アセタール類の接触還元に就いて (第2報)

抄録

It had previously been found that benzaldehyde dimethyl acetal could be catalytically reduced, with palladium and barium sulfate as a catalyst, to toluene. In the present series of experiments, aromatic aldehyde acetals, (II) to (XII), in which benzene is directly bonded to the aldehyde acetal group, were reduced to the corresponding hydrocarbons by the absorption of two moles of hydrogen by the same precess, but aliphatic acetals, keto acetals, and aldehyde acetates, (XIII) to (XVIII), did not undergo such reduction. From the absorption time (volume of hydrogen absorbed/period required for absorption), it may be said that the reaction time of compounds (I) to (V) decreases with the increase of the number of carbon atoms in the acetal group and that the nature of the aromatic ring combined directly with the acetal group has some effect on the reaction. For example, naphthalene and tetralene rings tend to slow the reaction compared to the benzene ring, and the presence of chlorine, methoxyl, or methylenedioxy group in the benzene ring increases the absorption time.