Synthesis of Thioketones

Treatment of steroid dienones with tetraphosphorus decasulphide gave the previously unreported purple-blue dienethiones (6). An analogous reaction is claimed to yield 2-arylindane-l,3-dithione. Sulphurization with boron sulphide or silicon sulphide was applied to the synthesis of pyran-4-thione rings. A new 

Barton and his group have prepared the interesting new di-t-butyl thio-ketone (7) in high yield by reaction of carbon disulphide with the lithium salt of the corresponding ketone imine. Independently, Ohno and his co-workers have published an analogous synthesis of this non-enethiolizable thioketone (7). Aliphatic thiones and, possibly, enethiols have been obtained by reaction of arylimines with benzoic anhydride and a stream of hydrogen sulphide. Treatment of a vinyl chloride with sodium monosulphide led to the isolation of thio-dimedone (8 R = H), which has an enethiol ketone structure. Basic hydrolysis 

Retro-Diels-Alder reactions yielding thioketones did not occur, contrary to the previous related results.  

A new type of thioketone (12), conjugated with an a-ester group, has been obtained by basic cleavage of a thiosulphate (Bunte salt) obtained from the a-chloro-ester. This unstable deep-blue thioketone dimerizes easily to a dithietan. Preparation of the a-dithione (13 R = p-MeaNCgHi) has been reported in detail. In the solid state it exists in the dithione form and in solution in 

A number of mostly novel thio-derivatives of squaric acid have been synthesized, mainly by Seitz et al. The monothione (16 X = O) and the dithione (16 X = S) were prepared by treatment of the corresponding carbonyl compounds with tetraphosphorus decasulphide. Monothio-, dithio-, and 

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Syntheses and reactions of thioaldheydes and thioketones have been reviewed by Whittingham,45 Metzner,46 Okuma,47 and synthesis of thioketones by McGregor and Sherrington.48... 

The conversion of a carbonyl to a thiocarbonyl group, or thionation , is a common procedure for the synthesis of thioketones. Several methods that use P4Sio,49 51 Lawesson s reagent (L.R.),2 52 57 H2S,58 59 NaHS,60 or hex-amethyldisilathiane (HMDST)61,62 are described. L.R. and P4S10 have been used to sulfurate partially and entirely perfluorinated carbonyl compounds,63 which are then trapped as anthracene adducts in a one-pot reaction. H2S has... 

The addition of H2S to an aldehyde or ketone can result in a variety of products. The most usual product is the trithiane 9.m a-Hydroxy thiols (6) can be prepared from polychloro and polyfluoro aldehydes and ketones.110 Apparently 6 are stable only when prepared from these compounds, and not even for all of them. Thioketones2 (7) can be prepared from certain ketones, such as diaryl ketones, by treatment with H2S and an acid catalyst, usually HCI. They are often unstable and tend to trimerize (to 9) or to react with air. Thioaldehydes111 are even less stable and simple ones112 apparently have never been isolated, though f-BuCHS has been prepared in solution, where it exists for several hours at 20°C.111 A high-yield synthesis of thioketones involves treatment of acyclic114 ketones with 2,4-bis(4-methoxyphenyl)- ,3,2,4-dithiadiphosphetane-2,4-disulfide 10 (known as Lawesson s... 

Scheme 2.2-20 Solventless synthesis of thioketones, thiolacto-nes, thioamides, and thionoesters using Lawesson s reagent.

Thionation of Ketones. The synthesis of thioketones from ketones by use of LR was described decades ago but several new review articles on this fundamental reaction have been published in recent years. ... 

Vallee Y., Ripoll J. L. Synthesis of Thioaldehydes, Thioketones and Thioketenes... 

Common synthesis of disulfonium dications involves formation of a S-S bond by oxidative coupling of two sulfide moieties. Involving for oxidative generation of S-S bond, thiocarbonyl compounds can lead to new-type dications containing disulfide moieties between two positively charged fragments. There are several disulfide dications of this type derived from thioureas, thiocarbon-ates and thioketones as well as selenium derivatives.137 148... 

Perfluorohalogenoorganosulfenyl halides are, like thiols, mercaptides, and thioketones, key compounds for the synthesis of new perfluorohalo-genoorganomercapto derivatives. The high reactivity of the S—X bond (X = Cl, Br) toward electrophilic as well as nucleophilic reagents causes them to be highly valued starting materials for the synthesis of new derivatives. The chemistry of the not very stable sulfenyl fluorides has... 

For preparative purposes, the reaction of thiocarbonyl ylides with carbonyl compounds can be considered as an alternative method for the synthesis of 1,3-oxathiolanes. Aromatic aldehydes, chloral, glyoxalates, mesoxalates, pyruvates as well as their 3,3,3-trifluoro analogues are good intercepting reagents for thioketone (5)-methylides (36,111,130,163). All of these [3 + 2] cycloadditions occur in a regioselective manner to produce products of type 123 and 124. 

Saito et al. <1995S87> described a new method for the synthesis of heterocycle-fused[c]thiophenes via reaction of aryl heteroaryl thioketones with the carbene precursors. Heteroaromatic thioketones A react with carbenoids generated from bis(arylsulfonyl)diazomethanes or phenyliodonium bis(phenylsulfonyl)methylides to give heterocycle-fused[f]thiophenes B. The reaction involves the ring closure of the intermediary thiocarbonyl ylides, followed by restorative aromatization via the elimination of a sulfenic acid (Equation 11). 

A number of higher thioketones have teen prepared by pyrolysis of hexa-substituted trithianes (40, 41). These trithianes were made by methods already discussed for synthesis of hexamethyl-s-trithiane. Those investigated include compounds of the structure... 

In addition to group 6 metal heterocarbonyl complexes, some thioketone complexes of other metals have also been prepared by the substitution route. The synthesis of the binuclear complex [Mn(CO)2 S = C(Ph)[(T75-C5FLt) Mn(CO)3] (775-C5H5)] (5) was achieved by reaction of [Mn(CO)2(thf) ( -CsHs)] with cymantrenyl(phenyl)thioketone." Similarly, the tetracar-... 

It must be noted that this selective synthesis of enethiols from thioketones is restricted to cases for which regio- and stereoselective deprotonation occurs, as was achieved above with the symmetrical thiones (2a)-(2d). 

This method has been applied to the synthesis of di-t-butyl thioketone [128]. 

An efficient synthesis of ethers involves hydrozirconation of thioketones with hydrochlorobis(cyclopentadienyl)zirconium [251]. 

The synthesis of 4-alkyl thioketones is possible by exploiting the stabilizing effect of a sulfur atom upon an adjacent carbanionic center. Ambident allylic anions react so that conjugate addition proceeds exclusively with the a-carbon of the nucleophile,129 243 244 as illustrated in equation (S3) 245 arylsulfinyl and arylsulfonyl groups normally246 behave similarly.247-249 Sulfur-stabilized vinylic carbanions can be prepared and function as Michael donors in difunctionalization sequences.250... 

The problem of the synthesis of thioaldehydes has been partly circumvented in recent years by using silyl thioketones as their synthetic equivalents. This clever methodology was introduced by Italian chemists and they have successfully exploited many different applications of these compounds, which have been reviewed by Bonini249. In this... 

In recent years, P4S10 has been successfully applied to the synthesis of bridged thioketones (adamantanethione, thiofenchone and thiocamphor)253 and other bicyclic thiones254 (equation 25). 

Enethiols 61 are tautomerically stable isomers of thioketones 60 and, in contrast to enols, enethiols have been isolated and characterized. This method provides a route for the selective synthesis of enethiols by deprotonation of 60 and quenching with trimethylchlorosilane, since under these conditions no isomerization takes place. 

The absence of a convenient method for the preparation of enethiolisab-le thioketones prompted us to fulfil this need. The development of aliphatic thioketones has so far been mostly restricted to examples with steric protection, such as thiocamphor and adamantanethione. Among the difficulties for a general synthesis of aliphatic and acyclic thioketones were easy enethiolisation (enethiols are stable tautomers with thermodynamic stabilities close to those of the thione form), oligomerisation, and susceptibility to air oxidation. They were solved by the adaptation of a former German reac-... 

This study was complemented by a selective synthesis of the tautomeric enethiols [77]. Aliphatic thioketones were deprotonated by LDA, silylated, and the resulting silyl vinyl sulfides were smoothly converted to enethiols by simple addition of methanol. These are stable compounds which do not equilibrate with thioketones, this behaviour probably related to the extremely mild conditions of the (easy) cleavage of the silicon-sulfur bond. 

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