Synthesis of Azepinoindoles and Oxepinoindoles through Brønsted-Acid-Catalyzed Cyclization of an <i>In Situ</i> Generated Dihydrospiroquinoline Intermediate

Abstract

We have developed a straightforward and efficient synthetic protocol to produce 5,6,7,12-tetrahydrobenzo[2,3]azepino[4,5- b ]indole and 7,12-dihydro-6 H -benzo[2,3]oxepino[4,5- b ]indole derivatives under mild conditions. This annulation process involves the intramolecular cyclization of the in situ generated ketimine moiety via the formation of dihydrospiroindolequinoline, which serves as a key intermediate in the reaction pathway. Several control experiments and spectroscopic studies were performed to elucidate the underlying reaction mechanism.

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