The Michael addition of 1,2-cyclohexanedione to β-nitrostyrenes (I): the synthesis of 3-aryl-5,6-dihydrobenzofuran-7(4H)-ones

The reaction of β-nitrostyrenes with 1,2-cyclohexanedione using K2CO3 as a base results in the formation of 3-aryl-5,6-dihydrobenzofuran-7(4H)-ones in good yields. A putative reaction mechanism involves an initial Michael addition of the dione C-enolate to the β-nitro-styrene, followed by intramolecular cyclization of the resulting O-enolate anion, elimination of nitrite ion, and air oxidation. Product formation is highly dependent on base stoichiometry.