Direct enantio-convergent transformation of racemic substrates without racemization or symmetrization

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Asymmetric reactions that transform racemic mixtures into enantio-enriched products are in high demand, however, classical kinetic resolution (KR) can afford enantiopure compounds in <50% yield even in an ideal case. Many deracemization processes thus have been developed including dynamic kinetic resolution (DKR) and dynamic kinetic asymmetric transformation (DYKAT), which can provide enantio-enriched products even after complete conversion of the racemic starting materials; however, these dynamic processes require racemization or symmetrization of the substrates or intermediates. We demonstrate a first chemical direct enantio-convergent transformation without racemization or symmetrization process. The copper(I)-catalysed asymmetric allylic substitution of a racemic allyl ethers afforded a single enantiomer of an α-chiral allylboronates with complete conversion and high enantioselectivity (up to 98% ee); one enantiomer of the substrate undergoes an anti-SN2'-type reaction whereas the other enantiomer reacts via a syn-SN2' pathway. The products, α-chiral allylboronates, cannot be prepared by dynamic procedures, were used in construction of all-carbon quaternary stereocentres.