Thionyl compounds

The most important thionyl compound is OSCI2 — it is readily prepared by chlorination of SO2 with PCI5 or, on an industrial scale, by oxygen-atom transfer from SO3 to SCI2 ... 

Hydrobromic instead of hydriodic acid has also been used in quantitative work. Thus Larsson83 evaluated thionyl compounds with a hydrobromic acid/acetic acid reagent, then adding potassium iodide and titrating with thiosulphate. 

This effect is less pronounced in sulfuryl derivatives, SO2X2, and is not detectable in thionyl compounds, SOX2 (X = NMc2, Me, Cl) ... 

In the above reactions SO ion is regarded analogous to H30 ion and S03 is regarded as analogous to OH ion in aqueous medium. Thus, thionyl compounds are considered acids and sulphites as bases. 

Thionyl compounds (SOCl ) are considered as acids and sulphites (NaSOj) are considered as bases in liquid SO2 medium. Reactions between thionyl compounds and sulphites are regarded as acid-base reactions. 

Table 5.13 Equilibrium constants Kc (I mol j and diiodine basicity scales pKsi2 thionyl compounds. 

The melting points of these esters are usually much lower than those of the corresponding 3 5 dinitrobenzoates their preparation, therefore, offers no advantages over the latter except for alcohols of high molecular weight and for polyhydroxy compounds. The reagent is, however, cheaper than 3 5 dinitrobenzoyl chloride it hydrolyses in the air so that it should either be stored under light petroleum or be prepared from the acid, when required, by the thionyl chloride or phosphorus pentachloride method. 

Reaction with Sulfur Electrophiles. Bisa2iridine compounds can be prepared from sulfur dichloride, thionyl chloride, or sulfuryl chloride... 

Sulfonic acids may be subjected to a variety of transformation conditions, as shown in Figure 2. Sulfonic acids can be used to produce sulfonic anhydrides by treatment with a dehydrating agent, such as thionyl chloride [7719-09-7J. This transformation is also accomphshed using phosphoms pentoxide [1314-56-3J. Sulfonic anhydrides, particulady aromatic sulfonic anhydrides, are often produced in situ during sulfonation with sulfur trioxide. Under dehydrating conditions, sulfonic acids react with substituted aromatic compounds to give sulfone derivatives. 

The reactions of thionyl chloride with organic compounds having hydroxyl groups are important. Alkyl chlorides, alkyl sulfites, or alkyl chlorosulfites form from its reaction with aUphatic alcohols, depending on reaction conditions, stoichiometry, and the alcohol stmcture ... 

Amino-pyridazines and -pyridazinones react with monomethyl- or iV,A-dimethyl-formamide and other aliphatic amides in the presence of phosphorus trichloride, thionyl chloride, phosgene or benzenesuUonyl chloride to give mono- or di-alkylaminomethyl-eneamino derivatives. The same compounds can be prepared conveniently with A,iV-dimethylformamide dimethyl acetal in high yield (Scheme 50). 

The direct combination of selenium and acetylene provides the most convenient source of selenophene (76JHC1319). Lesser amounts of many other compounds are formed concurrently and include 2- and 3-alkylselenophenes, benzo[6]selenophene and isomeric selenoloselenophenes (76CS(10)159). The commercial availability of thiophene makes comparable reactions of little interest for the obtention of the parent heterocycle in the laboratory. However, the reaction of substituted acetylenes with morpholinyl disulfide is of some synthetic value. The process, which appears to entail the initial formation of thionitroxyl radicals, converts phenylacetylene into a 3 1 mixture of 2,4- and 2,5-diphenylthiophene, methyl propiolate into dimethyl thiophene-2,5-dicarboxylate, and ethyl phenylpropiolate into diethyl 3,4-diphenylthiophene-2,5-dicarboxylate (Scheme 83a) (77TL3413). Dimethyl thiophene-2,4-dicarboxylate is obtained from methyl propiolate by treatment with dimethyl sulfoxide and thionyl chloride (Scheme 83b) (66CB1558). The rhodium carbonyl catalyzed carbonylation of alkynes in alcohols provides 5-alkoxy-2(5//)-furanones (Scheme 83c) (81CL993). The inclusion of ethylene provides 5-ethyl-2(5//)-furanones instead (82NKK242). The nickel acetate catalyzed addition of r-butyl isocyanide to alkynes provides access to 2-aminopyrroles (Scheme 83d) (70S593). 

Dicyano-l,2,3-trithiole 2-oxide (143) has been prepared from the silver salt of 2,3-dimercaptomaleonitrile (142) and thionyl chloride (66HC(2l-i)67). Similarly, the reaction of ethylene glycol (144) with thionyl chloride gave 1,3,2-dioxathiolane 2-oxide (145), the parent compound of saturated five-membered cyclic sulfites (see Chapter 4.33). 

When pyrazolecarboxylic acids (Section 4.04.2.3.3(iii)) are treated with thionyl chloride instead of the acid chloride, compound (254) is isolated. This corresponds to a double iV-acylation (67HC(22)1). 

Benzisothiazoles are best prepared by oxidative cyclization of o-aminothiobenz-amides (see Section 4.17.9.1.1), reaction of o-toluidines with thionyl chloride (see Section 4.17.9.2.1) or by sulfuration of 2,1-benzisoxazoles (see Section 4.17.10.2). 1,2-Benzisothiazoles can also be prepared from o-disubstituted benzene compounds, cyclodehydration of o-mercaptobenzaldoximes or oxidative cyclization of p-mercaptobenzylamines (see Section 4.17.9.1.1) being the most convenient. Both series of benzo compounds are readily substituted at the 5- and 7-positions by electrophilic reagents. 

The first large-scale use of chlorine was for bleaching paper and cotton textiles it also is widely used as a germicide for public water supplies. Presently it is used principally in production of the chemical compounds sulfur chloride, thionyl chloride, phosgene, aluminum chloride, iron(ni) chloride, titaniura(IV) chloride, tin(IV) chloride, and potassium chlorate. 

Jsomerides of Morphine and Codeine. When morphine is treated with thionyl chloride, phosphorus trichloride or tribromide, the alcoholic hydroxyl group is replaced by the halogen, forming a-chloromorphide and bromomorphide respectively. The former on treatment with concentrated hydrochloric acid is converted into /3-chloromorphide. Schopf and Hirsch have provided evidence that the two are structural isomerides. With the same reagents codeine yields a parallel set of compounds, viz., a- and -chlorocodides, and bromocodide. The chief characteristics of these products may be summarised thus —... 

N,N - Bis(trimethylsilyl)sulfur(rV) diimide Me3SiN=S=NSiMc3 is an especially versatile source of the N=S=N functionality in the formation of both acyclic and cyclic S-N compounds. It is conveniently prepared by the reaction of NaN(SiMc3)2 and thionyl chloride (Eq. 2.5). 

The reaction of diketosulfides with 1,2-dicarbonyl compounds other than glyoxal is often not efficient for the direct preparation of thiophenes. For example, the reaction of diketothiophene 24 and benzil or biacetyl reportedly gave only glycols as products. The elimination of water from the P-hydroxy ketones was not as efficient as in the case of the glyoxal series. Fortunately, the mixture of diastereomers of compounds 25 and 26 could be converted to their corresponding thiophenes by an additional dehydration step with thionyl chloride and pyridine. 

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