Palladium-catalyzed dehydrogenation of benzylic alcohols in molten ammonium salts, a recyclable system

Heating secondary benzylic alcohols in molten tetra-n-butyl ammonium bromide with catalytic amounts of palladium chloride under a gentle flow of argon produced corresponding ketones in good yields. Neither cooxidant nor additive were required, with the added advantage of catalyst and ammonium salt recycling. The dehydrogenation of primary benzylic alcohols was less selective. Such a reaction was ineffective from allylic and saturated alcohols.