Organophotocatalytic Regioselective C−H Alkylation of Electron‐Rich Arenes Using Activated and Unactivated Alkenes

Abstract

Direct alkylation of the C−H bond arenes in a selective manner is a long‐standing challenge. Herein, a metal‐free photocatalytic regioselective C−H alkylation method for electron‐rich arenes with both activated and unactivated alkenes was developed. The reaction tolerates a wide range of aromatic rings with diverse substitution patterns, as well as terminal and internal alkenes, providing a general and straightforward metal‐free method for C−C bond formation from inert C−H bonds. Moreover, alkynes are also compatible to give the C−H vinylation of electron‐rich arenes.

Enroute sustainability: metal free C–H bond functionalisation

“…Recently this year, Shu and co-workers developed a metal-free photocatalytic regioselective C–H alkylation method for electron-rich arenes 241a that employs both activated and unactivated alkenes 241b (Scheme 241). 306 The reaction tolerated both terminal and internal alkenes, as well as activated and unactivated alkenes, such as styrene derivatives, unsaturated alkenes, enols, acyl enamines, alkenyl borates, alkenyl halides, and aliphatic alkenes, providing direct access to linear alkylated electron-rich arenes. On the other hand, the reaction is permissive of a broad range of aromatic rings with various substitution patterns, and alkynes can be employed to generate C–H vinylation of electron-rich arenes.…”

Rapid Synthesis of β-Chiral Sulfones by Ni-Organophotocatalyzed Enantioselective Sulfonylalkenylation of Alkenes

“…Significant progress in asymmetric Ni-catalyzed and photocatalyzed two-component C–C coupling has been achieved over the past few years. − In comparison, a Ni-catalyzed and photocatalyzed asymmetric three-component reaction still remains a formidable challenge, partially due to the difficulties in tuning the reactivities of the different putative radical intermediates as well as controlling the enantioselectivity of the reaction. Due to the intrinsic advantage of nickel catalysis , and photocatalysis, radical-mediated transformations offer a potential alternative for the one-pot adjacent difunctionalization of unsaturated bonds. − During the preparation of this paper, Chu reported an elegant enantioselective three-component alkylarylation and alkylvinylation of electron-deficient alkenes by photoredox/nickel catalysis, providing convenient access to enantioenriched α-aryl/alkenyl carbonyls, phosphonates, and sulfones from readily available starting materials. − As part of our continuous interest in Ni catalysis and visible-light catalysis, − we envisioned the dual-catalyzed asymmetric three-component reaction of alkenes to furnish enantioenriched β-chiral sulfones via asymmetric alkenylsulfonylations from sulfinates and alkenyl halides (Scheme c). To realize this proposal, several challenges have to be tackled along with the control of enantioselectivity.…”

Photoelectrochemical Asymmetric Catalysis Enables Enantioselective Heteroarylcyanation of Alkenes via C–H Functionalization

“…The proposed mechanism for the photoelectrochemical asymmetric heteroarylcyanation of alkenes is illustrated in Figure D. Upon photoexcitation, the acridinium catalyst [Mes-Acr-Ph] + transforms into its highly oxidizing excited state [Mes-Acr-Ph] + * , which subsequently abstracts an electron from the heterocycle substrate, thereby forming a stable acridine radical [Mes-Acr-Ph] • and a concurrent heteroarene radical cation I . , Single electron oxidation on the anode reverts [Mes-Acr-Ph] • back to the ground-state acridinium [Mes-Acr-Ph] + . The open-shell species I reacts at position (a) with the aryl alkene substrate, which results in the formation of distal radical cation II .…”