We
disclose a transmetalation-initiated Ni(I)-catalyzed regioselective
β,δ-vinylarylation of γ,δ-alkenyl α-cyanocarboxylic
esters with vinyl triflates and arylzinc reagents. This reaction proceeds
via contraction of six-membered nickellacycles to five-membered nickellacycles
to form carbon–carbon bonds at the nonclassical homovicinal
sites, and it provides expeditious access to a wide range of complex
aliphatic α-cyanoesters, α-cyanocarboxylic acids, dicarboxylic
acids, dicarboxylic acid monoamides, monocarboxylic acids, nitriles,
and spirolactones. Control, deuterium labeling, and crossover experiments
indicate that (i) the nickellacycle contraction occurs by β-H
elimination, followed by hydronickellation on transiently formed alkenes,
and (ii) the Ni species are stabilized as Ni-enolates.
We disclose a Ni-catalyzed vicinal
alkylarylation of unactivated
alkenes in γ,δ-alkenylketimines with aryl halides and
alkylzinc reagents. The reaction produces γ-C(sp3)-branched δ-arylketones with the construction of two C(sp3)–C(sp3) and C(sp3)–C(sp2) bonds. Electron-deficient alkenes play crucial dual roles
as ligands to stabilize reaction intermediates and to increase catalytic
rates for the formation of C(sp3)–C(sp3) bonds. This alkene alkylarylation reaction is also effective for
secondary alkylzinc reagents and internal alkenes and proceeds with
a complete regio- and stereocontrol, affording products with up to
three contiguous all-carbon all-cis secondary stereocenters.
We disclose a palladium-catalyzed difunctionalization of skipped diene with alkenyl triflates and arylboronic acids to produce 1,3-alkenylarylated products. The reaction proceeded efficiently with Pd(acac) 2 as a catalyst and CsF as a base for a wide range of electron-deficient and electron-rich arylboronic acids as well as oxygen-heterocyclic, sterically hindered, and complex natural product-derived alkenyl triflates bearing various functional groups. The reaction produced 3-aryl-5-alkenylcyclohexene derivatives with 1,3-syn-disubstituted stereochemistry.
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