Synthesis of 2-Aminoimidazolones and Imidazolones by (3+2) Annulation of Azaoxyallyl Cations

The first examples of (3 +, 2) annulations between azaoxyallyl cations and cyanamides and nitriles, to give, the corresponding 2-aminoimidazolones and imidazolones, are reported. On the basis of the isolation of unexpected imidate products with certain substrates, it is proposed that the reaction proceeds via fast kinetic O-alkylation followed by rearrangement to the thermodynamically favored 2-aminoimidazolones and imidazolones. The method was applied to the formal synthesis of the antihypertensive drug irbesartan.