The one-carbon homologation of carbonyl compounds using diazo compounds is a frequently encountered synthetic objective. [1] Several related reactions have been developed and are known as the Arndt-Eistert reaction, [2] Buchner-Curtius-Schlotterbeck reaction, [3] Tiffeneau-Demjanov rearrangement, [4] and Roskamp-Feng reaction. [5] Among these reactions, Lewis acid catalyzed homologation of aldehydes or ketones with diazo compounds results in a carbon-chain extension or ring expansion at a carbonyl group, thus producing a synthetically useful carbonyl-containing backbone (Scheme 1). [6,7] Remarkably, the reactions found successful applications in natural product synthesis in recent years. [8] Intriguingly, a catalytic asymmetric variant of this transformation by using a-substituted a-diazo compounds will incorporate a chiral tertiary (for aldehydes) or quaternary (for ketones) carbon center [9] at the position adjacent to the carbonyl group (Scheme 1). Recently, innovative studies by several groups have been extended to the asymmetric reaction of aldehydes and cyclic carbonyl compounds. Asymmetric homologation of aldehydes with a-alkyl-a-diazo com-pounds were documented by Maruoka and co-workers, [10] ourselves, [11] and Ryu and co-workers. [12] Stereoselective construction of seven-membered rings from cyclohexanones was accomplished by the group of Maruoka by using a chiral aluminum complex of a binol derivative. [13] An asymmetric ring expansion of cycloalkanones with terminal diazoalkanes was reported by Kingsbury and co-workers by using chiral scandium complexes of oxazoline ligands. [14] We realized the corresponding ring-expansion reaction of isatins. [11c] Nevertheless, daunting challenges remain in the asymmetric carbonchain extention of acyclic ketones. Compared with the asymmetric homologation of cycloalkanones, the control of the enantioselectivity and regioselectivity of acyclic ketones (Scheme 1, path a) is more complex without the ring system. Additionally, acyclic ketones receive more steric hindrance than the relatively bare carbonyl group on a cyclic ring, which reduces the reactivity. Otherwise, the formation of epoxides from acyclic ketones is highly competitive relative to aldehydes and cyclic ketones. [1a,b] Continued improvement of asymmetric homologation of ketones achieved by new Lewis acid catalysts under mild reaction conditions is significantly desired. We report herein a breakthrough by using chiral N,N'-dioxide-yttrium(III) complexes. Asymmetric homologation of a-ketoesters with a-alkyl-a-diazoesters was achieved, thus generating enantiomeric enriched succinate derivatives with chiral all-carbon quaternary centers.After preliminary screening, we chose the a-ketoester 1 a and a-methyl-a-diazoester 2 a as the model substrates for catalysis using chiral N,N'-dioxide/metal complexes [15] (Table 1). Surprisingly, the catalyst L1/Sc(OTf) 3 , which was efficient in our previous study, [11] could not promote the reaction of the a-ketoester (entry 1). The complexes of Ni(OTf) 2 and Zn(OTf) ...