Autoxidation of 5, 5'-Biguaiazulene-3, 3'(5H, 5'H)-dione in Dirhlormethane, Dirhlormethane/Pyridine and Pyridine

Abstract

Autoxidation of 5, 5'-biguaiazulene-3, 3'(5H, 5'H) -dione (2) was studied in CH₂Cl₂ an pyridine (or a mixture) at 25° C for 24 h, giving preferentially 5-isopropylidene-3, 8-dimetyl-1 (5H) -azulenone (3)in CH₂Cl₂ and 3, 5-guaiazulenequinone (4) in pyridine as a major product. Compound 3 was converted into 3, 7-dimethy1-1-oxoindene-6-carbaldehyde (17, Y =95.1%), when the reddish-orange needles of 3 were allowed to stand at 25° C for 7 d. Possible reaction pathways for the formation of these products are also discused.