3-boronoacrolein as an exceptional heterodiene in the highly enantio- and diastereoselective Cr(III)-catalyzed three-component [4+2]/allylboration

This Communication reports the optimization of the first catalytic enantio- and diastereoselective hetero[4+2]/allylboration reaction to provide efficient access to α-hydroxyalkyl pyran derivatives. The key substrate 3-boronoacrolein pinacolate appears to be an exceptionally favorable heterodiene for use in Jacobsen's enantioselective reverse electron demand hetero[4+2] reaction with enol ethers, catalyzed by the tridentate (Schiff base)chromium complex 1. This one-pot three-component reaction was successfully applied to a concise total synthesis of (5R,6S)-6-acetoxy-5-hexadecanolide (2), the oviposition attractant pheromone of the female Culex mosquito capable of transmitting the West Nile virus. Copyright © 2003 American Chemical Society.