Ketones and Thiones

Scheffer et al. also reported hydrogen abstraction of thioketones in the solid state [42]. The nTi" and 7171" excited states differ in the spatial properties of the orbitals involved in abstraction, and it follows that ketones and thiones should exhibit significantly different hydrogen atom abstraction geometries. 

Bigot, B., Theoretical Study on the Origin of the Behavior of Ketones and Thiones in Hydrogen Photoabstraction Reactions, Isr. J. Chem. 1983, 23, 116 123. 

Cyclobutanols and cyclobutanethiols are often found amongst the products of irradiation of ketones and thiones having a y-hydrogen atom available for abstrac-... 

Dimethylgallium derivatives of aromatic hydroxyazomethines (36), (37) nd heterocyclic enamine ketones and thiones (38)—(42) were all prepared by the corresponding reactions of the active hydrogen organic compounds with [Me Ga EtaO] at 50—80°C in dry benzene. ... 

The problem of the synthesis of highly substituted olefins from ketones according to this principle was solved by D.H.R. Barton. The ketones are first connected to azines by hydrazine and secondly treated with hydrogen sulfide to yield 1,3,4-thiadiazolidines. In this heterocycle the substituents of the prospective olefin are too far from each other to produce problems. Mild oxidation of the hydrazine nitrogens produces d -l,3,4-thiadiazolines. The decisive step of carbon-carbon bond formation is achieved in a thermal reaction a nitrogen molecule is cleaved off and the biradical formed recombines immediately since its two reactive centers are hold together by the sulfur atom. The thiirane (episulfide) can be finally desulfurized by phosphines or phosphites, and the desired olefin is formed. With very large substituents the 1,3,4-thiadiazolidines do not form with hydrazine. In such cases, however, direct thiadiazoline formation from thiones and diazo compounds is often possible, or a thermal reaction between alkylideneazinophosphoranes and thiones may be successful (D.H.R. Barton, 1972, 1974, 1975). 

Thione-S-oxides react regiospecifically with allyl and benzylsilanes in the presence of a stoichiometric amount of tetra-n-butylammonium fluoride to produce allyl and benzyl sulphoxides [8], cf. the analogous fluoride initiated reaction of thio-ketones and dithiocarboxylic esters with silanes [9, 10]. The yields of sulphoxides... 

Similarly, aliphatic thiones are also readily reduced at microcathodes in DMF. Thus, thiocamphor exhibits a one-electron reversible step at —1.88 V versus SCE, which is about 0.9 V more positive than the potential of the reduction of camphor under the same experimental conditions. q , 8-unsaturated thiones such as (18) were also investigated polarographically in pro-tic media. Similarly [179-182], reduction of Q , 8-ethylenic ketones and aldehydes in acidic media yielded dimers. 

In a one-pot reaction, cyanothioacetamide 43 reacted with cyclic ketones and sulfur in the presence of a diethylamine catalyst to give the 2-spirothieno[2,3-d]pyrimidine-4(3//)-thiones 44 in moderate yields... 

Pyran-4-thiones reacting with potassium hydrogen sulfide lead to a-(l,2-dithiol-3-ylidene) ketones and/or thiopyran-4-thiones (Eq. 

Thiopyran-4-thiones give adducts with mercury dichloride which, by reaction with aqueous sodium carbonate, give a mixture of a-(l,2-dithiol-3-ylidene)ketone and thiopyran-4-one (Eq. 2).9> 10... 

The general procedure for the preparation of 1,3,4-thiadiazolidine-2-thiones with aliphatic substituents in the 3-, 4- and 5-positions is the reaction between an aliphatic aldehyde or ketone and a hydrazinium dithiocarbazate (Scheme 29). Ring opening to the salts or methyl esters of alkylidenedithiocarbazic acid occurs in the presence of hydroxide ion or methyl iodide, respectively (70ACS179). 

A further efficient and general synthesis of l,3-dithiole-2-thiones (169) with a variety of functional groups is the acid-catalyzed ring closure of j8-keto f-butyl trithiocarbonates of type (261) which are readily available from a-halo ketones and sodium t-butyl trithiocarbon-ate. The intermediates (262) fragment into isobutene and l,3-dithiole-2-thiones (169) (80JOC175). 

The characteristic feature of these three-centered unsaturated systems is their ability to undergo prototropic conversions. Ketone-enol, thione-thiol, enamine-imine, and other types of triad tautomerism are well-known some other examples of tautomeric conversions, in particular the existence of enediamines as tautomer of acetamidines, have been confirmed experimentally (Scheme 6) (81SC655 83JOC2667). 

Enol/ketone and thiol/thione prototropic tautomerism in 2-imidazolone and 2-thioimidazolone has been investigated by ab initio methods in terms of thermodynamic stability (Scheme 4) <2003JP047>. Semiempirical methods (AMI, PM3, and MNDO) have been used to evaluate the tautomerism of 2-, 4-, and 5-imidazolones and their thio- or azo-analogues in the gas phase <1996JMT(366)227>. 

Benzoyl-3-methyl-l-phenyl-2-pyrazolin-5-thione has been prepared by Michaelis and co-workers977,990 by the reaction of sodium and potassium hydrogen sulfide with 4-benzoyl-5-chloro-3-methyl-l-phenyl-pyrazole. The thiono compound forms a methiodide and gives the characteristic reactions of both ketones and 2-pyrazolin-5-thiones. 

Cyclopropyl ketones and lactams as well as amides of cyclopropanecarboxylic acids were converted to the corresponding thiocarbonyl compounds on reaction with 2,4-bis(4-methoxyphenyl)-l,3,2,4-dithiadiphosphetane-2,4-dithione (Lawesson s reagent) in benzene or toluene the yields were good. For example, reaction of lactam 1 to give thione 2. Thiones were also formed when hydrazones were treated with sulfur monochloride. ... 

With a-halo ketones and formation of zl4-thiazoline-2-thiones. . . 615... 

Aldehyde and ketone functions, and thione and thials, if suitably placed, can strongly interact with the ring sulfur by hypervalent or possibly polar effects <94SR3i7>. The exocyclic thione function is readily oxidized by, for example, peracetic acid. Thione-S -oxides (110) have been isolated. The reaction with more oxidizing agent under acidic conditions is a valuable synthesis of... 

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