Polyethylene glycol (PEG) as a reusable solvent medium for an asymmetric organocatalytic Michael addition. Application to the synthesis of bioactive compounds†
A highly stereoselective organocatalytic Michael addition of aldehydes to trans-β-nitrostyrenes using PEG as a recyclable solvent medium is presented. The scope of this organocatalytic system is demonstrated by the formation of several Michael adducts in good yields and stereoselectivities. Furthermore, applying this new protocol to acetaldehyde, we have disclosed an easy formal synthesis of (R)-pregabalin, (R)-phenibut and (R)-bacoflen with good yields and outstanding enantioselectivities.