Xihe Bi

Chemoselective Oxidative C(CO)C(methyl) Bond Cleavage of Methyl Ketones to Aldehydes Catalyzed by CuI with Molecular Oxygen

Aldehyde Termination: A novel copper-catalyzed transformation from methyl ketones into aldehydes has been accomplished. This method is applicable to a wide range of aromatic and aliphatic methyl ketones and chemoselectively produces aldehydes, accompanied by the release of hydrogen (H2 ) and carbon dioxide (CO2 ) as by-products.

Silver(I)-Catalyzed Hydroazidation of Ethynyl Carbinols: Synthesis of 2-Azidoallyl Alcohols†

The hydroazidation of alkynes is the most straightforward pathway to synthetically useful vinyl azides. However, a general hydroazidation of alkynes remains elusive. Herein, a chemo- and regioselective transformation of ethynyl carbinols into vinyl azides is described. This reaction produces a wide variety of 2-azidoallyl alcohols with high efficiency and in good to excellent yields. These compounds constitute a new class of densely functionalized synthetic intermediates. Their synthetic potential has been demonstrated by further transformations into NH aziridines. The mechanistic aspects of the reaction will attract the attention of chemists working on alkyne chemistry and silver catalysis. The findings that are described in this paper represent significant advances in the regioselective hydroelementation of alkynes and open a new reaction manifold for exploitation.

Silver-Catalyzed Cross-Coupling of Propargylic Alcohols with Isocyanides: An Atom-Economical Synthesis of 2,3-Allenamides

Cross-coupling reactions between propargylic alcohols and isocyanides, by means of silver catalysis, have been described. This new reaction is both atom and step efficient and is applicable to a broad scope of substrates, allowing the synthesis of a range of synthetically valuable 2,3-allenamides in moderate to excellent yields.

Silver‐Catalyzed Cross‐Coupling of Isocyanides and Active Methylene Compounds by a Radical Process

Isocyanides are versatile building blocks, and have been extensively exploited in C-H functionalization reactions. However, transition-metal-catalyzed direct C-H functionalization reactions with isocyanides suffer from over-insertion of isocyanides. Reported herein is a radical coupling/isomerization strategy for the cross-coupling of isocyanides with active methylene compounds through silver-catalysis. The method solves the over-insertion issue and affords a variety of otherwise difficult to synthesize β-aminoenones and tricarbonylmethanes under base- and ligand-free conditions. This report presents a new fundamental C-C bond-forming reaction of two basic chemicals.

[3+2] Cycloaddition of Propargylic Alcohols and α-Oxo Ketene Dithioacetals: Synthesis of Functionalized Cyclopentadienes and Further Application in a Diels–Alder Reaction†

Cyclopentadienes are valuable intermediates in organic synthesis and also ubiquitous as the Cp ligands in organometallic chemistry. As part of ongoing efforts to develop novel organic reactions that employ functionalized alkynes, a [3+2] cycloaddition of propargylic alcohols and ketene dithioacetals has been developed, which leads to fully substituted 2,5-dialkylthio cyclopentadienes in good to excellent yields. In an unusual dethiolating Diels-Alder reaction, the cyclopentadienes were further reacted with maleimides to afford a family of novel fluorescent polycyclic compounds.

Silver‐Catalyzed Stereoselective Aminosulfonylation of Alkynes

Abstract A silver‐catalyzed intermolecular aminosulfonylation of terminal alkynes with sodium sulfinates and TMSN3 is reported. This three‐component reaction proceeds through sequential hydroazidation of the terminal alkyne and addition of a sulfonyl radical to the resultant vinyl azide. The method enables the stereoselective synthesis of a wide range of β‐sulfonyl enamines without electron‐withdrawing groups on the nitrogen atom. These enamines are found to be suitable for a variety of further transformations.

Synthesis of 4-Ynamides and Cyclization by the Vilsmeier Reagent to Dihydrofuran-2(3H)-ones.

The room-temperature nucleophilic addition of vinyl azides to propargylic alcohols under BF3·Et2O catalysis provides an efficient synthesis of 4-ynamides. The procedure is operationally convenient, shows broad substrate scope, and is viable for the synthesis of multifunctional 4-ynamides. Further, a Vilsmeier intramolecular cyclization of 4-ynamides into dihydrofuran-2(3H)-ones has also been discovered, which represents the first report of alkynes being used as the nucleophiles in Vilsmeier-type reactions.

Silver-Catalyzed Tandem C≡C Bond Hydroazidation/Radical Addition/Cyclization of Biphenyl Acetylene: One-Pot Synthesis of 6-Methyl Sulfonylated Phenanthridines

A silver-catalyzed tandem carbon-carbon triple bond hydroazidation, radical addition, and cyclization of biphenyl acetylene is described under mild conditions, leading to the formation of 6-methyl sulfonylated phenanthridines in good yields. In this novel cascade reaction, most of the atoms are incorporated into the product without cleavage of the C≡C bond. Mechanistic studies suggest the reaction should proceed through an iminyl radical reactive intermediate.

Silver-Catalyzed [2+1] Cyclopropenation of Alkynes with Unstable Diazoalkanes: N-Nosylhydrazones as Room-Temperature Decomposable Diazo Surrogates

The [2+1] cycloaddition of alkynes with diazo compounds represents one of the most powerful and reliable methods for the construction of cyclopropenes. However, it remains a formidable challenge to accomplish the cyclopropenation of alkynes with non-stabilized diazoalkanes, owing to the fact that such compounds are unstable and prone to detonation. Herein, we report a general silver-catalyzed cyclopropenation reaction of alkynes with unstable diazoalkanes, by for the first time the discovery and application of N-nosylhydrazones as room-temperature decomposiable diazo surrogates. This method allows for the efficient assembly a wide variety of cyclopropene derivatives that are otherwise difficult to access by conventional methods.

Silver-Catalyzed Isocyanide–Isocyanide [3+2] Cross-Cycloaddition Involving 1,2-Group Migration: Efficient Synthesis of Trisubstituted lmidazoles

Imidazole ring is an important five-membered aromatic heterocycle that is widely present in natural products and synthetic molecules. The isocyanide-isocyanide [3+2] cross-cycloaddition reaction constitutes a straightforward method to access imidazoles starting from the easily available chemicals. So far, only three successive reports are known and all lead to the formation of 1,4-disubstituted imidazoles. Here, we report the first isocyanide-isocyanide [3+2] cross-cycloaddition reaction allowing for the formation of 1,4,5-trisubstituted imidazoles under silver catalysis. An unexpected 1,2-migration of sulfonyl, alkoxycaybonyl, and carbamoyl groups took place during the cyclization process that is responsible for the formation of trisubstituted imidazoles. This report displayed a mechanistically novel synthetic method toward a variety of imidazole derivatives, which are otherwise difficult to access by conventional methods.