Process for preparing mono or disubstituted cyclopentanone in position 2 and process for preparing a carboxylic diacid

摘要

Method for the preparation of mono or di_2-substituted cyclopentanone characterized in that it consists in performing in sequence four stages (a) to (d) which can be successively carried out, if desired, in the same reactor: (a) addition of alkyl acetoacetate to 1,3-butadiene, optionally 2-substituted; (b) the addition product formed is subjected to deacylation, following by an alkaline hydrolysis reaction and acidification to produce a carboxylic monacid having 6 carbon atoms in its main chain; (c) said monacid is subjected to hydroxycarbonylation to produce an alpha , omega -carboxylic diacid having 6 carbon atoms in its mains chain; and (d) said diacid is subjected to cyclizing decarboxylation. The invention is especially intended for the preparation of 2,2-dimethylcyclopentanone.