Dithiolates, geminal

Methylenedithiol was used to construct cyclic meat flavor compounds, such as l,3-dithian-5-one 217 <1998FFJ177>. The reaction of the geminal dithiol with a 1,3-dibromide proceeds with pyridine as base in 44% yield (Equation 81). 

Figure 3-19. The reaction of a ketone with hydrogen sulfide in the presence of lead(n) to give a chelation stabilised geminal dithiolate. The other ligands co-ordinated to the lead centre are indicated by Lv...

Contrasting the actions of sulfur and hydrogen sulfide on ketones is an instructive conclusion to this section. While sulfur results in the formation of various heterocycles as noted above, hydrogen sulfide in the presence of amines or ammonia at room temperature yields geminal dithiols or thioketones as exemplified in the report of Mayer and co-workers (15). 

Aliphatic ketones and aldehydes react with H2S under pressure to give a mixture of geminal dithiols and tri- and tetrasulfanes according to equations (67-69). ... 

In the search for a synthetic approach to monobenzo-TTF, it has been shown <78JOC4i6> that it is possible to prepare geminal dichloro derivatives by reaction of sodium cis ethene dithiolate or... 

Dithiins are produced by the reactions of geminal dithiols with enones such as chalcone and benzylidene acetophenone (Equation (54)) <62JOC4488, 66BSF1920>. Treatment of geminal dithiols with malononitrile also gives rise to 1,3-dithiins (Equation (55)) <62JPR2ll>. 

With hydrogen sulfide in the absence of hydrogen, however, aldehydes and ketones give geminal dithiols, the pressures required varying from 35 to 8500 atm according to the nature of the carbonyl compound 392 these dithiols can also be obtained without use of pressure and at room temperature in dimethylformamide as solvent containing a basic catalyst such as morpholine or butylamine.393... 

Preparation of geminal dithiols 393 A rapid stream of hydrogen sulfide is led for 7 h into an ice-cooled solution of a ketone (0.5 mole) in dimethyiformamide (100 ml) containing an amine catalyst (0.05 mole). The mixture is acidified with dilute hydrochloric acid and extracted with light petroleum. The extract is washed with water until free from acid, dried over sodium sulfate, and distilled through a 30-cm Vigreux column at a pressure such that the liquid boils below 100°. All operations must be conducted in a fume cupboard, and the extracted air and waste water must be purified chemically. 

Monomeric aliphatic thioketones can be obtained by passing geminal dithiols RR S(SH)2 in an inert gas over sea-sand, clay tiles, kieselguhr, active charcoal, or other porous material at 150-200°/5--10 mm.407 The thiones are formed in 60-96% in such high purity that in most cases they need not be distilled again before being used for further reactions. 

The reaction of sp3 organoalkali compounds with carbon disulfide usually does not stop at the stage of the initial adduct, but is followed by an extremely fast conversion of the dithiocarboxylate into a geminal ene-dithiolate ... 

Substituted 2-furfurylidenemalononitriles K have been reacted with geminal dithiols L to yield Cyclization of enaminonitriles N with sodium ethanolate yielded... 

Reaction of 179 with geminal dithiols 227 yielded dithiane 228, which was recyclized to pyridinethione 229. ... 

Although they are more stable than hydrates, simple geminal dithiols (Nos 1660 and 1661) can undergo hydrolysis to yield their parent aldehydes and to release hydrogen sulfide (Mayer et al., 1963). The metabolism of the other simple aliphatic dithiol (No. 1709) is predicted to involve the pathways described above for simple thiols. Urinary metabolites could result from methylation, S-oxidation of a sulfur atom to yield a polar sulfonate and the formation of mixed disulfides by combination with a low molecular weight endogenous thiol such as cysteine. 

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