Arylation of Terminal Alkynes: Transition-Metal-Free Sonogashira-Type Coupling for the Construction of C(sp)–C(sp²) Bonds

Abstract

Alkynes are attractive synthons for organic chemistry. Despite the prevalence of transition-metal-catalyzed Sonogashira reactions, a transition-metal-free version of the arylation of terminal alkynes is elusive. Herein, we report an efficient transition-metal-free Sonogashira-type coupling reaction for the one-pot arylation of alkynes to construct C(sp)−C(sp 2 ) bonds from a tetracoordinate boron intermediate with NIS as a mediator. With its high efficiency, wide substrate range, and good functional group tolerance, this method is further supported by the gram-scale synthesis and subsequent modification of complex molecules.

LiBF4-Promoted Aromatic Fluorodetriazenation under Mild Conditions

“…1-Fluoro-4-(phenylethynyl)benzene (3za). 30 Following general procedure A and purification by flash chromatography (silica gel, from 100:0 to 90:10 petroleum ether/ethyl acetate), compound 3za was obtained as a white solid (64 mg, 0.33 mmol, 65% Ethyl (E)-3-(4-Fluorophenyl)acrylate (3zb). 12 Following general procedure A and purification by flash chromatography (silica gel, from 100:0 to 90:10 petroleum ether/ethyl acetate), compound 3zb was obtained as a light yellow oil (76 mg, 0.39 mmol, 78%).…”

Cross‐Coupling Between Aryl Halides and Aryl Alkynes Catalyzed by an Odd Alternant Hydrocarbon

“…[25] Though not catalytically, a handful of C(sp)À C(sp 2 ) cross-couplings have been explored in several transition metal-free stoichiometric methods earlier. [26][27][28][29][30] In this context, accomplishing catalytic C(sp)À C(sp 2 ) cross-coupling between aryl halides and alkynes in the absence of any external stimulation (such as light, heat, microwave, cathodic current etc.) at room temperature without the aid of any transition metal is considered very challenging to address.…”

“…Furthermore, several heterogeneous transition metal‐based catalytic procedures [21,22] have also been explored for this cross‐coupling reaction which generally operates at higher temperatures or under microwave [23,24] /photostimulation [25] . Though not catalytically, a handful of C(sp)−C(sp 2 ) cross‐couplings have been explored in several transition metal‐free stoichiometric methods earlier [26–30] . In this context, accomplishing catalytic C(sp)−C(sp 2 ) cross‐coupling between aryl halides and alkynes in the absence of any external stimulation (such as light, heat, microwave, cathodic current etc.)…”

1,1-Oxycarbonation of Terminal Alkynes via Sequential Borylation, 1,2-Migration, and Oxidation with Oxone

“…Considering the ease of preparation of tetramethylammonium alkynyl tetracoordinate boron from terminal alkynes and its bench stability, as well as our continued interest in the transformations of this class of compounds, a model reaction of alkynyl tetracoordinate boron 1a with Oxone was performed. After a series of reaction conditions were screened, ketone product 2a was obtained in 91% GC yield using a 3:1 acetone/H 2 O mixed solvent (Table , entry 1).…”