title: Rerouting radical cascades: intercepting the homoallyl ring expansion in enyne cyclizations via C-S scission.
abstract: The switch from 5-exo- to 6-endo-trig selectivity in the radical cyclization of aromatic enynes was probed via the combination of experimental and computational methods. This transformation occurs by kinetic self-sorting of the mixture of four equilibrating radicals via 5-exo-trig cyclization, followed by homoallyl (3-exo-trig/fragmentation) ring expansion to afford the benzylic radical necessary for the final aromatizing C-C bond fragmentation. The interception of the intermediate 5-exo-trig product via β-scission of a properly positioned weak C-S bond provides direct mechanistic evidence for the 5-exo cyclization/ring expansion sequence. The overall cascade uses alkenes as synthetic equivalents of alkynes for the convenient and mild synthesis of Bu3Sn-functionalized naphthalenes.
authors.affiliation: Department of Chemistry and Biochemistry, Florida State University , Tallahassee, Florida 32306, United States.
authors.forename: Sayantan
authors.initials: S
authors.lastname: Mondal
authors.forename: Brian
authors.initials: B
authors.lastname: Gold
authors.forename: Rana K
authors.initials: RK
authors.lastname: Mohamed
authors.forename: Hoa
authors.initials: H
authors.lastname: Phan
authors.forename: Igor V
authors.initials: IV
authors.lastname: Alabugin