Sulfolene dioxide

The most synthetically useful cheletropic elimination involves 2,5-dihydrothiophene-1,1-dioxides (sulfolene dioxides). At moderate temperatures they fragment to give dienes and sulfur dioxide.301 The reaction is stereospecific. For example, the dimethyl derivatives 22 and 23 give the E,E- and Z,E-isomers of 2,4-hexadiene, respectively, at temperatures of 100°-150°C.302 This stereospecificity corresponds to disrotatory elimination. 

Sulfolene dioxide is subject to a-lithiation and alkylation, and this reaction has been used to introduce the ring into more complex molecules. 

Sulfolene dioxide thermolysis has also been applied to formation of o-quinodimethanes. 

A synthetically useful type of a cheletropic reaction involves 2,5-dihy-drothiophene-1-1-dioxides (sulfolene dioxides). These compounds can either be made by independent synthetic routes or made by cycloaddition reactions from dienes and sulfur dioxide. At elevated temperatures the ring fragments to sulfur dioxide and a diene.For example, the two dimethyl derivatives 5 and 6 fragment to sulfur dioxide and rmAT5, ran5-2,4-hexadiene and c/5,fr<2 5-2,4-hexadiene, respectively, at temperatures of 100-150°C. The cleavages are stereospecific and involve disrotatory motion of the substituents at C-2 and C-5 similar to the pyrroline decomposition described previously. This reaction has proven to be a satisfactory... 

Example 4.4 Butadiene sulfone (or 3-sulfolene) is an intermediate used for the production of solvents. It can be produced from butadiene and sulfur dioxide according to the reaction ... 

Production. Sulfolane is produced domestically by the Phillips Chemical Company (Borger, Texas). Industrially, sulfolane is synthesized by hydrogenating 3-sulfolene [77-79-2] (2,5-dihydrothiophene-l,1-dioxide) (2), the reaction product of butadiene and sulfur dioxide ... 

Sulfur dioxide acts as a dienophile ia the Diels-Alder reaction with many dienes (253,254) and this reaction is conducted on a commercial scale with butadiene. The initial adduct, sulfolene [77-79-2] is hydrogenated to a solvent, sulfolane [126-33-0] which is useful for selective extraction of aromatic hydrocarbons from... 

Sulfolane (tetramethylenesulfone) [126-33-0] M 120.2, m 28.5 , b 153-154 /18mm, 285 /760mm, d 1.263, n 1.4820. Prepared commercially by Diels-Alder reaction of 1,3-butadiene and sulfur dioxide, followed by Raney nickel hydrogenation. The principle impurities are water, 3-sulfolene, 2-sulfolene and 2-isopropyl sulfolanyl ether. It is dried by passage through a column of molecular sieves. Distd... 

Sulfolene (2,5-dihydrothiophene-l,1-dioxide) EK, MCB Isopropenyl acetate MCB Dimedon EK, MCB... 

A direct insertion of sulfur dioxide into a C—C bond has been observed under photochemical conditions 3 (equation 72) a related CH insertion followed by an intramolecular sulfinate to carbonyl addition yields the same system 3 (equation 73). A further sulfolene synthesis utilizes a three-component reaction see equation 74 (cf. Section IV below) 35. 

The reversible reaction between butadiene and sulfur dioxide, which yields sulfolene, has been known for a long time. Such cycloaddition reactions of sulfur dioxide, and of other sulfur oxides, have been reviewed by Block.49... 

The thiophene ring system can be utilized as a synthetic scaffold for the preparation of nonthiophene materials as the sulfur moiety can be removed by reduction (desulfurization) or extrusion (loss of SO2). The extrusion of sulfur dioxide from 3-sulfolenes (2,5-dihydrothiophene 1,1-dioxides) give dienes (butadienes or o-quinodimethanes) that can be utilized to prepare six-membered rings by cycloaddition chemistry. For example, thermolysis of 3-sulfolene 120 provided tricyclic pyrazole 122 via an intramolecular cycloaddition of the o-quinodimethane 121 that results by extrusion of sulfur dioxide <00JOC5760>. Syntheses of 3-sulfolenes 123 and 124 <00S507> have recently been reported. 

Dihydrothiophene 1,1-dioxide (butadiene sulfone, or 3-sulfolene) was purchased from the Aldrich Chemical Company, Inc. 

Pyrrole-fused 3-sulfolenes 221 undergo thermal extrusion of sulfur dioxide to produce highly reactive o-quinodi-methanes which can be trapped in Diels-Alder reactions (Scheme 23) <1997H(46)199, 1997TL3639>. The resulting cycloadducts 222-227 are important starting compounds in porphyrin synthesis. 

A series of 4,6-disubstituted-l,3-dihydrothieno[3,4- ]thiophene-2,2-dioxides (sulfolenes) 477-480 was obtained <2002JOC9267> from 5,7-disubstituted l,4-dihydrothieno[3,4-7l[2,3]oxathiin-3-oxides (thienosultines) 476a-d by heating in benzene in sealed tube (Equation 15). 

Trivial names which have found use in this article are thiolane (for tetrahydrothiophene), sulfolane (for tetrahydrothiophene 1,1-dioxide) and sulfolene (for 2,5-dihydrothiophene 1,1-dioxide). As with usual practice, thienyl refers to the radical corresponding to phenyl in benzene chemistry, and thenyl is analogous to benzyl . 

Sulfolene (2,5-dihydrothiophene 1,1-dioxide, 6) is well known to afford 1,3-butadiene and sulfur dioxide in a retrocheletropic cycloaddition (77MI1). 

Dihydrothiophene dioxide (2-sulfolene, 76) is partly converted to ethyne, ethene, and sulfur dioxide (93PHC1). Tetraphenylthiophene dioxide (77) is split to diphenylacetylene and S02 under FVP conditions, whereas solution thermolysis leads to different products (77RTC282). 

Ring expansion reactions are much better known and sulfolene substrates have received considerable investigation. Cyclopropanation with dichlorocarbene affords 6,6-dichloro-3-thiabicyclo[3.1.0]hexane 3,3-dioxides which may readily be ring enlarged by base or acid treatment. Base treatment, especially with LDA, cleanly affords 2//-thiopyran dioxides hydrochloric acid does likewise, but less cleanly, while hydrobromic acid treatment causes a more complex set of reactions leading to thiopyranones containing bromine in which the sulfur has been reduced. The intermediacy of thiopyrylium oxides has been invoked to rationalize the observations (Scheme 27) (81JOC4502). 

Since the first report in 1914 of the formation of a butadiene-sulfur dioxide adduct [538], much work has been carried out on the reaction of conjugated dienes with sulfur dioxide and its applications in synthetic strategies. Two pathways can and have been observed a cheletropic reaction (to 2s + ir 4s) yielding 3-sulfolenes and (4 -ns + tt 2s) hetero-Diels-Alder addition yielding sultines (see [539] and [540] and references... 

The direct alkylation of 3-sulfolene followed by thermal extrusion of sulfur dioxide led [548] to a convenient synthesis of ( )-l,3-butadienyl(tributyl)stannane. 

These direct metallation-alkylation reactions of sulfolene and dihydrothiepin dioxide are incentives for future new synthetic applications of the associated cheletropic processes. 

The thermal retro-reaction of 3-sulfolenes to dienes and sulfur dioxide occurs under mild conditions (about 120-200°C), and is, as predicted from the Woodward-Hoffmann rules, a disrotatory process so for 2,5-dimethyl-3-sulfolenes [541,542] ... 

The higher homologue of 3-sulfolene, 2,7-dihydrothiepin-l,1-dioxide could be similarly metallated at low temperatures. Reaction with reactive electrophiles followed by extrusion of sulfur dioxide led [549] to the corresponding hexatriene derivatives, as in the stereoselective synthesis of (Z,E)-l,3,5-decatriene (considered as an undecatriene in the publication) shown here. 

The cycloaddition of a variety of sulfur heterocycles to alkenes has also been reported. Dibromomaleic anhydride undergoes [ 2 + 2] cycloaddition to thiophen295 and to benzo[b]thiophen.296 The photoaddition of benzo-[(>]thiophen 1,1-dioxides to alkenes also affords cyclobutane derivatives.297 Of particular interest is the addition of 3-acetoxybenzo[6]thiophen (350) to cyclohexene to give the adduct (351), which on treatment with base, undergoes a retro-aldol ring opening to benzo[6]thiepinone (352).298 A mixture of stereoisomeric cyclobutane derivatives were obtained on irradiation of 2,6-diphenyl-4//-thiopyran-4-one 1,1-dioxide in cyclohexene.299 The [ 2 + 2] cycloaddition of sulfolen to maleic anhydride and to maleimide has been reported.300... 

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