated t...

New Acyl-Group Transfer Polymerization of Thiiranes Using Carboxylic Acid Derivatives and Quaternary Onium Salts

A new acyl-group transfer polymerization of thiiranes using carboxylic acid derivatives and quaternary onium salts was investigated. 3-Phenoxypropylene sulfide (PPS) was polymerized efficiently by S-phenyl thioacetate in the presence of tetrabutylammonium chloride, bromide, or tetrabutylphosphonium chloride to give the corresponding polysulfide with a S-acetyl group at the polymer terminal. The polymerization of 3-butoxypropylene sulfide (BPS) and cyclohexene sulfide (CHS) also proceeded under the similar conditions to afford the corresponding polymers. It was found from the polymer structures and results of post-polymerization that the polymerization proceeded transferring an acyl group in each propagating step. It was demonstrated that the acyl-group transfer polymerization has living nature. Furthermore, di- and tri-block copolymers of a variety of thiiranes were successfully synthesized by the present acyl-group transfer polymerization.

Activation of carbon–sulfur and carbon–chlorine bonds by the electrophilic ruthenium fragment ‘Ru(η-C5Me5)+’

The ‘Ru(η-C5Me5)+’ fragment generated by protonation of [{Ru(η-C5Me5)(OMe)}2] by CF3SO3H, reacted with cyclohexene sulfide to give [Ru(η-C5Me5)(η6-C6H6)]+1 and H2S. With 1,4-dithiane no C–S bond activation was observed but instead the successive formation of [Ru(η-C5Me5)(S2C4H8)(CF3SO3)]2 and [Ru(S2C4H8)3]2+3, whereas with 1,3-dithiane two compounds resulting from the sequential activation of C–S bonds were isolated as CF3SO3– salts, namely [{Ru(η-C5Me5)(SMe)(SCH2CHCH2)}2]2+4 and [{Ru[C5Me4CH2S(CH2)3SMe]}2]2+5. The fragment also reacted with neat dichloromethane to give two trinuclear clusters: [{Ru(η-C5Me5)}3(µ-Cl)3(µ3-CH)]+6 and [{Ru(C5Me5)}3(µ-Cl)2(µ-CO)(µ3-CH)]2+7 in 60 and 30% yield respectively. Its reaction with chlorocyclohexane, 1,2-dichlorocyclohexane and 1,2,3,4,5,6-hexachlorocyclohexane (lindane) yielded 1 and various amounts of H2 and HCl. In the case of lindane the conversion was only 30% and yielded a 9:1 mixture of 1 and [Ru(η-C5Me5)(η6-C6H5Cl)]+9. Finally the reaction of C–Cl versus C–O bond activation was compared using 2-chlorocyclohexanone, 2-chlorocyclohexanol and 2,2,6,6-tetrachlorocyclohexanol. It was found that in all cases the C–Cl activation was easier. The first reaction yielded 1, the second the new trinuclear cluster [{Ru(C5Me5)}3(µ-Cl)2(µ-CO)(µ3-CCl)]2+11 similar to 7. The latter reaction depended upon the reaction conditions, but in tetrahydrofuran at 80 °C, an 80% conversion was observed yielding a 1:7: < 1 mixture of 1, [Ru(η-C5Me5)(η6-C6H5OH)]+10 and [Ru(η-C5Me5)(η6-C6H5Cl)]+9 thus demonstrating a high selectivity for C–Cl activation in the presence of C–O bonds.

Syntheses and reactivities of 4-sila- and 8-phospha-4-silathiophenetriptycenes

The reactions of the trilithium salt 7, prepared from 5 or 6. with diethyl carbonate and triphenyl phosphite yield 4-sila and 8-phospha-4-silathiophenetriptycenes, 2 and 3, respectively. In the UV-Vis spectra of 2 and 3, the longest absorption maxima appear at 297 and 308 nm, respectively, and, in the 13P NMR, the phosphorus atom of 3 resonates at ° −92.15. Treatment of 3 with m-CPBA or cyclohexene sulfide gives the corresponding phosphine oxide ( 8) or phosphine sulfide ( 9), respectively, while the reaction of 3 with S 8/DBU gives the corresponding gives disiloxane 10.

The reaction of tetramesityldisilene with cyclohexene oxide and cyclohexene sulfide

Reaction of tetramesityldisilene, 1, with Cyclohexene oxide in benzene at 80 °C gives silyl enol ether, 2, as the major product along with the products of epoxide deoxygenation, Cyclohexene and the known tetramesityldisilaoxirane,3; reaction of 1 with Cyclohexene sulfide occurs rapidly at room temp, to give the known tetramesityldisilathiirane, 6, and Cyclohexene.

Asymmetric synthesis polymerization of meso oxiranes and thiiranes

AbstractThe asymmetric synthesis polymerization or “enantiogenic” polymerization of some meso oxiranes, cis‐dimethyloxirane (cis‐DMO) and cyclohexene oxide (CHO), and thiiranes, cis‐dimethylthiirane (cis‐DMT) and cyclohexene sulfide (CHS), initiated with different chiral systems was examined. Strong differences in behaviour were observed between oxiranes and thiiranes depending on the initiator used. The initiators based on ZnEt2 or CdMe2 and a chiral diol give optically active polymers from meso thiiranes but fail to induce an asymmetric polymer synthesis with meso oxiranes. A new chiral initiator based on ZnEt2 and (1S,2R)‐ephedrine allowed us to prepare optically active poly CHOs, which can be fractionated into fractions exhibiting opposite optical activities. © 1992 Wiley‐Liss, Inc.