Isoprene cyclic sulfone

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

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

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

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. 

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. ... 

Sulfur dioxide reacts with olefins in the presence of radical-forming catalysts to yield polysulfones,52 but cyclic sulfones can be obtained from butadiene, 2,3-dimethylbutadiene, isoprene, and hexadiene under specific conditions 53... 

Matthews and Strange [42] reported a similar reaction of isoprene with sulfur dioxide in the presence of hydrogen chloride. Seyer and King [Id] reported that 1,3-cyclohexadiene reacted with sulfur dioxide to give a white amorphous compound, as earlier reported by Hofmann and Damm [43]. 2-Methyl- and 4-methyl-1,3-pentadiene were reported by Morris and Van Winkle [44] to react with sulfur dioxide to yield a cyclic sulfone and some hydrocarbon polymer. Starkweather [45] in 1945 reported that chloroprene (2-chloro-l,3-butadiene) reacted with sulfur dioxide in an emulsion system to give a copolymer. Poly-sulfone is the major product when radical initiators are used. Cyclic products predominate when radical inhibitors (hydroquinone) or temperatures in excess of the ceiling temperature are used. For example ... 

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. 

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