title: Double Palladium Catalyzed Reductive Cyclizations. Synthesis of 2,2'-, 2,3'-, and 3,3'-Bi-1H-indoles, Indolo[3,2-b]indoles, and Indolo[2,3-b]indoles.
abstract: A palladium catalyzed, carbon monoxide mediated, double reductive cyclization of 1,4-, 1,3-, and 2,3-bis(2-nitroaryl)-1,3-butadienes to afford 2,2'-, 2,3'-, and 3,3'-biindoles, respectively, was developed. In contrast, reductive cyclizations of 1,2-bis(2-nitroaryl)ethenes were nonselective, affording mixtures of monocyclized indoles, indolo[3,2-b]indole, indolo[1,2-c]quinazolin-6(5H)-ones, and 5,11-dihydro-6H-indolo[3,2-c]quinolin-6-ones. Nonselective product formation was also observed from reductive cyclization of 1,1-bis(2-nitroaryl)ethenes, producing indolo[2,3-b]indoles and indolo[2,3-c]quinolin-6-ones. Carbon monoxide insertion to give the carbonyl containing products was the major or sole reaction path starting from 1,1- or 1,2-bis(2-nitroaryl)ethenes.
authors.affiliation: C. Eugene Bennett Department of Chemistry, West Virginia University , Morgantown, West Virginia 26506-6045, United States.
authors.forename: Nurul H
authors.initials: NH
authors.lastname: Ansari
authors.affiliation: C. Eugene Bennett Department of Chemistry, West Virginia University , Morgantown, West Virginia 26506-6045, United States.
authors.forename: Christopher A
authors.initials: CA
authors.lastname: Dacko
authors.affiliation: C. Eugene Bennett Department of Chemistry, West Virginia University , Morgantown, West Virginia 26506-6045, United States.
authors.forename: Novruz G
authors.initials: NG
authors.lastname: Akhmedov
authors.affiliation: C. Eugene Bennett Department of Chemistry, West Virginia University , Morgantown, West Virginia 26506-6045, United States.
authors.forename: Björn C G
authors.initials: BC
authors.lastname: Söderberg