Chemical and nuclear magnetic resonance studies of 3,3-diphenyltetrahydrofuran derivatives

Pyrolytic cyclization of a- and β-methadol methiodides afforded cis and trans isomers of 2-ethyl-3,3-diphenyl-5-methyltetrahydrofuran, respectively. Catalytic hydrogenation of 2-ethyli-dene-3,3-diphenyl-5-methyltetrahydrofuran yielded the cis and trans isomers in a 2:1 ratio. The nmr spectra of these and structurally related compounds have been analyzed in terms of a half-chair conformation for 2-ethyl-5-methyl, 2-ethyl, and 5-methyl derivatives. An envelope conformation has been suggested for the compounds containing a double bond at C-2.