Sulfones, bromination

Sulfolene, as a source of 1,3-buta-diene in situ, 50, 43 Sulfones, bromination, 50, 31 Sulfur, reaction with organo-lithium compounds, 50,105 Sulfuryl chloride, with 1,1-cyclo-butanedicarboxylic acid to give... 

PPO and PPOBr were sulfonated by reacting with chlorosulfonic acid in chloroform [49]. The degree of sulfonation was determined by acid-base titration method. Under the reaction conditions only mono-aryl substitution of PPO and PPOBr occurred. The polymers were converted to the salt form by replacing the proton of the sulfonic acid group with Na-cation. Sulfonated PPO (SPPO) and sulfonated brominated PPO (SPPOBr), both in the Na-cation form (SPPONa and NaSPPOBr), were used for water removal studies. 

Although the effect of bromination on PPO membrane performance was not spectacular, further sulfonation of PPOBr significantly improved the performance of the membrane compared to unsulfonated PPOBr membranes having similar degree of bromination. As a result the highest selectivity was obtained with sulfonated brominated PPO membrane with a reasonably high water permeability. 

For chemical processes, some examples are the elimination of aromatics by sulfonation, the elimination of olefins by bromine addition on the double bond (bromine number), the elimination of conjugated diolefins as in the case of the maleic anhydride value (MAV), and the extraction of bases or acids by contact with aqueous acidic or basic solutions. 

Sulfonation by oleum occurs as expected on C-5 (598). The same position is reactive toward bromination, thiocyanation, and nitration... 

When unsubstituted, C-5 reacts with electrophilic reagents. Thus phosphorus pentachloride chlorinates the ring (36, 235). A hydroxy group in the 2-position activates the ring towards this reaction. 4-Methylthiazole does not react with bromine in chloroform (201, 236), whereas under the same conditions the 2-hydroxy analog reacts (55. 237-239. 557). Activation of C-5 works also for sulfonation (201. 236), nitration (201. 236. 237), Friede 1-Crafts reactions (201, 236, 237, 240-242), and acylation (243). However, iodination fails (201. 236). and the Gatterman or Reimer-Tieman reactions yield only small amounts of 4-methyl-5-carboxy-A-4-thiazoline-2-one. Recent kinetic investigations show that 2-thiazolones are nitrated via a free base mechanism. A 2-oxo substituent increases the rate of nitration at the 5-position by a factor of 9 log... 

Complexation of bromine with iron(III) bromide makes bromine more elec trophilic and it attacks benzene to give a cyclohexadienyl intermediate as shown m step 1 of the mechanism (Figure 12 6) In step 2 as m nitration and sulfonation loss of a proton from the cyclohexadienyl cation is rapid and gives the product of electrophilic aromatic substitution... 

Electrophilic aromatic substitution (Sec tion 22 14) Arylamines are very reac tive toward electrophilic aromatic sub stitution It IS customary to protect arylamines as their N acyl derivatives before carrying out ring nitration chio rination bromination sulfonation or Friedel-Crafts reactions... 

TBPA is prepared in high yield by the bromination of phthalic anhydride in 60% oleum (51). The use of oleum as the bromination solvent results in some sulfonation of the aromatic ring (52). Sulfonated material is removed by hydrolyzing the anhydride with dilute NaOH, filtering and acidifying with dilute HCl. The precipitated acid is washed several times with hot water and reconverted to the anhydride by heating at 150°C for several hours. 

An asymmetric synthesis of estrone begins with an asymmetric Michael addition of lithium enolate (178) to the scalemic sulfoxide (179). Direct treatment of the cmde Michael adduct with y /i7-chloroperbenzoic acid to oxidize the sulfoxide to a sulfone, followed by reductive removal of the bromine affords (180, X = a and PH R = H) in over 90% yield. Similarly to the conversion of (175) to (176), base-catalyzed epimerization of (180) produces an 85% isolated yield of (181, X = /5H R = H). C8 and C14 of (181) have the same relative and absolute stereochemistry as that of the naturally occurring steroids. Methylation of (181) provides (182). A (CH2)2CuLi-induced reductive cleavage of sulfone (182) followed by stereoselective alkylation of the resultant enolate with an allyl bromide yields (183). Ozonolysis of (183) produces (184) (wherein the aldehydric oxygen is by isopropyUdene) in 68% yield. Compound (184) is the optically active form of Ziegler s intermediate (176), and is converted to (+)-estrone in 6.3% overall yield and >95% enantiomeric excess (200). 

Bromine can replace sulfonic acid groups on aromatic rings that also contain activating groups. PhenoHc sulfonic acids, for example, are polybrominated (24). 

Efforts to raise the alpha-selectivity have been made. Thus nitration of anthraquinone using nitrogen dioxide and ozone has been reported (17). l-Amino-4-bromoanthraquinone-2-sulfonic acid (bromamine acid) [116-81 -4] (8) is the most important intermediate for manufacturing reactive and acid dyes. Bromamine acid is manufactured from l-aminoanthraquinone-2-sulfonic acid [83-62-5] (19) by bromination in aqueous medium (18—20), or in concentrated sulfuric acid (21). l-Aminoanthraquinone-2-sulfonic acid is prepared from l-aminoanthraquinone by sulfonation in an inert, high boiling point organic solvent (22), or in oleum with sodium sulfate (23). 

A Methylanthrapyridone and Its Derivatives. 6-Bromo-3-methylanthrapyridone [81-85-6] (75) is an important iatermediate for manufacturiag dyes soluble ia organic solvents. These solvent dyes are prepared by replacing the bromine atom with various kiads of aromatic amines. 6-Bromo-3-methylanthrapyridone is prepared from 1-methyl amino-4-bromoanthra quin one (43) by acetylation with acetic anhydride followed by ring closure ia alkaU. The startiag material of this route is anthraquiaoae-l-sulfonic acid (16). 

This process was not acceptable for several reasons low yields, poor quaUty, and the high cost of bromine. Later, at BASF, a process was developed for the manufacture of ali2artn by the caustic fusion of anthraquinone-2-sulfonic acid (so-called silver salt) which was made by sulfonating anthraquinone with sulfuric acid. This process was patented in England on the 25th of June, 1869. One day later, W. Perkin appHed for a patent for the manufacture of ali2ariQ by a process almost identical to the German process except that the "silver salt" was prepared as follows ... 

In the section dealing with electrophilic attack at carbon some results on indazole homocyclic reactivity were presented nitration at position 5 (Section 4.04.2.1.4(ii)), sulfon-ation at position 7 (Section 4.04.2.1.4(iii)) and bromination at positions 5 and 7 (Section 4.04.2.1.4(v)). The orientation depends on the nature (cationic, neutral or anionic) of the indazole. Protonation, for instance, deactivates the heterocycle and directs the attack towards the fused benzene ring. A careful study of the nitration of indazoles at positions 2, 3, 5 or 7 has been published by Habraken (7UOC3084) who described the synthesis of several dinitroindazoles (5,7 5,6 3,5 3,6 3,4 3,7). The kinetics of the nitration of indazole to form the 5-nitro derivative have been determined (72JCS(P2)632). The rate profile at acidities below 90% sulfuric acid shows that the reaction involves the conjugate acid of indazole. 

Pyrazolesulfonic acids, like (493), have high melting points (Table 24) and probably exist as the zwitterions (497). They are very stable to hydrolysis and only afford pyrazolones at high temperatures. The replacement of the SO3H group by bromine has also been reported (B-76MI40402). Pyrazole-3-, -4- and -5-sulfonic acids react with phosphorus pentachloride to form sulfonyl chlorides. 

Imidazole, 4-methyl-annular tautomerism, 5, 363 association, 5, 362 boiling point, 5, 362 bromination, 5, 398 deuteration, 5, 417 diazo coupling, 5, 403 hydrogen bonding, S, 350 hydroxymethylation, 5, 404 iodination, 5, 400 kinetics, 5, 401 mass spectra, 5, 358 melting point, 5, 362 methylation, 5, 364 sulfonation, 5, 397 synthesis, 5, 479-480, 482, 484, 489 Imidazole, 5-methyl-annular tautomerism, 5, 363 Imidazole, l-methyl-4-chloro-ethylation, 5, 386 Imidazole, l-methyl-5-chloro-ethylation, 5, 386 nitration, 5, 395... 

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