Copper(I)-catalyzed Diastereoselective Dearomative Carboborylation of Indoles

Abstract

The first CB bond-forming dearomative carboborylation of heteroaromatic compounds has been achieved using copper(I) catalysis. This reaction includes the regioselective addition of a borylcopper(I) intermediate to indoles, followed by the diastereoselective methylation of the resulting copper(I) enolate intermediate to afford the corresponding 3-boryl-2-methylindolines bearing a quaternary stereogenic center with excellent regio-and diastereoselectivity.

Copper-Catalyzed Borylative Difunctionalization of π-Systems

“…Despite numerous reports of ring-opening reactions, the tendency of these bicyclic scaffolds to remain closed facilitated difunctionalization with iodomethane. The Ito lab built on their previous work in dearomative borylcuprations, , and discovered the cyclic enolate arising from dearomative conjugate borylation could be intercepted by an alkyl electrophile (Scheme b) . Similar to Zhong’s report, protodemetalation was difficult to avoid, leading to generally modest yields.…”

Saturated Boronic Acids, Boronates, and Trifluoroborates: An Update on Their Synthetic and Medicinal Chemistry

“…[266] An extension of the alkene scope included strained bycyclic alkenes [267,268] and indoles. [269] As in the case of Cu-catalyzed hydroboration (Scheme 51), the regioselectivity of carboboration can be controlled by adjusting the Cu environment. Xiao, Fu, and co-workers achived this through changing the steric bulk of the ligand.…”

Transition‐Metal‐Catalyzed Three‐Component Difunctionalizations of Alkenes

“…achieved the alkynylboration of styrenes with B 2 (pin) 2 and bromoalkynes, whereas Ito et al. realized the trans ‐methylboration of indole‐2‐carboxylate with B 2 (pin) 2 and MeI under similar reaction conditions . Recently, Popp et al.…”

“…Along this line, Fu et al achieved the alkynylboration of styrenes with B 2 (pin) 2 and bromoalkynes, [61] whereas Ito et al realized the trans-methylboration of indole-2-carboxylate with B 2 (pin) 2 and MeI under similarr eaction conditions. [62] Recently, Popp et al described ac opper-catalyzed regioselective borylcarboxylation of styrenes with B 2 (pin) 2 and gaseous CO 2 . [63a] Undert he reactionc onditions, various b-boryl a-aryl propionic acids were obtained in moderate-to-excellent yields.…”