Patent ID: 6184420
Filing Date: 2001-02-06
Classification: C07C,Y02P

Abstract:
A process for the preparation of unsaturated ketones of the formulae Ia and Ib ##STR17##where R.sup.1, R.sup.2, R.sup.3, R.sup.4 and R.sup.5 are each hydrogen or alkyl, alkenyl, cycloalkyl, cycloalkenyl, aryl or aralkyl radicals which are substituted or unsubstituted by oxygen-containing groups, it also being possible for R.sup.1 and R.sup.2 together to form a 5- or 6-membered carboxylic ring, which comprises the combination of the following reactions:a) reacting an allyl alcohol of the formula IIa or a propargyl alcohol of the formula IIb ##STR18##with an isopropenyl ether of the formula III ##STR19##where R.sup.6 is alkyl having 1 to 4 carbon atoms, with formation of a ketal of the formula IV ##STR20##where R.sup.6 has the abovementioned meaning, as a byproduct,b) preparation of the isopropenyl ether of the formula III by reacting a ketal of the formula IV with propyne or allene, and a mixture thereof in the gas phase at elevated temperatures in the presence of a heterogeneous catalyst containing zinc or cadmium together with silicon or oxygen, andc) feeding the ketal of the formula IV formed in the reaction (a) into stage (b) for the preparation of the isopropenyl ether of the formula III again.