Dimethyl ketazine

A convenient route to pyridazine derivatives is found in the reaction of monohydrazones of 1,2-diketones with DMAD. The reaction of benzil monohydrazone with DMAD, for example, gives a mixture of products consisting of dimethyl 5,6-diphenylpyridazine-3,4-dicarboxylate (135), benzil dimethyl oxaloacetate ketazine (136) and benzil bisketazine (137). A similar reaction of acenaphthenequinone... 

The Bayer Ketazine process is based on the reaction of chloramine with ammonia in the presence of acetone at pH 12 to 14. NaOCl, acetone and a 20% aqueous solution of ammonia (at a mole ratio of 1 2 20, respectively) are fed to a reactor at 35°C and 200 kPa to make the aqueous dimethyl ketazine solution. Excess ammonia and acetone are removed in a series of columns and recycled to the reactor. The ketazine solution is distilled to make a hydrazine hydrate containing 64% hydrazine. A sketch of this process is shown in Figure 18.4132. Use of NaOCl is estimated to be 3.5 pounds per pound of hydrazine. 

Hydrazine is currently prepared via a plethora of methods, the most popular of which is the Raschig process, which involves controlled hypochlorite oxidation leading to hydrazine formation. The Raschig process suffers from the formation of a stoichiometric quantity of sodium chloride by-product. The Bayer Ketazine process employs acetone to trap the hydrazine as dimethyl-ketazine. The acetone is re-cycled but sodium chloride is again formed. 

In other related syntheses, pyridazines were formed from l,2-diphenyl-3-(diacylmethylene)cyclopropenes, as shown in Eq. (I)46 or from trans-l,2-dibenzoyl-3,3-diphenylcyclopropane 47 Similarly, pyridazines are formed from hydrazines or semicarbazide and y-trichloromethyl-a,jS-unsaturated ketones.48-52 Pyridazines may also be obtained from 1,2-diketones. The reaction between benzoin and hydrazine was investigated in detail. A complex mixture of various compounds is formed, among them 3,4,5,6-tetraphenylpyridazine in low yield.53 Benzil monohydrazones and analogs when treated with vinyltriphenylphosphonium bromide also give 2,3-dihydropyridazines in moderate yield.54,55 Benzil monohydrazone and related compounds react with dimethyl acetylenedicarboxylate to give a mixture of the corresponding ketazine, bisketazine, and pyridazine 2.56 The last is the main product in the absence of solvent. 

Dimethyl-l,3-dioxan-4-ol acetate iV,JV-Dimethylethanamide iV,JV-Dimethylethanamine 2-(l,l-Dimethylethoxy)-l-propanol Dimethylethoxysilane 1,1-Dimethylethyl formate Dimethylformamide dimethyl acetal A/,1V-Dimethyl-1 -hexadecanamine Dimethyl ketazine... 

Exposure of l,l-dimethyl-2-vinylpiperidinium chloride (239) to sodamide gave a 94% yield of l-methylazacyclonon-4-ene (240) by a Sommelet-Hauser rearrangement. The catalytic co-oligomerization of ketazines and aldazines with butadienes... 

---