Jianxiao Li

Palladium-catalyzed cascade annulation to construct functionalized β- and γ-lactones in ionic liquids.

A highly efficient and mild palladium-catalyzed, one-pot, four-step cascade annulation has been developed to afford functionalized β- and γ-lactones in moderate to good yields with high regio- and diastereoselectivities in ionic liquids. The employment of ionic liquids under mild reaction conditions makes this transformation green and practical. Especially, this reaction provided a novel and convenient methodology for the construction of naturally occurring biologically active β- and γ-lactones.

Cu-Catalyzed Three-Component Cascade Annulation Reaction: An Entry to Functionalized Pyridines.

A concise copper-catalyzed N-O bond cleavage/C-C/C-N bond formation procedure has been described for the synthesis of multisubstituted pyridines. Various oxime acetates, activated methylene compounds, and a wide range of aldehydes bearing aryl, heteroaryl, vinyl, and trifluoromethyl groups were employed to provide the tri- or tetrasubstituted pyridines with flexible substitution patterns. Moreover, this method features inexpensive catalysts, no need for extra oxidant, and high step-enconomy, which make it pratical and attractive.

Palladium-Catalyzed Oxidative Sulfenylation of Indoles and Related Electron-Rich Heteroarenes with Aryl Boronic Acids and Elemental Sulfur

An efficient and convenient palladium-catalyzed C-H bond oxidative sulfenylation of indoles and related electron-rich heteroarenes with aryl boronic acids and elemental sulfur has been described. This procedure provides a useful and direct approach for the assembly of a wide range of structurally diverse 3-sulfenylheteroarenes with moderate to excellent yields from simple and readily available starting materials. Moreover, this synthetic protocol is suitable for N-protected and unprotected indoles. Notably, the construction of two C-S bonds in one step was also achieved in this transformation.

Palladium-catalyzed intermolecular oxyvinylcyclization of alkenes with alkynes: an approach to 3-methylene γ-lactones and tetrahydrofurans.

A novel chloropalladation-initiated intermolecular oxyvinylcyclization of alkenes with alkynoic acids or alkynols is developed. This protocol provides a series of 3-methylene γ-lactone and tetrahydrofuran derivatives in moderate to excellent yields with high stereoselectivities in the presence of PdCl2 and CuCl2 or CuCl2·2H2O. Besides a broad substrate scope, this method has the advantages of mild reaction conditions and easily accessible starting materials. Furthermore, the construction of C-Cl, C(sp(2))-C(sp(3)), and C-O bonds in one step was also achieved in this transformation.

Assembly of 3-Sulfenylbenzofurans and 3-Sulfenylindoles by Palladium-Catalyzed Cascade Annulation/Arylthiolation Reaction.

A novel and efficient palladium-catalyzed cascade annulation/arylthiolation reaction has been developed to afford functionalized 3-sulfenylbenzofuran and 3-sulfenylindole derivatives in moderate to good yields from readily available 2-alkynylphenols and 2-alkynylamines in ionic liquids. This protocol provides a valuable synthetic tool for the assembly of a wide range of 3-sulfenylbenzofuran and 3-sulfenylindole derivatives with high atom- and step-economy and exceptional functional group tolerance. Moreover, the employment of ionic liquids under mild reaction conditions makes this transformation green and practical. Furthermore, this approach enriched current C-S bond formation chemistry, making a valuable and practical method in synthetic and medicinal chemistry.

Palladium-Catalyzed Intermolecular Aerobic Annulation of o-Alkenylanilines and Alkynes for Quinoline Synthesis

A new approach to construct 2,3-disubstituted quinolines is described via Pd-catalyzed oxidative cyclization of o-vinylanilines and alkynes with molecular oxygen. This transformation is supposed to undergo intermolecular amination of alkyne, insertion of the olefin, and oxidative cleavage of C-C bond sequence.

Palladium-Catalyzed Tandem Annulation: A Strategy To Construct 2,3-Difunctionalized Benzofuran Derivatives in Ionic Liquids

An efficient and ecofriendly method for the construction of 2,3-difunctionalized benzofuran derivatives in moderate to good yields from readily available 2-alkynylphenols has been developed. This tandem annulation process, featuring one pot, three steps, good functional group tolerance, and high atom economy, makes this transformation efficient and practical. Moreover, this protocol is scalable, illustrating its potential applications in synthetic and pharmaceutical chemistry.

Palladium-catalyzed coupling of alkynes with unactivated alkenes in ionic liquids: a regio- and stereoselective synthesis of functionalized 1,6-dienes and their analogues.

A palladium-catalyzed regio- and stereoselective intermolecular tandem reaction of alkynes and unactivated 1,6-enols in ionic liquids is described, providing a practical, efficient, and versatile method for the synthesis of functionalized 1,6-dienes in moderate to good yields. The present reaction has high functional-group tolerance and gives products on a gram scale. Mechanistic studies indicate that the reaction might proceed via a chain-walking mechanism.

Iron-Catalyzed Synthesis of 2H-Imidazoles from Oxime Acetates and Vinyl Azides under Redox-Neutral Conditions

A novel and versatile method for the synthesis of 2H-imidazoles via iron-catalyzed [3 + 2] annulation from readily available oxime acetates with vinyl azides has been developed. This denitrogenative process involved N-O/N-N bond cleavages and two C-N bond formations to furnish 2,4-substituted 2H-imidazoles. This protocol was performed under mild reaction conditions and needed no additives or ligands. Furthermore, this is a green reaction involving oxime acetate as internal oxidant, acetic acid, and nitrogen as byproducts.

Highly efficient and practical synthesis of functionalized 1,5-dienes via Pd(II)-catalyzed halohomoallylation of alkynes

A Pd-catalyzed coupling of alkynes with homoallyl alcohols in ionic liquids has been reported, providing a practical, efficient, and versatile method for the synthesis of functionalized (1E)- or (1Z)-1,5-dienes in moderate to good yields. This reaction represents a rare instance of direct homoallylation of homoallyl alcohols.