title: Alkenes as alkyne equivalents in radical cascades terminated by fragmentations: overcoming stereoelectronic restrictions on ring expansions for the preparation of expanded polyaromatics.
abstract: Chemoselective interaction of aromatic enynes with Bu3Sn radicals can be harnessed for selective cascade transformations, yielding either Sn-substituted naphthalenes or Sn-indenes. Depending on the substitution at the alkene terminus, the initial regioselective 5-exo-trig cyclizations can be intercepted at the 5-exo stage via either hydrogen atom abstraction or C-S bond scission or allowed to proceed further to the formal 6-endo products via homoallylic ring expansion. Aromatization of the latter occurs via β-C-C bond scission, which is facilitated by 2c,3e through-bond interactions, a new stereoelectronic effect in radical chemistry. The combination of formal 6-endo-trig cyclization with stereoelectronically optimized fragmentation allows the use of alkenes as synthetic equivalents of alkynes and opens a convenient route to α-Sn-substituted naphthalenes, a unique launching platform for the preparation of extended polyaromatics.
authors.affiliation: Florida State University, Tallahassee, Florida 32306, United States.
authors.forename: Rana K
authors.initials: RK
authors.lastname: Mohamed
authors.affiliation: Florida State University, Tallahassee, Florida 32306, United States.
authors.forename: Sayantan
authors.initials: S
authors.lastname: Mondal
authors.affiliation: Florida State University, Tallahassee, Florida 32306, United States.
authors.forename: Brian
authors.initials: B
authors.lastname: Gold
authors.affiliation: Florida State University, Tallahassee, Florida 32306, United States.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Evoniuk
authors.affiliation: Florida State University, Tallahassee, Florida 32306, United States.
authors.forename: Tanmay
authors.initials: T
authors.lastname: Banerjee
authors.affiliation: Florida State University, Tallahassee, Florida 32306, United States.
authors.forename: Kenneth
authors.initials: K
authors.lastname: Hanson
authors.affiliation: Florida State University, Tallahassee, Florida 32306, United States.
authors.forename: Igor V
authors.initials: IV
authors.lastname: Alabugin