1.3.2- Dioxathiolane oxides, epoxide

Dioxathiolane oxides, epoxide equivalents and versatile synthons,... 

Lohray, B. B., Bhushan, V., 1,3,2-Dioxathiolane Oxides Epoxide Equivalents and Versatile Synthons,... 

Dioxathiolane Oxides Epoxide Equivalents and Versatile Synthons... 

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. 

B.B. Lohray V. Bhushan, 1,3,2-Dioxathiolane oxides epoxide equivalents and versatile synthons, Adv. Heterocycl. Chem. 68 (1997) 89-180. 

Several recent publications describe cleavage of 1,3,2-dioxathiolane. S -dioxides (cyclic sulfates) by halide nucleophiles that furnish halohydrines, which can be used as synthetic intermediates, primarily for preparation of corresponding epoxides or for further reactions with nucleophiles (Table 6). Similar reactions with chloride have been studied for 1,3,2-dioxathiolane J-oxides (cyclic sulfites) <1996ACS832>. 

The most widely used method for the preparation of 1,3,2-dioxathiolane. Y-oxides (cyclic sulfites) 65 bearing C-linked substituents is the reaction of the corresponding 1,2-diols with thionyl chloride in presence of pyridine or Et3N (Scheme 18). More reactive 1,3,2-dioxathiolane. Y,.Y-dioxidcs (cyclic sulfates) 66 are usually obtained by oxidation of sulfites 65 with sodium periodate, which is mediated by mthenium tetroxide generated in situ from a catalytic amount of ruthenium trichloride. Numerous derivatives 65 and 66 were obtained via this approach and its modifications for further transformations, mostly as the synthetic equivalents of epoxides <1997AHC89, 2000T7051> (see also Sections 6.05.5 and 6.05.6, and Tables 1-7). 

Heterocycles of this type occur widely. The benzo[l,3]dioxole ring system is often found in natural products and their degradation products, e.g., sesamol 38 lipoic acid 39 is a naturally occurring 1,2-dithiolane derivative. The 1,3-dithiolanes 40 are commonly known as 1,3-dithioacetals and have been extensively used in carbonyl group chemistry. In the absence of cyclic conjugation, ring sulfur atoms can readily exist in higher oxidation states as, for example, in the oxathiole S, -dioxide 41. 1,3,2-Dioxathiolane A-oxides 42 (cyclic sulfites) and 1,3,2-dioxathiolane A,A-dioxides (cyclic sulfates) are useful as synthetic equivalents of epoxides. 

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