Reaction of aromatic carboxylic acids with phenylacetylene with the participation of a zinc catalyst

Abstract

The reaction of benzoic, 4-methylbenzoic, 2-bromobenzoic and 4-bromobenzoic acids with phenylacetylene was carried out in a toluene solution at a temperature of 110 0C in the presence of a catalyst - 1 mol % [Zn(C4H7S2)4](NO3)2. In the coupling reaction of carboxylic acids with phenylacetylene a mixture of coupling products is formed according to the Markovnikov and anti-Markovnikov rules. A reaction mechanism was proposed and it was found that the yield of vinyl esters increased in the serie 4-CH3-C6H4COOH< C6H5COOH< 4-Br-C6H4COOH< 2-Br-C6H4COOH. It was found that with an increasing acidity of the carboxylic acids, the product formed by Markovnikov rule has been formed in a larger amount. On the contrary, as the acidity of the starting compounds decreased, the amount of the anti-Markovnikov coupling product has increased. The total yield of reaction products of phenylacetylene with carboxylic acid is 44% (65/35) in 4-methylbenzoic acid, 67% (80/20) in benzoic acid, 78% (82/18) in 4-bromobenzoic acid, 82% (85 /15) in 2-bromobenzoic acid. The structure of the synthesized vinyl esters was proved on the base of the analysis of IR, 1H, 13C NMR and Mass spectrums.