Silver oxide(I) promoted Conia-ene/radical cyclization for a straightforward access to furan derivatives

Highly Regio- and Diastereoselective Synthesis of 6,7-Dihydro-4H-furo[3,4-c]pyran Derivatives through Pd-Catalyzed Formal (3 + 3) Allylic Cycloaddition of 2-Butene-1,4-diols with 2-(1-Alkynyl)-2-alken-1-ones

A highly efficient synthesis of 7-vinyl-6,7-dihydro-4H-furo[3,4-c]pyran derivatives from 2-butene-1,4-diols and 2-(1-alkynyl)-2-alken-1-ones has been achieved with high regio- and diastereoselectivity (dr > 20:1) by Pd-catalyzed tandem heterocyclization/cross-coupling. The π-allyl palladium species Int II generated from 2-butene-1,4-diol by direct cleavage of the C-OH bond is the key to the success in this formal (3 + 3) cycloaddition reaction.

Electrocatalysis-Enabled Defluorinative Cross-Coupling of gem-Difluoroalkenes with Aldehydes and Ketones

An electrochemical defluorinative cross-coupling of gem-difluoroalkenes with carbonyl compounds was described, by which highly stereoselective monofluoroalkene allyl alcohols were synthesized. The reaction tolerates a broad range of functional groups and has successfully been applied to synthesize complex molecules. Mechanistic studies indicate that the reaction starts from electron reduction of gem-difluoroalkenes to generate radical negative ions, which undergo β-fluoride elimination and subsequent reduction to form anions. These anions are subsequently trapped by carbonyl compounds to furnish target products.

Regiocontrol via Electronics: Insights into a Ru-Catalyzed, Cu-Mediated Site-Selective Alkylation of Isoquinolones via a C-C Bond Activation of Cyclopropanols

A site-selective C(3)/C(4)-alkylation of N-pyridylisoquinolones is achieved by employing C-C bond activation of cyclopropanols under Ru(II)-catalyzed/Cu(II)-mediated conditions. The regioisomeric ratios of the products follow directly from the electronic nature of the cyclopropanols and isoquinolones used, with electron-withdrawing groups yielding predominantly the C(3)-alkylated products, whereas the electron-donating groups primarily generate the C(4)-alkylated isomers. Density functional theory calculations and detailed mechanistic investigations suggest the simultaneous existence of the singlet and triplet pathways for the C(3)- and C(4)-product formation. Further transformations of the products evolve the utility of the methodology thereby yielding scaffolds of synthetic relevance.

Access to Conjugated Enynes via Allenyl Silver Formation/Cyclization/Decarboxylation Reaction Catalyzed by Silver Carbonate(I)

Herein, we develop a novel and straightforward access to cyclic conjugated enynes catalyzed by silver carbonate/DBU from readily available substrates with good yields. The reaction is easy to set up, broad in scope, and can also be conducted in a one-pot fashion from easily accessible substrates through a sequence Michael addition reaction/cyclization. Based on our previous works, the mechanism proposed would involve an allenyl silver intermediate and decarboxylation reaction.