Liangbin Huang

Copper‐Catalyzed Coupling of Oxime Acetates with Sodium Sulfinates: An Efficient Synthesis of Sulfone Derivatives

Sulfone derivatives are important synthetic intermediates. However, the general method for their preparation is through traditional coupling reaction: the alkylation of sodium sulfinates with phenacyl halides. Based on our previous work on sodium sulfinates and oxime acetates, we herein report a novel method for sulfone derivatives by oxidative coupling with sodium sulfinates and oxime acetates using copper as catalyst. The sulfonylvinylamine products could be formed in excellent yields. Upon hydrolysis by silica gel in CH2 Cl2 , β-ketosulfones could also be efficiently constructed. Various sulfonylvinylamines and β-ketosulfones were obtained in good to excellent yields under the optimized reaction conditions. Mechanistic studies indicated that this transformation involved copper-catalyzed N-O bond cleavage, activation of a vinyl sp(2) C-H bond, and C-S bond formation. The oxime acetates act as both a substrate and an oxidant, thus the reaction needs no additional oxidants or additives.

One-Pot Silver-Catalyzed and PIDA-Mediated Sequential Reactions: Synthesis of Polysubstituted Pyrroles Directly from Alkynoates and Amines

The addition/oxidative cyclization of alkynes with amines in the presence of AgBF(4) catalyst and PIDA oxidant leads to polysubstituted pyrroles. The reaction corresponds to the construction of a pyrrole fragment, which also provides a new way to the formation of C-C bonds.

Copper-catalyzed aerobic oxidation and cleavage/formation of C–S bond: a novel synthesis of aryl methyl sulfones from aryl halides and DMSO

With atmospheric oxygen as the oxidant, a novel copper(I)-catalyzed synthesis of aryl methyl sulfones from aryl halides and widely available DMSO is described. The procedure tolerates aryl halides with various functional groups (such as methoxy, acetyl, chloro, fluoro and nitro groups), which could afford aryl methyl sulfones in moderate to high yields. The copper-catalyzed aerobic oxidation and the cleavage/formation of C-S bond are the key steps for this transformation.

Copper-catalyzed formal C-N bond cleavage of aromatic methylamines: assembly of pyridine derivatives.

An efficient copper-catalyzed C-N bond cleavage of aromatic methylamines was developed to construct pyridine derivatives. With neat conditions and facile operation, the fragment-assembling strategy affords a broad range of 2,4,6-trisubstituted pyridines in up to 95% yield from simple and readily available starting materials. Interestingly, when pyridin-2-yl methylamine was employed as the substrate, α-alkylation reaction of ketones readily occurred to give β-(pyridin-2-yl) ketones instead of the 2,4,6-trisubstituted pyridines.

Facile synthesis of benzofurans via copper-catalyzed aerobic oxidative cyclization of phenols and alkynes

Regioselective synthesis of polysubstituted benzofurans using a copper catalyst and molecular oxygen from phenols and alkynes in a one-pot procedure has been reported. The transformation consists of a sequential nucleophilic addition of phenols to alkynes and oxidative cyclization. A wide variety of phenols and alkynes can be used in the same manner.

Copper-catalyzed oxidative [2 + 2 + 1] cycloaddition: regioselective synthesis of 1,3-oxazoles from internal alkynes and nitriles

A robust and regioselective copper(II)-catalyzed cycloaddition of internal alkynes and nitriles providing an effective access to oxazole fragments is reported herein. Water substantially participated in this reaction. Control experiments proposed that this transformation may proceed via an enamide intermediate. This strategy enables the preparation of the core structure of a COX-2 inhibitor.

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.

Rh(III)-catalyzed ortho-oxidative alkylation of unactivated arenes with allylic alcohols

Versatile directed aromatic C–H bond activation and oxidative coupling with allylic alcohols is reported using a cationic Rh(III) catalyst. This method provides efficient and robust synthesis of functional β-aryl ketones and indolines in good yields with excellent regioselectivity, even the reaction runs at 3 g scale. The catalytic systems have good functional group tolerance, such as CONR2, NHAc, NO2, CF3, CN, Cl, Br and I.

Pd(II)-catalyzed sequential C-C/C-O bond formations: a new strategy to construct trisubstituted furans.

Palladium-catalyzed oxidative difunctionalization of enol ethers with 1,3-dicarbonyl compounds to construct trisubstituted furans in one step under mild conditions is described. The reaction is thought to proceed through a C-C bond formation along with a C-O bond closing the ring structure. Oxygen is the sole oxidant regenerating the Pd(II) catalyst.

Carbon Dioxide Triggered and Copper-Catalyzed Domino Reaction: Efficient Construction of Highly Substituted 3(2H)-Furanones from Nitriles and Propargylic Alcohols

A novel carbon dioxide triggered and copper-catalyzed domino reaction for the efficient synthesis of highly substituted 3(2H)-furanones from readily available nitriles and propargylic alcohols has been developed. Carbon dioxide is a prerequisite for achieving the present catalytic transformation, and one of the oxygen atoms of carbon dioxide is incorporated into the 3(2H)-furanones. Nitriles not only act as the reaction solvent but also as the reactant; copper salts play dual roles of activating both the propargylic alcohols and nitriles.