Visible‐Light‐Driven Intermolecular Reductive Ene–Yne Coupling by Iridium/Cobalt Dual Catalysis for C(sp³)−C(sp²) Bond Formation

Abstract

A new methodology to form C(sp3)−C(sp2) bonds by visible‐light‐driven intermolecular reductive ene–yne coupling has been successfully developed. The process relies on the ability of the Hantzsch ester to contribute in both SET and HAT processes through a unified cobalt and iridium catalytic system. This procedure avoids the use of stoichiometric amounts of reducing metallic reagents, which is translated into high functional‐group tolerance and atom economy.

Direct Synthesis of Adipic Esters and Adiponitrile via Photoassisted Cobalt‐Catalyzed Alkene Hydrodimerization

“…Based on the experimental data and previous studies in photoredox/cobalt catalysis, [14a–d,24] a plausible mechanism was proposed (Scheme 3, e). Frist, a single electron transfer (SET) from HE to the photoexcited 4‐CzIPN* generates HEH⋅ + (E ox (HE/EH⋅ + )=0.51 V vs. Fc in MeCN) [23e,25] and 4‐CzIPN⋅ − (E 1/2 red(4‐CzIPN*/4‐CzIPN⋅ − )=−1.21 V vs. SCE in MeCN) [26] .…”

Intermolecular Photocatalytic Chemo‐, Stereo‐ and Regioselective Thiol–Yne–Ene Coupling Reaction

“…Along with the generally accepted C−C cross‐coupling reactions involving unsaturated hydrocarbons with leaving groups (Sonogashira, Suzuki, Heck and other reactions), alternative methods of direct atom‐economical ene–ene, ene–yne and yne–yne couplings were developed [8–12] . These methods provide a great variety of possible products; however, at the same time, the control of chemo‐, regio‐ and stereoselectivity in these reactions becomes challenging, especially in the case of intermolecular processes [13–20] . In recent years, alkynes have also undergone a renaissance in the chemistry of radical photochemical processes involving metal complexes, since the triple bond is a convenient platform for selective bifunctionalization through C−C bond creation [21–24] …”

“…[8][9][10][11][12] These methods provide a great variety of possible products; however, at the same time, the control of chemo-, regio-and stereoselectivity in these reactions becomes challenging, especially in the case of intermolecular processes. [13][14][15][16][17][18][19][20] In recent years, alkynes have also undergone a renaissance in the chemistry of radical photochemical processes involving metal complexes, since the triple bond is a convenient platform for selective bifunctionalization through CÀ C bond creation. [21][22][23][24] The thiol-yne reaction is one of the most well-known processes in radical chemistry (Scheme 1A).…”

Intermolecular Photocatalytic Chemo‐, Stereo‐ and Regioselective Thiol–Yne–Ene Coupling Reaction

“…Along with the generally accepted C−C cross‐coupling reactions involving unsaturated hydrocarbons with leaving groups (Sonogashira, Suzuki, Heck and other reactions), alternative methods of direct atom‐economical ene–ene, ene–yne and yne–yne couplings were developed [8–12] . These methods provide a great variety of possible products; however, at the same time, the control of chemo‐, regio‐ and stereoselectivity in these reactions becomes challenging, especially in the case of intermolecular processes [13–20] . In recent years, alkynes have also undergone a renaissance in the chemistry of radical photochemical processes involving metal complexes, since the triple bond is a convenient platform for selective bifunctionalization through C−C bond creation [21–24] …”