Diazonium salts preparation

This technique is used to diazotise anilines carrying two or more electron-withdrawing substituents, such as 2,4-dinitro- and 2-cyano-4-nitro-aniline, as well as aminoanthra-quinones and heteroaromatic amines [4]. Some diazonium salts prepared by this technique, such as those from 6-halogeno-2,4-dinitroanilines, are unstable in water and have to be added directly to the coupling component solution. 

Phenyldiazonium Perbromide.—To a fresh ice-cold solution of one of the solid diazonium salts, prepared as described above, or to the diazo-solution from 2 g. of aniline, there is added the solution of 1-5 c.c. of bromine in 15 c.c. of potassium bromide solution (25 per cent), with ice cooling, until precipitation of dark-coloured oil ceases. The aqueous solution is then decanted when the residual perbromide is washed a few times with ice-water it crystallises. 

Several of these internal diazonium salts, prepared by diazotisation of anthranilic acids, are explosive in the solid state, or react violently with various materials. Individually indexed compounds (including analogous sulfonates) are Benzenediazonium-2-carboxylate, 2659 Benzenediazonium-3 or 4-carboxylate, 2661... 

A stabilized diazonium salt, prepared in a similar manner, is of interest. 

Another general method of preparing phenols is to hydrolyse a diazonium salt, prepared from an aniline group (NH2) ... 

Polymers contaming units with antimony (1 ) were prepared by treatment of diazonium salts prepared from 1,4-phenylenediamine with antimonium trichloride [21 and tested as retarders of high temperature oxidation of polymers. 

Stable diazonium salts were obtained upon nitrosation of 5-amino-2-phenyl-4-chloro-6(lW)-pyridazinone 98, whereas the diazonium salt prepared from 4-amino-5-chloro analog 99 is unstable and highly reactive (83MI15). Diazotization of 5-aminopyridazin-4-yl-p-chlorophenyl ketone gave the corresponding 4-one [86JCS(P1)169J. 

A general method of replacement of the primary aromatic amino group by hydrogen is reduction of aromatic diazonium salts, prepared by diazotization, typically by treatment of the primary amine or its salts with sodium or potassium nitrite in strongly acidic aqueous media. Conversion to the diazonium salts may also be accomplished in nonaqueous media using acetic acid, or using alkyl nitrites (equation 86). Most diazonium salts decompose at temperatures above 0-5 C. Only certain salts such as naphthalene-1,5-sulfonates,tetrafluoroborates ° ° and hexafluorophosphates ° ° are stable at room temperature. 

B) Reactions of Diazonium Salts. To the tube containing the diazonium salt (prepared in section [A]) add 10 ml of water and shake gently until solution is complete. Divide the solution equally among five test tubes, and perform the following tests. 

Note If the student has followed the semimicro method, using the stock solution of the diazonium salt prepared in Experiment 53 (C), the following preparations are recommended (A), (B), or (C), and (D) or (E). For macro work, sections (C) and (D) are recommended. For section (C) diazotize 7 ml of aniline in accordance with directions given in Experiment 53 (C), and then use five times the quantities ven in section (C) below. For section (D) the amounts given (or double) may be used. 

Two pathways for the preparation of 1,4-dihydropyridazine derivatives were envisaged. According to the first, dimethyl 3-oxopentane-l,5-dioate (dimethyl acetone-1,3-dicarboxylate) (1) was treated in ethanol and sodium acetate at 0 °C with acidic aqueous diazonium salts, prepared from aromatic or heteroaromatic amines, to give hydrazones 69 in 35-94% yields. They were next treated with DMFDMA in dichloromethane at room temperature to form the (dimethylamino) methylidene derivatives 70 as intermediates, which immediately cyclized into dimethyl 1 -(hetero)aryl-4-oxo-l, 4-dihydropyridazine-3,5-dicarboxy-lates 71 in 72-94% yields, except for 71 (R=lH-l,2,4-triazol-3-yl), which was obtained in 35% yield (08ZN(63b)407) (Scheme 23). 

R. Kuhn, G. Kruger, and A. Seeliger, Coupling Amadori compounds with diazonium salts preparation of lactulose fi om lactose, Justus Liebigs Ann. Chem., 628 (1959) 240-255. 

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