alpha , beta -substituted acroleins

Known and novel substituted acroleins of the general formula I I where R1 is alkoxy, phenoxy, halogen, haloalkyl, haloalkoxy, haloalkylthiyl or nitro, n is an integer from 1 to 5, in the case of n being greater than 1 the R1s being identical or different and in the event of nitro substitution the aromatic ring carrying not more than 3 nitro groups, and where R2 is alkyl, cycloalkyl, unsubstituted or substituted aryl or hetaryl or a nonaromatic heterocyclic radical, are prepared by reacting a phenylacetaldehyde of the general formula II II with an aldehyde of the general formula III [R2-CHO]III in the presence of a base and a solvent. These acroleins are useful to prepare hydroxymethyloxiranes which are intermediates in the synthesis of antimycotic and fungicidal azoylmethyloxiranes.