Dioxathiolanes, synthesis

Ethylene, /3-(dimethylamino)-nitro-in pyrrole synthesis, 4, 334 Ethylene, dithienyl-in photochromic processes, 1, 387 Ethylene, furyl-2-nitro-dipole moments, 4, 555 Ethylene, l-(3-indolyl)-2-(pyridyl)-photocyclization, 4, 285 Ethylene, l-(2-methyl-3-indolyl)-l,2-diphenyl-synthesis, 4, 232 Ethylene, (phenylthio)-photocyclization thiophenes from, 4, 880 Ethylene carbonate C NMR, 6, 754 microwave spectroscopy, 6, 751 photochemical chlorination, 6, 769 synthesis, 6, 780 Ethylene oxide as pharmaceutical, 1, 157 thiophene synthesis from, 4, 899 Ethylene sulfate — see 2,2-dioxide under 1,3,2-Dioxathiolane... 

A review of cyclic sulfites and sulfates in organic synthesis includes many examples of 1,3,2-dioxathiolane 5-oxides and 5,5-dioxides <0OT7O51>. Reaction of cyclic sulfates such as... 

Significant advances in the chemistry of these ring systems over the past 10 years include the first unambiguous detection, and characterization by microwave spectroscopy as 1,2,3-trioxolane, of the primary ozonide from ethene and ozone (cf. Section 4.15.3.2), and the introduction of 1,3,2-dioxathiolane 2,2-dioxides as epoxide equivalents in organic synthesis (cf. Section 4.15.5.3). Advances have also been made in the synthesis and characterization of the chemistry of 1,2,3-trithiolanes and 1,2,3-trithioles. 

The various possibilities for the first two types of syntheses are listed schematically in Table 4, and the possibilities for synthesis from other heterocycles are listed in Table 5. In each case the method is discussed in more detail in the following sections Tables 4 and 5 indicate the section(s) in which a particular reaction is described. In the case of sulfur-containing heterocycles, 5-oxides and 5,5-dioxides are treated alongside the basic parent structures, since for 1,3,2-dioxathiolane, 1,2,3-oxadithiolane, and 1,2,5-oxadithiolane the unoxidized rings are unknown. 

Similar geometries have been found for 1,3,2-dioxathiolane. Y-oxidc 15, the corresponding. Y,.Y-dioxidc 16 <2000IZV1586, 2000RCB1575>, and cis- and trans-isomers of the naphthyloxymethyl derivative 17, a precursor in the synthesis of propranolol <2006IZV1095>. 

Attempted thermal epimerization of the diastereomeric 1,3,2-dioxathiolane A-oxides 11 failed even when these compounds were refluxed in o-dichlorobenzene, which indicated a kinetic control of the diastereomeric ratio in the course of their synthesis <2003HAC587>. 

The syntheses and reactions of 1,3,2-dioxathiolane. Y-oxides and 1,3,2-dioxathiolane. Y,.Y-dioxides have been discussed in comprehensive reviews <1997AHC89, 2000T7051>. In publications on organic synthesis these compounds are usually named cyclic sulfites and cyclic sulfates, respectively (Sections 6.05.5 and 6.05.6 Tables 1-7). 

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). 

Trithioles and 1,3,2-dioxathiolanes. 1,2,3-Trithiolanes are prepared by reaction of alkenes with elemental sulfur . The synthesis of 1,3,2-dioxathiolane -oxides (cyclic sulfites) and 1,3,2-dioxathiolane S, -dioxides (cyclic sulfates) is discussed in comprehensive reviews <1997AHC(68)89, 2000T7051>. The most widely used method for the preparation of 1,3,2-dioxathiolane A-oxides 557 is the reaction of the corresponding 1,2-diols 556 with thionyl chloride in the presence of pyridine or triethylamine (Scheme 251). More reactive 1,3,2-dioxathiolane S,A-dioxides 558 are usually obtained by oxidation of sulfites 557 with sodium periodate, which is mediated by ruthenium tetroxide generated in situ from a catalytic amount of ruthenium trichloride <1997AHC89, 2000T7051, CHEC-III(6.05.10.3)183>. 

The second chapter in this volume, 1,3,2-Dioxathiolane Oxides Epoxide Equivalents and Versatile Synthons, is authored by Dr. B. B. Lohray and Dr. V. Bhushan of the Reddy Research Foundation, Hyderabad, India. These compounds are cyclic sulfates and, over the past seven or eight years they have become important intermediates in organic synthesis. 

---