Production of high molecular weight .alpha.,.beta.-unsaturated aldehydes

A process for the production of high molecular weight .alpha.,`-unsaturated aldehydes of the general formula (I):

• ##STR7## where R.sup.1 is hydrogen, alkyl of one to four carbon atoms, phenyl or phenyl bearing alkyl of one to four carbon atoms as a substituent;
• R.sup.2 is hydrogen, alkyl of one to four carbon atoms, phenyl or phenyl bearing alkyl of one to four carbon atoms as a substituent;
• R.sup.3 is hydrogen or alkyl of one to four carbon atoms;
• R.sup.5 is hydrogen or alkyl of one to four carbon atoms;
• R.sup.6 is hydrogen or alkyl of one to four carbon atoms;
• R.sup.7 is hydrogen or alkyl of one to four carbon atoms;
• R.sup.4 is hydrogen or a saturated or unsaturated, branched or linear aliphatic or cycloaliphatic hydrocarbon radical of one to twelve carbon atoms;
• R.sup.8 is alkyl of one to four carbon atoms or hydrogen;
• and
• R.sup.9 is ethyleneacetal, 1,3-propylene acetal, 2,2-dimethylpropylene acetal, 1,3-dimethylpropylene acetal, diethylacetal, a straight chain, saturated or unsaturated hydrocarbyl ether group having a total of up to 12 carbon atoms and the ether oxygen between carbon atoms of said group or CH.sub.3 COOCH.sub.2 --,
• wherein an allyl compound of the formula (II):
• ##STR8## in which R.sup.5 to R.sup.9 have the meanings given above and R.sup.10 is hydrogen or acyl or a carboxylic acid of one to five carbon atoms in reacted in the liquid phase with an .alpha.,.beta.-unsaturated aldehyde of the formula (III):
• ##STR9## in which R.sup.1 to R.sup.4 have the meanings given above, at elevated temperature of about 60.degree.-300.degree. C and in the presence of an acid catalyst with a pK value of -9 to 6 in such an amount of such acid catalyst that the reaction mixture has a pH of 1 to 7.