Unveiling the Synthetic Potential of Substituted Phenols as Fully Recyclable Organophotoredox Catalysts for the Iodosulfonylation of Olefins

Abstract

We describe an efficient photocatalytic procedure for the direct iodosulfonylation of terminal olefins 3 with α-iodo phenylsulfones 4. Specifically, the process uses the simple, robust, and fully recyclable phenol derivative 6e as the precatalytic system and occurs with visible-light irradiation (450 nm). Mechanistic investigations proved the key role of the in situ generated photocatalyst, namely phenolate anion 7e, which has shown high catalytic activity and considerable stability toward the operating conditions. Importantly, this photocatalytic transformation provides a wide variety of densely functionalized alkyl iodides 5 (23 examples, up to 95% yield). Finally, the synthetic potential of this photochemical transformation was demonstrated by scaling up the process under microfluidic conditions (up to 0.67 mmol h–1) while accessing a series of relevant product manipulations.

Binaphthol derivatives as catalysts for visible light induced aryl halide derivatizations

“…30,31 So, it is promising to use phenols for photocatalytic reduction reactions due to their reversible gain and loss of electrons under alkaline conditions. [32][33][34][35][36][37][38][39] Binaphthol (BINOL) is a common compound constructed of two β-naphthols bonded at the 1-position, exhibiting fine stability and diversified derivation. The conjugated structure of the naphthalene ring also endows it with a notable photoresponse.…”

“…30,31 So, it is promising to use phenols for photocatalytic reduction reactions due to their reversible gain and loss of electrons under alkaline conditions. 32–39…”

Halogen-Bonding-Promoted Photoinduced C–X Borylation of Aryl Halide Using Phenol Derivatives

“…For example, the “UV light” induced borylation of haloarenes using quaternary aryl ammonium salts under transition-metal-free conditions was reported by Li et al and Larionov et al Moreover, Jiao reported a noble organocatalytic reaction for the borylation of unactivated aryl chlorides by photoactivation of an in situ generated SED (super electron donor) complex . Shang et al also found that o -phosphinophenolates and analogues could act as an organophotocatalyst for the functionalization of aryl halides. , These photoinduced methodologies proceed through PET as the key step to form a carbon center radical, and we wondered if our developed XB-based photoreactions could be used …”

New Insights into the Exploitation of BODIPY Derivatives as Organic Photocatalysts

“…It is worth noting that also other organic photocatalysts (e. g., Eosin Y) can be used to drive ATRA reactions between olefins and alkyl halides. [14][15][16] From a mechanistic point of view, the BODIPY-based photocatalyst directly reaches an electronically singlet excited state upon light absorption (Figure 1a). The presence of the iodine atoms on the BODIPY skeleton, by means of the heavy atom effect, facilitates the intersystem crossing which drives the conversion of the singlet into the triplet excited state of PC1.…”

“…This is a relevant type of transformation, since it allows to simply prepare densely functionalized alkyl bromides ( 3 ) under mild reaction conditions. It is worth noting that also other organic photocatalysts (e. g., Eosin Y) can be used to drive ATRA reactions between olefins and alkyl halides [14–16] . From a mechanistic point of view, the BODIPY‐based photocatalyst directly reaches an electronically singlet excited state upon light absorption (Figure 1a).…”