An unprecedented
asymmetric acyl-carbamoylation of pendant alkenes
tethered on aryl carbamic chlorides with both aliphatic and aromatic
aldehydes has been developed via the cooperative catalysis of a chiral
nickel-PHOX complex and tetrabutylammonium decatungstate. This reaction
represents the first example of merging hydrogen-atom-transfer photochemistry
and asymmetric transition metal catalysis in difunctionalization of
alkenes. Using this protocol, a variety of oxindoles bearing a challenging
quaternary stereogenic center are furnished under mild conditions
in highly enantioselective manner.
By
merging C–O and C–F bond cleavage in cross-electrophile
coupling, we developed a method for efficient synthesis of gem-difluoroalkenes with an alkoxy-substituent on the homoallylic
position using easily accessible acetals as coupling partners with
α-trifluoromethyl alkenes. Remarkably, this Ni-catalyzed allylic
defluorinative cross-coupling reaction demonstrates high tolerance
of a wide range of sensitive functional groups and proves to be applicable
in late-stage functionalization of structurally complex compounds.
In
this protocol, we report an allylic defluorinative reductive
cross-coupling reaction for C–C bond formation. Under the Ni-catalysis
the challenging C(sp3)–F bond cleavage of trifluoromethyl-substituted
alkenes was achieved with easily accessible primary, secondary and
tertiary alkyl halides as the coupling partners and Zn-powder as reducing
agent. This process provides an efficient and convenient entry to gem-difluoroalkenes bearing various sensitive functional
groups under mild reaction conditions. Moreover, this method proves
to be suitable for late-stage functionalization of multifunctional
complex molecules.
Recently, transition-metal-catalyzed asymmetric dicarbofunctionalization of tethered alkenes has emerged as a powerful method for construction of chiral cyclic carbo-and heterocycles. However, all these reactions rely on facially selective arylmetalation of the pendant olefinic unit. Here, we successfully apply acylnickelation as the enantiodetermining step in the asymmetric nickel-catalyzed reductive carbo-acylation of aryl carbamic chloride-tethered alkenes with primary and secondary alkyl iodides as well as benzyl chlorides as the coupling partners, using manganese as a reducing agent. By circumventing the use of pre-generated organometallics, this reductive strategy enables the synthesis of diverse enantioenriched oxindoles bearing a quaternary stereogenic center under mild reaction conditions with high tolerance of a broad range of functional moieties.
By merging C−F and C−C bond activation in the crosselectrophile coupling, we developed an efficient cyanide-free synthesis of diverse functional-group-rich cyano-substituted gem-difluoroalkenes using cyclobutanone oxime esters and trifluoromethyl alkenes as precursors. Notably, this Ni-catalyzed reaction is bestowed with broad substrate scope, low catalyst loading, complete regioselectivities, and high tolerance of a wide range of sensitive functional groups. Preliminary mechanistic studies indicate that an iminyl radical-initiated C−C bond cleavage is involved in the reaction pathway.
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