Haloselective Cross-Coupling via Ni/Photoredox Dual Catalysis

Abstract

The chemoselective functionalization of polyfunctional aryl linchpins is crucial for rapid diversification. Although well-explored for Csp2 and Csp nucleophiles, the chemoselective introduction of Csp3 groups remains notoriously difficult and is virtually undocumented using Ni catalysts. To fill this methodological gap, a “haloselective” cross-coupling process of arenes bearing two halogens, I and Br, using ammonium alkylbis(catecholato)silicates, has been developed. Utilizing Ni/photoredox dual catalysis, Csp3–Csp2 bonds can be forged selectively at the iodine-bearing carbon of bromo(iodo)arenes. The described high-yielding, base-free strategy accommodates various protic functional groups. Selective electrophile activation enables installation of a second Csp3 center and can be done without the need for purification of the intermediate monoalkylated product.

Alkyl Carbon–Carbon Bond Formation by Nickel/Photoredox Cross‐Coupling

“…[46] Couplings with these reagents display exquisite chemoselectivity when dihalogenated arenes were used as coupling partners (Scheme 3C). [47] This class of radical precursors has also been cross-coupled with borylated aryl bromides [48] as well as aryl triflates,tosylates,and mesylates. [49]…”

Synergistic Photoredox/Transition‐Metal Catalysis for Carbon–Carbon Bond Formation Reactions

“…Later, the same team reported a novel haloselective reaction using a dual photoredox/Ni catalysis methodology and primary or secondary alkyl silicates 327 (Scheme ) . Indeed, using aryl halides bearing both bromine and iodine atoms, in any position on the ring, gave a very good selectivity of up to 98:2, reachable by tuning the conditions and ligands.…”

Alkyl‐C‐C‐Bindungsbildung durch Nickel/Photoredox‐Kreuzkupplung

“…Schema 1. [47] Diese Klasse von Radikalvorstufen reagierte auch in Kreuzkupplungen mit borylierten Arylbromiden [48] sowie Aryltriflaten, -tosylaten und -mesylaten. [42] 2015 wurde über eine Ni/Photoredox-katalysierte C(sp 2 )-C(sp 3 )-Kreuzkupplung zwischen 4-Brombenzonitril und einer Reihe von Alkylbis(catecholato)silicaten mit Kalium- [18]Krone-6-Gegenionen berichtet.…”

“…[46] Kupplungen mit diesen Reagenzien zeigen eine ausgezeichnete Chemoselektivitätb ei Verwendung von Dihalogenarenen als Kupplungspartner (Schema 3C). [47] Diese Klasse von Radikalvorstufen reagierte auch in Kreuzkupplungen mit borylierten Arylbromiden [48] sowie Aryltriflaten, -tosylaten und -mesylaten. [49]…”