Pd-catalyzed alkynylation of 2-chloroacetates and 2-chloroacetamides with potassium alkynyltrifluoroborates

Broadly Applicable Ion Pair-Assisted Nucleophilic Substitution of sp3-Carbon Electrophiles with Alkynyltrifluoroborates

Alkynyltrifluoroborate nucleophiles react smoothly with a wide range of sp³-carbon electrophiles, including propargyl methanesulfonates and unactivated alkyl triflates, to give Sonogashira-type products, via a novel ion pair-assisted nucleophilic substitution mechanism. An ion pair-organic complex, investigated using computational chemistry and in situ NMR experiments, may play a crucial role in this reaction.

Visible-Light-Driven α-Aminoalkyl Radical-Mediated C(sp3)-C(sp) Cross-Coupling of Iodoalkanes and Alkynyl Bromides

We herein report a simple protocol for metal-free cross-coupling between unactivated alkyl iodides and terminal alkynyl bromides promoted by visible light. The salient features of this transformation are the utilization of an organic photocatalyst and commercially available tri-n-butylamine as a reductant. This protocol couples a variety of unactivated iodoalkanes containing different functional groups and with a variety of terminal alkynyl bromides under mild reaction conditions to afford the substituted alkynes in good yields.

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 reductive cross-coupling between α-bromo carboxamides and terminal alkynes

A Pd-catalyzed reductive cross-coupling between α-bromo carboxamides and terminal alkynes was developed featuring a radical pathway and distinct from the Sonogashira coupling.

Palladium-Catalyzed Decarboxylative Alkynylation of α-Acyloxyketones by C(sp3 )-O Bond Cleavage

Palladium-catalyzed decarboxylative alkynylation of α-acyloxyketones triggered by C(sp³ )-O bond cleavage is disclosed. The decarboxylation strategy featuring a neutral reaction condition enabled an unprecedent catalytic alkynylation of a ketone enolate. The reaction was applied to a variety of substrates, giving desired products in good yields. We successfully obtained X-ray crystallography of a new palladium-enolate intermediate that was synthesized by a reaction of [Pd(cod)(CH₂ TMS)₂ ] with XPhos and α-acyloxyketone at room temperature, indicating facile C(sp³ )-O bond disconnection.

Visible light promoted coupling of alkynyl bromides and Hantzsch esters for the synthesis of internal alkynes

A metal-free visible light promoted C(sp3)-C(sp) coupling reaction of alkynyl bromides and Hantzsch esters was developed, giving internal alkynes with primary, secondary, tertiary alkyl or other functional groups in good to high yields.

Electrophilic alkynylation of ketones using hypervalent iodine

The efficient electrophilic alkynylation of ketones can be performed using hypervalent iodine compounds. This protocol was applied for an aldehyde.