Compounds are prepared of the formula ##STR1## where R' is a t-alkyl group having 4 to 18 carbon atoms, preferably t-butyl, t-amyl or t-octyl and R is a straight or branched chain alkyl group with 1 to 18 carbon atoms, preferably 1 to 10 carbon atoms or an alkyl group substituted with one or more phenyl group or a halogen atom, particularly a chlorine atom, or a cycloalkyl group with 3 to 8 carbon atoms, particularly cyclopropyl, which can be substituted by one or more 1 to 3 carbon atom alkyl groups or one or more halogen atoms, preferably chlorine, or phenyl or naphthyl or a five membered heterocyclic group or such phenyl, naphthyl or heterocyclic group substituted by halogen atoms, nitro groups, alkyl or alkoxy with 1 to 5 carbon atoms by condensing in acid medium an acyl cyanide of the formulaR--CO--CN (II)where R is as defined above with either(a) a tertiary alcohol of the formulaHO--R' (III) in which R' is as defined above, or preferably(b) an alkene of the formula ##STR2## where R.sub.1 and R.sub.2 are the same or different and are hydrogen or an alkyl group and wherein R.sub.3 and R.sub.4 are the same or different and wherein the alkyl groups in each case can be 1 to 15 carbon atoms. Some of the compounds are new. They are useful as intermediates for synthesizing herbicides and can be used directly as fungicides.