Silver nitrate-catalyzed reaction of methyl α,α-disubstituted α-isocyanoacetates with primary amines afforded 3,5,5-trisubstituted imidazolones in good to excellent yields. A silver salt-catalyzed insertion of the isocyano group into the N−H bond of the amine followed by in situ lactamization accounted for the reaction outcome. The same transformation between methyl 2 -isocyanobenzoate and amines afforded quinazolin-4-ones in excellent yields. The utility of this chemistry was illustrated by the development of concise syntheses of (±)-evodiamine and rutaecarpine.