Thioketones, synthesis

The mechanism of the Hantzsch s synthesis was studied at a very early stage by several authors. The intermediates were generally assumed to be open-chain a-thioketones, but in a series of papers by Murav eva and Schukina (470, 490) the isolation of hydroxythiazolines from the reaction between a-haloketones and a variety of thioureas was reported. 

It is interesting to note that in each of these cases only one intermediate, either the a-thioketone (93) or the hydroxythiazoline (94), was isolated from the reaction mixture, thus suggesting that hydroxythiazolines are in equilibrium with the corresponding a-thioketones. Similar conclusions are implicit in Baganz and Roger s production of 4-formylthiazoles by this synthesis (625). 

Another indole/oxindole synthesis achieves the critical ortho-substitution by Sommelet-Hauser rearrangement of an anilinosiilfonium ion intermediate. Use of P-thioketones (G = R, an alkyl group) generates 2-substituted indoles, whereas P-thioesters (G = OR) lead to oxindoles. In each case, a 3-thio substituent must be removed by desulfuri2ation. 

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

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... 

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... 

This chapter deals with [2 + 2]cycloadditions of various chromophors to an olefinic double bond with formation of a four-membered ring, with reactions proceeding as well in an intermolecular as in an intramolecular pattern. Due to the variety of the starting materials available (ketones, enones, olefins, imines, thioketones, etc.. . .), due to the diversity of products obtained, and last but not least, due to the fact that cyclobutanes and oxetanes are not accessible by such a simple one-step transformation in a non-photo-chemical reaction, the [2+2]photocycloaddition has become equivalent to the (thermal) Diels-Alder reaction in importance as for ring construction in organic synthesis. 

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... 

One particular class of a,/3 -unsaturated keto-substituted 1,3-dithietanes called desaurins has been known since 1888 (1888CB337). While several specific routes to their synthesis will be outlined later, the one illustrated here (Scheme 110) presumes the intermediacy of an a,/3 -unsaturated keto-substituted thioketone which then dimerizes. The methods used to... 

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... 

Usually these heteroaldehydes and heteroketones are generated in solution in the presence of suitable substrates and immediately trapped. The synthesis, properties, and reactivity of thioaldehydes and thioketones have been the subject of several reviews.1-5 The chemistry of selenocarbonyl compounds has likewise been reviewed in recent years.6-9... 

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]. 

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