Oxidation with lead tetraacetate. IV. Cyclization of phenylhydrazones of levulinic acid, levulinanilide, 5-ketohexanoic acid, 4-keto-1-pentanol, and of levulinic acid oxime

Abstract

The phenylhydrazones of levulinic acid (3a) and 5-ketohexanoic acid (4) are cyclized by lead tetraacetate (LTA) to γ-phenylazo-γ-valerolactone (9a) and δ-phenylazo-δ-caprolactone (11), respectively. Oxidation of levulinanilide phenylhydrazone (3b) leads, by analogous oxygen-to-carbon ring closure, to γ-phenylazo-α-phenylimino-γ-valerolactone (15) which is hydrolyzed to 9a. Similarly, the phenylhydrazone of 4-keto-1-pentanol (5) is cyclized to 2-phenylazo-2-methyl tetrahydrofuran (12) and the oxime of levulinic acid (7) is converted to γ-nitroso-γ-valerolactone which is isolated as the dimer, trans-bis[γ-nitroso-γ-valerolactone] (14).