Thioketones addition

Thioketones of various types are readily available and are well documented as effective dienophiles. Representative thioketone cycloadditions are listed in Table 5-1. In general, it appears that thioketones usually add to most dienes in high yield at exceptionally low temperatures to afford stable adducts, although some of these adducts tend to undergo retro-Diels-Alder reactions. - Very little has been done toward establishing the regiochemical selectivity of thioketone additions to unsymmetrical 1,3-dienes, and the few such entries in Table 5-1 indicate that mixtures were obtained. The exo/endo stereochemistry of [4 + 2] cycloadditions with unsymmetrical thioketones has not been probed to date. It has been reported that Diels-Alder cycloadditions of thioketones can also be pho-tochemically induced. 

Hydrogen chloride has also been eliminated from sulfinyl chlorides by addition of triethylamine. The thioketone oxide obtained from 9-fluorene-sullinyl chloride reacted with morpholinocyclohexene to give a zwitterionic adduct (475). 

The addition of H2S to an aldehyde or ketone can result in a variety of products. The most usual product is the trithiane (8). ° ot-Hydroxy thiols (5) can be prepared from polychloro and polyfluoro aldehydes and ketones.Apparently, compounds 5 are stable only when prepared from these compounds, and not even for all of them. Thioketones (6) can be prepared from certain ketones, such as diaryl ketones, by treatment with H2S and an acid catalyst, usually HCl. They are often unstable and tend to trimerize (to 8) or to react with air. Thioaldehydes are even less stable and simple ones apparently have never been isolated, though t-BuCHS has been... 

Hetero Diels-Alder reactions of 114 with thioaldehydes and thioketones were also reported to give the syn addition products exclusively [64]. 

The addition of thioketones to olefins is very interesting indeed. Unsubstituted electron-rich olefins yield 1,4-dithianes as final products(112) ... 

The a/ -unsaturated thioketone (20) undergoes Michael addition of trimethyl phosphite to give (21), which cyclizes to (22).15 A similar addition of benzylalkyl (or... 

Dimethylbisthiomalonic acid (120), when treated with an acylated enol, produced intermediate 121 thietanediones 122 and 123 then were formed by elimination of thioketone and acetic acid (see Eq. 12). Similarly, cyclobutane-l,l-bisthiolcarboxylic acid gave 123, a previously unknown sulfur analog of malonic anhydride, (Eq. 12). Thermolysis of 120 also results in the formation of the four-membered heterocycles in addition to carbonyl sulfide, hydrogen sulfide, and thiocarbonic acid. ... 

In some cases involving aliphatic thiocarbonyl ylides, a 1,4-H shift occurs to afford vinyl thioethers. As an example, thiocarbonyl ylides (41), generated by the addition of isopropylidene carbene to aliphatic thioketones, are converted to divinylthioethers (42) (84) (Scheme 5.16). 

The thiocarbonyl group is a highly reactive dipolarophile and in general this group dominates the reactivity of nonenolisable exocyclic thioketones as illustrated for the systems shown 5-methylene-2-thioxo-l,3-thiazolinin-4-one (260) (161), pyrimidone-2- and -4-thiones (261, 262) (134), pyrazolo[l,5,4-e/][l,5]benzodi-azepin-6-thione (263) (162). 2-Thiono-4-imidazolidinone (264) also gave a C=S cycloadduct as expected but, in the case of the analogue 265 with an additional exocyclic methylene group, the latter proved to be more reactive (163). 

It is very well known that polymers of high commercial value are obtained from formaldehyde by addition polymerization of its carbon-oxygen double bond. Not so well known is the addition polymerization capability of the carbon-sulfur double bond, probably because none of the polymers so obtained has yet become commercially acceptable. However, the polymerization chemistry of the carbon-sulfur double bond has been the subject of a number of studies and these have defined the preparation and properties of polythioformaldehyde, polythio-acetone, polymers from a small number of higher thioketones, and polymers from fluorine analogs of thioaldehydes and thioketones. The monomers have great reactivity beyond polymerization, and their general chemistry has been discussed in earlier reviews (/, 2). 

CB2527). The latter are formed in a stepwise manner and are not directly formed from the educts by a simple extrusion of N2. In the first step a fragmentation into thioketones and diazomethane occurs, followed by the generation of methylene from diazomethane. Addition of methylene to the thioketones finally leads to the ylides.3... 

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-... 

Complexes with a,/3-unsaturated thioketones as ligands (49) were obtained in addition to other compounds when [(CO)5M=C(OEt)Aryl] (M = Cr, Aryl = Ph, C4H6Ph-o M = W, Aryl = Ph) were treated at -78°C with LiC(S)NMe2 [prepared from HC(S)NMe2 and LiNEt2 at -100°C] and then protonated at ambient temperature with acetic acid [Eq. (10)]. However, the yield of 49 was rather low (3-8%).96... 

In a closely related reaction the thioketene complex 106210 was reduced by sequential addition of H and H+ to give the thioketone complex 107. However, compared to the reaction of 104 the sequence of H+ and H addition is inverse. Complex 107 is coordinatively unsaturated and therefore added PPh3 rapidly (Scheme 25).109... 

The reactions of dinuclear thioaldehyde and -ketone complexes with PR3 take a different course. When the dimeric complexes 112 are treated with PMe3 a Ti-S bond in 112 is cleaved and the monomeric complexes 113 are reversibly formed (see Scheme 26), 69 The reaction of 112 with benzene-thiol led to a Ti-C cleavage and formation of 1,3-propanedithiolato-(phenylthiolato) complex.69 The reaction of binuclear p-191 rf-thioketone molybdenum complexes related to 115 (M = Mo, E = S, R = Aryl) with P(OEt)3 also gave mononuclear complexes [Mo(CO)2(Et) i72-S = C(Aryl)2 (i75-C5H5)] by a rather complicated reaction sequence. When other phosphites were employed additionally binuclear complexes derived from addition of the phosphite to one molybdenum atom were isolated.225... 

The cleavage of the S = C thioaldehyde bond was observed when the manganese thioketone complex related to 8 (Scheme 2 R1 = R2 = NMe2) was treated with LiAlD4. The C(C6H4OMe-p)2-moiety of the complex was recovered as tetra(p ra-methoxyphenyl)ethane bearing a deuterium in the ortho position of two vicinal phenyl groups each and additionally two deuterium atoms on the ethane skeleton.127... 

Reformatsky reagents were shown to undergo carbophilic addition with a variety of thiocarbonyl compounds (thioketones, dithioesters, trithiocarbonates and xanthates). Elimination of sulfur (or of an alkylthio group) led to the formation of carbon-carbon double (or single) bonds [448]. Typically ... 

As mentioned before, it was with thioketones that the first cases of thiophilic addition were evidenced, but many other modes of reaction have been observed concurrently carbophilic addition, reduction, coupling, double addition, and enethiolization [357]. We will not discuss these reactions here, which have not been used much for synthetic purposes. 

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... 

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