The solid‐state michael addition of 3‐methyl‐1‐phenyl‐5‐pyrazolone

A novel solid‐state Michael addition between pyrazolone 1 and 4‐arylidenepyrazolones 2 at ambient temperature produced Michael adducts, 4,4′‐arylidenebis(3‐methyl‐1‐phenyl‐5‐pyrazolones) 3. Pyrazolones 3 formed salts 4 with Cu2+ in solution, indicating the enolic structure of the pyrazolone rings. The reactivity of 2 with 1 is discussed in terms of the electronic and steric effects of the substituent on the arylidene group of compounds 2. Pyrazolone 1 also underwent the solid state Michael addition reaction with maleimide at 100° to give the adducts 7,8 and 9.