Abstract
1-Ethoxycarbonyl-5-oxo-4-oxaspiro [2.3] hexane (3), on treatment with sodio methyl acetoacetate in THF, was transformed into 3-hydroxy-4-ethoxycarbonyl-2-cyclopenten-1-one (5) in 82% yield. Reaction of compound 3 with malononitrile (4a) in the presence of sodium hydride in THF gave the cyclopentenone 5 and 2-amino-3-cyano-6-ethoxycarbonylethyl-4-pyrone (6) in 49% and 24% yields, respectively. Similarly, reaction of compound 3 with ethyl cyanoacetate (4b) afforded compound 5 and 2-amino-3-ethoxycarbonyl-6-(2-ethoxycarbonylethyl)-4-pyrone (7) in 63% and 19% yields, respectively. Reaction of 1-dimethylphosphono-1-methyl-5-oxo-4-oxaspiro [2.3] hexane (1c) with 4a and 4b under similar conditions gave 2-amino-3-cyano-6-(2-dimethylphosphonopropyl)-4-pyrone (10) and 2-amino-3-ethoxycarbonyl-6-(2-dimethylphosphonopropyl)-4-pyrone (11) in 58% and 63% yields, respectively.
