Temperature Tunable Synthesis of Tetrahydro-4H-pyrrolo[3,2-c]quinolin-4-ones and Dihydro-1H-benzo[b]azepines from 2-Aminobenzonitriles and Donor–Acceptor Cyclopropanes

Tetrahydro-4H-pyrrolo[3,2-c]quinolin-4-ones and dihydro-1H-benzo[b]azepines are efficiently synthesized from 2-aminobenzonitriles and donor-acceptor cyclopropanes mediated by SnCl4 in moderate to good yields. The reaction involves the initial ring opening of a cyclopropane ring due to activation by SnCl4 followed by nucleophilic attack by amine to give an adduct, which after unprecedented rearrangement at two different reaction temperatures provides two nitrogen heterocyclic compounds. This methodology can be used for the synthesis of hexahydropyrrolo[3,2-c]quinolinone derivatives, the structure of which is found in biologically active molecules.