Preparation of Sulphones

Preparation of Sulphones.—Routine oxidation methods give sulphones, starting from sulphides and sulphoxides, and, again, a warning has appeared about the use of H2O2 in acetone which led to a delayed explosion during an attempt to oxidize a sulphur heterocycle to the sulphone.  

The majority of papers concerned with preparations of sulphones in the recent literature deal with sulphinic acids as reagents. The reaction of a tetrabutyl-ammonium sulphinate with an alkyl halide has been developed further, and the addition of a sulphinic acid to a Schiff base to give ArNHCH(Ar)S02Ar, to a bromo-nitro-styrene (PhCH=CBrN02 + RSOgH - RS02CHPhCHBrN0a), or to 3-phenylcyclobutene-l,2-dione (67), has been studied. 

Allylic sulphones are available through the reaction of a t-butyl sulphoxide and an allyl alcohol with A -chlorosucdnimide, and through the reaction of an allyl alcohol with di(AT-phthalimido) sulphide or di(iV-imidazolyl) sulphide to give a sulphoxylate, e.g. CHa=CHCH20S0CH2CH=CH2, which rearranges to the bis(allyl) sulphone by way of the sulphinate. Further study of the rearrangement of iV-aryl arenesulphonamides to iV-(u-aminoaryl) aryl sulphones has been described.  

General methods for the synthesis of a-arylsulphonyl- and a-alkanesulphonyl phenyldiazomethanes have been surveyed.  

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A. General Methods of Preparation of Sulphones from Sulphoxides. . . 970... 

A wide range of chlorine-containing oxidants have been used for the preparation of sulphones from sulphoxides. These reagents include chlorine, hypochlorites, sulphuryl chloride and IV-chloro compounds. 

There are many transition metal ion oxidants used in organic chemistry for the interconversion of functional groups. Those which have been used for the preparation of sulphones from sulphoxides will be discussed below. It is very interesting to note that this type of oxidant often reacts more rapidly with sulphoxides than with sulphides and so sulphoxides may be selectively oxidized with transition metal ion oxidants in the presence of sulphides. This is in direct contrast to the oxidation of sulphides and sulphoxides with peracids and periodate, for example, where the rate of reaction of the sulphide is more than 100 times that for the corresponding sulphoxide. 

If a mixture of diphenyl sulphide and the corresponding sulphoxide are treated with osmium tetroxide in boiling ether for 48 hours the sulphide is unchanged whilst the sulphoxide is converted into the sulphone in 96% yield with concomitant production of osmium trioxide140. It thus seems that this method would be useful synthetically for the preparation of sulphones from sulphoxides containing sulphide functionalities. Ruthenium tetroxide may be used in place of osmium(VIII) oxide148. 

The oxidation of sulphones leads to either a sulphonic acid (or a sulphonic acid derivative) or to sulphate. Such reactions have rarely been used for the preparation of sulphonic acids since these are usually readily available by other well-established routes. However, polyhalogenated sulphones can be oxidized relatively easily to sulphonic acids and these reactions will be discussed here. 

Using a soliddiquid two-phase system of the sodium arenesulphinite in 1,2-dimethoxyethane, or in the complete absence of a solvent, permits the use of less reactive haloalkanes [3,4], This is a particularly good method for the preparation of sulphones where the sulphinic acid salts are readily available and, in addition to the synthesis of the tolyl sulphones listed in Table 4.28, it has been used to prepare phenyl sulphones [3]. Phenyl sulphones have also been prepared in good yield using a polymer supported catalyst [5] (Table 4.29). As the system is not poisoned by iodide ions, reactive iodoalkanes can be used and there is the additional advantages in the ease of isolation of the product and the re-use of the catalyst. 

After preparation of sulphonate salt, a second deprotonation step effects the ring closure ... 

The iodonium triflate (460 mg, 1 mmol) was added to a stirred slurry of anhydrous sodium p-toluene sulphinate (180 mg, 1.01 mmol) in dichloromethane (15 ml) at 20°C under nitrogen. After 15 min water (10 ml) was added and the phases were separated the aqueous layer was extracted with additional dichloromethane (2 x 5 ml), and the combined organic extracts were dried. The filtered solution was treated with hexanes (30 ml) and concentrated. The solid residue was purified by radial chromatography (silica gel, 200-400 mesh, dichloromethane-hexanes) to afford 3-tosyl-bicyclo[3.2.0]-3-heptene-2-one (197 mg, 75%), m.p. 164-165°C. The method is general for the preparation of sulphones with a cyclopentenone moiety other alkenyl iodonium salts gave alkynyl sulphones with sulphinates (Section 9.4.4). 

Isoprenylated Quinones.—A review has been published on the chemistry and biochemistry of ubiquinone (236) and plastoquinone (237) in plants.273 Chemistry. Methods have been presented for the preparation of sulphone-function-alized prenylhydroquinones.274 Thus the ubiquinol (238), plastoquinol (239), and... 

Preparation of sulphonic acids, esters, amides and halides... 

This chapter concerns the preparation of sulphonic acids and their derivatives and considers reactions occurring via one of the following three different methodologies ... 

By far the most common method for the industrial preparation of sulphonic acids and their salts is by direct sulphonation. Consequently, there are many hundreds of patents covering the industrial applications of these reactions, especially with reference to aromatic sulphonic acids, and the reader is referred to the reviews of Knaggs, Nunfaum and Schultz2 and of Gilbert5 for key references to this patent literature. 

Sulphites and hydrogen sulphites may be used for the preparation of sulphonic acids however, it is important to note that there is potential biological hazard involved in this process. This danger is discussed briefly below. 

This section covers the preparation of sulphonic acids by the oxidation of three different types of sulphur-containing functionality. Thiols, disulphides and related functional group oxidations are covered in the first part. The oxidation of both thiols and disulphides to sulphonic acids is one of the classical methods for the preparation of aliphatic and aromatic sulphonic acids. 

The preparation of sulphonic acids by the oxidation of sulphinic acids and their derivatives has been studied, by many workers, for at least the last hundred years. Much... 

The preparation of sulphonate esters by oxidation of sulphur(II)- and sulphur(IV)-containing moieties has rarely been reported. This is probably because of the wide range of other synthetic routes that are available (as described in Sections III. A and III.C) and the fact that yields in the oxidative processes so far reported are usually low. There are, however, a few noteworthy attempts at this method of preparation and these are covered below. 

Sulphinic acid esters have also been oxidized, to the sulphonic acid ester, with hydrogen peroxide although the reaction usually proceeds in poor yield345,346. This resistance to oxidation is also evident when other oxidants are used233,347. A much improved procedure for the oxidation of aromatic sulphinate esters uses potassium permanganate in aqueous solution, as oxidant345,348,349, as shown in equation 79. Mefa-chloroperbenzoic acid has also been used with success for the oxidative preparation of sulphonate esters. Indeed, it has resulted in the preparation of unstable sulphonate esters that are hard to form by other means350. 

Sulphonamides have also been used for the preparation of sulphonate esters, by reaction with alcohols423, as exemplified in equation 97. 

Preparation of sulphonamides by carbon-sulphur(VI) bond formation has been used rather rarely compared with the preparation of sulphonic acids and sulphonyl halides (as discussed in Sections II.A and V.A of this chapter). There have, however, been a few interesting reports of this type of synthetic procedure and these are discussed below. 

Preparation of sulphonic acids, esters, amides and halides equation 107438, where R" is derived from the olefin, with a chloro substituent. 

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