Exploring the Reactivity of α-Lithiated Aryl Benzyl Ethers: Inhibition of the [1,2]-Wittig Rearrangement and the Mechanistic Proposal Revisited

By carefullycontrolling the reactiontemperature,treatment of aryl benzylethers with tBuLi selectivelyleadsto a-lithiation, generating stable organolithiums that can bedirectlytrapped with avariety of selected electro philes,before they can undergo the expected [1,2]-Wittigrear-rangement. This rearrangement has been deeplystudied,both experimentally and computationally,with aryl a-lithiat-ed benzyl ethers bearing different substituents at the arylring. The obtained resultssupport the competence of acon-certedanionic intramolecular addition/elimination sequenceand aradical dissociation/recombination sequence for ex-plaining the tendency of migrationfor aryl groups.Themore favored rearrangementsare found for substrates withelectron-poor aryl groups that favor the anionic pathwayJunta de Castilla yLejnandFEDER (BU237U13 and BU076U16) and Ministerio de Econom&ayCompetitividad (MINECO) and FEDER (CTQ2013-48937-C2-1Pand 2-P