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The diketene/acetone adduct, 2,2,6-trimethyl-4if-l,3-dioxin-4-one, efficiently acetoacetylates aliphatic and aromatic alcohols, amines, and thiols. These acetoacetylation reactions are fast and stoichiometric, require no catalysis, and give only volatile byproducts.

in 3 mL of toluene-dg was treated with a trace (ca. 0.005 g) of p-TsOH and heated to 70-90 °C (steam bath) for 1 h. NMR analysis showed loss of 5 and formation of 1 to be complete. Evaporation of solvent and IR analysis confirmed the product structure as 1.B. Under Acetone-Diketene Reaction Conditions. A mixture of 3.0 g of acetone, 1.30 g of diketene, 2.15 g of isopropenyl acetoacetate (5), and 0.05 g of p-TsOH was heated under reflux and monitored by NMR (aliquots were added to CDC13 containing benzene as internal standard). Compound 5 disappeared with tl/2 = 5 min; dioxinone 1 was the only product observed. After 45 min, conversion of 5 to 1 was complete, and conversion of diketene to 1 was about half complete. After 4 h, 1 and acetone were the only components observable in the reaction mixture.Cyclization of Vinyl Acetoacetate 12 to Dioxinone 13. A.In Toluene. To a solution of 0.01 g of p-TsOH in 50 mL of dry toluene was added 1 g of vinyl acetoacetate (12). After 10 min at reflux, NMR analysis showed about 75% conversion to 13. The mixture was refluxed for another 15 min, let stand at 22 °C overnight, stripped of solvent at reduced pressure, and distilled to give 0.73 g (73%) of 2,6-dimethyl-4if-l,3-dioxin-4-one (13): bp 60-65 °C (2 mm);

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