Thiobenzophenone reduction

Fig. 13. Dependence of half-wave potentials for the reduction of substituted benzenes on the total polar substituent constant, ax- Examples shown benzophenones [pH 0], benzophenone-oximes [pH 0], thiobenzophenones [pH 0], nitrobenzenes [pH 2-0], azo derivatives [pH 2-6]. (Taken from Zuman, 1969.)...

In general, it may be expected that thiocar-bonyl compounds are easier to reduce ca-thodically than the corresponding carbonyl structures. There are a few examples dealing with the cathodic reduction of thiones. Let us quote the case of thiobenzophenone, which affords readily a rather stable radical anion at a potential that is -1-0.5 V more positive than that of benzophenone, when... 

Modifications of the route described earlier are (a) the conversion of [M(CO)6] (M = Mo, W) into the chloro-bridged binuclear trianions 10, which subsequently react with S = C(C6H4OMe-p)2 to give the thioketone complexes, and (b) reduction of [W(CO)6] by sodium amalgam to give the dianion [W2(CO)i0]2 and treatment of the latter with thiobenzophenones, adamantanethione, or thiocamphor (Scheme 3).128... 

Fig. 26. Relation of half-wave potentials for the reduction of substituted benzene derivatives in acid media to Hammett substituent constant trx. Benzophenones, benzophenone oximes and thiobenzophenones at pH 0 nitrobenzenes at pH 2,0 azo dyes at pH 2.6...

This procedure is adapted from the method of Schlenk and Bergmann.3 Tetraphenylethylene has been prepared by the reaction of diphenylmethane with diphenyldichloromethane 4 by the reaction of diphenyldichloromethane with silver or zinc 4 by the reaction of thiobenzophenone with copper 6 by the reaction of diphenylmethane with sulfur 6 by the reduction of benzophenone with amalgamated zinc in the presence of hydrochloric acid 7 and by the rearrangement of 1,2,2,2-tetraphenylethanol with acetyl chloride.8... 

In general only very electron-deficient double bonds will react spontaneously with 1,4-dihydropyr-idines. (This statement applies to nonenzymic chemistry enzymatically, as in LAD, NAD(P)H, with a lesser reduction potential than many of the 1,4-dihydropyridines used in abiotic reactions, reduces unactivated carbonyl groups.) Thiobenzophenone, quinone, maleic acid, and hexachloroacetone react spontaneously with simple dihydropyridines and undergo reduction (the carbon-carbon double bond of maleic anhydride is reduced). Trifluoroacetophenone will also often react spontaneously with 1,4-dihydro-pyridines. 

Z2A [CijHjoS]- Anion radical from thiobenzophenone S 1 o CsJ IsJ Diphenylmethyl radicals with snUhr and 4.7.22.4.1 Anion radicals from thiobet Electrolytic reduction/ ACN sulfur conta tzophenone a EPR/ 300 ining substituents nd derivatives It C(7) 4H(o) 0.235 4H(m) 0.095 2H(p) 0.275 71Lun2 113 ... 

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. ... 

Irradiation of thiobenzophenone with cyclo-octatetraene at A > 340 nm gives a 1,4-adduct (40), but, in contrast, 6,6-diphenylfulvene yields" a 1,1-adduct. The photochemical reaction of o-benzylthiobenzophenone has been examined because of its relevance to the reduction of thiobenzophenone." An intramolecular transfer of hydrogen was postulated to give an enethiol, which could be trapped. It is suggested that the photoreduction of thiobenzophenone involves the initial formation of a radical, PhaCSH. The photochemical behaviour of adamantanethione (41) has also been studied. In the ( ,rr ) state it gives the... 

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