Sonochemical synthesis of novel C60 fullerene 1,4-oxathiane derivative through the intermediate fullerene radical anion

We have discovered a selective and efficient method for the synthesis of previously unknown 1,9-(1',4'-oxathiano)-1,9-dihydro-(C-60 -I-h)[5,6]fullerene, a compound with the direct attachment of the sulfur atom to the fullerene core. The method is based on the reaction of C-60 with 1,2-hydroxythiols in the presence of inorganic bases in air under ultrasonication. The significance of ultrasound has been exemplified with the comparative conventional methods. The title compound has been identified with mass-(MALDI TOF/TOF), one- and two-dimensional NMR H-1 and C-13 (COSY, HSQC, HMBS), IR, UV-Vis spectroscopic techniques. Using the direct EPR method, we have detected radical anion C-60(center dot-) (g = 2.0046 and Delta H = 2 G) as a key reaction intermediate of the sonochemical reaction. Based on the experimental results and quantum chemical calculations, we have proposed a mechanism for the conversion of C-60 and 2-mercaptoethanol to the C-60 -1,4-oxathiane adduct.