1 research outputs found
Double Palladium Catalyzed Reductive Cyclizations. Synthesis of 2,2′‑, 2,3′‑, and 3,3′-Bi‑1<i>H</i>‑indoles, Indolo[3,2‑<i>b</i>]indoles, and Indolo[2,3‑<i>b</i>]indoles
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-<i>b</i>]indole, indolo[1,2-<i>c</i>]quinazolin-6(5<i>H</i>)-ones, and 5,11-dihydro-6<i>H</i>-indolo[3,2-<i>c</i>]quinolin-6-ones. Nonselective product formation
was also observed from reductive cyclization of 1,1-bis(2-nitroaryl)ethenes,
producing indolo[2,3-<i>b</i>]indoles and indolo[2,3-<i>c</i>]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