Michael addition of anilines or phenols without solvent under microwave irradiation

Abstract

It is well known that microwave irradiation methods are useful to shorten reaction time of certain organic reactions. During our investigation of Michael addition using phenol as a Michael donor, we recognized that no solvent conditions were useful for the reaction, and that the reaction rate was accelerated by microwave irradiation. In order to clarify the scope and limitation of the microwave assisted Michael addition, we used not only phenol but also aniline and their derivatives as Michael donors. When we applied microwave assisted Michael addition conditions to the reaction between acrylonitrile and phenol or aniline, the Michael addition proceeded in the presence of aqueous benzyltrimethylammonium hydroxide or aqueous tetramethylammonium hydroxide to yield Michael adducts for both Michael donors. The reactions proceeded more smoothly without solvent in the presence of 4-dimethylaminopyridine (DMAP) in both cases. Another hand, Michael addition between phenol and chalcone did not proceed under microwave irradiation conditions without solvents, otherwise Michael addition between aniline and chalcone proceeded in the same conditions. Then, we applied the same conditions to the reaction between anilines and methyl acrylate. The Michael addition proceeded smoothly in the presence of DMAP without solvents.