Kinetic Resolution of β‐Alkenyl‐, β‐Alkynyl‐ and β‐Flavenyl‐Substituted β‐Hydroxy Esters in Asymmetric Dehydration

Abstract Catalytic asymmetric dehydration of β‐alkenyl‐ or alkynyl‐substituted β‐hydroxy esters by kinetic resolution has been investigated with five different chiral ligands 3–7. The kinetic resolution of a variety of racemic β‐hydroxy tert‐butyl esters in the presence of a prolinol chiral ligand and BrZnCH2CO2tBu provided highly enantio‐enriched β‐hydroxy esters 9–22 with selectivity factors ranging from 11 to 59. In addition, the application of this asymmetric synthetic methodology to the preparation of enantio‐enriched flavene derivatives 23–29 is demonstrated. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)