Regioselective synthesis of 3-heteroarylpiperidin-2-ones and diazacyclopenta[a]phenalenone via carbenoid reactions

Rhodium(II) catalyzed carbenoid reactions of 3-diazopiperidin-2-ones were carried out with indoles and pyrroles to afford the respective (3-indol-3-yl)- and (3-pyrrol-2-yl)piperidones with regioselectivity. Interestingly, the reaction of bis-diazoimide in the presence of Rh2(OAc)4 catalyst furnished diazacyclopenta[a]phenalenone in a tandem manner.