Styrene cyclohexene oxide

The preparation of block copolymers by combination of thermally radical and photoinduced cationic polymerization processes has also been reported [151], Indeed, styrene/cyclohexene oxide (CHO) copolymers have been synthesized by using a bifunctional azobenzoin initiator such as ABME, previously described, through a two-step procedure. In the first step, thermal Iree radical polymerization of styrene in the presence of the above azobenzoin initiator gives poly(styrene) prepolymers with benzoin photoactive end groups, as reported in Scheme 38. These prepolymers, upon photolysis and subsequent oxidation to the corresponding carbocations in the presence of l-ethoxy-2-methylpyridinium hexafluoro phosphate (EMP+PFg ), finally give block copolymers by cationic polymerization of cyclohexene oxide (Scheme 45). 

The participation of (3-metaloxy metal species in this context was first discussed by Kochi, Singleton, and Andrews in 1968 [7] in relation to their deoxygenation of styrene and cyclohexene oxide by chromium(II) reagents, as shown in Scheme 12.2. 

The synthesis of the Y zeolite-encapsulated manganese complex of the salen ligand has been reported recently [51]. It was found to have catalytic activity in the oxidation of cyclohexene, styrene, and stilbene with PhlO. Typically, 1 Mn(salen) is present per 15 supercages, resulting in catalytic turn-overs in the order of 60. The reactions investigated with the respective product yields are given in Scheme 5. Typical oxidation products are epoxides, alcohols and aldehydes. In comparison to the homogeneous case encapsulation seems to lower the reaction rate. From cyclohexene the expected oxidation product cyclohexene oxide is present in excess and is formed on the Mn(salen) site. 2-cyclohexene-l-ol is probably formed on residual Mn cations via a radical mechanism. 

Treatment of epoxides with DAST results in the formation ofgem-difluorides, vicinal difluorides and bis(2-fluoroalkyl) ethers.54 The product distribution is dependent upon the nature of the epoxide. For example, cyclohexene oxide (1) gives a mixture of eis-difluorides and bis(a-fluoro) ethers, whilst styrene oxide (2) affords a mixture of difluorophenylethanes. This reaction is of little practical use due to the problems associated with the isolation of pure products. 

A recent paper by Kwiatek and co-workers1891 discloses the use of a homogeneous catalysis system for the hydrogenation of epoxides. Reduction of cyclohexene oxide to cydohexanol, and of styrene oxide to 2-phenylethanol, was carried at atmospherio pressure, using Ks[Co(CN) ] to catalyze the reaction. 

Meriting special comment on account of certain recent findings is the reagent o-aminothiophenol. This substance was reported, first in J 949 and again on several subsequent occasions,2 Bl B to yield 3.3-dihydrophenothiazine on condensation with ethylene oxide in base, Mid the corresponding substituted 2,3-dihydrophenothiazines with propylene oxide, cyclohexene oxide, and styrene oxido respectively. It Las now been established, however, in three laboratories,5 M that previous reports were in error. The products formed are in fact normal open-chain adducts, aa shown in Eqa. (670)-<672). Styrene... 

Alkaline carbon disulfide, for example, gives rise to cyclic trithio-c rbon te derivatives on addition to ethylene oxide, cyclohexene oxide, and styrene oxide (Eq. 661 and 662). The same derivatives were obtainable from the corresponding episulfidea, which led the authors to... 

Groves et al. found that a simple heme-iodosobenzene system mimics the enzymic reactions.127 Cyclohexane and cyclohexene are oxidized to cyclohexanol and a mixture of cyclohexene oxide and cyclohexenol respectively by this system. Using meso-tetrakis-a,/J,a,/J-(o-acylamidophenyl)por-phinatoiron(III) chloride where the acyl group is (i )-2-phenylpropionyl or (S)-2 -methoxy-carbonyl-l,T-binaphthyl-2-carbonyl, optically active styrene oxides are obtained in 51% e.e. The Fe(TPP)Cl-PhIO system can also oxygenate arenes to arene oxides.128 Based on the following observations, mechanisms involving O—Felv(Por) t as the active species have been proposed (Scheme 30).127... 

Gold-catalyzed oxidation of styrene was firstly reported by Choudhary and coworkers for Au NPs supported on metal oxides in the presence of an excess amount of radical initiator, t-butyl hydroperoxide (TBHP), to afford styrene oxide, while benzaldehyde and benzoic acid were formed in the presence of supports without Au NPs [199]. Subsequently, Hutchings and coworkers demonstrated the selective oxidation of cyclohexene over Au/C with a catalytic amount of TBHP to yield cyclohexene oxide with a selectivity of 50% and cyclohexenone (26%) as a by-product [2]. Product selectivity was significantly changed by solvents. Cyclohexene oxide was obtained as a major product with a selectivity of 50% in 1,2,3,5-tetramethylbenzene while cyclohexenone and cyclohexenol were formed with selectivities of 35 and 25%, respectively, in toluene. A promoting effect of Bi addition to Au was also reported for the epoxidation of cyclooctene under solvent-free conditions. 

The rate constants for oxidation of a series of cycloalkenes with ozone have been determined using a relative rate method. The effect of methyl substitution on the oxidation of cycloalkenes and formation of secondary organic aerosols has been analysed.155 Butadiene, styrene, cyclohexene, allyl acetate, methyl methacrylate, and allyl alcohol were epoxidized in a gas-phase reaction with ozone in the absence of a catalyst. With the exception of allyl alcohol, the yield of the corresponding epoxide ranged from 88 to 97%.156 Kinetic control of distereoselection in ozonolytic lactonization has been (g) reported in the reaction of prochiral alkenes.157... 

The monomers of styrene oxide, 1,4-cyclohexene oxide, trioxane, and vinyl ether were polymerized at satisfactory rates. However, tetrahydrofuran, e-caprolactone, and cc-methylstyrene could not be polymerized7). 

The evidence in the case of styrene, where both modes of radiation-induced polymerization can be conveniently studied, is quite convincing that reduction of the concentration of water changes the predominating mode of propagation from purely free radical to essentially ionic. Evidence for an ionic propagation initiated by radiation has also been obtained in pure a-methylstyrene (3, 24), isobutylene (12, 32), cyclopenta-diene (5), / -pinene (2), 1,2-cyclohexene oxide (II), isobutyl vinyl ether (6), and nitroethylene (38), although the radical process in these monomers is extremely difficult, if not impossible, to study. 

In another example, Yildirim et al. photochemically generated anthracene radical cations in the presence of TEMPO [29]. TEMPO immediately trapped the radical to form the TEMPO-anthracene cation, which was subsequently used to initiate cationic polymerization of cyclohexene oxide (CHOX). The resulting alkoxyamine-functional polycyclohexene oxide was used to macroinitiate styrene polymerization, resulting in the formation of S-6/-CHOX (Scheme 8.9). 

Examples of intramolecular trapping of carbonyl ylide dipoles by alkenes have now been reported.These include, for example, the conversion of the oxirane (172) into the tetrahydrofuran (173). Carbonyl ylides have also been prepared by irradiation of 2,3-bis-(p-methoxyphenyl)oxirane in the presence of dicyanoanthracene as electron-transfer sensitizer direct or triplet-sensitized irradiation, however, leads mainly to rearrangement via carbon-oxygen bond cleavage. In contrast, cyclohexene oxide and styrene oxide, on naphthalene-sensitized irradiation in alcohols, undergo solvolysis via oxide anion-radical intermediates. ... 

A number of monomers has already been investigated, e.g., cyclo-pentadiene [86], styrene [89, 93], a-methylstyrene [87, 89, 95], formaldehyde [94], alkyl vinyl ethers [85, 89], isobutene [84], nitroethylene [96] and also the cyclic monomer cyclohexene oxide [97]. For most of these reliable quantitative data is now available. Because the number of active centres formed is small all of these systems are particularly susceptible to traces of impurities, especially water and spurious basic materials. Indeed much of the early data [82, 83] from 7-ray initiation was confused because of the use of relatively wet monomers. Furthermore the intrinsic lifetime of a free cation is limited because the... 

Opening of epoxides with azide ions represents a very interesting route to azidocarbinols. The large number of examples quoted in the literature proves the broad scope of this technique." " On treatment of nonsymmetrically substituted oxiranes, the products expected from an 5n2 process are usually obtained. In boiling aqueous dioxane, cyclohexene oxide gives rise to 61% of rrans-2-azidocyclohexa-nol. The reported formation of (35 Scheme 46) with styrene oxide is unexpected, particularly if the formation of (36) from the analogous diphenyl precursor is considered. ... 

The ABA-type block copolymers B-86 to B-88 were synthesized via termination of telechelic living poly-(THF) with sodium 2-bromoisopropionate followed by the copper-catalyzed radical polymerizations.387 A similar method has also been utilized for the synthesis of 4-arm star block polymers (arm B-82), where the transformation is done with /3-bromoacyl chloride and the hydroxyl terminal of poly(THF).388 The BAB-type block copolymers where polystyrene is the midsegment were prepared by copper-catalyzed radical polymerization of styrene from bifunctional initiators, followed by the transformation of the halogen terminal into a cationic species with silver perchlorate the resulting cation was for living cationic polymerization of THF.389 A similar transformation with Ph2I+PF6- was carried out for halogen-capped polystyrene and poly(/>methoxystyrene), and the resultant cationic species subsequently initiated cationic polymerization of cyclohexene oxide to produce... 

Some alkyl-substituted cyclopropanes have been obtained by treating cyclopropylidene-triphenyl-2 -phosphane with various electrophiles. Formation of a C-C bond to the ring at the expense of a C-P bond takes place very efficiently when a phosphorus ylide is treated with both cyclohexene oxide and styrene oxide. The products obtained, 9,9-ethylene-8,8,8-triphenyl-... 

Key Words Ethylene oxide, Propylene oxide. Epoxybutene, Market, Isoamylene oxide. Cyclohexene oxide. Styrene oxide, Norbornene oxide. Epichlorohydrin, Epoxy resins, Carbamazepine, Terpenes, Limonene, a-Pinene, Fatty acid epoxides, Allyl epoxides, Sharpless epoxidation. Turnover frequency, Space time yield. Hydrogen peroxide, Polyoxometallates, Phase-transfer reagents, Methyltrioxorhenium (MTO), Fluorinated acetone, Alkylmetaborate esters. Alumina, Iminium salts, Porphyrins, Jacobsen-Katsuki oxidation, Salen, Peroxoacetic acid, P450 BM-3, Escherichia coli, lodosylbenzene, Oxometallacycle, DFT, Lewis acid mechanism, Metalladioxolane, Mimoun complex, Sheldon complex, Michaelis-Menten, Schiff bases. Redox mechanism. Oxygen-rebound mechanism, Spiro structure. 2008 Elsevier B.V. 

Materials. Cyclohexene oxide and styrene oxide were dried over calcium hydride, then purified by fractional distillation. 3,4-Epoxycyclohexylmethyl-3, 4 -epoxycyclohexane carboxylate (ERL 4221) was obtained from the Union Carbide Company and purified as described above. Triarylsulfonium salts used as photoinitiators... 

Styrene oxide presents further complications and is polymerized most readily by catalysts which are poor for homopolymerization of cyclohexene oxide such as trlfllc acid, but phenyl dlsulfone, which Is an active catalyst for cyclohexene oxide. Is surprisingly slow for styrene oxide (Figure 4). 

DS and MDS, on the other hand, were partially deactivated when cyclohexene oxide was used. Combination of MDS with styrene oxide gave induction followed by acceleration. 

Table II. Sunmary of catalyst performance in the presence of various epoxides. CHO-cyclohexene oxide BO-butene oxide SO-styrene oxide.

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