Process for the preparation of ketones

Process for the preparation of a ketone comprising reacting an unsaturated compound of the formula ##STR14## wherein R.sup.1, R.sup.2 and R.sup.3 are identical or different and represent hydrogen or an optionally substituted C.sub.1-12 aliphatic, C.sub.3-18 cycloaliphatic, C.sub.6-18 araliphatic with C.sub.1-6 in the aliphatic moiety, phenyl, naphthyl or heterocyclic radical or a carboxylic acid ester group, and

• R.sup.4 represents the nitrile radical, or the group --CO--R.sup.5 or --CO--O--R.sup.5
• wherein
• R.sup.5 denotes an optionally substituted aliphatic, araliphatic, aromatic or heterocyclic radical
• or wherein
• it is also possible for any of R.sup.1 and R.sup.2 or R.sup.3, R.sup.2 and R.sup.4, and R.sup.3 and R.sup.4 to be bonded to one another directly, with formation of a carbocyclic or heterocyclic ring,
• with an aldehyde in the presence of a weak base other than cyanide and, as catalyst, a quaternary ammonium salt of the formula ##STR15## wherein X represents oxygen, sulphur, selenium or the --NR.sup.12 -- group,
• Y and Z are identical or different and each represents an optionally substituted carbon atom or nitrogen atom,
• R.sup.11 and R.sup.12 are identical or different and each represents a C.sub.1 to C.sub.12 aliphatic radical, a C.sub.5 to C.sub.12 cycloaliphatic radical, a C.sub.6 to C.sub.12 araliphatic radical which contains up to 6 carbon atoms in the aliphatic part, a C.sub.6 to C.sub.10 aromatic radical or a 5-membered ring which in addition to the carbon atoms contains an oxygen and/or a sulphur atom, and
• A represents an acid radical other than cyanide.