Oxidative Photochlorination of Electron‐Rich Arenes via in situ Bromination

Abstract

Electron‐rich arenes are oxidatively photochlorinated in the presence of catalytic amounts of bromide ions, visible light, and 4CzIPN as organic photoredox catalyst. The substrates are brominated in situ in a first photoredox‐catalyzed oxidation step, followed by a photocatalyzed ipso‐chlorination, yielding the target compounds in high ortho/para regioselectivity. Dioxygen serves as a green and convenient terminal oxidant. The use of aqueous hydrochloric acid as the chloride source reduces the amount of saline by‐products.

Organic thermally activated delayed fluorescence (TADF) compounds used in photocatalysis

“…82). 231 An in situ bromination of the arene is first implicated before a halogen exchange occurs, generating the corresponding chlorinated product (Fig. 83).…”

Visible light-enabled regioselective chlorination of coumarins using CuCl2via LMCT excitation

“…Recently, visible light-enabled halogenation using halide ions as a halogen source has been developed (Scheme 1B). 13 For example, the König group developed an elegant bromination method for electron-rich arenes using sodium anthraquinone sulfonate (SAS) as a photocatalyst. 13 e In our previous work, 7 f we developed a CuX 2 /ZnX 2 activation of NXS to chlorinate or brominate biologically useful coumarins.…”

C–H chlorination of (hetero)anilines via photo/organo co-catalysis

“…In recent years, chlorination of arenes has been documented through methods such as directed metalation, 3 electrophilic aromatic substitution, 4 enzyme catalysis, 5 oxidative chlorination, 6 photo-redox chlorination, 7 and halide electrolysis. 2,8 Effective and selective chlorination or other halogenation methods will bring great synthetic convenience for organic synthesis and pharmaceutical chemistry.…”

“…15 Recent studies have demonstrated that a radical process via single electron transfer (SET) or proton-coupled electron transfer (PCET) in the presence of 4CzIPN or its analogues is a promising alternative for activating amines. 6,16 Traditionally, the chlorination selectivity in traditional Lewis acid/Lewis base promoted NCS mediated methods is controlled to a large extent by the steric effect and electronic effect of anilines. 17 Herein, we propose that a SET or PCET process can activate amines and the Cl + agent ( i.e.…”