Ruthenium Alkylidene-Catalyzed Reaction of 1,6-Heptadiynes with Alkenes

Ruthenium carbene catalysts are able to catalyze cross [2 + 2 + 2] cyclotrimerizations of 1,6-diynes with cyclic and acyclic double bonds. A plausible mechanistic competition is described in which electron-deficient alkenes follow similar pathways as those of other ruthenium catalysts previously utilized and produce mixtures of trienes and cyclohexadienes. On the contrary, allylethers give different isomers of the same final products, suggesting that a metathetic cascade pathway operates in these cases

Nucleophilic Aromatic Substitution (S_NAr) as an Approach to Challenging Carbohydrate–Aryl Ethers

A general and practical route to carbohydrate–aryl ethers by nucleophilic aromatic substitution (S_NAr) is reported. Upon treatment with KHMDS, C–O bond formation occurs between carbohydrate alcohols and a diverse range of fluorinated (hetero)­aromatics to provide the targets in good to excellent yields. Commercially available arylating agents, high atom economy, and high regioselectivity are notable features of the protocol. The aryl ether products have potential for wide-ranging applications as exemplified by the synthesis of a novel chiral P,N-ligand

Stereoselective Glycosylation of 2‑Nitrogalactals Catalyzed by a Bifunctional Organocatalyst

The use of a bifunctional cinchona/thiourea organocatalyst for the direct and α-stereoselective glycosylation of 2-nitrogalactals is demonstrated for the first time. The conditions are mild, practical, and applicable to a wide range of glycoside acceptors with products being isolated in good to excellent yields. The method is exemplified in the synthesis of mucin type Core 6 and 7 glycopeptides