title: Boyer's Reaction and Transetherification: Mechanism and New Perspectives.
abstract: The progress and stereochemistry of Boyer's reaction were analyzed using several simple, chiral, alcoholic substrates, a variable amount of BiBr3 and different solvents. Basic solvents inhibit the reaction, while cyclohexane works very well; thus, it was our choice for the present study. In contrast to previous works, BiBr3 behaves as a true catalyst, being not consumed during the reaction. Although poisoning of the catalyst occurs to some extent, it does not prejudice the reaction yields (>90%). Gas chromatography/mass spectrometry (GC-MS) monitoring of the reaction revealed that, for example, in the presence of alcohol , isomeric ethers transetherificate to . We propose a unifying mechanistic model for both Boyer's and transetherification reactions, in which the electronic properties of n-adducts intermediates, formed by combination of bismuth(III) of BiBr3 and oxygen atoms of alcohols and ethers, play the key role for both the reactivity and the stereochemical outcome of the reaction.
authors.affiliation: Dipartimento di Chimica e Tecnologie del Farmaco - Sapienza, University of Rome, Rome, Italy.
authors.forename: Caterina
authors.initials: C
authors.lastname: Fraschetti
authors.affiliation: Dipartimento di Chimica e Tecnologie del Farmaco - Sapienza, University of Rome, Rome, Italy.
authors.forename: Maurizio
authors.initials: M
authors.lastname: Speranza
authors.affiliation: Dipartimento di Chimica e Tecnologie del Farmaco - Sapienza, University of Rome, Rome, Italy.
authors.forename: Laura
authors.initials: L
authors.lastname: Guarcini
authors.affiliation: School of Science & Technology (Chemistry Division), University of Camerino, Camerino, Italy.
authors.forename: Graziella
authors.initials: G
authors.lastname: Roselli
authors.affiliation: Dipartimento di Chimica e Tecnologie del Farmaco - Sapienza, University of Rome, Rome, Italy.
authors.forename: Antonello
authors.initials: A
authors.lastname: Filippi
keywords: Lewis acid catalysis; benzylation; bismuth bromide; ethers; stereoselectivity