Synthesis and Solid-state Reaction of 1-[3′-(Benzotriazol-2″-yl)-4′ -hydroxybenzoyl]-3-methyl-5-pyrazolones

A new kind of UV stabilizers, 1-(3′-(benzotriazol-2″-yl)-4′-hydroxy-benzoyl)-3-methyl-5-pyrazolones (1a-d), was synthesized with the aim to bind them chemically to certain polymers. The reaction of 1d with substituted benzaldehydes 4 in the molten state at 150°C and in the solid state at room temperature produced the condensation products l-(3′-(5″-chlorobenzotriazol-2″-yl)-4′-hydroxyl-5′-chlorobenzoyl)-3-methyl-4-arylmethylene-5-pyrazolones (2) and 4,4′-arylmethylene-bis [1-(3′-(5″-chloro-benzotriazol-2″-yl)-4′-hydroxy-5′-chloro-benzoyl)-3-methyl-5-pyrazolone] s (3), respectively, as the major product. On the other hand, the reaction of 1d with 4 at 50°C in chloroform solution proceeded non-selectively to give a mixture of 2 and 3.