The heck reaction of allylic alcohols catalyzed by palladium nanoparticles in water: Chemoenzymatic synthesis of (R)-(-)-rhododendrol

Abstract

The use of phosphine-free perfluoro-tagged palladium nanoparticles immobilized on fluorous silica gel (FSG), either through fluorous-fluorous interactions or covalent bonding, in the Heck reaction of aryl iodides with allylic alcohols under aerobic conditions in water is described. 4-(4-Methoxyphenyl)-butan-2-one, an important fine chemical, is readily accessed by this procedure. A two-step one-pot process, involving a Heck reaction followed by an enantioselective enzyme-catalyzed reduction, to form chiral alcohols is applied to the synthesis of (R)-(-)-rhododendrol. The palladium catalysts can be recycled several times, both in the Heck reaction and in the one-pot chemoenzymatic process. Between Heck and high water: Phosphine-free perfluoro-tagged palladium nanoparticles immobilized on fluorous silica gel can be successfully used in the Heck reaction of aryl iodides with allylic alcohols under aerobic conditions in water (see scheme). The reaction is applied to a two-step one-pot chemoenzymatic process to form chiral alcohols and to the synthesis of R-(-)-rhododendrol. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.