title: Theoretical study on the BF3-catalyzed Meinwald rearrangement reaction.
abstract: The mechanisms of the BF3-catalyzed Meinwald rearrangement reactions of five epoxides in dichloromethane solution have been studied at the M062X/6-311++G(2df,2pd) level. Accordingly, the Lewis acid-epoxide complex can react through several alternative pathways, though three phases (ring opening, C-C bond rotation, and hydrogen or alkyl group migration) are required in any path. In some cases, a concerted pathway (involving all three successive phases) is found. Otherwise, the reaction takes place through a reaction mechanism involving a zwitterion or a BF3 addition compound (formed by fluoride transfer from the BF3 moiety to the incipient carbocationic center generated by C-O bond rupture) or both as reaction intermediate(s). The BF2-bound fluorohydrin yields the reaction product through a concerted process involving fluoride transfer from the C-F bond to the OBF2 group and hydrogen or alkyl group migration, as first demonstrated in this work. Effects of a number of features (solvent effects, concurrent hydrogen/alkyl group migration, carbocation substitution, benzylic conjugation) are also discussed.
authors.affiliation: Instituto de Sı́ntesis Quı́mica y Catálisis Homogénea-ISQCH, CSIC-Universidad de Zaragoza , Pedro Cerbuna 12, 50009 Zaragoza, Spain.
authors.forename: José María
authors.initials: JM
authors.lastname: Fraile
authors.forename: José Antonio
authors.initials: JA
authors.lastname: Mayoral
authors.forename: Luis
authors.initials: L
authors.lastname: Salvatella