The results of alkylation of dicarbonyl compounds with 1,2,3-trihalopropane are presented, which is accompanied by rearrangement of the carbon skeleton and leads to the formation of β-substituted furans. Alkylation of β-dicarbonyl compounds with 1,2-dibromoethane at room temperature gives a C,C-cycloalkylation product, which isomerizes at a temperature above 180°C into a C,O-dialkylation product, a dihydrofuran derivative. Alkylation of dimetylacetonedicarboxylate with methyl iodide occurs similarly, the primary O-alkylation product undergoes rearrangement into a C-alkylation product at 180°C. It is also shown that such rearrangements occur with small radicals. The product of O-alkylation of dimethylacetone dicarboxylate with dimethyl acetal of bromoacetic aldehyde is stable at a temperature of 200°C, whereas the product of its hydrolysis isomerizes into a product of C-alkylation with further conversion into furan derivatives.