Visible light sensitizer-catalyzed highly selective photo oxidation from thioethers into sulfoxides under aerobic condition

Abstract

We report herein a visible light sensitizer-catalyzed aerobic oxidation of thioethers, affording sulfoxides in good to excellent yields. The loading of the catalyst was as low as 0.1 mol%. The selectivity was excellent. Mechanism studies showed both singlet oxygen and superoxide radical anion were likely involved in this transformation.

Selective Photooxidation of Sulfides Catalyzed by Bis‐cyclometalated IrIII Photosensitizers Bearing 2,2′‐Dipyridylamine‐Based Ligands

“…Previously, aerobic photooxidation of sulfides has been successfully accomplished by using metal complexes or organic dyes as PSs. Noteworthy systems reported recently used photosensitizers based on tetra‐ O ‐acetyl riboflavin, Rose Bengal, thioxanthones, Pt II complexes, Ru II Cu II complexes, coenzyme NAD + , and BODIPY dyes . However, as far as we know, Ir III complexes have not been used in similar studies and, furthermore, improvements can still be made in the field to shorten reaction times, enhance the photostability and recyclability of PSs, optimize the selectivity of the reaction, expand the substrate scope, and avoid organic solvents and UV light.…”

Understanding the Synergistic Effects Observed When Using Tethered Dual Catalysts for Heat and Light Activated Catalysis

“…The photocatalytic competency of the BDP 1 motif was assessed using the representative oxidation reaction of thioanisole 10 (Table 2). [35][36][37] Pleasingly, not only was the BDP motif still active in the catalysts 3-5, kinetic analyses showed that their activities were substantially enhanced when compared to the parent BDP 1 catalyst (Table 2 and S3). This effect can be clearly seen by comparing the conversion to the product 11 after 10 hours ( Table 2): for BDP 1, only 8 � 5 % of the product had formed, whereas an approximately 10-fold increase in product formation was seen for Ir(I)-BDP SS 3 (97 � 1 %), with significant enhancements also seen for Ir(I)-BDP HH 4 and Ir(I)-BDP HS 5 (76 � 5 % and 60 � 8 %, respectively).…”

“…As the oxidation of thioanisole can involve either singlet oxygen ( 1 O 2 ), the superoxide radical anion (O 2 * À ) or both 1 O 2 and O 2 * À , [36,[42][43][44][45] chemical trapping experiments were performed to investigate the reaction mechanism. Control reactions in the presence of a singlet oxygen trapping agent [36,46] resulted in greatly reduced thioanisole 10 oxidation, confirming that 1 O 2 is involved in the reaction mechanism for both BDP 1 and Ir(I)-BDP SS 3 (Figure 3 and Table S7). However, control reactions using a superoxide radical anion trap [36,47] also resulted in reaction inhibition, indicating that the photooxidation of thioanisole 10 proceeds through a reaction pathway where both 1 O 2 and O 2 * À are required (Figure 3, Table S7 and S8).…”

Interconnection of sulfides and sulfoxides in medicinal chemistry

“…Photodegradation has been implicated to play an essential role in the inactivation of certain cephalosporins . A very recent study claimed a good to excellent yield in the synthesis of sulfoxides by introducing very low concentrations (0.1 mol%) of light sensitizer under aerobic conditions . Moreover, some sulfide containing pesticides, including disulfoton, methiocarb, and fenthion, were reported to undergo rapid photooxidation to the corresponding sulfoxide when adsorbed on soil surfaces .…”