Aerobic Oxidation of Thiols to Disulfides Catalyzed by Diaryl Tellurides under Photosensitized Conditions

Abstract

Aerobic oxidation of thiols is efficiently catalyzed by diaryl tellurides such as bis(4-methoxyphenyl) telluride under photosensitized conditions to give the corresponding disulfides in good to excellent yields. In this catalytic system, the tellurone oligomer, produced by the reaction of a telluride with singlet oxygen, is assumed to be the active species and is capable of oxidizing 4 equiv of a thiol.

4,4′-Azopyridine as an easily prepared and recyclable oxidant for synthesis of symmetrical disulfides from thiols or alkyl halides(tosylates)/thiourea

“…Because this thiol is in equilibrium with its thioxo forms, the corresponding oxo compound might be produced as a by-product instead of the disulfides. [94,95] However, the oxidation of 2-mercaptobenzothiazole gave only 2,2'-dibenzothiazyl disulfide 4m in 88% yield, and we did not detect the oxo product, 2-benzothiazolinone.…”

First Metal‐ and Base‐Free Selective Oxidative Coupling of Thiols in Neat Ionic Liquids: NMR Probed “Ambiphilic” Character of Neutral [hmim]Br towards Atom‐Efficient Synthesis of Disulfides

“…In this context, only few efficient systems using molecular oxygen4 have been reported for the catalytic oxidation of thiols using metal complexes like Fe(BTC) (BTC=1,3,5‐benzenetricarboxylate),4a Mn(III)(BHBPDI)Cl [BHBPDI=bis(2‐hydroxybenzene)phthaldiimine],4f and also in basic conditions (Et 3 N/DMF) 4c. Recently Oba et al 4d. have also reported the aerobic oxidation of thiols catalyzed by diaryl tellurides in the presence of halogen and light at 0 °C.…”

7.28 Oxidation of Sulfur, Selenium, and Tellurium

“…17 The oxidation of thiols to disulfides can also be performed in less than 1 h under aerobic photochemical conditions by employing 1 mol% loading of bis(4-methoxyphenyl)telluride irradiated with a 500-W halogen lamp in the presence of tetraphenyl porphyrin (TPP) at 0 1C in dichloromethane or polar protic solvents (Scheme 4). 18 Excellent yields of aromatic, heteroaromatic, alkyl, and functionalized disulfides are generally observed. However, this system affords a complex reaction mixture when starting from a,o-dithiol.…”

“…Diaryl tellurones can be generated by photooxidation 393 and they are in situ used to promote the oxidation of thiols to disulfides. 18 [MoO(O 2 ) 2 (H 2 O)(HMPA)] is another useful oxidant to produce diaryl tellurones starting from either tellurides or telluroxides. 367 Similarly to the leaving group ability shown by selenones with nucleophiles (Scheme 49), alkyl aryl tellurides when treated with an excess of MCPBA (up to 5 equivalents) in alcoholic solvents at room temperature are converted into dialkyl ethers according to the mechanism illustrated in Scheme 62.…”