| Abstract
| - Catalytic asymmetric alkylation reactions of branched racemic carbonates 1a and 1b with sodiumdimethyl malonate, promoted by molybdenum and ligand 5, proceed by a kinetic resolution intoluene, THF, tetrahydropyran, i-PrOAc, 1,2-dichloroethane, and MeCN with krel of 7−16. In THF,MeCN, tetrahydropyran, and i-PrOAc using the (S,S)-5 ligand, the fast reacting (S)-carbonateenantiomer provides the branched product with high ee (97−99.5%) and branched/linear selectivity,but the ee erodes as the reaction of the slow-reacting (R)-enantiomer takes place. This impliesthat the rate of equilibration of the oxidative addition complexes in these solvents is competitivewith the subsequent malonate displacement step. In toluene and dichloroethane, the ee andbranched/linear ratios diminish during the reaction of the slow-reacting (R)-isomer, but not nearlyas much as in the other solvents. This is most likely due to either an increase in the rate ofequilibration of the oxidative addition complexes relative to the malonate displacement step, orvice versa. Because of the minimal stereochemical memory effect in toluene and 1,2-dichloroethane,the reactions in these solvents can be carried to completion (dynamic kinetic asymmetrictransformation) and still provide product with excellent ee (>95%). The anion of dimethylmethylmalonate also reacts via a kinetic resolution, although the ee's, rates, and krel values differfrom those of the reactions with dimethyl malonate.
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