1.3- diketones reaction with hydrogen sulfide

Monothio -diketones can be prepared by the action of hydrogen sulfide and hydrogen chloride on the appropriate -diketone in alcohol solution. Nevertheless the conditions are rather critical. At room temperature -dike-tones are in tautomeric equilibrium between the diketo form (I) and the chelated hydrogen-bonded form (II), and in polar solvents the concentration of the diketo form (I) is increased. Reaction with hydrogen sulfide occurs only with the diketo tautomer (I). Consequently, higher concentrations of hydrogen chloride are required for those -diketones which exist predominantly in the... 

Oxazinium perchlorates (267) are obtained by reactions of 1,3-diketones and benzonitrile in the presence of perchloric acid and acetic anhydride (88ZOR1561, 88ZOR2232, 91ZOR1986). 1,3-Thiazinium perchlorates are synthesized by treating oxazinium salts with hydrogen sulfide in absolute acetonitrile and then with perchloric acid (72S333). 

Figure 3-20. The reaction of a 1,3-diketone with hydrogen sulfide only gives a monothio derivative, 3.11, rather than a 1,3-dithioketone.

This reaction was first reported by Baumann and Fromm in 1891. It is the synthesis of 2,4-diaryithiophenes via the reaction between substituted styrenes and sulfur. Besides the major product of 2,4-diarylthiophene, some minor 2,5-diarylthiophenes are also found in this reaction. Similarly, butadiynes can react with hydrogen sulfide to afford thiophenes. However, at 600°C in the presence of a ferrous sulfide-alumina catalyst, styrene reacted with hydrogen sulfide to give 60% benzothiophene." On the other hand, thiophenes can also be prepared via the reaction between ethylbenzene and sulfur, acetophene and hydrogen sulfide, or 1,4-diketones and phosphorus trisulfide (or phosphorus pentasulfide). The preparation of 2,4-diarylthiophene has been reviewed. ... 

This route can be used to prepare thiophenes with adjacent bulky groups 3,4-di-ferf-butylthiophene [102] and 3,4-di(adamant-l-yl)thiophene [103] can be accessed. Another nice example (Scheme 64) is the reaction of 1,3-dichloropropanone with hydrogen sulfide, which produces diketone 40. The application of the pinacol-forming conditions gives rise to the diol 41 and double dehydration produces the bicyclic l//,3//-thieno[3,4-c]thiophene 42 [104],... 

A thioamide of isonicotinic acid has also shown tuberculostatic activity in the clinic. The additional substitution on the pyridine ring precludes its preparation from simple starting materials. Reaction of ethyl methyl ketone with ethyl oxalate leads to the ester-diketone, 12 (shown as its enol). Condensation of this with cyanoacetamide gives the substituted pyridone, 13, which contains both the ethyl and carboxyl groups in the desired position. The nitrile group is then excised by means of decarboxylative hydrolysis. Treatment of the pyridone (14) with phosphorus oxychloride converts that compound (after exposure to ethanol to take the acid chloride to the ester) to the chloro-pyridine, 15. The halogen is then removed by catalytic reduction (16). The ester at the 4 position is converted to the desired functionality by successive conversion to the amide (17), dehydration to the nitrile (18), and finally addition of hydrogen sulfide. There is thus obtained ethionamide (19)... 

The parent hexathiaadamantane (185) is obtained preparatively when a solution of formic acid and hydrochloric acid in nitrobenzene is allowed to stand for several weeks in a hydrogen sulfide atmosphere the product which separated is almost insoluble in all common solvents and purification presents a problem. Only large volumes of dimethyl sulfoxide at reflux serve for recrystallization.224 The reaction of thioacetic acid with formic acid in the presence of zinc chloride gives tetramethyl-(186), monomethyl-, dimethyl-and trimethylhexathiaadamantane derivatives (187).225 Other variations include the reaction of thioacetic acid with a /i-diketone,226 and the use of boron trifluoride227 or aluminum chloride as a catalyst.228... 

The first recorded attempt to prepare a thio derivative of a /1-diketone resulted in the isolation of the colourless dimer (57 R = R = Me) from the reaction of acetylacetone and hydrogen sulfide in hydrochloric acid.243 Similar dimers with various R and R groups have been reported244 and the structure (57) has been confirmed from NMR and MS data.245 Other attempts to prepare dithio-/ -diketones (58) yielded 1,2-dithiolium salts (59).246... 

In the presence of hydrogen chloride, a-acetylenic ketones react with thioacetic acid to give a monothio-)S-diketone which is converted to a 1,2-dithiolium ion by phosphorus pentasulfide or hydrogen sulfide. These reactions, which involve some sort of oxidation, are discussed in the next paragraph. 

The halogen atoms of the geminal dihalo derivatives of diaryl diketones and of heterocyclic ketones can be replaced in reactions with sulfur compounds 0e.g., sodium hydrogen sulfide, thioacetic acid, phosphorus pentasulfide), thioketones being formed.318,319 Staudinger and Freudenberger,320 for instance, obtained thiobenzophenone in 46% yield from benzophenone dichloride (dichlorophenylmethane) and a hot alcoholic solution of sodium hydrogen sulfide ... 

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