Description
Lanthanum trifluoromethanesulfonate is a Lewis acid catalyst useful for aldol, Michael, Diels-Alder, and other C-C bond forming reactions; also useful for preparing organolanthanum reagents, which react with hindered tertiary amides to afford ketones.
Chemical Properties
white to light beige crystalline powder
Uses
Lanthanum trifluoromethanesulfonate is a water-tolerant Lewis acid used in the Aldol reaction of silyl enol ethers with aldehydes. It is an effective catalyst for the Baylis-Hillman reaction. It also catalyzes Michael additions to methyl vinyl ketone in water.
reaction suitability
core: lanthanum
reagent type: catalyst
Synthesis
To an aqueous solution of triflic acid (50% v/v), a slight excess of lanthanum oxide (La2O3) is added; the resulting mixture is stirred for 15 min at rt and then filtered to remove the unreacted oxide; the filtrate is concentrated in vacuo at about 60 °C; residual water is removed by azeotropic distillation with toluene in vacuo to dryness; the resulting hydrate is placed in a flask equipped with a stirring bar, a stopcock filled with a glass wool plug, and a NaOH trap, and is then dehydrated by heating under vacuum (140 °C/0.1 mmHg or 180 °C/1.0 mmHg) for 16 h. The anhydrous Lanthanum trifluoromethanesulfonate La(OTf)3 is a white to gray-white solid.
storage
Anhydrous La(OTf)3 is hygroscopic and should be stored and weighed in a glove-box. Use in a fume hood.
