a, Typical aryl radical precursors in visible-light-mediated arylation reactions. b, Reported strategies of visible-light-induced aryl halide activation. c, Redox-neutral photochemical Heck-type arylation of vinylphenols with (hetero)aryl halides

June 18, 2024

• Title:       

  a, Typical aryl radical precursors in visible-light-mediated arylation reactions. b, Reported strategies of visible-light-induced aryl halide activation. c,  Redox-neutral photochemical Heck-type arylation of vinylphenols with (hetero)aryl halides

• Image Source:

  Redox-neutral photochemical Heck-type arylation of vinylphenols activated by visible light

• Mark:

  Scheme 1

• Associated context:

   As depicted in Scheme 1b, recent examples of successful activations of (hetero)aryl halides with visible light are involved in three mechanistic scenarios: (i) direct single electron transfer (SET)  from strongly reducing iridium, copper, N-phenylphenothiazine (CAS 7152-42-3) (PTH), or 9-anthrolate anion photocatalysts; (ii) indirect two-photon processes with organic dyes, such as perylene bisimides (PDIs), rhodamine (CAS 81-88-9) 6G (Rh-6G), 1,8-dihydroxyanthraquinone (CAS 117-10-2) (Aq-OH), and 9,10-dicyanoanthracene (CAS 1217-45-4) (DCA) by consecutive photo-induced SET cascades or with butane-2,3-dione (CAS 431-03-8) (BD, sensitizer) and 2,5-di-phenyloxazole (PPO, annihilator) by triplet-triplet annihilation; (iii) two-center photo-redox catalysis in which Ru(bpy)₃Cl₂ absorbs the visible light and transfers the energy to pyrene that enables the redox reactions. Herein, we demonstrated that the colored vinylphenolate anions, in situ generated by deprotonation of vinylphenols, reached an electronically excited state upon visible-light irradiation and then acted as effective photo-reductants for the reductive activation of non-activated  (hetero)aryl halides (Scheme 1c).