1.2- Dithietes ring-opening

Oxidation of the dithiete 175 with MCPBA (1 equiv.) yielded the dithiete 1-oxide 202 which, when heated in refluxing toluene, formed a mixture of the ring-opened product sulflne 203 (blue, A ax 576 nm) and 202 in the ratio 7 1 (95TL8583). Further oxidation of 202 or oxidation of 175 with... 

Theoretical studies on the ring-opening reaction of 1,2-dithiete by using unrestricted density functional theory (DFT) with fractionally occupied frontier orbitals were reported. The topic addressed in these studies was the question of the relative energies of the sulfur species 1,2-dithiete 19a and dithioglyoxal trans-20a <1999JCP7705>. 

Five-membered heterocycles 206-209, in which two 1-adamantyl groups occupy cis positions, were synthesized from 175 (98BCJ1181).The reaction of tosyl azide with 175 gave 210, which has no tendency to cyclize to 211. These results, together with the fact that compound 173 exists in the ring-opened form, led to the conclusion that, when four-membered rings are constituted by a combination of one S—X (X = N, O, S) and one C—C double bonds, 1,2-dithietes are probably the only species that can adopt a ring-closed structure as the predominant isomeric form. 

Bis-3,4-(trifluoromethyl)-l,2-diselenete 651 is prepared by refluxing selenium with hexafluoro-2-butyne. It reacts with triphenylphosphine and triphenyl-arsine. Triphenylphosphine selenide was isolated, but no other compounds were identified.Ring-opened complexes with nickel, copper, vanadium, molybdenum (652), tungsten, iron, and cobalt are analogous to complexes of the 1,2-dithiete (527) (Section XXXV.2.C.). 

Special ring-openings are [2+2] cycloreversions (oxetan-2-ones, 1,2-dioxetanes, l,2-dioxetan-3-ones, 1,2-diazetidines, l,2-diazetidin-3-ones) and valence isomerizations (1,2-dithiete, 1,2-dihydro-1,2-diazete). 

Several bi- and tri-cyclic thiepan derivatives were obtained by autoxidation of the cyclobutadiene (111) or by various reactions with strained sulphur-containing acetylenes, e.g.. the dithiet (112). The ylides derived from cis- and trans-ill) were alkylated stereoselectively at low temperatures, and they reacted with carbonyl compounds to give ring-opened oxirans (113). Reduction of the 6-methoxy-carbonyl derivative of (72) afforded the ten-membered cyclic sulphide (114). ... 

The photochemical decomposition of vinylene dithiocarbonate (226) gave dithiobenzil (227), which was in equilibrium with the corresponding dithiet (228). The activation energy for ring opening of the dithiet was ca. 15 kcal... 

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