Efficient synthesis of disulfides by air oxidation of thiols under sonication

Alkyl, aryl and heteroaryl symmetrical disulfides can be easily obtained by heating the corresponding thiols for several hours at 80 °C with Et3N in DMF under atmospheric oxygen. These reactions are markedly accelerated by ultrasounds (few minutes at rt). Aromatic groups bearing electron donating and electron withdrawing groups, heteroaromatic, and alkyl thiols are analogously efficient affording disulfides in almost quantitative yields. Aminothiols and L-cysteine provide the corresponding disulfides without affecting the nitrogen function.