DIASTEREOSELECTIVE CARBONYL ADDITION-REACTIONS PROMOTED BY YTTERBIUM(III) TRIFLATE

The addition of organolithium and organomagnesium reagents to diverse classes of chiral aldehydes and ketones generally proceeds in high yie lds and often with excellent diastereoselectivities when the reactions are mediated by ytterbium(III) trifluoromethanesulfonate [ytterbium t riflate, Yb(OTf)(3)]. A variety of functionalized organolithiums and o rganomagnesiums were examined in conjunction with a similarly diverse series of carbonyl substrates. The results of the Yb(OTf)(3)-promoted reactions were compared with those obtained without this additive. Alt hough in some cases the advantages of Yb(OTf)(3) were evident, in othe r cases comparable or even better results were obtained with the paren t organometallic itself. The Yb(OTf)(3)-promoted reactions appear part icularly effective in achieving non-chelation controlled (Felkin-Anh) addition to alkoxy-substituted aldehydes and ketones.