GB480617A - Process for the introduction of aryl groups into ª -ª -unsaturated carbonyl compounds and their derivatives - Google Patents

Abstract

a - b - Unsaturated non - quinonoid carbonyl compounds such as aldehydes, ketones, or carboxylic acids, and also their derivatives in so far as they contain a hydrogen atom on the a -carbon atom are reacted with aromatic diazonium salts or compounds convertible thereinto such as acylnitrosamines in dilute inorganic acid or in organic acid solution, and at elevated temperature so that nitrogen is split off and the a -hydrogen atom in the carbonyl compound is replaced by an aryl group. Quinonoid compounds are defined as compounds with two carbonyl groups and two double bonds in one cyclohexane ring. There are obtained from benzal acetone or cumarin with diazo compounds a -acetylstilbenes or 3-arylcumarins respectively. In the case of certain a -b -unsaturated carboxylic acids such as cinnamic acid, the carboxyl group is split off as carbon dioxide during the reaction. The arylated a -b -unsaturated carbonyl compounds are sometimes obtained as their hydrogen halide addition products and are treated with agents splitting off hydrogen halide, e.g. by heating with sodium acetate in glacial acetic acid. An addition of copper or copper salts favours the reaction, which can be carried out in strong acetic acid, aqueous-alcoholic or aqueous-acetone solution with the addition of alkali acetates or alkali salts of other weak acids such as the acid to be arylated. Other solvents such as methylene chloride or acetylene tetrachloride may be used. The presence of negative substituents in the diazo compound is favourable. In examples: (1) p-nitrobenzene diazonium chloride is reacted with cumarin in aqueous-acetone solution in presence of sodium acetate and copper sulphate to give 3-p-nitrophenylcumarin; if the diazo compounds from p - chloraniline, b - naphthylamine, p - aminobenzoic acid or sulphanilic acid are used there are obtained 3-p-chlorphenylcumarin, 3-b -naphthylcumarin, 3-phenyl-cumarin-41- carboxylic acid and 3-phenyl-cumarin-41-sulphonic acid; (2) p-chlorbenzene diazonium chloride is reacted with cinnamic acid as in (1) to give small quantities of a -p-chlorphenylcinnamic acid but mainly p-chlorstilbene; if crotonic acid is used, a -p-chlorphenylcrotonic acid is the chief product, but p-chloropropenylbenzene is also obtained; (3) p - chlorbenzene diazonium chloride is reacted with benzal acetone as in (1), but splitting off hydrogen halide from the product to give a -acetyl-p-chlorostilbene; (4) p-chlorbenzene diazonium chloride is reacted with cinnamic aldehyde as in (1) to give a -p-chlorphenyl cinnamic aldehyde; (5) p-chlorbenzene diazonium chloride is reacted with cumarin as in (1) but in absence of copper or a copper salt, to give a small yield of 3-p-chlorphenyl-cumarin; the yield is increased if copper chloride is present.