Carboxylic sulfuric anhydrides

The O acylation of phenols with carboxylic acid anhydrides can be conveniently catalyzed m either of two ways One method involves converting the acid anhydride to a more powerful acylatmg agent by protonation of one of its carbonyl oxygens Addi tion of a few drops of sulfuric acid is usually sufficient... 

Sulfur compounds have also been widely studied as activating agents for polyesterification reactions. p-Toluenesulfonyl chloride (tosyl chloride) reacts with DMF in pyridine to form a Vilsmeir adduct which easily reacts with carboxylic acids at 100-120° C, giving highly reactive mixed carboxylic-sulfonic anhydrides.312 The reaction is efficient both for aromatic dicarboxylic acid-bisphenol312 and hydroxybenzoic acid314 polyesterifications (Scheme 2.31). The formation of phenyl tosylates as significant side products of this reaction has been reported.315... 

Carboxylic acid anhydrides generally react with sulfur tetrafluoride in the same manner as carboxylic acids to give acid fluorides, then trifluoromethyl derivatives. Various cyclic anhydrides, which are particularly stable under acidic conditions, react without cleavage to give, in a stepwise fashion, difluoro lactones and a,a,a, a -tetrafluoro ethers. Conversely, the corresponding diacids are readily dehydrated by sulfur tetrafluoride to give anhydrides in the first step of the reaction. Therefore, in this section reactions of carboxylic acids and carboxylic acid anhydrides are discussed together. 

The low basicity of the thione sulfur in 444 [M] = Fp, Re(CO)j was expected to allow its nucleophilic addition to acetyl chloride or carboxylic acid anhydrides to form 5-acyl adducts. These reactions, however, result in... 

Anhydrous hydrogen fluoride or pyridinium poly(hydrogen fluoride), sulfur tetrafluoride, iodine fluoride, or N-F compounds can be used as fluorinating agents too. Glycosyl fluorides 6-8 are formed under the action of the hydrogen fluoride, on the protected furanosydes, in nitromethane/carboxylic acid anhydride... 

As shown, an asymmetric carboxylic-sulfonic acid anhydride is formed, but the cellulose attack occurs on the C = O group, since a nucleophilic attack on sulfur is slow, and the tosylate moiety is a much better leaving group than the carboxylate group [193]. Similar to other acylation reactions, there is a large preference for tosylation at the 5 position, and cellulose tosylates... 

So do anhydrides and many compounds that enolize easily (e.g., malonic ester and aliphatic nitro compounds). The mechanism is usually regarded as proceeding through the enol as in 12-4. If chlorosulfuric acid (CISO2OH) is used as a catalyst, carboxylic acids can be ot-iodinated, as well as chlorinated or brominated. N-Bromosuccinimide in a mixture of sulfuric acid-trifluoroacetic acid can mono-brominate simple carboxylic acids. ... 

An alternative route to anthraquinone, which involves Friedel-Crafts acylation, is illustrated in Scheme 4.3. This route uses benzene and phthalic anhydride as starting materials. In the presence of aluminium(m) chloride, a Lewis acid catalyst, these compounds react to form 2-benzoyl-benzene-1-carboxylic acid, 74. The intermediate 74 is then heated with concentrated sulfuric acid under which conditions cyclisation to anthraquinone 52 takes place. Both stages of this reaction sequence involve Friedel-Crafts acylation reactions. In the first stage the reaction is inter-molecular, while the second step in which cyclisation takes place, involves an intramolecular reaction. In contrast to the oxidation route, the Friedel-Crafts route offers considerable versatility. A range of substituted... 

Among the oxyacids of sulfur the predilection to form an anhydride with a sulfur-sulfur bond, rather than one with an oxygen bridge between the two sulfurs, is not restricted to sulfenic acids. We will see in a subsequent section that sulfinic acids also do this. Their anhydrides have the sulfinyl sulfone structure. RS(0)S02R, rather than RS(0)0S(0)R. What is unique about the sulfenic acid-thiolsulfinate system, however, is the fact that the anhydride (thiolsulfinate) is strongly preferred thermodynamically over the acid at equilibrium. With any other type of common acid the reverse is true, of course. The uniqueness of the sulfenic acid-thiolsulfinate situation can perhaps best be appreciated by realizing that, if the same stability relationship between acid and anhydride were to exist for carboxylic acids, acetic acid would spontaneously dehydrate to acetic anhydride ... 

The carbonyl group of an acid chloride is also a sufficiently electropositive center that acylation of a sulfinate ion occurs at oxygen (123) rather than sulfur (Schank, 1967 Kobayashi, 1966b). The mixed sulfinic-carboxylic anhydrides... 

Pyrido[l,2,3-t/e]-l,4-benzoxazine-6-carboxylate (683) was prepared in 96% yield by the cyclization of (l,4-benzoxazin-4-yl)methylenemalonate (272) on the action of a mixture of acetic anhydride and concentrated sulfuric acid at room temperature [84JAP(K)122493], or in 58-94% yields by heating in a mixture of acyl halides and concentrated sulfuric acid at 80-110°C for 1 hr [84JAP(K)216890], or in 75% yields by heating in... 

Diethyl (arylamino)methylenemalonates (684) were cyclized with a 2 1 mixture of acetic anhydride and concentrated sulfuric acid at ambient temperature to give 4-hydroxyquinoline-3-carboxylates (685) in 15-80% yields (54JIC555, 54JIC711, 54JIC951). 

The ring closure of A-cyclopropyl-7V-(trisubstituted phenyl)aminometh-ylenemalonate (686) was carried out in a mixture of acetic anhydride and concentrated sulfuric acid to give l-cyclopropylquinoline-3-carboxylate (687) in 41% yield (85NKK2054). When the cyclization was carried out in polyphosphoric acid at 100-110°C for 30 min, l-cyclopropylquinoline-3-carboxylate (687) was obtained in 44% yield [86JAP(K)143364]. 

N-Cyclopropyl-N-(2,3-disubstituted 4-fluoro-6-nitrophenyl)aminometh-ylenemalonates (689) were cyclized to l-cyclopropylquinoline-3-carboxyl-ates (690) in a mixture of acetic anhydride and concentrated sulfuric acid at 50-70°C in 29-66% yields [86JAP(K) 143363 87NEP471 88EUP287951 89USP4874764],... 

Nakagome and co-workers effected the successful cyclization of N-ethyl-N-arylaminomethylenemalonates (749) in poly phosphoric acid, prepared from orthophosphoric acid and phosphorus pentoxide in polyphosphate ester (PPE), prepared from phosphorus pentoxide and anhydrous diethyl ether in chloroform in phosphoryl chloride on the action of boron trifluoride etherate on the action of acetic anhydride and concentrated sulfuric acid or on the action of phosphorus pentoxide in benzene [71GEP2033971, 71JHC357 76JAP(K) 18440]. Depending on the work-up process, l-ethyl-4-oxoquinoline-3-carboxylates (750, R1 = Et), l-ethyl-4-oxoquinoline-3-carboxylic acids (750, R2 = H) and 3-ethoxycarbonyl-4-chloroquinolinium iodides (751) were obtained. Only the cyclization of... 

Renault et al. cyclized 7V-(3-methylphenyl)aminomethylenemalonate (757, R = Me, R1 = H) in a mixture of acetic anhydride and concentrated sulfuric acid to give a mixture of 5- and 7-methyl-quinoline-3-carboxylates (758 and 759, R = Me, R1 = H) (76MI3). The ratio of the 5- and 7-methyl isomers was determined by H-NMR (see Table VI). Mapara and Desai reported that only the 5-methyl isomer (758, R = Me, R1 = H) was obtained, in 74% yield, under similar conditions (54JIC951). 

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