An efficient synthesis of chromene derivatives through a tandem michael addition-cyclization reaction

Abstract

The racemic synthesis of ethyl esters of 2-amino-5-oxo-4-aryl-5, 6, 7, 8-tetrahydro-4H-chromene-3-carboxylic acid 3a-d was achieved through a tandem Michael addition-cyclization reaction of easily available cyclohexane-1,3-dione 2a, 5, 5-dimethyl-1,3-cyclohexanedione 2b and ethyl esters of 2-cyano-3-arylacrylic acid 1a-d. The reaction of 1b with 2a yielded 2,5-dioxo-4-phenyl-3,4,5,6,7,8-hexahydro- 2H-chromene-3-carbonitrile 4e resulting from a different mode of cyclization. High addition-cyclization efficiency was observed with good yields (up to 93%) using alcoholic sodium ethoxide as a base catalyst, which provides a competitive method for the synthesis of chromene derivatives under a simple efficient way.