A new procedure is described for the synthesis of a,/?-glycosyl cyanides by the reaction of per-O-benzylated S-a-D-glycopyranosyl phosphorothioates with trimethylsilyl cyanide in the presence of Lewis acid. Starting S-glycosyl phosphorothioates are prepared, directly, from O-benzyl protected reducing D-hexopyranoses (gluco-, galacto-, manno-) and alkylammonium salt of phosphorothioic acid under...

A triple cascade was developed using a simple copper catalyst to trans-selectively access bicyclic isoxazolidines in a one-pot synthesis. This strategy features the in situ generation of nitrones and subsequent trapping by [3 + 2] cycloaddition. In this method, copper serves three catalytic functions: as a Lewis acid for the ene reaction, as an organometallic for aerobic oxidation, and as a Lew...

Solution phase titrations are made easy by multi-nuclear FlowNMR spectroscopy with automated, continuous titre addition to give accurate insights into Brønsted acid/base, hydrogen bonding, Lewis acid/base and metal/ligand binding equilibria under native conditions.

An efficient synthesis of a valuable intermediate of coenzyme Q(10) by microwave-assisted Lewis acidic ionic liquid (IL)-catalyzed Friedel-Crafts alkylation is reported. The acidity of six [Etpy]BF(4)-based ionic liquids was characterized by means of the FT-IR technique using acetonitrile as a molecular probe. The catalytic activities of these ionic liquids were correlated with their Lewis acid...

One possible way to take advantage of such abilities may be to apply a ‘combined acids system’ [2] to the catalyst design. The concept of combined acids, which can be classified into Brønsted acid-assisted Lewis acid (BLA), Lewis acid-assisted Lewis acid (LLA), Lewis acid-assisted Brønsted acid (LBA), and Brønsted acid-assisted Brønsted acid (BBA), can be a particularly useful tool for the desi...

Cationic zirconocene or hafnocene complexes serve as a novel class of Lewis acid with unique reactivities, which are to be exploited in organic synthesis. Four categories of reactivities are discussed, that is, (A) C-F bond activation/cleavage, (B) Coordinative activation of ether linkages, (C) Carbonyl activation, and (D) C-0 bond cleavage via zirconocene alkoxide. Introduction Lewis acid-prom...

Silica Vanadic Acid, SVA, (oxo-vanadium has been supported on silica) as a dual Lewis and Bronsted acid ability was prepared and efficiently catalyzed one-pot multi-component condensation of enolizable ketones or alkyl acetoacetates with aromatic aldehydes, acetonitrile and acetyl chloride. The described reaction was produced β-acetamido ketone or ester derivatives in high to excellent yields i...

In the direct Mannich reaction and synthesis of α,β-unsaturated ketones, the use of organobismuth complexes as catalysts leads to high diastereoselectivity and products of single trans conformation. In this paper, we illustrate the relationship between structure and catalytic activity as well as diastereoselectivity of organobismuth complexes having a 5,6,7,12-tetrahydrodibenz [c,f][1,5]thiobis...

This overview paper summarizes the current status of the Lewis acid-base or generalized donor-acceptor concepts and their application to solubility theory and related problems in the fields of surface and colloid chemistry. Simple second-order perturbation theory is then used to evaluate the pros and cons of various empirical treatments or Lewis acid-base strengths currently found in the litera...

TiCl4/nano-cellulose as a biodegradable and eco-friendly Lewis acid catalyst was synthesized via reaction of nano-cellulose and TiCl4. This catalyst was characterized and used for synthesis of asymmetric highly functionalized tetrahydropyridines via a five-component condensation reaction of p-substituted anilines, aldehydes and ethyl acetoacetate under solvent-free condition. Simple methodology...