C(sp³)−C(sp³) Cross‐Coupling of Alkyl Bromides and Ethers Mediated by Metal and Visible Light Photoredox Catalysis

Abstract

We report a C(sp3)−C(sp3) cross‐coupling of alkyl bromides and alkyl chlorides with ethers by dual photoredox‐nickel catalysis. The catalytic system comprises of the organic photocatalyst 1,2,3,5‐tetrakis(carbazol‐9‐yl)‐4,6‐dicyanobenzene (4‐CzIPN) and bench stable nickel (II) acetylacetonate in the presence of visible‐light, providing the coupling products in up to 92% yield. Preliminary mechanistic studies suggest two catalytic cycles, as well as the photogeneration of bromine or chlorine radicals from halide atoms that are present in the structures of the coupling partners. The halide radical mediates the hydrogen atom transfer event, avoiding the need of an additional HAT catalyst.

Organic thermally activated delayed fluorescence (TADF) compounds used in photocatalysis

“…91a) 254 or with ethers (Fig. 91b), 255 allylic alcohols with DHP radical precursors (Fig. 91c) 256 or oxabenzonorbornadiene with alkylamines (Fig.…”

“…92. 255 Oxidative addition of the alkyl bromide to the Ni(0) species produces a Ni(II) alkyl halide complex, which reductively quenches the excited PC. Photoelimination of the Ni(III) species releases an electrophilic bromyl radical, which undergoes HAT with the ether.…”

Recent Advances in C(sp3)–C(sp3) Cross-Coupling via Metalla­photoredox Strategies

“…In this realm, König et al disclosed a catalytic C(sp 3 )-C(sp 3 ) cross-coupling of alkyl bromides or chlorides with ethers by performing dual photoredox/nickel catalysis (Scheme 25). 41 Alkyl halides serve as both the HAT reagent and the coupling partner, thereby avoiding the need for an external HAT catalyst. The scope of this protocol was largely limited to tetrahydrofuran substrates, as six-membered cyclic ethers as well as acyclic ethers were not compatible.…”

The PhotoFlexys: A Multi‐Purpose Reactor Platform to Simplify Process Intensification and Mechanistic Studies in Photochemistry

“…[25][26][27][28] In general, batch reactions are commonly conducted in standard glassware, which is irradiated from either the side [29] or the bottom. [30] Under continuous flow conditions, various approaches like the utilization of coiled capillary reactors, [31] plate-based microreactors, [32] falling-film [33] or vortex reactors [34] have been demonstrated. Further, different commercially available photoreactors have proven their applicability in either batch [35][36][37][38] or continuous flow photochemistry.…”

“…Driven by the larger availability of light emitting diodes (LED) as an efficient irradiation source, different types of photoreactors have been developed for batch and continuous flow applications [25–28] . In general, batch reactions are commonly conducted in standard glassware, which is irradiated from either the side [29] or the bottom [30] . Under continuous flow conditions, various approaches like the utilization of coiled capillary reactors, [31] plate‐based microreactors, [32] falling‐film [33] or vortex reactors [34] have been demonstrated.…”