Copper-Catalyzed Annulation Cascades of Alkyne-Tethered α-Bromocarbonyls with Alkynes: An Access to Heteropolycycles

Copper-Catalyzed Bifunctionalization/Annulation of Unactivated Alkene with Alkyl Bromides

β-Lactam is a ubiquitous scaffold in bioactive compounds and pharmaceuticals. Herein, we disclose a streamlined method for the construction of β-lactams starting from unactivated alkenes and alkyl bromides via a Cu-catalyzed inter-/intramolecular carboamidation. This reaction proceeded smoothly under mild reaction conditions and exhibited a broad substrate scope and various functional groups. This protocol is not only compatible with 1, 2, and 3° alkyl bromides but also suitable for α-bromo nitrile as well as various benzyl bromides. The mechanism exploration indicated that sequential radical addition/reductive elimination was involved.

Photoredox and Copper Dual-Catalyzed Cyclization of Alkyne-tethered α-Bromocarbonyls

The synergistic systems of photoredox and copper catalyst have already appeared as a novel formation of green synthetic chemistry, which open new avenues for chemical synthesis applications. We describe a novel strategy for the cyclization of alkyne-tethered α-bromocarbonyls initiated by the cleavage of C(sp3 )-Br bond via the collaboration of photoredox and copper catalyst. The present protocol exhibits mildness using economical copper catalyst and visible-light at room temperature. The gram-scale and sunlight irradiation experiments proceeded smoothly to show the practicality of the methodology. It is notable that the newly generated oxygen in the product originates from H2 O.

Expeditious Access to Spiro-Fused 2,5-Cyclohexadienones via Thio(seleno)cyanative ipso-Cyclization

A facile oxidative dearomatization of N-(p-methoxyaryl)propiolamides has been established for the synthesis of spiro-fused 2,5-cyclohexadienone frameworks via thio(seleno)cyanative ipso-cyclization in the presence of ceric ammonium nitrate (CAN) as the oxidant. The present method, involving the formation of C-S and C-C bonds, was also extended to (p-methoxyaryl)propiolates for thiocyanative ipso-cyclization. Furthermore, the obtained chalcogeno-spirocyclohexadienones were transformed into uniquely functionalized spirocyclohexadienone derivatives.

Controlling alkyne reactivity by means of a copper-catalyzed radical reaction system for the synthesis of functionalized quaternary carbons

A terminal alkyne is one of the most useful reactants for the synthesis of alkyne and alkene derivatives. Because an alkyne undergoes addition reaction at a C-C triple bond or cross-coupling at a terminal C-H bond. Combining those reaction patterns could realize a new reaction methodology to synthesize complex molecules including C-C multiple bonds. In this report, we found that the reaction of 3 equivalents of terminal alkyne 1 (aryl substituted alkyne) and an α-bromocarbonyl compound 2 (tertiary alkyl radical precursor) undergoes tandem alkyl radical addition/Sonogashira coupling to produce 1,3-enyne compound 3 possessing a quaternary carbon in the presence of a copper catalyst. Moreover, the reaction of α-bromocarbonyl compound 2 and an alkyne 4 possessing a carboxamide moiety undergoes tandem alkyl radical addition/C-H coupling to produce indolinone derivative 5.

The Fascinating Chemistry of α-Haloamides

The aim of this review is to highlight the rich chemistry of α-haloamides originally mainly used to discover new C-N, C-O and C-S bond forming reactions, and later widely employed in C-C cross-coupling reactions with C(sp3), C(sp2) and C(sp) coupling partners. Radical-mediated transformations of α-haloamides bearing a suitable located unsaturated bond has proven to be a straightforward alternative to access diverse cyclic compounds by means of either radical initiators, transition metal redox catalysis or visible light photoredox catalysis. On the other hand, cycloadditions with α-halohydroxamate-based azaoxyallyl cations have garnered significant attention. Moreover, in view of the important role in life and materials science of difluoroalkylated compounds, a wide range of catalysts has been developed for the efficient incorporation of difluoroacetamido moieties into activated as well as unactivated substrates.

Palladium-catalyzed cascade carboesterification of norbornene with alkynes

An efficient and convenient palladium-catalyzed cascade carboesterification of norbornenes (NBE) with alkynes has been accomplished to afford functionalized α-methylene γ-lactone and tetrahydrofuran derivatives in good to excellent yields. This new strategy exhibits excellent atom- and step-economy, good functional group tolerance and broad substrate scope. In particular, NBE-palladium species was proposed to be the key intermediate in the catalytic cycle to suppress the β-H elimination process. Notably, the developed protocol provides a straightforward and practical tool for the construction of diverse oxygen-containing heterocycle frameworks, illustrating a promising application in synthetic and pharmaceutical chemistry.

Cu-Catalyzed atom transfer radical addition reactions of alkenes with α-bromoacetonitrile

A practical, simple, and efficient copper-catalyzed atom transfer radical addition reaction of alkenes with α-bromoacetonitrile is realized. With this methodology, various γ-bromonitriles and β,γ-unsaturated nitriles were efficiently constructed.

Cascade Annulation of 2-Alkynylthioanisoles with Unsaturated α-Bromocarbonyls Leading to Thio-Benzobicyclic Skeletons

A protocol of Cu-catalyzed annulation of phenylethynylsulfanes with unsaturated α-bromocarbonyls for the construction of thio-benzobicyclic skeletons is described. In this single reaction, three new bonds and two new rings can be established, highlighting the step-economics and high efficiency of this protocol.

Visible-light photocatalytic bicyclization of β-alkynyl propenones for accessing diastereoenriched syn-fluoren-9-ones

A novel visible-light photocatalytic bicyclization of β-alkynyl propenones with α-bromocarbonyls for highly diastereoselective synthesis of richly decorated syn-fluoren-9-ones is described. The reaction proceeds via a radical-triggered 5-exo-dig cyclization/1,6-H-abstraction/6-endo-trig cyclization cascade and offers a new and practical method for the assembly of 6/5/6 carbocyclic skeletons via C(sp3)-H alkenylation.