Bovine serum albumin triggered waste-free aerobic oxidative coupling of thiols into disulphides on water: An extended synthesis of bioactive dithiobis(phenylene)bis(benzylideneimine) via sequential oxidative coupling–condensation reactions in one pot from

• A mild and environmentally benign protocol was developed using bovine serum albumin as a catalyst.
• Aerobic oxidation using water as green solvent.
• Broad substrates scope.
• Extended for the synthesis of bioactive bis(aminophenyl)disulphidediimines in one pot from aminothiophenol and benzaldehydes in sequential manner.
• Good recyclability up to four cycles.

Bovine serum albumin (BSA) has been explored for aerobic oxidative coupling of thiols (aromatic, heterocyclic as well as aliphatic) “on water” towards formation of disulphides (SS) without using any metal/non-metal complexes, bases and additives, which renders the process environmentally benign and economically attractive with good recyclability (up to four cycles). The developed green protocol was further extended for synthesis of diallyldisulphide (DADS), an important constituent of natural occurring allicin. Among various synthesized disulphides, bis(2-aminophenyl)disulphide, obtained by oxidative coupling of 2-aminothiophenol in BSA, was further utilized for condensation with benzaldehyde in the same pot thus enabling easy access to bioactive dithiobis(phenylene)bis(benzyldeneimine). This is the first example of BSA catalysed sequential (oxidation/condensation) reaction where one SS and two CN bonds are formed solely “on water.”

A green and clean route for the aerobic oxidative coupling of thiols including aromatic, heteroaromatic and aliphatic thiols employing BSA as a biocatalyst “on water” has been developed towards formation of (SS) disulphides under metal/non-metal- or base-free conditions. The methodology also applicable for successful synthesis of diallyldisulphide (DADS), an important precursor of bioactive allicin. Interestingly, bis(aminophenyl)disulphide generated by oxidation of aminothiophenol could directly react with benzaldehyde to form bioactive bis(aminophenyl) disulphidediimines in sequential (oxidation–condensation) manner with one SS and two CN bonds in one pot.Figure optionsDownload as PowerPoint slide