Donor–Acceptor Complex Enables Alkoxyl Radical Generation for Metal‐Free C(sp³)–C(sp³) Cleavage and Allylation/Alkenylation

Abstract

The alkoxyl radical is an essential and prevalent reactive intermediate for chemical and biological studies. Here we report the first donor-acceptor complex-enabled alkoxyl radical generation under metal-free reaction conditions induced by visible light. Hantzsch ester forms the key donor-acceptor complex with N-alkoxyl derivatives, which is elucidated by a series of spectrometry and mechanistic experiments. Selective C(sp )-C(sp ) bond cleavage and allylation/alkenylation is demonstrated for the first time using this photocatalyst-free approach with linear primary, secondary, and tertiary alkoxyl radicals.

Hantzsch Ester as a Visible‐Light Photoredox Catalyst for Transition‐Metal‐Free Coupling of Arylhalides and Arylsulfinates

“…When 1 a or 2 a is added, the resonance of HE − protons at δ =3.98, 2.03 and 1.15 ppm shows remarkable downfield shifts. So an electron donor–acceptor (EDA) complex is formed between HE − and arylhalide (or arylsulfinate) in the photocatalytic process . The light on/off experiments showed that a smooth transformation under the light irradiation, but no further conversion was observed when the mixture was kept in the dark (Figure S12, Supporting Information).…”

“…So an electron donor-acceptor (EDA) complex is formed between HE À and arylhalide (or arylsulfinate) in the photocatalytic process. [24] The light on/off experiments showed that as mooth transformation under the light irradiation, but no further conversion waso bserved when the mixture was kept in the dark (Figure S12, Supporting Information). The coupling reactions were carried out at 100 8Ct or esult in the formation of 3aa in about2 5% yield with or without2 ,2'-azobis(2-methylpropionitrile) (AIBN) (Table S1,e ntries 1a nd 2, Supporting Information).…”

A Convenient Synthesis of Sulfones via Light Promoted Coupling of Sodium Sulfinates and Aryl Halides

“…[20] It was believed that an electron donor-acceptor (EDA) complex is formed to promote the electron transfer. [21][22] Using the similar strategy, Miyake group reported a mild, efficient, visible-light promoted protocol for the CÀS cross-coupling of thiols and aryl halides. [23] Wang group developed a new synthetic method of vinyl sulfones via light-promoted formation of EDA complex from arylsulfinic acid and biaryl isocyanide.…”

Synergistic Catalysis for the Umpolung Trifluoromethylthiolation of Tertiary Ethers

“…The resulting highly electrophilic thiyl radical 4 rapidly undergoes a HAT event with the most hydridic α‐C−H group of the ether to generate alkoxyl radical 5 . This then cleaves the C−O bond homolytically to form a tertiary alkyl radical 6 . There are two plausible pathways, paths A and B (Scheme ) for tertiary alkyl radical trifluoromethylthiolation.…”