Rare earth complexes in organic synthesis

Metal mediated reactions play an important role in organic chemistry. It has recently been found that rare earth trifluoromethane sulfonate complexes may be substituted for conventional Lewis acids in a variety of organic reactions. 

Lanthanide(III) trifluoromethane sulfonates in the hydrated form can be prepared by reacting the rare earth oxide with triflic acid in aqueous solution. The product is hydrated salt which is heated under vacuum to produce an anhydrous rare earth trifluoromethane sulfonate. The anhydrous salts are used in organic reactions. Some of the advantages of using rare earth triflates over conventional Lewis acids are (i) they act as catalysts rather than stoichiometric reagents, (ii) they are effective catalysts in aqueous solutions and (iii) they can be easily recovered without any loss of catalytic activity for subsequent use. 

The rare earth triflates are used in three types of organic reactions, namely (i) carbon-carbon bond formation, (ii) carbon-oxygen bond formation and (iii) carbon-nitrogen bond formation. 

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