4.5- Diphenyl-1,3,2-dioxathiolane 2-oxide

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... 

The reaction of phenylmagnesium bromide with 1,3,2-dioxathiolane 2-oxide (16) gave 3.4-23% ethylene bromohydrin (131) and 42-60% diphenyl sulfoxide (132), depending on the conditions of the reaction. The bromohydrin (131) arises from a nucleophilic displacement at carbon by bromide ion, presumably via (129) and (130), while the sulfoxide (132) is formed by repeated attack of the Grignard reagent at sulfur (56JA454). 

Interestingly, thermal decomposition of 4,5-diphenyl-l,3,2-dioxathiolane 2-oxide depends on the stereochemistry of the starting diols. For example, the cyclic sulfite derived from meso-hydrobenzoin (66a) decomposed on heating to give a good yield of desoxybenzoin (67), while the trans isomer 66b (derived from if/-hydrobenzoin) furnished diphenylacetaldehyde (68) quantitatively [Eqs. (16) and (17)]. 

Photolysis of meso- and d/-4,5-diphenyl-l,3,2-dioxathiolane 2-oxide also furnished similar products. The formation of different products is rationalized in term of the pathways shown in Scheme 16. 

---