Mercuric oxide, use in oxidation of hydrazones

Mercuric oxide, use in oxidation of hydrazones, 50, 28 with 3-chlorocyclobutanecar-boxylic acid and bromine to give l-bromo-3-chlorocyclo-butane, 51, 106 MERCURIC OXIDE-MODIFIED HUNS-DIECKER REACTION 1-BRQMO-... 

A stock solution of potassium hydroxide in ethanol was prepared and stored under nitrogen. Old stocks are brown and contain a dark sediment, but they are apparently just as effective as the freshly prepared reagent. Methanolic potassium hydroxide has also been used by the submitters this remains clear and colorless for long periods but offers no other advantage over the ethanolic solution. In absence of the basic solution, the acetone hydrazone is not oxidized by mercuric oxide. 

Mercuric oxide, HgO (yellow modification or the less reactive red modification), resembles silver oxide in its oxidizing properties. This reagent transforms phenols and hydroquinones into quinones [383, 384] and is used especially for the conversion of hydrazones into diazo compounds [355, 386, 387, 388, 389, 390, 391, 392]. Dihydrazones of a-diketones furnish acetylenes [393, 394, 395, 396], A -Aminopiperidines are dehydrogenated to tetrazenes [397] or converted into hydrocarbons [395]. 

Preparation. The reagent can be prepared in 70-90% yield by oxidation of acetone hydrazone with yellow mercuric oxide (British Drug Houses) catalyzed by potassium hydroxide. In the absence of base the hydrazone is not oxidized by mercuric oxide.1 Unstable solutions are obtained by use of silver oxide in place of mercuric oxide.2... 

Diphenyldiazomethane 386 A mixture of benzophenone hydrazone (13 g, 0.066 mole), anhydrous sodium sulfate (15 g)> ether (200 ml), ethanol saturated with potassium hydroxide (5 ml or 10 ml if red mercuric oxide is used), and yellow (or red) mercuric oxide (35 g) is shaken in a pressure flask for 75 min. The solids are then filtered off and the solvents are removed in a vacuum at room temperature. The dark red oily product is dissolved in light petroleum (b.p. 30-60°) and this solution is filtered and the solvent is again removed in a vacuum at room temperature. The oil produced is frozen in Dry Ice and gradually allowed to warm to room temperature, whereupon dark red crystals, of m.p. 29-32°, are obtained in 89% yield [cf. also Organic Syntheses, 24, 53 (1944)]. 

---