β‑Chloroaldehydes from Trapping Zirconium Enolates Produced in Asymmetric 1,4-Additions
journal contributionposted on 31.12.2018, 19:03 by Jiao Yu Joseph Wang, Thomas Palacin, Stephen P. Fletcher
Zirconium enolates, derived from copper-catalyzed asymmetric conjugate additions, are trapped with the Vilsmeier–Haack reagent. Asymmetric additions generate quaternary carbon centers with high enantioselectivity (generally ∼90% ee), and the enolates are converted to unsaturated β-chloroaldehydes (41–57% yields). The reaction tolerates changes to the nucleophile, can be used to form five-, six-, or seven-membered ring products, and is scalable to 5 mmol, and the products are readily elaborated by condensation, cross coupling, and addition reactions.