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Cyclometalations on the imidazo[1,2-a][1,8]naphthyridine framework
P. Daw, , H. Doucet, J.K. Bera
Published in
Volume: 32
Issue: 15
Pages: 4306 - 4313
Cyclometalation on the substituted imidazo[1,2-a][1,8]naphthyridine platform involves either the C3-aryl or C4′-aryl ortho carbon and the imidazo nitrogen N3′. The higher donor strength of the imidazo nitrogen in comparison to that of the naphthyridine nitrogen aids regioselective orthometalation at the C3/C 4′-aryl ring with Cp*IrIII (Cp* = η5-pentamethylcyclopentadienyl). A longer reaction time led to double cyclometalations at C3-aryl and imidazo C5′- H, creating six- and five-membered metallacycles on a single skeleton. Mixed-metal Ir/Sn compounds are accessed by insertion of SnCl2 into the Ir-Cl bond. Pd(OAc)2 afforded an acetate-bridged dinuclear ortho-metalated product involving the C3-aryl unit. Metalation at the imidazo carbon (C5′) was achieved via an oxidative route in the reaction of the bromo derivative with the Pd(0) precursor Pd 2(dba)3 (dba = dibenzylideneacetone). Regioselective C-H/Br activation on a rigid and planar imidazonaphthyridine platform is described in this work. © 2013 American Chemical Society.
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