Ytterbium trifluoromethanesulfonate hydrate

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. 

Related Reagents. Ytterbium(III) trifluoromethanesulfonate ytterbium(in) trifluoromethanesulfonate hydrate cerium(ni) trifluoromethanesulfonate scandium trifluoromethanesulfonate. 

Preparation of Ytterbium Triflate-. To 21 mL of a mixture of trifluoromethanesulfonic acid and H,0 (v/v = 1/1) 1 i.8 g (30 mmol) of Yb20, are added and the suspension is heated at 100 CC for 2 h. Al ter cooling, the unrcacted oxide is removed by filtration and the filtrate is concentrated under reduced pressure. The hydrate thus prepared is dried in vacuo at 200cC/0.5 Torr for 40 h to give an ytterbium triflate. Preparation of the Catalyst ... 

A proposed mechanism for this reaction involves the following three steps to generate the nitronium ion. The trifluoromethanesulfonate (triflate) ions act as spectators. The ytterbium cation is believed to be hydrated by the water present in the aqueous nitric acid solution. Nitric acid binds strongly to the hydrated ytterbium cation, as shown in equation 1. A proton is generated, as shown in equation 2, by the strong polarizing effect of the metal. Nitronium ion is then formed by the process shown in equation 3. Although the nitronium ion may serve as the active electrophilic species, it is more likely that a nitronium carrier, such as the... 

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