syn-Selective alkylarylation of terminal alkynes via the combination of photoredox and nickel catalysis

Abstract

Substituted alkenes are pivotal structural motifs found in pharmaceuticals and agrochemicals. Although numerous methods have been developed to construct substituted alkenes, a generally efficient, mild, catalytic platform for the conversion of alkynes to this highly functionalized scaffold via successive C–C bond forming steps remains in high demand. Here we describe an intermolecular, regio- and syn-stereoselective alkylarylation of terminal alkynes with tertiary alkyl oxalates via photoredox-Ni dual catalysis. This catalytic protocol, synergistically combining Ir/Ni-catalyzed alkyne difunctionalization with photoinduced alkene isomerization, affords trisubstituted alkenes with excellent efficiency and syn-stereoselectivity. The mild conditions tolerate many functional groups, allowing for a broad scope with respect to terminal alkynes, aryl bromides, and alkyl oxalates.

Mechanisms of Nickel-Catalyzed Cross-Coupling Reactions

“…Alkyl halides [92] and phthalimides [63] are versatile radical precursors that can be activated electrocatalytically, photocatalytically, and by transition metals. Oxalates have found utility in both transition-metal and photocatalytic reactions [93]. Dual photoredox-Ni catalysis is particularly useful in light of the large library of available alcohols and carboxylates.…”

Recent advances in photoredox and nickel dual-catalyzed cascade reactions: pushing the boundaries of complexity

“…Scheme 10 Dicarbofunctionalization of vinyl boronates via photoredox and nickel dual catalysis. 11,[4051][4052][4053][4054][4055][4056][4057][4058][4059][4060][4061][4062][4063][4064] This journal is © The Royal Society of Chemistry 2020…”

“…24 The arylsulfonylation of alkynes with high chemo-, Scheme 13 Radical ring-opening-arylation, -vinylation and -alkylation cascades via photoredox and nickel dual catalysis. 11,[4051][4052][4053][4054][4055][4056][4057][4058][4059][4060][4061][4062][4063][4064] This journal is © The Royal Society of Chemistry 2020 regio-, and stereo-selectivity was achieved via the cross-coupling of aryl halides with sodium sulnates and alkynes under mild conditions. Notably, the cross-coupling products of trisubstituted alkenes can be obtained with either E-or Z-selectivity by choosing an appropriate photocatalyst with a suitable triplet state energy.…”

Site‐Selective 1,2‐Dicarbofunctionalization of Vinyl Boronates through Dual Catalysis

“…As part of our interest in cross‐electrophile coupling reactions and site‐selective functionalization of olefins, we recently questioned whether it would be possible to design a catalytic reaction that would allow the incorporation of two different electrophilic partners into readily accessible vinyl boronates in a 1,2‐fashion with total control of the regioselectivity pattern . In line with the elegant work of the Nevado and Chu groups, we hypothesized that a dual catalytic approach might be suited for our purposes. Specifically, we propose that nucleophilic alkyl radicals, generated upon SET from an electron donor, might undergo regioselective addition to a vinyl boronate en route to I , the stability of which is dictated by the effective delocalization of the radical through the vacant p ‐orbital of the boron atom (Scheme ) .…”