Visible
light-promoted dearomative [2 + 2] cycloaddition of indole
derivatives tethered with olefins at the N1 position has been considered
thermodynamically unfeasible due to the high triplet excited-state
energies. We describe visible light-promoted [2 + 2] cycloaddition
with concomitant dearomatization of indole derivatives tethered with
olefins at the N1 position via the energy transfer process, providing
cyclobutane-fused polycyclic indoline derivatives that are potentially
useful in drug design and discovery. These cyclobutane-fused indoline-based
polycycles are obtained in high yields and with good diastereoselectivities
(>99:1). The key to the success of the reaction is the formation
of
H-bond(s) between N-alkenoylindole and solvent, enabling
the reduction of the triplet energy of the indole derivatives, which
greatly improved the efficiency of the protocol. The applicability
of the method is demonstrated by late-stage skeletal diversification
of indole-containing bioactive molecules, which provides a powerful
strategy for the rapid skeleton remodeling. DFT calculations were
used to give a deep understanding of the reaction pathways.
Photocatalytic deoxygenative carboimination of unstrained γ,δ‐unsaturated oximes with π‐acceptors including trifluoromethyl alkenes, 1‐trifluoromethyl‐1,3‐butadienes, gem‐difluoroalkenes, acrylates, and styrenes has been achieved which provides an efficient and mild approach to construct structurally diverse and highly functionalized pyrrolines with good functional group tolerance. Importantly, upon utilization of trifluoromethyl alkenes as the coupling partners, the developed protocol not only allows the introduction of the extremely valuable gem‐difluoroalkene functionality and pyrroline moiety into one molecule, but could also further transform the resulting gem‐difluoroalkene‐functionalized pyrrolines to the architecturally intriguing indolizine alkaloids via oxidation/reduction and sequential C−F bond cleavage. The mechanistic studies indicated that a free‐radical and anionic process was probably involved in this photocatalytic deoxygenative transformation.
A visible-light-induced method for the construction of heterocyclic scaffolds such as pyrido[1,2-a]indoles and indolizines via sulfonyl radical-triggered relay cyclization without employing any external photocatalyst has been developed. Preliminary mechanistic investigation indicated that indole and pyrrole derivatives could serve as pre-photocatalysts to promote the sulfonylation/cyclization, thereby providing a facile method to synthesize valuable sulfonylated heterocycles.
A new TEMPO-catalyzed
aminophosphinoylation of ethers with amines
and H-phosphine oxides was developed for the synthesis of α-aminophosphine
oxides. This metal-free aminophosphinoylation reaction could be conducted
under mild conditions through tandem C(sp3)–H and
C(sp3)–O bond cleavage. The present method offers
a facile and efficient approach to broad range of α-aminophosphine
oxide derivatives in moderate to good yields with excellent functional
group tolerance.
β-arylated ketones widely exist in many biologically active molecules and natural products. Herein, we disrcibled a photocatalytic redox-neutral arylation of cyclopropanols with cyanoarenes via radical-mediated C–C and C–CN bond cleavage...
The redox-sensitive functionalities such as aliphatic amines with low oxidation potential which could be easily oxidized by the photocatalysts, are generally not compatible in photocatalytic reactions. We describe the visible...
A new transition-metal-free PhI(OAc)2-promoted highly selective hydroboration of terminal alkynes with bis(pinacolato)diboron has been developed at room temperature under air.
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