Synthetic Photochemistry. LI. Structure Elucidation of the Pyrolysates Formed by “Retro-Benzilic Acid Rearrangement” of the Proto-Photocycloadducts of Methyl 2,4-Dioxopentanoate-Olefins
Pyrolysates obtained from the proto-photoadducts of methyl 2,4-dioxopentanoate with olefins were shown to be 3-acetyl-1,2-cyclopentanedione derivatives. One-pot formation of polyfunctionalized cyclopentane derivatives via a photocycloaddition has no precedence. Intentional preparation of the ring system was also achieved by a diethyl azodicarboxylate–triphenylphosphine treatment of the proto-adducts.
FUNCTIONALIZED CYCLOPENTANE DERIVATIVES FROM THE PHOTOADDUCTS OF METHYL 2,4-DIOXOPENTANOATE-OLEFINS: ALTERNATIVE SYNTHESES OF<i>dl</i>-DEHYDROIRIDODIAL AND<i>dl</i>-CHRYSOMELIDIAL
Functionalized cyclopentane derivatives were prepared by the retro-ozonolys of methyl 2,6-dioxoheptanoates, which are readily accessible from the photocycloaddition of methyl 2,4-dioxopentanoate with olefins. By this method, 3-isopropenyl-2-methoxycarbonyl-1-methylcyclopentene, a versatile intermediate to iridoid terpenoids, and 1-methoxycarbonyl-2,6,6-trimethylfulvene were synthesized from isoprene. Alternative syntheses of dl-dehydroiridodial and dl-chrysomelidial were accomplished.