The first generalsynthesis of bis-α-acyloxy-1,4- and -1,5-diketones has been accomplished in a catalyticoxidativeopening of bis-acylated THF and THP (tetrahydropyran) diols, which were synthesised by osmium- or ruthenium-catalysed oxidative cyclisation of 1,5- and 1,6-dienes. The overall sequence corresponds to the regioselective double ketoacyloxylation of the starting diene. The synthesised bis-α-acyloxy-1