Divergent Approach for Regioselective Synthesis of Linearly and Angularly Fused Benzoimidazoquinazolinones from Isatoic Anhydrides.

Ph 3 P-I 2 -mediated condensation reactions of isatoic anhydrides and o -phenylenediamines have been developed for the regioselective syntheses of a wide range of linearly and angularly fused benzoimidazoquinazolinones. The selectivity of the products relies on the generation of either highly electrophilic oxyphosphonium or less reactive imidate intermediates. A direct amine attack at the C-2 position of the oxyphosphonium intermediate presumably drives the reaction toward the linearly fused products, whereas an attack of the diamine at the C-4 position of the in situ generated cyclic imidate leads to the angularly fused derivatives. This strategy serves as a practical handle for the efficient synthesis of other related heterocycles.