Reversibility and reactivity in an acid catalyzed cyclocondensation to give furanochromanes - a reaction at the 'oxonium-Prins' vs. 'ortho-quinone methide cycloaddition' mechanistic nexus.

ABSTRACT: Herein we report a combined experimental and computational investigation of the acid catalyzed cyclocondensation reaction between styrenyl homoallylic alcohols and salicylaldehyde to form furanochromanes. We disclose a previously unreported isomerisation of the 'unnatural' trans-fused products to the diastereomeric 'natural' cis-fused congeners. Notwithstanding the appeal of assuming this corresponds to endo to exo isomerisation of Diels-Alder (D-A) adducts via concerted retro-cycloaddition/cycloaddition reactions of an in situ generated ortho-quinone methide with the styrenyl alkene, our combined Hammett/DFT study reveals a stepwise Prins-like process via discrete benzylic carbocation intermediates for all but the most electron defic

SUBMITTER: Nielsen CD 

PROVIDER: S-EPMC6334628 | biostudies-literature | 2019 Jan

REPOSITORIES: biostudies-literature