Free‐Amine‐Directed Alkenylation of C(sp²)H and Cycloamination by Palladium Catalysis

Abstract

A new protocol for the palladium-catalyzed free-amine-directed alkenylation of C(sp(2))-H bonds and cycloamination is described. Substituted biaryl-2-amines react with various alkenes, including electron-deficient alkenes, aryl alkenes and alkyl alkenes, to give the corresponding phenanthridines with exclusive regioselectivity. The use of α-branched styrenes leads to the formation of tricyclic compounds with a seven-membered amine ring. The method operates through a free-amine-directed alkenylation and a subsequent hydroamination cyclization reaction.

Cobalt(II)‐Catalyzed [5+2] C−H Annulation of o‐Arylanilines with Alkynes: An Expedient Route to Dibenzo‐[b,d]azepines

“…Transition metal catalyzed C−H functionalization has emerged as an ideal way for rendering shorter synthetic routes to these frameworks through nitrogen‐group‐assisted annulations of less pre‐functionalized precursors with different coupling partners . In 2012, Zhang's group reported the first Pd‐catalyzed free‐amine‐directed alkenylation/cycloamination sequence of biphenyl‐2‐amines with α ‐branched styrenes to furnish dibenzo[ b , d ]azepines bearing a quaternary center . Inspiringly, the group of Luan described a stereoselective Pd(II)‐catalyzed [5+2] oxidative annulation of biphenyl‐2‐amines with internal alkynes, leading to a various imine‐type dibenzo[ b , d ]azepines, despite its unsuccess when using terminal alkynes .…”

Emergence of Unactivated Olefins for the Synthesis of Olefinated Arenes

“…Zhang and co‐workers disclosed a palladium‐catalyzed free‐amine‐directed alkenylation and subsequent hydroamination cyclization reaction in 2012 . A variety of alkenes were treated with substituted biaryl‐2‐amine derivatives in the presence of 10 mol‐% PdCl 2 catalyst and CuCO 3 /Cu(OH) 2 cooxidant.…”

Silver Ion Promoted, PdII‐Catalyzed Arylation of Arenes with a Free Amine as Directing Group in Aqueous Medium

“…We previously investigated free-amine-directed, palladium-catalyzed alkenylation of arenes in the presence of acetic acid, but the free amines subsequently underwent cycloamination with the alkenes to generate phenanthridines as the final products. [13] Given the known strong coordinative interaction between silver ions and amines, we speculated that the binding ability of the amino group could also be tuned by employing the appropriate silver salt, which acts like an acid. Herein, we report a palladium-catalyzed, freeamine-directed Suzuki-Miyaura-type coupling reaction [14] of biaryl-2-amines with aryl boronic acids in the presence of silver nitrate in aqueous media.…”