A study of methods of preparation of phthalaldehyde

Considerable work has been done in recent years on the general field centering around the chalcones, flavones, and anthocyanidins. Members of the three classes of compounds exist as natural products and occur widely as coloring matter in flowers and plant saps. An attempt has been made to work out a new method for the preparation of phthalaldehyde. Two lines of research have been followed, neither of which produced the desired compound. The first method, low-pressure hydrogenation of dibutylphthalate over Raney nickel catalyst has supported the contention that the principal product of the hydrogenation of aromatic esters over Raney nickel arises by hydrogenation of the benzene nucleus. Evidence indicates that the compound formed by the present method was dibutyl-2,6-cyclohexadiene-1,2-dicarboxylate. The second method was an attempt to use the Stephen method for the reduction of nitriles to prepare phthalaldehyde from phthalonitrile. The method apparently failed completely of aldehyde formation, but the eventual fate of the nitrile in the reduction was not ascertained. The possibility exists that with a stronger reducing couple such as stannous bromide and hydrogen bromide, the reaction might be adapted for use to the preparation of phthalaldehyde