Boyer's Reaction and Transetherification : Mechanism and New Perspectives

The progress and stereochemistry of Boyer's reaction were analyzed using several simple, chiral, alcoholic substrates, a variable amount of BiBr 3 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, BiBr 3 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 rac-1 , isomeric ethers 4 transetherificate to 3 . 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 BiBr 3 and oxygen atoms of alcohols and ethers, play the key role for both the reactivity and the stereochemical outcome of the reaction. Chirality 28:269–275, 2016 . © 2016 Wiley Periodicals, Inc.