Pyranones from Potassium Salts of Acyclic Tricarbonyl Compounds

Significance

The instability towards decarboxylation of the free acids of 5-hydroxy-3-oxopent-4-enoic esters 1, prepared by selective γ-acylation of the dianion of ethyl acetoacetate and N-acyl-2-methylaziridines, has been overcome by conversion into their corresponding bispotassium salts 2 in excellent yields. These easily purified salts may then be lactonized to 6-substituted-4-hydroxy-2H-pyran-2-ones 3, pyrazole 4, and isoxazole 5 derivatives under mild conditions in good to excellent yields. To further demonstate the utility of this chemistry, naturally occurring 5-hydroxy-pyran-2-one, Sch-419560 6 (M. Chu et al. J. Antibiot. 2002, 55, 215-218), and 3,3-dimethylallyl conrauanalactone derivative 7 (R. A. Hussain, P. G. Waterman Phytochemistry 1982, 21, 1393-1396) have been prepared in 62% and 79% overall yields, respectively.