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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).

The azoalkenes (IV) are prepared from the hydrazides (I) and α‐halo ketones (II) via the intermediate hydrazones (III).