Patent GB-562753-A (GB)
Title: Manufacture of new pyrrole derivatives
IPC: C07D207/333
Filed: 1942-07-13
Abstract: Sulphonic acids are produced by reacting with a sulphonating acid (e.g. fuming sulphuric acid or chlorosulphonic acid) by conventional methods a 2 : 4-diarylpyrrole of the formula <FORM:0562753/IV/1> where R1 and R11 each stand for aryl radicals (e.g. of the benzene or naphthalene series) substituted or not and the same or different, and where R111 stands for hydrogen or for a non-reactive substituent, e.g. an aryl-, alkyl-, or acylamino radical.  2 : 4-Diarylpyrroles specified are 2 : 4-diphenylpyrrole, 2-phenyl-4-(p-methoxyphenyl) - pyrrole, 2 - (p - methoxyphenyl) - 4 - phenylpyrrole, 2-(m-hydroxyphenyl)-4-phenylpyrrole, 2 - (o - chlorophenyl) - 4 - phenylpyrrole, 2-(p-acetylaminophenyl)-4-phenylpyrrole, 2-a -naphthyl-4-phenylpyrrole, 2-phenyl-4-b -naphthylpyrrole, 2 : 3 : 4 - triphenylpyrrole, 3 - ben - zoylamino - 2 : 4 - diphenylpyrrole, 3 - acetyl - amino - 2 : 4 - diphenylpyrrole, 3 p  - benzoylamino-2 : 4-di-p-tolylpyrrole, and 3-acetoacetylamino-2 : 4-diphenylpyrrole. The 2 : 4-diarylpyrrole in a finely divided state may be added portionwise to the sulphonating acid which is stirred and maintained at 25-40 DEG  C.  One or more sulphonic acid groups may be introduced.  The products may be isolated by pouring on to ice and filtering or by formation of the alkali metal salts. In example 1, the sodium salt of 2 : 4-diphenylpyrrole monosulphonic acid is prepared by adding 2 : 4-diphenylpyrrole to 20 per cent oleum at 25-30 DEG  C., pouring on to crushed ice, heating the mixture to boiling, and adding saturated sodium chloride.  The benzylthiouronium salt may be formed.  In example 2, 2 : 4-diphenylpyrrole disulphonic acid is prepared by adding 2 : 4-diphenylpyrrole to 20 per cent oleum, adding 60 per cent oleum and maintaining at 35-40 DEG  C.  In example 3, the sodium salt of 2 - phenyl - 4 - (o - chlorophenyl) - pyrrole monosulphonic acid is prepared by adding 2-phenyl-4-(o-chlorophenyl)-pyrrole to 20 per cent oleum at 20-25 DEG C., pouring into water, heating and adding sodium hydroxide solution. 3-Benzoylamino-2 : 4-diphenylpyrrole is prepared by treating 3-amino-2 : 4-diphenylpyrrole (obtained by condensing two molecules of o -aminoacetophenone) with benzoyl chloride in presence of NaOH. 3 - Acetylamino - 2 : 4 - diphenylpyrrole, 3 - acetoacetylamino - 2 : 4 - diphenylpyrrole, and 3 - benzoylamino - 2 : 4 - di-p-tolylpyrrole are similarly prepared.  o -Amino-4-methylacetophenone is prepared by warming o -bromo-4-methylacetophenone with alcoholic ammonia. o-Chlorobenzylideneacetophenone is prepared by reacting o-chlorobenzaldehyde with acetophenone.  o-Chlorophenyl-b -benzoylpropionitrile is prepared by reacting o-chlorobenzylideneacetophenone with HCN. 2-Phenyl-4-(o-chlorophenyl)-pyrroline is prepared by reducing o-chlorophenyl-b -benzoylpropionitrile. 2-Phenyl-4-(o-chlorophenyl)-pyrrole is prepared by dehydrogenating 2 - phenyl - 4 - (o - chloro - phenyl)-pyrrole.  The Provisional Specification refers also to compounds in which R111 is an alkylamino or benzylideneamino radical.  Samples have been furnished under Sect. 2 (5) of (a) sodium 2 : 4-diphenylpyrroletrisulphonate and (b) sodium 2 : 4-diphenylpyrrolemonosulphonate, obtained respectively by sulphonation of 2 : 4-diphenylpyrroledisulphonic acid and of 2 : 4-diphenylpyrrole with chlorosulphonic acid, hydrolyzing the resultant sulphonyl chlorides, and neutralizing with sodium hydroxide.  Specifications 554,102 and 556,156 are referred to.