Condensation ytterbium triflate

Important variants for the synthesis of benzimidazoles allow the use of aldehydes, rather than acids ytterbium triflate (best for aliphatic aldehydes) or scandium triflate catalyse the condensation and the subsequent air oxidation of the dihydrobenzimidazole immediate product. Incorporating nitrobenzene in the reaction mixture as the oxidant can also be used. orf/to-Nitroanilines can be used by incorporating a reducing agent in the reaction mixture - e.g. hydrogen over palladium or sodium dithionite - for in situ generation of the orffto-phenylenediamine. 2-Aryl-benzothiazoles can be made from 2-aminobenzenethiol, aromatic aldehydes and air, in the presence of activated carbon. ... 

Considerable rate enhancements have been observed when water is used as solvent compared with alcoholic or hydrocarbon media for Mannich reactions, i.e. condensations of ketones with secondary amines in the presence of formaldehyde [65]. Allylsilanes [66] and allylstannanes [67] in aqueous media were used in organic synthesis under Mannich-like conditions. More recently, Kobayashi reported the catalysis of the reaction of vinyl ethers with iminium salts by ytterbium triflate in tetrahydrofuran-water mixtures [68]. 

Place 0.375 g ytterbium (III) trifluoromethanesulfonate hydrate catalyst (ytterbium triflate) into a 25-mL round-bottom flask. Add 10 mL of 1,2-dichloroethane solvent followed by 0.400 mL of concentrated nitric acid (automatic pipette). Add two boiling stones to the flask. To fhis solution, weigh out and add approximately 6 millimoles of the aromatic substrate. Connect the round-bottom flask to a reflux condenser and clamp it into place on a ring stand. Use a very slow flow of water through the condenser. With a hot plate, heat the mixture to reflux for 1 hour. 

The self-condensation of furan-2-yl alcohols and subsequent intramolecular Friedel-Crafts-type reaction and elimination of an aldehyde catalyzed by ytterbium triflate gave rise to di(furan-2-yl) methanes, which are precursors for the synthesis of biofuels (130BC8030). 

L. M. Wang, Y. H. Wang, H. Tian, Y. Yao, J. Shao, B. Liu, J. Fluorine Chem. 2006,127,1570-1573. Ytterbium triflate as an efficient catalyst for one-pot synthesis of substituted imidazoles through three-component condensation of benzil, aldehydes and ammonium acetate. 

Type of reaction C-N bond formation Reaction conditions Solvent-free, room temperature Synthetic strategy One-step condensation Catalyst Ytterbium triflate [Yb(OTf)3]... 

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