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

Abstract

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.

Marine natural products

“…139 Total synthesis of all four stereosiomers of 263 enabled its absolute conguration to be assigned. 139 The remaining rst total syntheses were for 2,2 0 ,5,5 0 -tetrabromo-3,3 0 -bi-1H-indole, 140 biselyngbyaside, 141 and wewakazole B. 142,143 Only one structure revision was reported for this phylum in 2017.…”

Palladium-Catalyzed Double Reductive Cyclization of 2,3-Dinitro-1,4-dialkenylbenzenes. Synthesis of 1H,8H-Pyrrolo[3,2-g]indoles

“…2,3-Dinitro-1,4-di(1-propen-1-yl)benzene (7). To a solution of 1 (106 mg, 0.327 mmol), PdCl 2 (PPh 3 ) 2 (4.7 mg, 0.01 mmol), and triphenylphosphine (PPh 3 , 3.4 mg, 0.01 mmol) in 1,4-dioxane (3 mL), under a nitrogen atmosphere, was added the solution of 1propen-1-yl tributyltin (4) (282 mg, 0.852 mmol) in 1,4-dioxane (1 mL) via a syringe.…”

“…We have extensively studied applications of palladium-catalyzed, carbon monoxide mediated, reductive cyclizations of 2-nitrostyrenes to furnish functionalized indoles. − It was envisioned that this methodology could be applied to the synthesis of pyrolloindoles via a double reductive cyclization of 2,3-dinitro-1,4-dialkenylbenzenes as seen in the retrosynthetic analysis in Figure . The relatively mild conditions used in the cyclization allow for broad functional group compatibility and offer significant improvements over the previously discussed methods.…”

Efficient approach to 1,1′-bisindoles via copper(i)-catalyzed double domino reaction

“…Söderberg et al were able to show that the Pd-catalyzed, carbon monoxide mediated, double reductive cyclization is suitable for the construction of 2,2′-, 2,3′-, and 3,3′bisindoles. 18,19 Müller et al demonstrated that unsymmetrical 2,2′-bisindoles can be synthesized by reacting two differently substituted o-iodanilines with a TIPS-protected butadiene in a one-pot alkynylation-desilylation-alkynylation-cycloisomerization (ADAC) sequence. Among others, this 3-component reaction was used to construct tjipanazole I.…”