Palladium-Catalyzed 1,2-Alkynylarylation of Vinyl Arenes with Haloalkynes and Arylboronic Acids.

We herein disclose a novel palladium-catalyzed 1,2-alkynylarylation of vinyl arenes using haloalkynes and arylboronic acids as coupling partners. This reaction is characterized by broad substrate scope, controllable reaction sequence, and excellent chemo- and regioselectivities. Mechanistic investigations suggest that the reaction is initiated by regioselective insertion of vinyl arenes into the alkynyl-Pd(II) species, and the silver salt is crucial for this transformation, serving as both the Lewis acid and halide scavenger. This protocol provides efficient access to new carbon skeletons, which are embedded in the key biologically active motifs.

Palladium-Catalyzed Tandem Cyclization of Bromoalkynes, Anilines and CO: Access to 1,3-Substituted Maleimides.

A novel palladium-catalyzed three-component carbonylation reaction for the assembly of various 1,3-substituted maleimide derivatives from haloalkynes and simple anilines. The nucleophilic addition reaction of haloalkynes, anilines and CO, and insertion of carbonyl have been achieved sequentially in this reaction. The high chemo- and regioselectivities, as well as no need of expensive ligands or additives further illustrate the synthetic value of this approach.

Palladium-Catalyzed Tandem Nucleophilic Addition/C-H Functionalization of Anilines and Bromoalkynes for the Synthesis of 2-Phenylindoles.

A novel and efficient palladium-catalyzed annulation of anilines with bromoalkynes for the synthesis of 2-phenylindoles has been described. This approach features excellent regio- and stereoselectivities and good functional group tolerance. Preliminary mechanistic studies indicate that anilines undergo anti-nucleophilic addition to bromoalkynes to generate (Z)-N-(2-bromo-1-phenylvinyl) anilines, followed by sequential C-H functionalization to deliver different substituted 2-phenylindoles. This method provides potential applications for the construction of various biologically active compounds.

Palladium-catalyzed acetalization/cyclization of enynones with alcohols: rapid access to functionalized dihaloalkenyl dihydrofurans.

Herein, we report a straightforward method to access alkenyl dihydrofurans via palladium-catalyzed acetalization/annulation from conjugated enynones and alcohols. The reaction undergoes a 5-exo-dig cyclization process, with the formation of four new chemical bonds including two carbon-halogen bonds on the exocyclic alkenyl moiety. Preliminary mechanistic studies suggest that the haloalkyne generated in situ should be involved in this transformation.

Palladium-Catalyzed Sequential Three-Component Cross-Coupling to 1,3-Dienes: Employing Alkenes as Hydride and Alkenyl Donors.

This report discloses a novel Pd-catalyzed sequential three-component multiple reaction of alkenes, bromoalkynes, and boronic acids using alkenes as hydride and alkenyl donors, leading to highly stereoselective assembly of (Z,E)-1,3-diene derivatives. Mechanistic studies demonstrate that the generation and reutilization of palladium hydride species are critical to the success of this transformation. In addition, the good functional group compatibility, late-stage modification, and investigation of photophysical properties of 1,3-diene products illustrate the synthetic value of this strategy.

Palladium-catalyzed oxidative C-H activation/annulation of N-alkylanilines with bromoalkynes: access to functionalized 3-bromoindoles.

A straightforward approach to the synthesis of 3-bromoindoles via palladium-catalyzed oxidative C-H activation/annulation of N-alkylanilines with bromoalkynes has been described. This protocol features high atom economy, excellent chemo- and regioselectivities, and good functional group tolerance. Moreover, the resultant 3-bromoindoles can be transformed to various functionalized indole derivatives, which demonstrates the practicability of this method in organic synthesis.

Palladium-catalyzed regioselective C-H alkynylation of indoles with haloalkynes: access to functionalized 7-alkynylindoles.

A palladium-catalyzed uniquely regioselective C-H alkynylation of indoles has been described. In this protocol, simple and readily available haloalkynes are employed as efficient alkynylating reagents, affording a series of functionalized 7-alkynylindoles in moderate to good yields. Moreover, further transformations of 7-alkynylated products were performed, which demonstrated the potential application of this method in organic synthesis.

Direct Assembly of Polysubstituted Propiolamidinates via Palladium-Catalyzed Multicomponent Reaction of Isocyanides.

A straightforward approach for the assembly of different polysubstituted propiolamidnates via palladium-catalyzed multicomponent reaction of isocyanides, haloalkynes, and amines has been reported in which the C(sp)-C(sp2) and C(sp2)═N bonds were constructed in one pot. This reaction featured in high efficiency, excellent chemoselectivity, and good functional group compatibility. The synthetic utility of this method was also demonstrated.

Palladium-Catalyzed Cyclization of N-Acyl- o-alkynylanilines with Isocyanides Involving a 1,3-Acyl Migration: Rapid Access to Functionalized 2-Aminoquinolines.

A simple and expedient approach for the synthesis of functionalized 2-aminoquinolines via palladium-catalyzed annulation of N-acyl- o-alkynylanilines with isocyanides has been developed with high atom economy, in which an unconventional 6- endo-dig cyclization process is observed. Further investigations of the mechanism demonstrated that an intramolecular acyl migration of the N-protecting groups was involved in this transformation.