Abstract
A metal-free synthesis of biologically important benzazepines is achieved through a single synthetic operation involving an oxidative C-H bond functionalization and ring expansion with diazomethanes as key reagent. This represents a new, strong methodology for the straightforward construction of the seven-ring N-heterocyclic structures under mild conditions using a 2,2,6,6-tetramethylpiperidine ...
Abstract
A metal-free synthesis of biologically important benzazepines is achieved through a single synthetic operation involving an oxidative C-H bond functionalization and ring expansion with diazomethanes as key reagent. This represents a new, strong methodology for the straightforward construction of the seven-ring N-heterocyclic structures under mild conditions using a 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) oxoammonium salt as oxidant. Moderate to good yields are achieved from simple, readily available tetrahydroisoquinolines, and this methodology has been further successfully applied for the synthesis of the 3-benzazepine drug Lorcaserin. A possible mechanistic pathway for the ring expansion step, comprising the extrusion of nitrogen in a concerted asynchronic process, is proposed based on both mechanistic proof and density function theory (DFT) calculations.
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