Abstract
2-Alkyl 3-or 4-methyl furans and 2-alkylfurans, naturally occuring compounds, were synthesized from γ-oxoaldehydes or γ-oxoaldehyde acetals.
3-Methyl-4-oxoaldehydes were synthesized from aliphatic aldehyde and crotonaldehyde by radical addition reaction in 4860% yields. γ-Oxoaldehydes were treated with pyrophosphoric acid in benzene under reflux with the azeotropic removal of water to give alkylfurans in 342% yields. A furnace, consisting of silica-calsia or silica-almina beads packed into a Pyrex tube, was heated at 200°C. γ-Oxoaldehyde acetal was added dropwise under reduced pressure to the Pyrex tube at a rate of 0.5 mL/min. Alkylfurans were obtained in 3578% yields.
Menthofurans, a minor but important olfactive ingredient of peppermint oil, was also obtained from 9, 10-epoxy-3, 3-ethylenedioxy-p-menthane in a 64% yield.
