Highly Efficient One-Pot Synthesis of 1,2-Dihydro-2-oxo-3-pyridine-carboxylate Derivatives by FeCl3-Promoted [3+3] Annulation

An efficient one-pot synthesis of 1,2-dihydro-2-oxo-3-pyridinecarboxylate derivatives starting from enones and ethyl cyanoacetate in moderate to good yields is described. This novel tandem [3+3] annulation method mediated by FeCl3 involves Michael addition and ketone-nitrile annulation followed by aromatization-dehydrogenation. A plausible mechanism is also proposed.