Gold-Catalyzed Unexpected Ring Transformation of Pyrimidodiazepine Derivatives

Pyrimidodiazepine derivatives underwent an unexpected gold-catalyzed retro-Mannich-type carbon-carbon bond cleavage and intramolecular nucleophilic cyclization. The pyrimidodiazepines bearing an alkyne moiety showed novel orthogonal reactivity in the presence of a gold catalyst, as opposed to the alkynophilicity that is commonly observed with gold catalysts. The ring transformation reaction of pyrimidodiazepines probably proceeds through an acyclic iminium intermediate. The potential of this synthetic method for the skeletal diversification of pyrimidine-containing macrocycles was also demonstrated.