Iridium-catalyzed dehydrogenation intermediates

Ishii and coworkers reported that the JV-heterocyclization of naphthylamines with diols can be achieved with an iridium catalyst. In a typical example, the reaction of 1-naphthylamine with 1,3-propanediol was carried out with a catalytic amount of IrClg (5 mol%), r c-2,2 -bis(diphenylphosphino)-l,l -binaphthyl (BINAP) (10 mol%), and the corresponding 7,8-benzoquinoline was obtained in 96% yield (Scheme 11.11) [159]. The proposed reaction mechanism indicates that the imine intermediate is formed by the reaction of the amine and aldehyde by Ir-catalyzed dehydrogenation. Subsequent hydrogenation by the in situ generated Ir hydride leads to an aminoalcohol followed by cyclization to the desired quinoline products. 

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