title: Access to ring-fused homo- and heteroaromatic derivatives via an initial ring-opening of 3-nitro-4-(phenylsulfonyl)thiophene.
abstract: Within an overall ring-opening/ring-forming protocol, the (E,E)-4-methylthio-2-nitro-3-phenylsulfonyl-1-pyrrolidino-1,3-butadiene (7) [derived from the initial opening of 3-nitro-4-(phenylsulfonyl)thiophene (6) with pyrrolidine and silver nitrate in EtOH] is revealed to be an excellent precursor of nitro(phenylsulfonyl) derivatives of ring-fused aromatic (naphthalene, phenanthrene) or heteroaromatic (benzothiophene) compounds whose substitution pattern cannot be easily achieved by conventional methods. The key step is represented by a thermal electrocyclic rearrangement of (E,E)-1-aryl-4-methylsulfonyl-2-nitro-3-phenylsulfonyl-1,3-butadienes (9), which, thanks to proper geometric and electronic factors, occurs in unprecedentedly mild conditions and is followed by an irreversible, concerted syn beta-elimination of methanesulfinic acid to aromatize the newly formed cyclohexadienic ring.
authors.affiliation: Dipartimento di Chimica e Chimica Industriale, Università di Genova, Via Dodecaneso 31, I-16146 Genova, Italy.
authors.forename: Lara
authors.initials: L
authors.lastname: Bianchi
authors.forename: Carlo
authors.initials: C
authors.lastname: Dell'Erba
authors.forename: Massimo
authors.initials: M
authors.lastname: Maccagno
authors.forename: Angelo
authors.initials: A
authors.lastname: Mugnoli
authors.forename: Marino
authors.initials: M
authors.lastname: Novi
authors.forename: Giovanni
authors.initials: G
authors.lastname: Petrillo
authors.forename: Fernando
authors.initials: F
authors.lastname: Sancassan
authors.forename: Cinzia
authors.initials: C
authors.lastname: Tavani