Reactivity of 3‐(1‐acylhydrazonoethyl)‐2H‐pyran‐2‐ones 1a–k and 4a–d towards various acetylating agents and nitrous acid, respectively, is studied. Treatment of dehydroacetic acid (DHA) (thio)acylhydrazones 1a, c, f with Ac2O/Et3N afforded the 3‐(1‐triacetylhydrazinoethenyl) derivative 3a. The analogous coumarin derivative 5 was obtained by treatment of acetylhydrazone 4a with AcCl/PhNMe2. With concomitant N–N bond cleavage acylhydrazones 1c–f were converted to the pyrano‐isoxazole 6 by treatment with NaNO2/AcOH whereas coumarin derivative 4d was converted to the imine 4e.
- Dehydroacetic acid (DHA)
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