A versatile
rhodium-catalyzed/copper-mediated C–H/C–C
activation and cascade annulation reaction was described to form 2-arylindole
derivatives. Highly selective C–C bond cleavage of γ-substituted tert-propargyl alcohols occurred, together with pyridine-directed ortho C(sp2)–H bond activation, affording
a series of 2-arylindoles with yields up to 90%. Subsequent derivations
were smoothly conducted to access polyfunctionalized 2-arylindoles,
illustrating the potential applications of this method.
A rhodium-catalyzed Suzuki–Miyaura coupling reaction
via
C(O)-C bond activation to form 2-benzoylpyridine N-oxide derivatives is reported. Both the C(O)–C(sp2) and C(O)–C(sp3) bond could be activated during
the reaction with yields up to 92%. The N-oxide moiety
could be employed as a traceless directing group, leading to free
pyridine ketones.
A chelation-assisted
palladium-catalyzed CC bond cleavage
of α, β-unsaturated ketone to form alkenyl nitrile in
the presence of nitrile is disclosed on the basis of a formal group-exchange
reaction formulated as C1C2 + C3 → C1C3 + C2, differing from normal alkene oxidative cleavage and metathesis
type. The isolated key active Pd(II) complex as well as deuterium-labeled
experiment revealed the necessity of the chelation group, and a plausible
catalytic pathway was proposed.
A straightforward strategy for direct benzylic C–H
bond
amination via an electrochemical Ritter-type reaction
is developed. The reaction demonstrates simpler and milder reaction
conditions over the existing methods without extra mediator. Moderate
to excellent yields up to 94% of the desired amide products were obtained
with a broad substrate scope. The removal of the Ac group by a simple
step can afford NH-free benzylic amines, providing a suitable approach
for the late-stage functionalization of bioactive molecules.
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