ChemInform Abstract: Formation of 2‐Acetylpyridines by the Base‐Catalyzed Ring Opening of Dihydro‐4H‐furo(2,3‐e)oxazines.

Abstract

ChemInform Abstract Treatment of (Ia)-(Ie) with DBU gives the corresponding 2-acetylpyridines (III) (detailed discussion of mechanisms). The intermediacy of 1,2-oxazines (II) is confirmed both by the formation of (IIf) from the derivative (If) ((IIIf) is produced only under more forcing conditions in low yield), and by the transformation (Ia) → (IIa) → (IIIa) according to the scheme. By contrast, the N-anologue (IV) only undergoes the initial elimination reaction to afford (V).