Abstract 2, 5-Dimethylene-2, 5-dihydrothiophene (1), prepared by the pyrolysis of 5- methylthenyl benzoate (3), has been detected by low-temperature NMR spectroscopy. 1 reacts with triplet oxygen to form a cyclic bisperoxide 6. Upon heating, 6 decomposes to give 2, 5-bis (hydroxymethyl) thiophene (7), 2-formyl-5-hydroxymethylthiophene (8) and 2, 5- diformylthiophene (9) in a ratio of 1: 2: 1, respectively.
