Acidic alumina as a useful heterogeneous catalyst in the Michael reaction of β-dicarbonyl derivatives with conjugated nitroalkenes

Addition of a variety of 1,3-dicarbonyl derivatives to conjugated nitroalkenes was efficiently performed under heterogeneous catalysis by acidic alumina in the presence of a minimum amount of solvent (Et2O, 0.5 mL/mmol). The procedure allows satisfactory to good yields of a diastereomeric mixture (similar to 1: 1) of polyfunctionalized adducts. Moreover, work-up can be avoided since the reaction mixture can be directly charged into a chromatographic column for immediate purification.