3-Dimethylamino-2,2-dimethyl-2H-azirine (1) reacts with alkyl phenyl substituted cyclopropenones 2 in benzene at 130 °C to give a mixture of the two isomeric 4(3H)-pyridones 3 and 4, resulting from a nucleophilic attack at C(2) and C(1) of the cyclopropenone. In acetonitrile the isomer 3 is formed exclusively. The crystal structure of the 5-isopropyl derivative 3a (R = CH(CH3)2) has been established by X-ray structure determination.
