Organoelectrophotocatalytic C–H Silylation of Heteroarenes

Abstract

An organoelectrophotocatalytic approach for the C−H silylation of heteroarenes through dehydrogenation crosscoupling with H 2 evolution has been developed. The organoelectrophotocatalytic strategy is carried out under a simple and efficient monocatalytic system by employing 9,10-phenanthrenequinone both as an organocatalyst and as a hydrogen atom transfer (HAT) reagent, which avoids the need for an external HAT reagent, an oxidant, or a metal reagent. A variety of heteroarenes can be compatible in satisfactory yields with excellent regioselectivity.

Organophotoelectrochemical silylation cyclization for the synthesis of silylated 3-CF3-2-oxindoles

“…Based on the above results and our previous investigation, 20 a possible mechanism for the organophotoelectrochemical silylation cyclization of N -methyl- N -phenyl-2-(trifluoromethyl)acrylamide ( 1 ) with t BuMe 2 SiH ( 2 ) is proposed (Scheme 5). In the beginning, the irradiation of PQ with 420–425 nm LEDs produces excited PQ*.…”

Electrochemically Driven Hydrogen Atom Transfer Catalysis: A Tool for C(sp3)/Si–H Functionalization and Hydrofunctionalization of Alkenes

“…Upon light excitation, photoelectrochemical HAT catalysis can proceed via type-II or type-III mechanisms. In the type-II mechanism (Figure d), the excited photocatalyst (PC*) abstracts hydrogen atoms from R–H to give alkyl radicals (R • ), and this process is closely related to the direct photoinduced HAT. , The major difference is that the photocatalyst (PC) is regenerated via anodic oxidation of (PC • )–H. The type-III mechanism (Figure e) generates a hydrogen atom abstractor (Cl • or N +• ) through sequential anodic oxidation and photoexcitation, , and the hydrogen atom abstractor then triggers the HAT process.…”

C–H Bond Silylation of Heteroarenes

“…Recently, Wang and co-workers reported an organo-electrophotocatalytic C–H silylation of heteroarenes by merging photochemistry and electrochemistry (Scheme 38 ). 58 This direct dehydrogenative C–H silylation relies on the dual function of 9,10-phenanthrenequinone (PQ) as a photo-electrocatalyst and a hydrogen atom transfer (HAT) reagent, and thereby avoids the requirement for metal reagents and traditional oxidants. Using the standardized reaction conditions, Wang showed that differently substituted quinolines, isoquinolines, pyridines, pyridazine, pyrimidine and other types of heterocycles gave the corresponding silylated products in good yields and excellent regioselectivity.…”