Abstract
The dye-sensitized photooxygenation of cyclopentadiene provides a novel one-step synthesis of 4,5-epoxy- cis-2-pentenal ( 3) and cis-1,2:3,4-diepoxycyclopentane ( 4) presumably via a facile thermal isomerization of the transannular peroxide ( 1). Spectrometric identification of the cis- and trans-epoxy- aldehyde is presented. Some unique transformations of 3 are described. For example, 4,5-epoxy- cis-2- pentenal undergoes a facile acid-catalyzed rearrangement in aqueous solutions to furfuryl alcohol. As a dienophile, 3 produces an adduct with cyclopentadiene and ethyl vinyl ether. Hydrogenation of 3 with Raney nickel in methanol provides 5-hydroxypentanal ( 8) and 1,5-pentanediol. Hydrogenolysis of 3 with Raney nickel in aqueous solutions at higher pressure affords 1,5-pentanediol in 61% yield. In a novel thermal process, the epoxyaldehyde fragments to furan and formaldehyde.
Published Version
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