Diastereoselective carbonyl addition reactions promoted by ytterbium(III) triflate

Resumen

The addition of organolithium and organomagnesium reagents to diverse classes of chiral aldehydes and ketones generally proceeds in high yields and often with excellent diastereoselectivities when the reactions are mediated by ytterbium(III) trifluoromethanesulfonate [ytterbium triflate, Yb(OTf) 3 ]. A variety of functionalized organolithiums and organomagnesiums 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. Although in some cases the advantages of Yb(OTf) 3 were evident, in other cases comparable or even better results were obtained with the parent organometallic itself. The Yb(OTf) 3 -promoted reactions appear particularly effective in achieving non-chelation controlled (Felkin-Anh) addition to alkoxy-substituted aldehydes and ketones.L'addition de reactifs organolithies ou organomagnesies sur diverses classes d'aldehydes et cetones chirales a lieu en general avec des rendements eleves et souvent avec d'excellentes diastereoselectivites quand les reactions sont realisees en presence de trifluoromethanesulfonate d'ytterbium(III) [Yb(OTf) 3 ]. Une variete d'organolithiens et organomagnesiens fonctionnalises ainsi qu'une variete de derives carbonyles ont ete examinees. Les resultats des reactions induites avec Yb(OTf) 3 ont ete compares a ceux obtenus sans utilisation de Yb(OTf) 3 . Ainsi dans certains cas les avantages de Yb(OTf) 3 paraissent evidents, dans d'autres cas, comparables a ceux obtenus avec l'organometallique apparente. Les reactions induites par Yb(OTf) 3 s'averent particulierement efficaces dans l'addition, sans controle chelatant (Felkin-Anh), sur les aldehydes et les cetones alcoxy substitues.