A Ni-catalyzed intermolecular enantioselective
hydroamination of
branched 1,3-dienes is reported. The method is broadly applicable,
highly regio-, chemo-, and enantioselective, and provides direct access
to valuable chiral allylic amines starting from linear or α-branched
aliphatic primary amines or secondary amines. Mechanistic studies
have been conducted using 31P NMR spectroscopy for reaction
progress monitoring, isotopic labeling experiments (2H),
and kinetic analysis. The resting state of the catalyst is a Ni−π-allyl
complex, and the outer-sphere nucleophilic attack of H-bonded amine
aggregates is proposed to be the rate-determining step. This hypothesis
guided the identification of an improved set of reaction conditions
for the enantioselective hydroamination of branched 1,3-dienes.
A [Rh(I)]/bisphosphine/base catalytic system for the ortho-selective C–H alkylation of azines by acrylates and acrylamides is reported. This catalytic system features an unprecedented complete linear or branched selectivity that is solely dependent on the catalytic base that is used. Complete branched selectivity is even achieved for ethyl methacrylate, which enables the introduction of a quaternary carbon center. Excellent functional group compatibility is demonstrated for both linear and branched alkylations. The operational simplicity and broad scope of this transformation allow for rapid access to functionalized azines of direct pharmaceutical and agrochemical relevance.
An easy access to 5-fluoropyridazines by a [2 + 1]/[3 + 2]-cycloaddition sequence between terminal alkynes, a difluorocarbene, and a diazo compound is reported. This approach does not necessitate the isolation of any intermediates, and a wide range of novel 5-fluoropyridazines was synthesized from readily available starting materials. Additionally, these compounds were used as a platform to access novel and highly diversified pyridazines.
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