Catalyst-free tandem aldol condensation/Michael addition of 1,3-cyclohexanediones with enolizable aldehydes.

An efficient tandem aldol condensation/Michael addition process of unactivated aldehydes and 1,3-cyclohexanedione is described. This transformation proceeds without any catalyst at room temperature with high isolated yields. By a fine-tuning of reaction conditions an access to both the aldol condensation/Michael addition products or to the dehydrated cyclized 9-substituted 1,8-dioxo-xanthenes is given.