Sulphonic Anhydrides

Mixed anhydrides such as benzenetellurinyl acetate (PhTe(O)OAc), benzenetellurinyl trifluoroacetate (PhTe(0)OCOCF3) and benzenetellurinyl trifluoromethanesulphonate (PhTe(0)0S02CF3), prepared by reacting benzenetellurinic anhydride with acetic anhydride, trifluoroacetic anhydride and trifluoromethane-sulphonic anhydride, respectively, have been recognized as valuable oxidizing reagents, in some cases superior to the parent benzenetellurinic anhydrides. ... 

The novel enol sulphonates (331) have been prepared from the 3-oxo-steroids with the appropriate sulphonic anhydride in dimethylformamide. They are stable to aqueous acids and bases, but attacked at sulphur by methoxide ion, regenerating the ketone. Reduction with lithium aluminium hydride afforded mainly the 3)8-alcohol, and no olefin (see p. 400 for rearrangement). 

The enol toluene-p-sulphonate of testosterone (readily prepared with toluene-p-sulphonic anhydride in DMF) undergoes free-radical rearrangement to the 3-oxo-... 

TABLE 19. 13C NMR chemical shifts" and substituent constants for some sulphonic anhydrides, (RS02)2060... 

Most aliphatic compounds are resistant to sulphonation by reaction with sulphuric acid. However, under forcing conditions some aliphatic compounds react to produce a complex mixture of sulphonic acids, sulphonic anhydrides, alkyl sulphates and sulphones. Therefore this reaction is rarely of any synthetic utility. One exception is the reaction of terminal alkynes with sulphuric acid, which yields the terminal sulphonic acid upon removal of water, as shown in equation 682. Another exception is a rather obscure report that reaction of an alkene and a nitrile with sulphuric acid, in the presence of acetic anhydride, produces 90-100% yield of the 2-amido sulphonic acid, as shown in equation 783. 

The synthetic utility of these methods is rather restricted since sulphonic anhydrides and peroxides are usually prepared from the sulphonic acid, the latter of which may be directly converted, readily, into the sulphonate ester, as discussed above. 

In mixed anhydrides in which thiophosphoryl phosphorus is bonded to another heteroatom other than phosphorus, attack by a nucleophile may be diverted away from the phosphorus should the second reactive centre be more electrophilic. So, in the case of phos-phinothioic sulphonic anhydrides, although hydrolysis or acid-catalysed methanolysis of 101 (X = H) proceeds with inversion at phosphorus, attack by HO occurs at sulphur with retention of configuration of phosphorus whilst the hydrolysis of the much more reactive 101 (X = F) in aqueous dioxane proceeds with preponderant inversion of phosphorus... 

Reference has already been made to properties of mixed phosphinic-sulphonic anhydrides. / rr-Butylphenylphosphinothioic trifluoromethanesulphonic anhydride (101) was prepared, in both racemic and optically active forms, from the phosphinothioic acid and trifluoromethanesulphonic anhydride in dichloromethane at -50 °C... 

The phosphinosulphonates (5), prepared from the appropriate phosphino-imidazole (4), are oxidizable to the phosphinyl compounds (6). More interestingly, they can isomerize into the phosphinylsulphinate (7) when allowed to come to ambient temperature. Other examples of (5) in which = R = OEt or OPr do not isomerize in this way. The preparation of phosphorus-sulphonic anhydrides (6) has been re-investigated and three efficient methods have been described for their synthesis these are (a) the trifluoromethanesulphonic acid-assisted reaction of a phosphinic acid with a sulphonic triazolide, (Jb) interaction of a phosphinyl-imidazole and a sulphonic acid, and (c) the use of a sulphonic anhydride in reaction (6). ... 

Sodium amalgam-reduction of the salt (69) (obtained from the reaction of acyl-stabilized ylides with trifluoromethane sulphonic anhydride) provides a new synthesis of acetylenes (Scheme 11). A new synthesis of ethynyltriphenyl-phosphonium salts (70) is provided by the reaction of acylmethylenetriphenyl-phosphoranes with dibromotriphenylphosphorane and base. ... 

In the first step, an SO3 molecule is implanted in the ester bond to form a mixed anhydride that exists in a very fast equilibrium with its enolic form. Then fast electrophilic addition of a second SO3 molecule occurs to the enolic double bond, and the a-sulphonated anhydride is formed. In the second (slower) step, the intermediate reacts with other fatty acid ester molecules by releasing SO3 that serve in new reaction cycles. The sulphonation goes with air-diluted SO3 at 80-90 C followed by ca. 30 min ageing at 90-95 C. The neutralisation gives rise to sodium salt of the a-sulphocarboxylic acid ester and disodium salt of the a-sulpho-carboxylic acid as a by-product. Before neutralisation, reesterification of the semifinished item has been proposed in consequence of the bad detergency of a-sulphocarboxylates. 

T. Gramstad, R. N. Haszeldine, J. Chem. Soc. 1957,4069-4(179. Perfluoroalkyl derivatives of sulphur. Part VII. Alkyl trifluoromethanesulphonates as alkylating agents, trifluoromethane-sulphonic anhydride as a promoter for esterification, and some reactions of trifluoromethane-sulphonic add. 

Sulphonic anhydride formation is promoted by high excess SO3 (mole ratio) ... 

Sulphonic anhydride is reacting with H2SO4 and LAB, forming LABSA (see before). Insufficient ageing will leave this reaction incomplete. 

Trifluoroacetic anhydride is a most effective catalyst for the direct esterification of carboxylic acids by primary, secondary, and tertiary alcohols. Esterification proceeds under mild conditions via a mixed anhydride but is not successful with carboxylic acids of very low pKa and hydroxy acids when the reagent promotes lactonisation or polymerization [23, 24]. Dibasic acids may be esterified if they do not readily form cyclic anhydrides. Reagents such as trifluoromethane sulphonic anhydride [25], acetyl chloride [26], pyridine/p-toluene-sulphonyl chloride [27], sulphury chloride [28], thionyl chloride [29], and pyridine/phosphorus oxychloride [30] probably act in a similar way to trifluoracetic anhydride as reagents for direct esterification. 

Sulphonic Anhydrides.—Unstable mixed sulphonic anhydrides ArSOgOSOaCFa, prepared from the arenesulphonyl bromide and silver trifluoromethane-sulphonate, are useful reagents for Friedel-Crafts sulphonoxylation. Aromatic amines are some ten times more reactive than MeOH towards benzene-sulphonic anhydride in the presence of pyridine. ... 

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