Copper(I)-Catalyzed Heterocyclization of α-Acyl-α-alkynyl Ketene Dithioacetals: Synthesis of 3-Cyanofurans

Divergent copper-catalyzed syntheses of 3-carboxylpyrroles and 3-cyanofurans from O-acetyl oximes and β-ketoesters/nitriles

The reaction between O-acetyl oximes and β-ketoesters/nitriles catalyzed by copper generated polysubstituted pyrroles and furans, respectively, under redox–neutral reaction conditions. Using this protocol, pyrroles or furans could be obtained simply by choosing an appropriate active methylene compound. Although both transformations occur essentially under the same reaction conditions, control experiments indicated that they follow different mechanistic pathways.

A copper-catalyzed heteroannulation of O-acetyl oximes and β-ketoesters/nitriles to afford polysubstituted pyrroles and furans was successfully achieved.

Indium-Catalysed Transfer Hydrogenation for the Reductive Cyclisation of 2-Alkynyl Enones towards Trisubstituted Furans

Indium tribromide catalysed the transfer hydrogenation from dihydroaromatic compounds, such as the commercially available γ-terpinene, to enones, which resulted in the cyclisation to trisubstituted furan derivatives. The reaction was initiated by a Michael addition of a hydride nucleophile to the enone subunit followed by a Lewis-acid-assisted cyclisation and the formation of a furan-indium intermediate and a Wheland intermediate derived from the dihydroaromatic starting material. The product was formed by protonation from the Wheland complex and replaced the indium tribromide substituent. In addition, a site-specific deuterium labelling of the dihydroaromatic HD surrogates resulted in site specific labelling of the products and gave useful insights into the reaction mechanism by H-D scrambling.

Sulfur-containing polymers from terpolymerization of active methylene compounds, carbon disulfide, and dihalohydrocarbons: synthesis and properties

Sulfur-containing polymers with a high refractive index were synthesized via terpolymerization of active methylene compounds, CS₂, and dihalohydrocarbons in excellent yields with high molecular weights.

Zinc-catalyzed regioselective C–P coupling of p-quinol ethers with secondary phosphine oxides to afford 2-phosphinylphenols

A highly regioselective C–P coupling reaction of p-quinol ethers with secondary phosphine oxides is developed as a new synthesis method for 2-phosphinylphenols by using Zn(OTf)₂ as the catalyst.

Insights into the mechanisms of Cu(i)-catalyzed heterocyclization of α-acyl-α-alkynyl ketene dithioacetals to form 3-cyanofurans: the roles of NH4OAc

NH₄OAc is decomposed into NH₃ and HOAc, and both NH₃ and HOAc as the proton shuttle can prompt catalytic reactions.

C6′ steric bulk of cinchona alkaloid enables an enantioselective Michael addition/annulation sequence toward pyranopyrazoles

A C6′ silyloxyl quinine catalyzed asymmetric Michael addition/annulation cascade between pyrazolones and enynones was developed.

Facile synthesis of cyanofurans via Michael-addition/cyclization of ene–yne–ketones with trimethylsilyl cyanide

Carbene migratory insertion? No! Ene–yne–ketones were utilized as a Michael-addition acceptor to react with TMSCN, affording a series of cyanofurans.

Triflic acid promoted solvent free synthesis of densely functionalized furans

A simple, efficient and novel methodology has been developed for the synthesis of substituted furans mediated by triflic acid. In the reaction initial step involves the Friedel–Crafts arylation, followed by the dehydrative cyclization.