Cb. Castellani et al., RARE-EARTH TRIFLUOROMETHANESULFONATES AS CATALYSTS IN SOME MEERWEIN-PONNDORF-VERLEY TYPE REDUCTIONS, Journal of molecular catalysis, 85(1), 1993, pp. 65-74
Rare earth cations catalyze the reduction of aldehydes and ketones by
isopropanol. The reaction rate constants have been determined by H-1 N
MR spectroscopy in the presence of La3+, Y3+, Lu3+, Sc3+, using Cl-, C
lO4- and TfO- as counterions; the values obtained indicate that the re
action rates increase as the cation size decreases and with the use of
poorly co-ordinating counterions. Scandium trifluoromethanesulphonate
turned out to be by far the best catalyst for these reactions. By com
parison of strictly analogous aldehydes and ketones it has been found
that the former compounds are more easily reduced than the latter. The
formation of mixed ethers with isopropanol was observed during the re
duction of aromatic carbonyl compounds substituted with electron donat
ing groups.