Studies on tertiary amine oxides. LXXVI. Reactions of aromatic N-oxides with 1,3-cyclohexanediones in the presence of acetic anhydride.

Abstract

Quinoline 1-oxides (1a-c) readily reacted with dimedone (2) and 1, 3-cyclohexanedione (10) in acetic anhydride or in dimethylformamide (DMF)-containing 1.2 eq of acetic anhydride to afford the corresponding 2-substituted quinolines (3a-c and 11a-c). The reaction of 3-bromoquinoline 1-oxide (1d) with 2 in DMF-acetic anhydride gave the 2-substituted quinoline (3d), whereas that in acetic anhydride alone afforded the enol acetate of 3d (3d'). The reactions of isoquinoline 2-oxide (5) with 2 and 10 similarly gave the 1-substituted isoquinolines (6 and 12). While pyridine 1-oxide (7) reacted with 2 to give the 2-substituted pyridine (8), the reaction with 10 produced 3-(2, 6-dioxocyclohexylidene)-2-(4-pyridyl) cyclohexanone (13).