Aldol Condensations Catalyzed by Co(II) Complexes of Pyridine-containing Copolymers

The cross aldol condensations of aldehydes and ketones catalyzed by Co(II) complexes of pyridine-containing copolymers proceed under neutral conditions in DMF or DMSO to afford α,β-unsaturated ketones without any byproduct. The solid complex catalysts are capable of repeated use. The reactions of aromatic aldehydes and ketones give good results but not those of aliphatic compounds. Effects of substituent groups in chalcone formation are observed. The catalytic reaction features with the polymer-complex catalysts are compared with that with Co(II)–pyridine complex. The polymer-complex-catalyzed aldol condensations are discussed briefly in relation to the enzymatic reaction of Class II aldolase (metalloenzyme).