1.2- Oxathietanes synthesis

There is one report on the synthesis of several pentacoordinate 1,2A4- and l,2A6-oxathietanes, which is outside the categories discussed above <1996JA697, 1996JA12455>. Treatment of diols 61a or 61b with bromine under basic conditions leads to the formation of pentacoordinate l,2A4-oxathietanes 62a and 62b in 8% and 62% yields, respectively (Scheme 17). Oxidation of these substrates furnishes the observed pentacoordinate l,2A6-oxathietanes 63a and 63b in poor yield. 

While the previous version of this chapter contained small sections on the synthesis of fluorinated and nonfluorinated /3-sultones along with /3-sultines and 1,2-oxathietanes, there has been no major new advances on the synthesis of these types of systems over the last decade. It appears that until practical industrial or medicinal uses are found, new methodologies for the constmction of such systems will not be developed. 

Jiang has expanded the Carreira method of alkyne addition to aldehydes to include other ligands and Zn(II) salts (Eq. 13) [17]. Thus use of stoichiometric quantities of Zn(II) difluoromethane sulfonate salt and (lS,2S)-3-(tert-butyldi-methylsilyloxy)-2-N,N-dimethylamino-l-(p-nitrophenyl)propane-l-ol (3) in the addition reaction can afford propargylic alcohols in high ee. Difluoromethanesul-fonic acid is prepared from 3,3,4-,4-tetrafluoro[1.2]oxathietane the amino alcohol has been used in the synthesis of chloramphenicol and is also readily accessible. Application of a combination of this same amino alcohol ligand with Zn(OTf)2 has also been shown to afford products in high yield and ee in addition reactions (Eq. 14) [18]. 

The synthesis of the 4,5-dimethoxy-l,3,2-dioxathiolane 2,2-dioxide (98) from perfluoro-2-butene involved reaction with sodium methoxide, resulting in a mixture of cis and trans isomers of the vinyl diether (197). Subsequent action of sulfur trioxide on (197) gave, probably via the 1,2-oxathietane 2,2-dioxide (198), the cyclic sulfate (98) (77JA1214), a convenient precursor to hexafluorobiacetyl (c/. Section 4.33.3.3.1). 

IZV118) and the formation of (31) is analogous to the reaction (197)->(98) via a four-membered 1,2-oxathietane 2,2-dioxide intermediate. Subsequent products derived from (31) by electrophilic addition reactions at the alkenic double bond have been described in Section 4.33.3.2.2 and the synthesis of 4,5-dichloro-l,3,2-dioxathiolane 2,2-dioxide (154) by chlorination of ethylene sulfate (18) is discussed in Section 4.33.3.5. Cyclic sulfites, on the other hand, cannot be halogenated without ring opening (cfSection 4.33.3.2.4). 

Oxathietane 2,2-dioxides are claimed to be useful in the synthesis of pharmaceuticals diseases, ... 

Ohno, F., Kawashima, T., Okazaki, R. Synthesis, Crystal Structure, and Thermolysis of a Pentacoordinate 1,2> 6-Oxathietane An Intermediate of the Corey-Chaykovsky Reaction of Oxosulfonium Ylides J. Am. Chem. Soc. 1996, 118, 697-698. 

A fluorinated heterocycle, 3,3,4,4-tetrafluoro-l,2-oxathietane-2,2-dioxide more commonly called tetralluoroethylene sultone (XXVll), is the starting material for the synthesis of Nalion perfluorinated ion exchange resins. This compound was synthesized independently at DuPont and the Russian Academy of Sciences by the reaction of tetralluoroethylene and sulfur trioxide (Eq 13.24). 

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