The new compound ##STR1## is prepared and converted to the new acetal ##STR2## which is reacted with an alkali phenolate or alkaline earth metal phenolate in the presence of copper or a copper compound as a catalyst and in the presence of a diluent at a temperature between about 100.degree. and 200.degree. C. to produce the new acetal ##STR3## which can be hydrolyzed to the corresponding aldehyde which is a known intermediate for pyrethroid-like insecticides.