Thiocarbonyl compound

There is an enormous literature on thiocarbonyl compounds, due in part to the technical and industrial importance of many of them, including thioamides, thioureas, xanthates, dithiocarbamates and so forth. An excellent, and recent, general review is available.107 There are also specialized reviews germane to the present chapter Griffin, Woods, and Klayman2 discussed the use of thioureas in the synthesis of heterocycles the preparation of thiazoles from thioamides is included in a three-part volume on Thiazoles 108 the use of carbon disulfide in the synthesis of trithiones and related heterocycles has been reviewed by Mayer109 and Huisgen110 has reported numerous examples of 1,3-dipolar cycloadditions in which carbon disulfide was used. 

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The mercapto form is much more strongly favored than is the hydroxy form for the corresponding oxygen compounds. A pertinent comparison in this respect is the greatly reduced inclination of enethiols to tautomerize to the corresponding thiocarbonyl compounds, in contrast to the facile ketonization of vinyl alcohols. 

The reaction of thiocarbonyl compounds with diazoalkanes (alkyl, aryl substituted) frequently gives good to excellent yields of thiiranes. The mechanism may involve addition of a carbene across the thiocarbonyl group, especially in the presence of rhodium(II) acetate... 

Thiocarbonyl compounds can be converted into difluoromethylene compounds usually under milder conditions than the conesponding carbonyl compounds Ethylene trithiocarbonate reacts smoothly with sulfur tetrafluoride at 110 °C in the absence of catalyst to give 2,2-difluoro-l,3-dithiolane in high yield. Thiuramsul/ides under similar conditions are readily converted into dialkyItrifluo-rometkylamines [11] (equations 13 and 14). 

These reactions differ from those of sulfur tetrafluoride with carbonyl compounds in that a formal oxidation-reduction of the sulfur atoms m the thiocarbonyl compound and sulfur tetrafluoride molecule occurs, resulting in the formation of free sulfur and the complete utilization of the fluorine atoms in sulfur tetrafluoride. 

E. Azoles with Chelated Potential Tautomeric Groups 1. Hydroxycarbonyl (Thiocarbonyl) Compounds... 

Unusual reactions occur between diazomethane and heterocyclic thiocarbonyl compounds. For example, pyran-4-thiones give methylene ethers of 1,2-dimercaptans formed by dimerization (cf. 115 —>116). 4-Thioflavones and 4-thiochromones react similarly. 

Application of radical reactions to organic synthesis has recently received much atrendon, and various important reacdons have been discovered in this field. Alkyl halides, sulfides, seleniJes, and thiocarbonyl compounds have been used as precursors to alkyl radicals. Some examples are illustrated in Scheme 7.18. ... 

In carbonyl compounds the aryl radical attacks the carbonyl carbon atom, whereas in thiocarbonyl compounds the sulfur atom reacts. Petrillo et al. (1988) obtained various S-arylthioacetates in 40-60% yield by treating arenediazonium... 

Reagents are also available to convert thiocarbonyl compounds back to carbonyls. Simple hydrolysis is the most common method for converting thiocarbonyls to carbonyls. Stirring thioketones with 4-nitrobenzaldehyde and a catalytic amount of TMSOTf gives the ketone. ... 

Metzner P (1999) Thiocarbonyl Compounds as Specific Tools for Organic Synthesis. 204 127-181... 

Beside thioamides, dithioesters are the most stable and accessible thiocarbonyl compounds. Their specific reactivity, in particular towards nucleophiUc reagents and their apphcations to the formation of carbon-carbon bonds, have already been reviewed [8]. However, as shown below, the presence of a phosphonate function alpha or beta to the thiocarbonyl group in phosphonodithioformates and phosphonodithioacetates makes these difunctional compounds very versatile building blocks. Moreover, for the phosphonodithioacetates, the substitution of the methylenic hydrogen atoms by fluorine increases again their potential as intermediates for the synthesis of modified natural and bioactive phosphorylated structures. 

ZHANG Y, WADE K L, PRESTERA T and TALALAY p (1996) Quantitative determination of isothiocyanates, dithiocarbamates, carbon disulfide, and related thiocarbonyl compounds by cyclocondensation with 1,2-benzenedithioT, Anal Biochem, 239 160-67. 

Sakamoto M (2005) Photochemical Aspects of Thiocarbonyl Compounds in the Solid-State. 254 207-232... 

Tc(V) and Re(V) are thiols, thioethers and thiocarbonyl compounds and molecules containing combinations of their functional groups. There exist significant differences in the ability of the various groups to form stable complexes and in the kind of complexes formed. Unlike thiols, a neutral S-donor shows a preference for the metals in oxidation states lower than +5. 

Reaction of lithium trimethylsilyldiazomethane (TMSC(Li)N2) with thiocarbonyl compounds has proved to be a convenient method for the preparation of 5-substituted 1,2,3-thiadiazoles. This reaction is very similar to the Pechmann-Nold reaction but probably does not proceed through a dipolar cycloaddition pathway. A number of examples of this type of reaction were described in CHEC-II(1996). More recently, it was reported that TMSCN2Li also reacts with diethylaminothiocarbonyl chloride to afford a mixture of 1,2,3-thiadiazoles 66 and 67 (Equation 19) <1997BSB533>. 

The use of thiocarbonyl compounds and also trimethylsilyldiazomethane in the Pechmann-Nold synthesis has greatly increased the scope of this reaction in recent years. Wolff s synthesis has also benefited from advances in the synthesis of both diazoketones and thionating reagents. 

Monothiodiacylhydrazines 127, derived from the acylation of thiosemicarbazides or as intermediates in the reactions of (1) thiohydrazides with carboxylic acids and their derivatives (see Section 5.10.9.2.2(i)) or (2) hydrazides with thiocarbonyl compounds (see Section 5.10.9.2.3(i)), cyclize in the presence of an acid catalyst to give 1,3,4-thiadiazoles 128 (Equation 39, Table 4). 

Hydrazides react with thiocarbonyl compounds to give directly 1,3,4-thiadiazoles via monothiodiacylhydrazine intermediates. The monothiodiacylhydrazines, however, are often isolated and cyclized to thiadiazoles under acidic conditions (see Section 5.10.9.1.1). 

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... 

Nitrosonium tetrafluorobprate was used later as oxidant for convertion of dithiolanthione 150 to dication 151.151 This technique was found to be general for oxidation of number of thiocarbonyl compounds (Scheme 56).146... 

Direct oxidation of thiocarbonyl compound by triflic anhydride results in stable dication salts containing disulfide framework. For example, reaction of thiocarbonate 155 with Tf2Q yields the dication salt 156 (Scheme 58).154... 

Disulfide dications are remarkably stable to water, in contrast to disulfonium dications. However, all they can be hydrolyzed by alkali water solution to give starting thiocarbonyl compound or more hydrolyzed product. For example, exposition of salt 157 to the aqueous NaOH gives formamidinium salt 158 and thiourea (Scheme 60).154... 

The formation of thietanes from thiones and olefins has been less exploited for synthetic purposes than the corresponding oxetane-forming reaction. It should be remarked that thiocarbonyl compounds very often undergo efficient photoreactions from the second excited singlet state S2 U4). One interesting synthetic application is found in the photochemical preparation of quinolines from N-thioamides (4.84)498). The primary photochemical step is assumed to be the intramolecular thietane formation. 

Organometallic betaines of type I can be considered as the closest structural analogs of carbon betaines of the (+ )P-C-C-X( ) type (IV), which were regarded for a long time as possible intermediates in classical reactions of carbonyl and thiocarbonyl compounds with phosphorus ylides (Wittig and Corey-Chaykovsky reactions and related processes,5,6 Scheme 1). Vedejs and coworkers7,8 proved unambiguously that oxapho-sphetanes (III) are true intermediates in the reactions of nonstabilized phosphorus ylides with carbonyl compounds. The formation of oxabetaines (+)p-c-c-o(-> was detected only in the form of their adducts with lithium salts.9,10... 

Reactions of Phosphorus Ylides with Carbon Disulfide, Stable Thiocarbonyl Compounds, and Thiosilanones... 

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