Modular access to chiral cyclopentanes via formal [2+2+1] annulation enabled by palladium/chiral squaramide relay catalysis

Abstract

An enantio- and diastereodivergent [2+2+1] annulation reaction of allyl ketones, acidic methylene compounds, and nitroalkenes to assemble highly functionalized cyclopentanes from readily available substances enabled by asymmetric relay catalysis of chiral bifunctional squaramide and palladium complex has been established. This method showcases that allyl ketones can serve as latent 1,2-dication synthons via a linear-selective allylic C–H functionalization and sequential 1,4-conjugated addition, enabling the rapid assembly of cyclopentane skeleton with a broad scope of methylene nucleophiles and nitroalkenes. Notably, chiral bifunctional squaramide catalyst engages in both the intermolecular and intramolecular Michael addition reactions accompanying with a kinetic resolution behavior to amplify the enantioselection. In addition, the stereodivergent synthesis of diastereomers from the resultant chiral cyclopentane derivatives is also accessible by a simple manipulation with base.