The Chemistry of Compounds Derived by Microbial Oxidation of Benzene and Derivatives: Cycloadditions Involving 1,2- Isopropylidenedioxycyclohexadienes.

Various cycloadditions involving the cyclohexadiene derivatives 7–10 have been investigated. Diets–Alder reactions involving dimethyl acetylenedicarboxylate, nitrosobenzene and N-ethylmaleimide gave the adducts 11–14, 16–17 and 18–23 respectively. Hydrolysis of the tricyclic compound 11 with pig liver esterase provided the optically active monoester 15. Tropone, and three carbenes reacted with the diene 7 to give the polycyclic compounds 24 and 29, 31 and 33 as expected. The structure of the adduct 24 was elucidated by X-ray crystallography. The ester 32 was converted into the lactone 36 by way of an oxa-Cope rearrangement of the aldehyde 34. The dienes 7 and 8 reacted with diphenylketene in an unexpected fashion giving the enol ethers 27 and 28 as well as the expected [2 + 2] cycloaddition products 25 and 26.