Thionyl halides

DihaIogenothiazoIes (271) thus can be prepared from sodium acetylaminomethane sulfonate (270) and thionyl halide, but this reaction proceeds in low yield. With X — Cl, the yield is 20%, while with X = Br the yield decreases to 2% (Scheme 140). 

Practical experience enables us to emphasize the simplicity and the efficiency of the activation of aldehydes by their conversion into N- -haloalkyl)heteroarylium halides upon treatment with an azine and a thionyl halide. Preparation of these salts requires a minimum of precautions, and a wide variety of solvents can be used. Special glassware and/or the use of an inert gas is not necessary. Tire salts can be reacted under numerous experimental conditions and, in most cases, it is unnecessary to isolate them. Tire flexibility of the method represents an interesting feature for the study of the reactivity of A-(l-haloalkyl)heteroarylium halides and deserves further investigations in this held. Many elegant compromises can be found in a judicious choice of the precursors and of the experimental conditions, and it is possible to design readily a salt suitable for each individual purpose. 

TABLE 1. Bond lengths (rg) and bond angles (ra) of thionyl halides from electron diffraction... 

The propargyl alcohols react with trivalent phosphorus halides to give allenic phosphorus esters as described in Scheme 3 and Table VI. In the case of aryl-substituted alkynols or highly hindered t-propargyl alcohols which contain no free acetylenic —H, thionyl halides or phosphorus trihalides yield bromo- or chloroallenes [74d], Thionyl chloride also reacts in a similar fashion with a wide variety of unhindered secondary alcohols (structure XV) to give a mixture of the chloroallene and chloroalkyne [74a-d]. 

Otromiiun(UI) halide should be treated with appropriate thionyl halide hefore reaction. h Because of weakness of bands assignment of v(Cr—-S) is tentative. 

The application of the solvent system concept to liquid sulfur dioxide chemistry stimulated the elucidation of reactions such as those of aluminum sulfite. However, there is no direct evidence at all for the formation of S02+ in solutions of thionyl halides. In fact, there is evidence to the contrary. When solutions of thionyl bromide or thionyl chloride are prepared in 3JS-labeled (S ) sulfur dioxide, almost no exchange takes place. The half-life for the exchange is about two years or more. If ionization took place ... 

One of the chief difficulties with the solvent system concept is that in the absence of data, one is tempted to push it further than can be justified. For example, the reaction of thionyl halides with sulfites in liquid sulfor dioxide might be supposed to occur as follows, assuming that autoionization occurs ... 

Accordingly, sulfite salts may be considered bases because they increase the sulfite ion concentration. It might then be supposed that thionyl halides behave as adds because of dissociation to form thionyl and halide ions ... 

To overcome difficulties and achieve ionization of primary (and less reactive secondary) alcohols at low temperatures, it was found, in some cases, that it is advantageous to convert them to the corresponding haloformates or halosulfites with carbonyl halides [Eq. (3.16)] or thionyl halides [Eq. (3.17)]. These, in turn, ionize readily in SbF5-S02 solution and lose C02 or S02.129... 

A variety of iV-halomethylpyridinium salts may be accessed by condensation of pyridines with thionyl halides and formaldehyde <1999JOC3113> (Equation 40). While it is predicted that such salts should undergo displacement of... 

This group has only two symmetry elements E and a. The aforementioned HOD belongs to this group. Other examples include thionyl halide SOX2 and secondary amines R2NH (Fig. 6.2.1). 

Examples of molecules with Cs symmetry thionyl halide (SOX2) and secondary amines R2NH. 

Thionyl halides and A-heteroaromatics are known to be in equilibrium with the corresponding A-(halosulfinyl)heteroarylium halides. A-(Chlorosulfinyl)pyridinium chloride (36), for example, readily reacts with a second molecule of pyridine to give the A-[l-chlorosulfinyl-l,4-dihydro-pyridine-4-yl]pyridinium chloride (37a). The intermediate 37a is probably involved in the preparation of A-(pyridine-4-yl)pyridinium chloride hydrochloride (37b). However, the authors could not detect either 37a or 37b in their experiments (91CB2013) (Scheme 10). 

Molecules with C, symmetry are fairly numerous. Examples are the thionyl halides and sulfoxides (A5-III), and secondary amines (A5-IV). Molecules having a center of symmetry as their only symmetry element are quite rare two types are shown as (A5-V) and (A5-VI). The reader should find it very challenging, though not impossible, to think of others. Molecules of C2 symmetry are fairly common, two examples being (A5-VII) and (A5-VIII). 

Covalent hahdes can be prepared by various synthetic routes. The simplest are direct reactions of elemental halogens (equation 9), or hydrogen halides with elements (equation 10) or oxides (equation 11). In other processes, the oxides are reacted with a halogen halide in the presence of carbon to combine with the oxygen (equation 12) or other reactive carbon-halides (equation 13). Exchange of halogens can also take place (equations 14 16). Anhydrous halides can also be obtained by dehydration of metal halide hydrates, using reactants such as thionyl halide, which react with the hydrated water (equation 17). 

The thionyl halides hydrolyze in water to give sulfin dioxide and HX. A common inorganic application of this reaction is for the preparation of anhydrous metal chlorides (although it can lead to difficulties for some metal chlorides). Industrially, thionyl chloride is used for the preparation of anhydrous metal halides and oxyhalides as well as in organic transformations, where it converts hydroxyl groups to chlorides. Over 50000 tonnes a year are manufactured. 

Gmelin Handbook of Inorganic Chemistry , Springer, Berlin, includes the following Sulfur A1 (History, 1942) A2 (Occurrence, Technology, 1953) A3 (The Element, 1953) B1 (Hydrides and Oxides, 1953) B2 (Sulfur-Oxygen Acids, 1960) B3 (Compounds, 1963) Sulfur Suppl. Vol. 1 (Thionyl Halides, 1978) Sulfur Suppl. Vol. 2 (Sulfur Halides, 1978) Sulfur Suppl. Vol. 3 (Sulfur Oxides, 1980) Sulfur Suppl. Vol. 4a/b (Sulfanes, 1983) as well as several volmnes on S-N chemistry. 

The titanium(II) derivatives Ti(02CCFg)X (where X = Cl or Br) have been prepared by the reaction between Ti(02CCF3)2 and the corresponding thionyl halide in ether. All of these titanium(II) trifluoro-acetates are effective as catalysts for the stereospecific polymerization of butadienes (44). 

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