A convenient synthesis of α,α′-bis(substituted benzylidene)cycloalkanones catalyzed by Yb(OTf)₃ under solvent-free conditions

An array of aromatic aldehydes undergoes crossed aldol condensation with ketones in the presence of a catalytic amount of Yb(OTf)₃ under solvent-free conditions to afford the corresponding α,α′- bis(substituted benzylidene)cycloalkanones in excellent yields without occurrence of any side reactions. This method is very general, simple and environmental friendly in contrast with the existing methods, which use many classical Lewis acids. Furthermore, the catalyst can be recovered conveniently and reused efficiently without the loss of activity.