A solvent-free protocol for the synthesis of 3-formyl-2H-chromenes via domino oxa Michael/aldol reaction

A new solvent-free, TBD-catalyzed protocol for the synthesis of 3-formyl-2H-chromenes is presented. Substituted salicylaldehydes 1 and 3-methyl-2-butenal 2 in the presence of 10 mol % of TBD underwent a domino oxa Michael/aldol reaction to effectively yield the corresponding 2H-chromene derivatives 3. The methodology represents an improvement either in terms of efficiency and sustainability as a small amount of catalyst is required and the work-up procedure is simple and straightforward.