5-ACYLOXY-4(5H)-OXAZOLONIUM SALTS, PROCESS FOR THEIR PREPARATION, AND THEIR USE AS INTERMEDIATES FOR THE SYNTHESIS OF HERBICIDALLY ACTIVE TRIAZINONES

Novel 5-acyloxy-4(5H)-oxazolonium salts of the formula (I) < IMG > in which R1 represents an optionally substituted aliphatic group with up to 12 carbon atoms, an optionally substituted cycloalkyl group with 3 to 10 carbon atoms, an optionally substituted phenyl or naphthyl group or an optionally substituted heterocyclic group and R2 and R3 are identical or different and represent a hydrogen atom or an optionally substituted aliphatic group with up to 8 carbon atoms or an optionally substituted phenyl group and X.THETA. represents the anion of an inorganic or organic acid having a pKa value of less than 2, are obtained in solution when an acyl cyanide of the general formula R1-CC-CN (II) is reacted with a carboxylic acid anhydride of the general formula R2-CO-O-CO-R3 (III) wherein R1, R2 and R3 each have the abovementioned meaning, in the presence of one or more inorganic or organic acids having a pKa value of less than 2, and if appropriate in the presence of a solvent, and if appropriate at a temperature between 0 and 120.degree.C. The novel oxazolonium salts (I) can be used as intermediate products for the preparation of known, herbicidally active 3,4,6-trisubstituted 1,2,4-trianzin-5(4H)-ones.