Isoprene sulfone

Relatively little has been known about photoisomerization reactions of organic sulfur compounds. Irradiation of a solution of isoprene sulfone (I, R = CH3) in water-ether mixture with ultraviolet light does not result in isomerization but in the presence of alkalies, rearrangement of I to III takes place via the intermediate (II).64... 

The pyrolysis products of 1,3-diene-sulfur dioxide copolymers were analyzed in a field-ion mass spectrometer and the fragmentation results suggest an alternating 1 1 copolymer for poly(butadiene sulfone), poly(isoprene sulfone) and poly(2,3-dimethylbutadiene sulfone) [48]. 

Isoprene, sulfonated Single 7g transparency II had 5-10 % substituted and partly cyclized immiscible when n had 2 % substituted Eisenberg et al. (1982), ou and Eisenberg (1983)... 

Ethylthio)-2-propenoic acid, E-60055 Isoprene cyclic sulfone, in D-70231 a-Isoprene sulfone, in D-70228... 

Styrene-co-4-vinylpyridine Isoprene, sulfonated Single Tg, transparency II had 5-10% substituted and partly 210,896... 

Other examples that involve intermediate allyl cations are illustrated in Scheme 1.4. The cationic palladium(II) complex [Pd(dppp)(PhCN)2](BF4)2 coordinates the carbonyl oxygen of benzaldehyde and the activated carbonyl carbon attacks the isoprene, forming the allyl cation 10 which then cyclizes to give the 4-methyl-6-phenyl-5,6-dihydro-2H-pyran [22]. 2-Oxopropyl acrylate 11, in the presence of trimethylsilyltrifluoromethane sulfonate (TMSOTf) and methoxytrimethylsilane (MeOSMT), generates the cation 11a which is an efficient dienophile that reacts easily with the cyclohexadiene to give the Diels-Alder adduct in good yield [23]. 

Nafion-H (144), a perfluorinated resin-sulfonic acid, is an efficient Bronsted-acid catalyst which has two advantages it requires only catalytic amounts since it forms reversible complexes, and it avoids the destruction and separation of the catalyst upon completion of the reaction [94], Thus in the presence of Nafion-H, 1,4-benzoquinone and isoprene give the Diels-Alder adduct in 80% yield at 25 °C, and 1,3-cyclohexadiene reacts with acrolein at 25 °C affording 88 % of cycloadduct after 40 h, while the uncatalyzed reactions give very low yields after boiling for 1 h or at 100 °C for 3.5 h respectively [95], Other examples are given in Table 4.24. In the acid-catalyzed reactions that use highly reactive dienes such as isoprene and 2,3-dimethylbutadiene, polymerization of alkenes usually occurs with Nafion-H, no polymerization was observed. 

The product 303 from disulfur dichloride and 2,3-dimethylbuta-l,3-diene rearranges spontaneously to the tetrahydrothiophene 304 (equation 159)150. The reaction of liquid sulfur dioxide with conjugated dienes 305 (e.g. butadiene, isoprene) results in cyclic sulfones which dissociate into their components on heating (equation 160)151 152. 

An exclusive 1,4-addition has also been observed88 in iodosulfonylation of conjugated dienes with in situ generated tosyl iodide. With symmetrical acyclic dienes the corresponding (5-iodobut-2-enyl sulfones were obtained. In the case of asymmetrical acyclic dienes, with the exception of isoprene, mixtures of regioisomeric products were isolated (equation 62). 

The complexes of sulfur trioxide with various nucleophiles (dioxane, pyridine etc.) are mild sulfonating reagents. Unlike other complexes of sulfur trioxide, dimethyl sulfide-sulfur trioxide readily adds to conjugated multiple bonds. Consequently, not only the sulfo group but also the dimethyl sulfide group add at the multiple bond. The reactions of dimethyl sulfide-sulfur trioxide complex with butadiene, isoprene and 2,3-dimethylbutadiene take place as conjugated l,4- -additions of dimethyl sulfide and sulfonate groups at the double bonds of the diene (equation 103).124... 

Selenosulfonylation of olefins in the presence of boron trifluoride etherate produces chiefly or exclusively M products arising from a stereospecific anti addition, from which vinyl sulfones can be obtained by stereospecific oxidation-elimination with m-chloroper-benzoic acid134. When the reaction is carried out on conjugated dienes, with the exception of isoprene, M 1,2-addition products are generally formed selectively from which, through the above-reported oxidation-elimination procedure, 2-(phenylsulfonyl)-l,3-dienes may be prepared (equation 123)135. Interestingly, the selenosulfonylation of butadiene gives quantitatively the 1,4-adduct at room temperature, but selectively 1,2-adducts at 0°C. Furthermore, while the addition to cyclic 1,3-dienes, such as cyclohexadiene and cycloheptadiene, is completely anti stereospecific, the addition to 2,4-hexadienes is nonstereospecific and affords mixtures of erythro and threo isomers. For both (E,E)- and ( ,Z)-2,4-hexadienes, the threo isomer prevails if the reaction is carried out at room temperature. 

The solid sulfone can be recrystallized, and the isoprene can be regenerated by heating the purified sulfone (45,46). With S03—DMF (dimethylfomiamide) complex, a six-membered ring can form the delta sulfone (47) ... 

Miyaki and Fujimoto and co-workers [16,17] have obtained an even finer distribution of fixed charge groups by casting films from multicomponent block copolymers such as poly(isoprene- >-styrene- >-butadiene- >-(4-vinyl benzyl)dime-thylamine- Msoprene). These films show a very regular domain structure with a 200-500 A spacing. After casting the polymer film, the (4-vinyl benzyl) dimethy-lamine blocks were quatemarized with methyl iodide vapor, and the styrene blocks were sulfonated with chlorosulfuric acid. 

Low concentrations of S02 and TBHP were used to initiate the polymerization of MMA and other vinyl monomers. DPPH and hydroquinone do not inhibit this MMA polymerization. End-group analysis indicates the incorporation of sulfonate and hydroxyl end groups in the polymers, and copolymerization results (MMA-isoprene and MMA-acrylic acid) with this S02-TBHP initiator system and AIBN are in good agreement. The over-all polymerization appears to be primarily radical in nature. Inert solvents (benzene, toluene, and xylene) enhance the rate of polymerization of MMA but not of other vinyl monomers (AN, Sty, V A, EM A, MA, etc.). An initiation mechanism involving monomer and solvent appears to be predominant in the case of MMA, while with other monomers an initiation reaction involving only the monomer is predominant. 

The reaction of acrylonitrile with ethanolic RhCls yields a product of approximate composition (CH2=CH—CN)2RhCl2 in which one of the acrylonitrile moieties is cr-bonded to Rh(III) and the other perhaps 7r-bonded as indicated by the chlorine-bridged structure (175) since it can be displaced by pyridine to yield (CH3CHCN)RhCl2(C5H5N)3 (168). The reaction is thought to involve an intermediate Rh(III) hydride. The comparable reaction with crotononitrile, methacrylonitrile, cinna-monitrile, methyl vinyl ketone, methyl vinyl sulfone, and isoprene does not occur (168). 

ISOPRENE CYCLIC SULFONE (Thiophene, 2,5-dihydro-3-methyl-, 1-dioxide)... 

A 600-ml. steel reaction vessel (Note 1) is precooled before loading by filling it between one fourth and one half full of methanol and Dry Ice. After removal of the methanol and Dry Ice, the autoclave is charged with 120 g. (176 ml., 1.76 moles) of isoprene (Note 2), 113 g. (80 ml, 1.76 moles) of liquid sulfur dioxide, 88 ml. of methanol, and 4 g. of hydroquinone. The vessel is sealed, heated slowly to 85°, and maintained at that temperature for 4 hours. It is then cooled, the sulfone removed, the bomb rinsed with methanol, and the combined product and washings are treated hot with 5 g. of Norite. The filtered solution is concentrated to a volume of 250-300 ml., and the sulfone is allowed to crystallize. The material is filtered and washed with 50 ml. of cold methanol. Recrystallization from methanol (20 ml. per 25 g. of sulfone) yields 140-150 g. of thick, colorless plates. Concentration of the mother liquors raises the total yield to 182-191 g. (78-82%) (Note 3), melting at 63.5-64° (Note 4). 

The yield of the cyclic sulfone depends upon the purity of isoprene. In one experiment, the checkers obtained the sulfone in 86% yield, using freshly distilled isoprene of 99 mole per cent purity, while the yield fell to 77% with commercial isoprene which had been distilled and stored at 5° for 1 week before use. 

The checkers consistently obtained a slightly higher melting point (uncor.) in the range 64.4-65.4°. The purified cyclic sulfone serves as an ideal intermediate for the preparation of extremely pure isoprene, since the latter can be regenerated nearly quantitatively at 135-140°. Other sulfones that can be prepared by this method and that are uscfid in the purification of dienes are those of butadiene, m.p. 65.5°, and 2,3-dimethyl-butadiene, m.p. 135°. The sulfone of piperylene is a liquid. ... 

Isoprene cyclic sulfone has been prepared only from isoprene and sulfur dioxide. ... 

Iron(III)sulfate, 223-224 Isatin, 331 Isatoic acid, 331 Isoatlantolactone, 263, 264 Isobutenyl acetate, 153 Isobutyronitrile, 110 Isocyanates, 14-15 Isoflavones, 410 Isopavine, 217 Isopenams, 325 Isophorone, 197, 198 Isopinocampheylborane, 224 Isoprene epoxide, 4 Isopropenyl phenyl sulfone, 316 Isopropenyltriphenylphosphonium bromide, 225... 

Star-branched lonomers composed of short sulfonated polystyrene outer blocks and hydrogenated butadiene or isoprene inner blocks, with narrow molecular weight distributions have been synthesized by living... 

Although the model studies indicated that selectivity of sulfonation was considerably less than desired, it was decided to proceed with the synthesis of the polyisoprene/polybutadiene star-block copolymer, anyway. It was felt that selectivity was good enough so that an appreciable fraction of the isoprene units could be sulfonated while limiting sulfonation of the butadiene units to some negligible level. For example, the data in Table II indicates that at 21 C, with a 1 1 mole ratio of sulfonating reagent, one should obtain about 50% sulfonation of the isoprene units with virtually no sulfonation of the butadiene units. This was deemed acceptable since the number of isoprene units at the chain ends could be simply doubled, and... 

To achieve absolutely regiospecific sulfonation, the diene inner blocks have been hydrogenated to yield a frilly saturated poly(ethylene-alt-propylene) elastomer, in the case of isoprene, and poly(ethylene-co-l-butene) in the case of butadiene. Due to ease of the linking reaction, most of the latest work has dealt with polybutadiene-based samples, and the remaining discussion will deal with them, although the reactions and techniques are also applicable to the polyisoprene-based samples. 

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