Chiral reactants have been employed for assessing the real stereochemistry of the BiBr3-catalyzed synthesis of benzylic ethers, a very useful reaction for protecting alcoholic groups. The results of this investigation are in clear contrast with the conclusions of previous studies (Boyer et al., Tetrahedron 2001;57:1917-1921). Indeed, chiral GC-MS analysis of the ethereal products gives unequivocal evidence of the complete racemization of the benzylic moiety and the complete retention of configuration of the protected alcoholic substrate. Such findings make BiBr3 a powerful and stereochemically preservative catalyst for benzylation of chiral alcohols, and a potential candidate for orthogonal protecting group strategies applicable to polyhydroxy compounds.
Copyright 2009 Wiley-Liss, Inc.