Syntheses of three naturally occurring polybrominated 3,3′-bi-1H-indoles

[Display omitted] •Syntheses of three polybrominated biindole alkaloids have been completed.•A palladium catalyzed reductive cyclization was used as key ring-closing step.•N-bromosuccinimide was used brominate the biindoles. The naturally occurring polybrominated indoles 2,2′,5,5′-tetrabromo-3,3′-bi-1H-indole, 2,2′,6,6′-tetrabromo-3,3′-bi-1H-indole, and 2,2′,5,5′,6,6′-hexabromo-3,3′-bi-1H-indole were synthesized using a palladium catalyzed, carbon monoxide mediated, double reductive N-heterocyclization of 2,3-bis(2-nitro-4(or 5)-bromophenyl)-1,4-butadienes as the key step.