On direct photolysis of 2, 2-dialkyl-5-diazo-4, 6-dioxo-1, 3-dioxanes in the presence of pyridine, methanol or dimethyl sulfide as carbene traps, the yield of 'carbene'products does not exceed 27–28%. At the same time photochemical transformations of the related 3, 3- diacyldiazirines and dioxosulfonium ylides of this series, evidently, occur without generation of carbene intermediates.