title: Synthesis of benzonorbornadienes: regioselective benzyne formation.
abstract: This report details the synthesis of several benzonorbornadienes by Diels--Alder cycloaddition of cyclopentadiene derivatives with substituted benzyne intermediates, which were generated by low-temperature metal--halogen exchange of halobenzenes. General conditions were developed, allowing synthesis of most benzonorbornadienes described herein at the multigram scale with isolated yields approaching 90% in some cases. Cycloaddition of the benzyne produced by substitution of a chlorodifluorobenzene for a bromodifluorobenzene in the metal--halogen exchange reaction unexpectedly gave a different benzonorbornadiene. The benzyne, which resulted by a deprotonation pathway rather than by metal-halogen exchange, formed in a highly regioselective elimination step.
authors.affiliation: Lord Corporation, Materials Division, 110 Lord Drive, Cary, North Carolina 27511, USA. ken_caster@lord.com
authors.forename: K C
authors.initials: KC
authors.lastname: Caster
authors.forename: C G
authors.initials: CG
authors.lastname: Keck
authors.forename: R D
authors.initials: RD
authors.lastname: Walls