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4082075 
Journal Article 
LANTHANIDE TRIFLATES AS WATER-TOLERANT LEWIS-ACIDS - ACTIVATION OF COMMERCIAL FORMALDEHYDE SOLUTION AND USE IN THE ALDOL REACTION OF SILYL ENOL ETHERS WITH ALDEHYDES IN AQUEOUS-MEDIA 
Kobayashi, S; Hachiya, I 
1994 
Yes 
Journal of Organic Chemistry
ISSN: 0022-3263
EISSN: 1520-6904 
59 
13 
3590-3596 
Lanthanide trifluoromethanesulfonates (triflates), especially ytterbium triflate (Yb(OTf)(3)), were found to be stable Lewis acids in water. In the presence of a catalytic amount of lanthanide triflate, formaldehyde in water solution (commercial formaldehyde solution) was activated and the hydroxymethylation reaction of silyl enol ethers proceeded smoothly. Lanthanide triflates were also quite effective in the aldol reaction of silyl enol ethers with aldehydes in aqueous media, and water-soluble aldehydes such as acetaldehyde, acrolein, and chloroacetaldehyde could be employed for direct use. Moreover, in all these reactions, lanthanide triflates were quantitatively recovered after the reactions were completed and could be reused.