Organophotoredox-Catalyzed Three-Component Coupling of Heteroatom Nucleophiles, Alkenes, and Aliphatic Redox Active Esters

Abstract

This manuscript describes a visible-light-mediated organophotoredox catalytic process for vicinal difunctionalization of alkenes using heteroatom nucleophiles and aliphatic redox active esters. A wide range of heteroatom nucleophiles including alcohols, water, carboxylic acids, amides, and halogens can be used for this reaction. This radical relay type reaction allows forging of C­(sp3)–C­(sp3) with a carbon-centered radical and C­(sp3)–heteroatom bonds with a benzyl cation on the vinylarenes with complete regioselectivity in a single step.

Organophotoredox‐Catalyzed Decarboxylative N‐Alkylation of Sulfonamides

“…The proposed mechanism is outlined in Figure 2B. Based on our previous report, PTH1 and a redox active ester ( 2 ) form an EDA complex ( A ) which has absorption bands in the visible region [10b] . Subsequently, photo‐induced single electron transfer from PTH1 to 2 occurs to afford the radical cation form ( B ) of PTH1 and the radical anion form ( C ) of 2 .…”

“…We took advantage of the characteristic radical‐mediated process of our pathway by employing it in a radical‐relay type difunctionalization of an alkene [15] . As in our previous study on organophotoredox‐catalyzed alkene difunctionalization, [10b] PTH4 was used as the catalyst. Although the yields were moderate, our photoredox catalysis could assemble sulfonamides, styrenes and redox active esters to form complex benzyl sulfonamides ( 5 aaf , 5 eaf and 5 abf ).…”

“…In previous reports, our group developed an organophotoredox-catalyzed reaction for the decarboxylative cross-coupling between heteroatom nucleophiles and aliphatic carboxylic acidderived redox active esters. [10,11] In this reaction, a photoexcitable phenothiazine acted as a radical-polar crossover catalyst, [12] which causes a single electron transfer to a redox active ester, producing the phenothiazine cation radical and the corresponding alkyl radical upon decarboxylation. The alkyl radical is oxidized to the carbocation equivalent by the phenothiazine cation radical.…”

Alkylation Reactions with Alkylsulfonium Salts

“…49c The protocol was also amenable to the vicinal difunctionalization of alkenes 243 , enabling the assembly of various nitrogen, oxygen, and halogen nucleophiles 244 with 243 and 233 into highly functionalized C(sp 3 )-rich motifs 245 (Scheme 26c ). 49d The catalytic cycle of the reaction begins similarly with the photoinduced SET within an EDA complex composed of sulfide 236b and 233 , which is then coupled with vinylarene 243 to form a benzylsulfonium intermediate. Finally, the benzylsulfonium salt is intercepted by 244 to afford the bifunctionalized products 245 .…”

Gram-Scale Synthesis of the N-Phenyl Phenothiazine Photocatalyst by Benzyne Addition

“…4 As an example, N-phenyl phenothiazine is the only photoredox catalysts that has been shown to add SF5 to alkenes via reduction of SF6. 5 Aryl phenothazines have additionally been used as photocatalysts for atom-transfer, 6 atom-transfer radical polymerization reactions, 7 lignin reduction, 8 carbofunctionalization, 9 and olefin-alcohol addition. 10 Phenothiazine radical cations have also been shown to be powerful super-oxidants, especially in their excited states.…”