Background: The introduction of a cyano group has been widely investigated because a
cyano group may easily be transformed into both a methylamino moiety and a carboxylic acid moiety.
Therefore Michael addition between phenol and acrylonitrile for the introduction of a cyanoethoxy
moiety has been reported by several groups, however, the long reaction time (20-40 h) of this reaction
was problematic. In order to solve this difficulty, we investigated the Michael addition with the assistance
of microwave irradiation.
Methods: 4-Dimethylaminopyridine was added to a mixture of phenol and acrylonitrile, and the suspension
was irradiated (107-115 W) for 4 h. Reaction conversion was determined by 1H NMR analysis
of the mixture.
Results: The addition reaction between phenols and acrylonitrile in the presence of 4-dimethylaminopyridine
under microwave irradiation proceeded smoothly to afford the corresponding Michael
adducts in good to moderate yield. Microwave-accelerated Michael addition in the presence of 4-
dimethylaminopyridine proceeded more effectively without the use of additives such as solvents. This
method was applicable to Michael addition between phenol and methyl acrylate, between aniline and
acrylonitrile, and also between anilines and methyl acrylate.
Conclusion: We have described a highly efficient and rapid method for Michael addition between
phenols and acrylonitrile, between aniline and acrylonitrile, between phenol and methyl acrylate, and
between anilines and methyl acrylate. Considering the present results, it is possible that the combination
of microwave irradiation and the use of DMAP as a base constitute one of the most suitable procedures
for the Michael addition of phenols and anilines.