Thiirane dioxides synthesis

Thiirane dioxide (episulfone) synthesis by reaction of diazomethane with sulfenes or S02 (see 1st edition). 

The thiirane dioxides decompose with elimination of sulfur dioxide. The reaction is useful for the synthesis of certain types of olefins. 

The Ramberg-Backlund reaction converts a-halo sulfones into alkenes in the presence of a base with extrusion of S02. The a-metallated intermediates formed by the action of a polar base undergo 1,3-elimination with formation of unstable thiirane dioxides of type 83 that decompose into alkenes - - SO2 (cheletropic elimination). Halogenation is done under basic conditions using CBr2F2. The reactions has been applied to the synthesis of C-glycosides of type 84, as illustrated in Scheme 22.23. " ... 

Methylene thiirane is obtained by thermolysis of several spirothiirane derivatives which are formally Diels-Alder adducts of methylenethiirane and cyclopentadiene or anthracene <78JA7436). They were prepared via lithio-2-(methylthio)-l,3-oxazolines (c/. Scheme 121). A novel synthesis of the allene episulfide derivatives, 2-isopropylidene-3,3- dimethylthiirane (good yield) or its 5-oxide (poor yield), involves irradiation of 2,2,3,3-tetramethyl-cyclopropanethione or its 5-oxide (81AG293). Substituents on the thiirane ring may be modified to give new thiiranes (Section 5.06.3.9). The synthesis of thiirane 1-oxides and thiirane 1,1-dioxides by oxidation is discussed in Section 5.06.3.3.8 and the synthesis of 5-alkylthiiranium salts by alkylation of thiiranes is discussed in Section 5.06.3.3.4. Thiirene 1-oxides and 1,1-dioxides may be obtained by dehydrohalogenation of 2-halothiirane 1-oxides and 1,1-dioxides (Section 5.06.4.1.2). 

Table 6 Synthesis of vinyl sulfones 197 from thiirane 1,1 -dioxides...

There are three main synthetic methods for synthesis of thiiranes C-S bond-forming reactions, C-G bond-forming reactions, and two bond-forming reactions. These methods are described in detail in CHEC(1984) and CHEC-11(1996), and the references until 1995 are cited therein <1984CHEC(7)131, 1996CHEC-11(1)174>. Described here are methods published after 1996 for synthesis of thiirane, thiirane-Toxide, thirane-1,1-dioxide, and thiirene-1-oxide. 

Use of thiirane 1,1-dioxide affords a useful synthesis of ethanesulfinates with the following functions in the 2-position thiol, disulfide, trisulfide, thiosulfate, thiosulfonate, and phos-phorthioate. Reaction of episulfone (83) with sodium p-toluenethiolate gives the sulfinate (84), which can be converted to the sulfone (85) (Scheme 35). Similarly, (83) is converted to the benzyl counterpart (86), which is desired for possible debenzylation to the thiol since the salt (86) is difficult to purify, it is converted to the ethyl ester (87) <86JOC5235>. 

There are three main approaches for the synthesis of thiiranes the first is C—S bond formation (Scheme 64), the second is C—C bond formation (Scheme 65), and the third is based on the formation of two bonds (Scheme 66), which includes the reaction of elemental sulfur with alkenes and the reaction of thiocarbonyl compounds or elemental sulfur with carbenes derived from diazo compounds. These methods are described in detail in CHEC-I, and references until 1983 are cited therein <84CHEC-i(7)i7i>. A survey of reports, published mainly after 1983, of the formation of thiiranes, thiirane 5-oxide, and thiirane S,S-dioxides is given in the following sections. 

A unique approach to the synthesis of fused-ring thiiranes and thiirenes involves the utilization of cycloaddition methodology. The use of diphenylthiirene oxide and the corresponding dioxide as dieneophiles in [2 + 2], [4 + 2], and 1,3-dipolar cycloadditions is well established. Often the initial... 

The isolation of 3-sulphinopropionic acid from Pseudomonas fluorescens has been reported and the structure confirmed by synthesis involving cleavage of bis(2-carboxyethyl)sulphone. Cleavage of thiiran 1,1-dioxides with metal halides or metal thiolates gives j8-halogeno- and jS-alkylthio-alkane-sulphinates, respectively. 

Intermediates in Reactions.— The utility of the Ramberg-Backlund rearrangement and the involvement of thiiran 1,1-dioxides in synthesis has been reviewed. Treatment of d,l- and meso-bis-oc-bromobenzyl sulphone with triphenylphosphine gave trans- and cis-stilbene, respectively, via a-sulphonyl carbanions which undergo cyclization at the remaining chiral centre to yield trans- and cis-2,3-diphenylthiiran 1,1-dioxides as intermediates (Scheme 3). Inversion occurred at each chiral centre. Thiiran... 

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