Thiocarbonyl halides

Thiocarbonyl halides. In the period covered by this review we are only aware of the theoretical study of Kwiatkowski and Leszczynski52 where the harmonic vibrational frequencies of all possible symmetric and asymmetric halides, including F, Cl and Br, are reported. These harmonic vibrational frequencies were obtained at both the HF/6-311G(d,p) and MP2/6-311G(d,p) levels of theory. Comparison with the experimental values, when available, clearly show that electron correlation contributions are essential for reliable prediction of the relative intensities of the IR absorption bands. For HFCS, HC1CS and FBrCS species, for which the experimental spectra are not known, the C=S stretching bands are predicted to appear at 1206, 1108 and 1264 cm-1, respectively. 

Aryl thionoesters (54a) may be prepared by nucleophilic substitution reactions of aryl thiocarbonyl halides with alcohols or phenols for instance, thiobenzoyl chloride (58) condenses with phenol to yield the diaryl ester (54a) (Scheme 30). 

In general, thiocarbonyl halides (59) function as thioacylation reagents with a variety of nucleophiles to yield the appropriate thio derivatives (60) (Scheme 31). For example, (59) on condensation with thiols, amines, potassium cyanide or potassium thiocyanide yields the corresponding thio compounds (60). Thiolocarboxylic acids (50) characteristically acylate alcohols and amines with desulfuration (Scheme 32). Dithiocarboxylic acid esters (54b) react with organolithium or Grignard reagents to give the dithioketals (61) after treatment with an alkyl halide (Scheme 33). 

Carbonyl halides and thiocarbonyl halides. All the compounds COCl2/ and COBr2/ have been studied in the vapour state by e.d. and/or m.w., and COCI2 (phosgene) has also been studied in the crystalline state/ The C-X bond lengths are close to the values expected for single bonds, while the C=0... 

The Stable carbonyl and thiocarbonyl halide molecules have been studied by IR as well as Raman spectroscopy. Normal coordinate analyses based on force constants transferred from other molecules (Urey-Bradley type), or from ab initio calculations, have aided in the vibrational assignments. Some of the unstable molecules which have been observed in the microwave have been characterized by infrared spectroscopy. The somewhat lower sensitivity of this method means that long path lengths of the gas may be needed. The identification of the various stable and unstable species in the microwave spectrum is simplified by the fact that the absorption lines are usually well resolved from each other. The widths of the bands in the infrared may make the transient species difficult to detect against the stronger absorptions of the stable side products. IR and Raman spectroscopies do have the advantage that they can be used on solid and liquid samples. Since the bands in a low temperature rare gas matrix have a narrower profile, the infrared spectrum is usually simplified over the room temperature gas phase spectrum. Moreover, the vibrational frequencies are only mildly perturbed by solid state effects. For example, CF Se has not been observed in the vapor phase, yet its vibrational dynamics are known from its matrix isolation spectrum. Table 9 gives the vibrational data for the carbonyl, thiocarbonyl, seleno-carbonyl and formyl halides. 

Reviews.— Two papers, surveying the progress in the chemistry of simple aliphatic and aromatic thioketones during the period 1964—1972, have appeared recently. Two other comprehensive reviews deal with the chemistry of thiocarbonyl halides and the synthesis of N-substituted thioureas." Synthesis, co-ordination chemistry, and analytical application of monothio- 3-diketones, synthesis and properties of transition-metal... 

Photoelectron and E.S.C.A. Spectra. The diselenide structure of thiuram diselenides has been established by means of Rdntgenphotoelectron spectroscopy. The photoelectron spectra of thiocarbonyl halides have been studied and interpreted on the basis of CNDO calculations by two groups of workers. ESCA investigations have been performed on dithio-esters derived from active-methylene compounds and carbon disulphide, and on isocoumarins, thioisocoumarins, and isoquinolines containing the thiocarbonyl function." ... 

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. ... 

Sulfenyl halides do not react with thiocarbonyls unless irradiated with UV light. 

Disulfane Starting materials Thiocarbonyl Sulfenyl compound halide Reaction time (hr) Yield (%)... 

Fluorine-substituted thiocarbonyl compounds have been studied even more intensively than thioformaldehyde and thioacetone. These compounds have a very rich chemistry of which polymerization is only a part. The simplest member of this class is fluorothiocarbonyl fluoride, CF2==S, which also forms the most interesting polymers. Other members that have been investigated include a variety of fluorothioacyl halides and a number of fluorothioketones. Because... 

Monomers that copolymerize with thiocarbonyl fluoride include olefins, vinyl halides, vinyl esters, ally esters, acrylates, vinyl ethers, and vinyltrichloro-silane. Nonconjugated diolefins lead to crosslinked products. Conjugated dienes inhibit polymerization. 

The lithium derivatives described above react with electrophiles such as alkyl halides, carbonyl compounds, and thiocarbonyl compounds, resulting in the corresponding 3-substituted derivatives (190). Hydrolysis of these products by dilute acid as described in Section B,1 gives the new nonproteinogenic amino acid ester (191) along with the original amino acid ester used as the chiral auxiliary. The chemical yields are above 80% (83MI1). 

With allylic Grignard reagents, the carbophilic addition on the thiocarbonyl of phenylisothiocyanate occurred as expected exclusively with inversion of the allylic chain. From crotyl and prenyl magnesium halides the compounds (4f) and (4g) were obtained in yields of 77 and 72%, respectively. 

The complexes are reactive towards nucleophilic as well as electrophilic attack. Attack by alkyl halides yields thioalkylated compounds. Mostly an alkylation at one sulfur atom takes place, but examples of alkylation at both sulfur atoms are known (reactions 1 and 2). The facile sulfur abstraction with PPh3 yielding a thiocarbonyl complex is a nucleophilic reaction (reaction 3). 

Activated alkyl halides react with sodium thiosulfate to form the Bunte salts 438 which, on treatment with base, generate thiocarbonyl compounds <1984CC922>. Trapping with 1,3-dienes affords 3,6-dihydro-2-//-thiopyrans in satisfactory yields and in a one-pot reaction, although with unsymmetrical dienes the regio and diastereo selectivities are not good (Scheme 143) <1996JOC4725>. 

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