Thioketones substituted thiobenzophenones

A full paper by Alper and Chan, describing in detail the formation of sulphur-donor ligand ortho-metallated complexes (74) by the reaction of substituted thiobenzophenones with di-iron enneacarbonyl, Fe2(CO)>, has appeared. The complexes (74) appeared to be valuable starting materials in the synthesis of the little-known isobenzothiophen heterocycles. Related ortho-metallated thiobenzophenone complexes of ruthenium were found to have a different structure (75). Some non-aromatic thioketones also react with di-iron enneacarbonyl, but these reactions appear to be more complicated. Thus adamantanethione yielded no less than four different complexes, of which (76) was the prevailing one (71%). Thiocamphenilone (77) formed a complex analogous with (76), but such a complex could not be obtained with thiofenchone (78), presumably for steric reasons. Two... 

Photocycloaddition of thiones to alkenes is the most popular and fruitful method for the preparation of the thietane system. In analogy to the formation of the oxetanes by cycloaddition of the electronic excited ( ,tc ) carbonyls, thietanes can be expected to arise photochemically from aromatic thioketones and substituted olefins as well as 1,2- and 1,3-dienes. ° Thiobenzophenone serves as a source of a sulfur atom and, because of its blue color, which disappears on photocycloaddition, permits exact control over the reaction time. A mixture of thiobenzophenone and a-phellandrene must be irradiated for 70 hr before the blue color disappears (Eq. 2) and... 

Coordinated olefins are also readily displaced by thioketones, e.g., stil-bene, in the molybdocene complex 14 by thiobenzophenone to form the complex 15 [Eq. (6)].138 Similarly, thiobenzophenone is substituted for ethene in [Rh(C2H4)(PMe3)(7/5-C5H5)] to yield [Rh(PMe3)(V-S = CPh2) ( -C5H5)]. m... 

Barton and coworkers exploited this strategy in the preparation of overcrowded ethylenes456 usually the desulfurization of a thiirane is accomplished by one equivalent of tertiary phosphine, mainly triphenylphosphine. However, spontaneous loss of sulfur from thiiranes substituted by aryl or halogen has sporadically been reported. Huisgen has reviewed this subject455 and performed many kinetic studies. He found that the desulfurization step can be accomplished by catalytic thiolates and also by thiobenzophenone or other thioketones, although in this case the reaction is slower (equation 131). 

Type II intermolecular ene reaction of thioaldehydes was reported by Vedejs and coworkers492 and already mentioned by Schaumann1. Type in has recently appeared and involves the formation of a C—S bond instead of a C—C bond, as in the case of type I. Type III intramolecular ene reaction has been reported for thioketones and for thioaldehydes. The group of Motoki489 examined the thermal cyclization of o-(2-substituted allyloxy) thiobenzophenones 137 leading to 1,5-oxathiocine derivatives 138 (equation 148). 

Reactions of thioketones with nucleophilic reagents have been studied to some extent. Thiobenzophenone (20) and its 4,4 -substituted derivatives react with cyclopentadienyliron dicarbonyl anion and cyclopentadienyl-molybdenum or -tungsten tricarbonyl anion at room temperature to give fulvenes. Phase-transfer catalysis conditions improve the yields. An electron-transfer mechanism has been proposed for this desulphurization and coupling reaction. An electron-transfer mechanism has also been proposed for the reduction of thiopivalophenone (54) by 1-benzyl-1,4-dihydronicotinamide in acetonitrile. 2,3-Diphenylcyclopropene-thione (55) reacts with 7V-methylarylamines to give the bicyclic thioamides (56). The formation of a thioketen as an intermediate has been suggested. A similar reaction scheme has also been proposed for the reaction of (55) with 3,4-dihydroisoquinoline. ... 

The heavily substituted A -dihydrothiopyran (7) results from Diels-Alder addition of thiobenzophenone and 1,1,3-trimethyl-1,3-butadiene, and related spiro-compounds have been obtained from cyclic thioketones. The equilibria between tautomers (8 R = Me, Et, etc.) and (9) have been studied under acidic conditions, form (8) is always the major component. 

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