Sulphonic acids synthesis

Alkane sulphonation by SOz + Oz and a-sulphonation of N-alkyl-j3-alanines illustrate conventional studies in sulphonic acid synthesis sulphonation at C-1 in cyclopentanesulphonic acid proceeds via a relatively stable mixed anhydride when SO3 is used as sulphonation reagent. ... 

Chapter IV. a-Chloromethylnaphthalene (IV,23) benzylamine (Gabriel synthesis) (IV,39) i r.N -dialkylanilines (from amines and trialkyl orthophosphates) (IV,42) a-naphthaldehyde (Sommelet reaction) (IV,120) a-phenyl-cinnamic acid (Perkin reaction using triethylamine) (IV,124) p-nitrostyrene (IV,129) p-bromonaphthalene and p naphthoic acid (from 2 naphthylamine-1 -sulphonic acid) (IV,62 and IV,164) diphenic acid (from phenanthrene) (IV,165). 

Naphthylamine-5,7-disulphonic acid and 2-naphthylamine-l-sulphonic acid, which are intermediate products in Scheme 4.28, as well as 2-naphthylamine-l,5-disulphonic acid (obtained by careful low-temperature sulphonation of Tobias acid), are all used in the synthesis of azo dyes. 

In all the above sequences, single isomers are produced by careful control of the reaction conditions combined with purification by selective isolation at various points in the synthesis. Occasionally two isomers are produced which give dyestuffs that have very similar properties in these cases it is often quite acceptable and economically beneficial not to separate the individual components but to use the total mixture in dye preparation. An example is the mixture of l-naphthylamine-6- and 7-sulphonic acids (4.46 mixed Cleve s acids), which arises by nitration and reduction of naphthalene-2 Sulphonic acid (Scheme 4.30). 

A similar behaviour is observed in the case of the phenolsulphonic acids and in particular in that of anthraquinone, which, in its substitution reactions, is extraordinarily like naphthalene. Anthraquinone is sulphonated with more difficulty than is naphthalene, and in consequence the conditions of increased temperature which must be applied bring about the formation of the /8-acid, the important starting point for the synthesis of alizarin. In industrial practice, however, ways and means have been found for producing also anthraquinone-a-sulphonic acid, which was formerly not readily obtainable. a-Substitution takes place when the sulphonation is catalysed by mercury1 (R. E. Schmidt). 

Fig. 3.12. Synthesis of the compounds by the methods (a) and (b). A = -NHC6H4S03H (dye la) A = -NHCH2CH=CH (dye lb) A = -OCH2CH=CH2 (dye lc). SP = N-(4 -sulpho)phenyl-3-methy 1-5-pyrazolone m-PDA = l,3-phenylendiamine-4-sulphonic acid. Reprinted with permission from T. Konstantinova et al. [90],...

A reaction which is analogous to the orthoester synthesis but which utilises glycosyl oxazolines affords means of synthesising, 2-trans-2 amino-2-deoxy-glycoside derivatives. Treatment of the gluco compomd (17) with phenol in the presence of toluene- -sulphonic acid thus gave the glycoside (18), and it was also utilised in a nucleoside synthesis 48). 

Aryl glycosides of 2-amino-2-deoxy sugars, as might be expected, can be prepared by similar techniques as was illustrated by the synthesis of phenyl 3,4,6-tri-0-acetyl-2-acetamido-2-deoxy-p-D-glucoside and -D-galactoside by toluene -sulphonic acid catalysed reactions between phenol and the hexosamine penta-acetates These products were then anomerised using zinc chloride as catalyst to provide means of obtaining -anomers. 

Dihydrocarvone [l] was treated with isopropenyl acetate in the presence of p-toluene sulphonic acid and converted into a mixture of enol acetates [2] and [3], separated by GLC Treatment of [2] with boron trifluoride in methylene chloride at room temperature for 10 minutes gave (+) Camphor [U]. This synthesis is particularly interesting in that it is a chemical analogy for the biosynthesis conversion of a monocyclic into a bi-cyclic monoterpenoid. 

For the synthesis of orfbo-bromotoluene we use a sulphonic acid. o-Bromotoluene could be synthesised by bromination of toluene or by Friedel-Crafts alkylation of bromobenzene (Fig. T). However, the reaction would also give the para substitution product and this is more likely if the electrophile is hindered from approaching the ortho position by unfavourable steric interactions. Alternatively we can substitute a group at the para position before carrying out the bromination. 

This group would then act as a blocking group at the para position and would force the bromination to occur ortho to the methyl group. If the blocking group could then be removed, the desired product would be obtained. The sulphonic acid group is specially useful in this respect since it can be easily removed once the synthesis is over (Fig. U). 

The Kuehne synthesis has also been adapted to the preparation of 18-methylenevincadifformine (230).108" Unexpectedly, when (230) was hydrolysed by alkali, and the acid thus obtained was heated briefly in 3% aqueous hydrochloric acid, the only product that could be isolated was a diene-imine which has been assigned the structure (231). This is the first report of an intramolecular [4tt + 2n cycloaddition reaction involving an indolenine. When heated in benzene in the presence of toluene-p-sulphonic acid, 18-methylenevincadifformine (230) is smoothly hydrolysed and decar boxy lated, with exclusive formation of the indolenine (232) this can be quantitatively transformed into (231) by heating with 3% aqueous hydrochloric acid (Scheme 33). 

Synthetic work includes a one-step synthesis of various THC compounds starting from (-I-)-trafis-car-2-ene oxide (337) and olivetol (338). An equimolar amount of each in the presence of toluene-p-sulphonic acid in benzene gives a mixture of 23% (339) (equivalent to 54% of the olivetol reacted), 7%... 

From Sulphonic Acids.—As previously stated, the methods of formation of phenols are wholly different from those of alcohols, and, together with their reactions, prove the constitution to be as we have given it, viz.. Ring—OU. The synthesis which is most generally used industrially is that from sulphonic acids, i. 520). When a salt of benzene sulphonic acid is fused with potassium or sodium hydroxide, phenol is formed together with a sulphite salt of the metal, according to the following reaction ... 

From Diazo Compounds.—Another synthesis of phenols that is often used in the laboratory, especially if the desired sulphonic acid is not... 

The best methods of synthesis are the potash fusion of phenol ortho-sulphonic acid and from ortho-chlor phenol with alkali. 

This is similar to the use of chlor formic acid and chloi formamide in the preceding syntheses. The method was first used by Victor Meyer. Sulphonic acids are also the starting point for the synthesis of acids through the intermediate acid nitrile as described next. 

Th synthesis of the acid from the nitrile thus becomes in reality a synthesis from sulphonic acids. An exactly analogous reaction takes place when an aryl halide, with the halogen in the side chain, is distilled with potassium cyanide, as discussed later (p. 678). 

Synthesis from meta- or para-Hydroxy Benzoic Acid.—The constitution is proven by its synthesis by sidphonation and then alkali fusion of either meta-hydroxy benzoic acid or para-hydroxy benzoic acid. As this synthesis introduces into each of these acids first a sulphonic acid group and then in place of this a second hydroxyl group the two hydroxyls in the final product, protocatechuic acid, must be in the 3-4 positions as only such positions could be occupied in a product obtained from either the meta or para hydroxy benzoic acid. 

---