Thioketones reactivity

Five-membered rings. Most five-membered rings arise from the 1,3-dipolar-ophile behaviour of thioketones and studies in this field have been carried out mainly by Huisgen, Mloston, Heimgartner, and their co-workers. An exemplified thioketone reactivity to form five-membered rings with several classes of compounds is shown in Table 2. 

Table 2 Exemplified thioketone reactivity to form five-membered rings... 

Compounds containing double-bonded silicon and germanium atoms are the nearest analogues of olefins, ketones and thioketones. However, most of them are very unstable and highly reactive species. 

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... 

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). 

Unlike carbonyl compounds, /nbcarbonyl compounds such as thioketones, RiR2C=S, are very reactive and often impossible to isolate in a pure state. Apply principles of orbital interaction theory to explain ... 

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... 

The reactivity of the complexes 25 is similar to that of a dimeric-orthometallated thioketone complex obtained by the reaction of 2,5-... 

Retro-Diels-Alder reactions giving thiocarbonyl compounds are favored when simultaneously a comparatively stable diene is formed1. This is the case with anthracene and cyclopentadiene Diels-Alder adducts 81 and 82 which, upon heating, afford a wide array of thioaldehydes and thioketones (equation 84). These adducts are stable at room temperature and have become a convenient way of storing very reactive thiocarbonyl compounds. Cyclopentadiene is the cheapest and most reactive diene for use in Diels-Alder reactions. Also, strain in the bridged cycloadducts facilitates retro-Diels-Alder cleavage224. 

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