Pyrroloindoline/Pyridoindoline Synthesis via C3-Dearomative Arylation/Cyclization of Tryptamine/Homotryptamine Derivatives Using Palladium-Dihydroxyterphenylphosphine Catalyst

A palladium-dihydroxyterphenylphosphine (DHTP)catalystwas successfully applied to the dearomative C3-arylation of tryptaminederivatives with aryl nonaflates. The intramolecular cyclization ofthe resulting 3,3-disubstituted indolenines afforded C3a-arylatedpyrroloindolines in one pot. We postulate that the formation of complexesbetween the lithium salts of DHTP and the tryptamine derivative isthe key to promoting selective arylation at the C3-position of theindole ring. Furthermore, reactions using homotryptamine derivativessuccessfully provided C4a-arylated pyridoindolines.

Automated summary

A palladium-dihydroxyterphenylphosphine catalyst was used for the selective C3-arylation of tryptamine derivatives with aryl nonaflates, leading to the formation of C3a-arylated pyrroloindolines via intramolecular cyclization. Complex formation between the lithium salts of DHTP and the tryptamine derivative is proposed as the key factor for promoting arylation at the C3-position of the indole ring. Additionally, C4a-arylated pyridoindolines were obtained by reactions using homotryptamine derivatives.