Synthesis of indoline-2,3-fused tetrahydroquinolines bearing two free N-H groups using a protecting-group-free
Raju Chouhan1, Sajal Kumar Das1
1Department of Chemical Sciences, Tezpur University, Napaam, Tezpur, Assam, 784028, India. sajalkd@tezu.ernet.in.
Abstract:
We report the first general synthesis of tetrahydro-5H-indolo[2,3-b]quinolines via a transition-metal- and protecting-group-free two-step approach. The strategy combines NaOtBu/Et3B-promoted alkylative dearomatization of indoles with a B2(OH)4-mediated cascade nitro reduction and amine-imine cyclization. The method is mild, diastereoselective, high-yielding, scalable, and has a broad substrate scope. Importantly, it furnishes products with two free N-H groups, enabling further downstream functionalization.
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