A new chiral Brønsted acid, generated in situ from a chiral phosphoric acid boron (CPAB) complex and water, was successfully applied to asymmetric indole reduction. This “designer acid catalyst”, which is more acidic than TsOH as suggested by DFT calculations, allows the unprecedented direct asymmetric reduction of C2‐aryl‐substituted N‐unprotected indoles and features good to excellent enantioselectivities with broad functional group tolerance. DFT calculations and mechanistic experiments indicates that this reaction undergoes C3‐protonation and hydride‐transfer processes. Besides, bulky C2‐alkyl‐substituted N‐unprotected indoles are also suitable for this system.
An oxidant-controlled divergent reactivity of 3-aminoindazoles is presented, which enables the [3 + 3] annulation and C–H arylation of ketene dithioacetals in disparate pathways to assemble pyrimido[1,2-b]-indazoles and aromatic nitrile-derived dithioacetals.
The transition-metal-catalyzed allylation
reaction is an efficient
strategy for the construction of new carbon–carbon bonds alongside
allyl or homoallylic functionalization. Herein we describe a Ni-catalyzed
reductive allylation of α-chloroboronates to efficiently render
the corresponding homoallylic boronates, which could be readily converted
into valuable homoallylic alcohols or amines or 1,4-diboronates. This
reaction features a broad substrate scope with good functional group
compatibility that is complementary to the existing methods for the
preparation of homoallylic boronates.
gem-Difluoroalkenyl boronates are attractive synthons
for constructing diverse gem-difluoroalkenes and
organoboron compounds. However, the strategies for the construction
of gem-difluorohomoallyl boronates has scarcely been
described. Herein, we develop an efficient protocol for the construction
of gem-difluorohomoallylic boronates through a Ni-catalyzed
radical-promoted defluoroalkylborylation of α-trifluoromethyl
alkenes with α-haloboronates under mild conditions. This reaction
features a broad substrate scope with good functional group tolerance
and diverse transformations.
We
disclose a novel Cu-catalyzed denitrogenative transannulation
of 3-aminoindazoles to afford diverse functionalized 3-aminobenzothiophenes
and 1-aminoisoquinolines, in which denitrogenative transannulation
of 3-aminoindazoles is reported for the first time. This transformation
proceeds via an “extrude-and-sew” strategy with an unprecedented
radical reactivity of 3-aminoindazoles.
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