The enantioselective synthesis of Nitrogen-containing heterocycles (N-heterocycles) represents a substantial chemical research effort and resonates across numerous disciplines including the total synthesis of natural products and medicinal chemistry. In this manuscript, we describe the highly enantioselective palladium-catalyzed decarboxylative allylic alkylation of readily available lactams to form 3,3,-disubstituted pyrrolidinones, piperidinones, caprolactams, and structurally related lactams. Given the prevalence of quaternary N-heterocycles in biologically active alkaloids and pharmaceutical agents, we envision that our method will provide a synthetic entry into the de novo asymmetric synthesis of such structures. As an entry for these investigations we demonstrate how the described catalysis affords enantiopure quaternary lactams that intercept synthetic intermediates previously employed in the synthesis of the Aspidosperma alkaloids quebrachamine and rhazinilam, but that were previously only available by chiral auxiliary approaches or as racemic mixtures.
A salt-free procedure for the generation of a wide variety of metal(0) particles, including Fe, Co, Ni, and Cu, was achieved using 2,3,5,6-tetramethyl-1,4-bis(trimethylsilyl)-1,4-diaza-2,5-cyclohexadiene (1), which reduced the corresponding metal precursors under mild conditions. Notably, Ni particles formed in situ from the treatment of Ni(acac)2 (acac = acetylacetonate) with 1 in toluene exhibited significant catalytic activity for reductive C-C bond-forming reactions of aryl halides in the presence of excess amounts of 1. By examination of high-magnification transmission electron microscopy images and electron diffraction patterns, we concluded that amorphous Ni nanoparticles (Ni aNPs) were essential for the high catalytic activity.
A binaphthyl-based primary amine (R)- was designed for the Diels-Alder reaction of alpha-substituted alpha,beta-unsaturated aldehydes; in the presence of the TfOH salt of (R)-, the Diels-Alder reaction of alpha-substituted alpha,beta-unsaturated aldehydes with cyclopentadiene proceeded to afford the corresponding cycloadducts having one all-carbon quaternary stereocenter in good yield with good to high stereoselectivity.
A catalyst system of [Ni(MeCN)6](BF4)2, 1,10-phenanthroline, and 1,4-bis(trimethylsilyl)-2,3,5,6-tetramethyl-1,4-dihydropyrazine (Si–Me4-DHP) assisted cyanation of aryl halides in acetonitrile to give the corresponding aryl nitriles.
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