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Acidity of Nitroguanylhydrazones 5693 heated on a steam-bath for one-half hour. The solid, which separated, was removed, washed with ether and recrystallized from ethanol. Although the first crop of crystals was mainly collidine hydrobromide, concentration of the mother liquor followed by addition of ethyl acetate caused the separation of 75 mg. (21%) of yellow crystals, m.p. 206-212°, as expected for dehydroquinolizinium iodide. A sample of these crystals was converted to the corresponding picrate, m.p. 179-180°, alone or mixed with an authentic sample of dehydroquinolizinium picrate.Dehydrogenation of the 3H,4H-Quinolizinium Ion.-The results of many experiments on the dehydrogenation of the 3H,4H-quinolizinium bromide, iodide and picrate salts can be summarized: (a) N-bromosuccinimide led to the introduction of bromine and the product on treatment with triethylamine gave the dehydroquinolizinium ion (I) in 6% yield; (b) selenium dioxide gave I in 3% yield; (c) chloranil gave I in 10% yield, (d) molecular oxygen with a reduced platinum catalyst was effective in either acetic acid or nitrobenzene as solvent giving I in yields of 23 to 26%. The most satisfactory method thus far developed, however, was that using palladium-on-charcoal as follows. A solution of 800 mg. of 3H,4H-quinolizinium picrate in 60 ml. of «-butyl alcohol containing 160 mg. of a 10% palladium-oncharcoal catalyst was boiled under reflux for three hours. After the hot reaction mixture had been filtered to remove tarry impurities, the filtrate on cooling deposited 450 mg. of crude yellow crystals. These after recrystallization from ethanol gave 270 mg. (34%) of yellow needles, m.p. 180-181°.

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