Activation of sp 3 C−H Bonds with Cobalt(I): Catalytic Synthesis of Enamines

C-H bond activation has been extensively studied with (Cp*)M(L)n (M = Ir, Rh), but cobalt, the third member of this triad, has not previously been shown to activate sp3 C-H bonds. Further, practical functionalization of the metal alkyl products of oxidative addition has not been fully explored. Toward these ends, we have developed catalytic dehydrogenation of alkyl amines with a Co(I) catalyst. Amine substrates are protected with vinyl silanes, followed by catalytic transfer hydrogenation, to yield a broad range of stable protected enamines and 1,2-diheteroatom-substituted alkenes, including several unprecedented heterocycles. (Cp*)Co(VTMS)2 catalyzes transfer hydrogenation under surprisingly mild conditions with high chemo-, regio-, and diastereoselectivity, while tolerating additional functionality

Intramolecular hydrogen transfer reactions catalyzed by pentamethylcyclopentadienyl rhodium and cobalt olefin complexes: Mechanistic studies

The mechanism of intramolecular transfer dehydrogenation catalyzed by [Cp * M(VTMS) 2 ] ( 1 , M=Rh, 2 , M=Co, Cp* = C 5 Me 5 , VTMS = vinyltrimethylsilane) complexes has been studied using vinyl silane protected alcohols as substrates. Deuterium-labeled substrates have been synthesized and the regioselectivity of H/D transfers investigated using 1 H and 2 H NMR spectroscopy. The labeling studies establish a regioselective pathway consisting of alkene directed α C-H activation, 2,1 alkene insertion, and finally β-hydride elimination to give silyl enol ether products

Intramolecular hydrogen transfer reactions catalyzed by pentamethylcyclopentadienyl rhodium and cobalt olefin complexes: Mechanistic studies

The mechanism of intramolecular transfer dehydrogenation catalyzed by [Cp(*)M(VTMS)(2)] (1, M=Rh, 2, M=Co, Cp* = C(5)Me(5), VTMS = vinyltrimethylsilane) complexes has been studied using vinyl silane protected alcohols as substrates. Deuterium-labeled substrates have been synthesized and the regioselectivity of H/D transfers investigated using (1)H and (2)H NMR spectroscopy. The labeling studies establish a regioselective pathway consisting of alkene directed α C–H activation, 2,1 alkene insertion, and finally β-hydride elimination to give silyl enol ether products