Does a Chiral Alcohol Really Racemize when Its OH Group Is Protected with Boyer's Reaction?

Chiral reactants have been employed for assessing the real stereochemistry of the BiBr(3)-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 BiBr(3) a powerful and stereo-chemically preservative catalyst for benzylation of chiral alcohols, and a potential candidate for orthogonal protecting group strategies applicable to polyhydroxy compounds. Chirality 22:88-91, 2010. (C) 2009 Wiley-liss, Inc.