METHOD FOR PREPARING A-(4-ISOBUTYLPHENYL) PROPIONIC ACID OR ITS PRECURSOR

摘要

A method for preparing .alpha.-(4-isobutylphenyl) propionic acid or its precursor is here disclosed which comprises a step (I) of dehydrogenating p-isobutylethyl-benzene in a gaseous phase in the presence of a dehydrogenating metal catalyst to form p-isobutylstyrene and at least one unsaturated hydrocarbon compound selected from the group consisting of 4-(2'-methyl-1'- propenyl)ethylbenzene, 4-(2'-methyl-1'-propenyl) vinylbenzene, 4-(2'-methyl-2'-propenyl)ethylbenzene, and 4-(2'-methyl-2'-propenyl)vinylbenzene; a step (II) of reacting p-isobutyl-styrene obtained in the step (I) with carbon monoxide and hydrogen or with carbon monoxide and water or a lower alcohol in the presence of a transition metal complex carbonylating catalyst to form .alpha.-(4-isobutylphenyl)propionic acid or its precursor; and a step (III) of hydrogenating at least one unsaturated hydrocarbon compound selected from the group A obtained in the dehydrogenation step (I) to form p-isobutylethylbenzene, and recycling the thus formed p-isobutylethylbenzene through the step (I) as the raw material of the step (I). The .alpha.-(4-isobutylphenyl) propionic acid so prepared is useful as a medicine (an analgesic).