Autoxidation of Guaiazulene and 4,6,8-Trimethylazulene in Polar Aprotic Solvent: Structural Proof for Products

Autoxidation of guaiazulene and 4,6,8-trimethylazulene at 100–120°C in DMF (or HMPA) respectively yielded 25 and 17 separable products, including several known compounds. Most of these new compounds were derivatives of 1,5- and 1,7-azulenequinone, 1H-inden-1-one, naphthoquinone, and benzenoid, or dimeric and trimeric forms; structures of these products were established on the basis of spectroscopic (NMR, UV, IR, and MS) and half-wave potential (E1⁄2) data. 1H NMR (200-MHz) parameters of various azulene derivatives are given for comparative study. Possible reaction pathways are suggested for the formation of such a wide variety of interesting products.