Why is thiol unexpectedly less reactive but more selective than alcohol in phenanthroline-catalyzed 1,2-- and -furanosylations?

The lack of catalytic stereoselective approaches for producing 1,2--furanosides emphasizes the critical need for further research in this area. Herein, we present a stereoselective -furanosylation method, utilizing a 4,7-dipiperidine-substituted phenanthroline catalyst. This developed protocol fills a gap in the field, enabling the coupling of cysteine residues and thiols with furanosyl bromide electrophiles.

Stereoselective 1,2- Furanosylations Catalyzed by Phenanthroline.

Stereoselective formation of the 1,2- furanosidic linkage, a motif of many biologically relevant oligosaccharides and polysaccharides, remains an important synthetic challenge. We herein report a new stereoselective 1,2- furanosylation method promoted by phenanthroline catalysts under mild and operationally simple conditions. NMR experiments and density functional theory calculations support an associative mechanism in which the rate-determining step occurs from an inverted displacement of the faster-reacting phenanthrolinium ion intermediate with an alcohol nucleophile.

Diastereoselective sp C-O Bond Formation via Visible Light-Induced, Copper-Catalyzed Cross-Couplings of Glycosyl Bromides with Aliphatic Alcohols.

Copper-catalyzed cross-coupling reactions have become one of the most powerful methods for generating carbon-heteroatom bonds, an important framework of many organic molecules. However, copper-catalyzed C(sp)-O cross-coupling of alkyl halides with alkyl alcohols remains elusive because of the sluggish nature of oxidative addition to copper. To address this challenge, we have developed a catalytic copper system, which overcomes the copper oxidative addition barrier with the aid of visible light and effectively facilitates the cross-couplings of glycosyl bromides with aliphatic alcohols to afford C(sp)-O bonds with high levels of diastereoselectivity.

Regioselective Benzoylation of Diols and Carbohydrates by Catalytic Amounts of Organobase.

A novel metal-free organobase-catalyzed regioselective benzoylation of diols and carbohydrates has been developed. Treatment of diol and carbohydrate substrates with 1.1 equiv.