Clean solvent-free dipolar cycloaddition reactions assisted by focused microwave irradiations for the synthesis of new ethyl 4-cyano-2-oxazoline-4-carboxylates

Abstract

1,3-Dipolar cycloaddition reactions without solvent under focused microwave irradiation are reported. Imidate 3, derived from ethyl α-cyano α-amino acetate as potential azomethine ylide, undergoes highly regioselective cycloadditions to a wide range of aldehydes 4a–f as dipolarophiles in short reaction times. This simple, efficient and environmentally-friendly methodology has been applied to the synthesis of new ethyl 4-cyano-2-oxazoline-4-carboxylates 6a–f in good yields (81–98%) and moderate diastereoisomeric ratios.