SYNTHESIS aryldiazonium salts

Owing to their particular interest two individual reactions will now be discussed separately. The reaction of methoxycarbonylhydrazine and 3-bromo-2,4-pentanedione affords, in addition to the expected pyrazole (608), a pyrazolium salt (609), the structure of which was established by X-ray crystallography (74TL1987). Aryldiazonium salts have been used instead of arylhydrazines in the synthesis of pyrazolines (610) and pyrazoles (611) (82JOC81). These compounds are formed by free radical decomposition of diazonium salts by titanium(n) chloride in the presence of a,/3-ethylenic ketones. 

Arenesulphinylation 264 Arenesulphinylethanes, synthesis of 267 2-Arenesulphonyl-3-aryloxaziridines, as oxidizing agents 254 Arenesulphonyl azides, reactions of 641 At-Arenesulphonyliminopyridinium betaines, mass spectra of 160-162 Arenesulphonyl radicals 215, 1091 Aryldiazonium salts, reactions of 280, 281 Aryl(methylsulphinyl)(methylthio)alkenes, synthesis of 614... 

The synthesis of some new mesoionic triazoloquinazoles 485 has been reported by Abbott et al. <2002T3185>. These authors reported that treatment of 484 with an aryldiazonium salt followed by reaction with acetic anhydride in pyridine results in a ring closure to 485. The first step is an azo-coupling on the ring nitrogen atom, whereas the second part of the transformation is the removal of a molecule of water. 

The synthesis of A, A -disubstituted 2-amino-5-arylazo-4-phenyl-l,3-selenazoles 62 has been carried out by addition of 2-amino-4-phenyl-l,3-selenazole to an aryldiazonium salt, for example, an aryldiazonium tetrafluoroborate, in DMSO or in acetic acid (Equation 3) <2000JPR169>. 

It is generally observed that chemical companies include homogeneous catalysis in their research and production. For example, Ciba-Geigy coimnercialized their first organometallic homogeneous catalytic process (100 tons per year), the synthesis of the herbicide Prosulfuron via the Pd(dba)2-catalyzed Matsuda reaction of 3,3,3-trifluoropropene with an aryldiazonium salt [98]. 

Another useful approach to styrenes via sp -sp -coupling reactions, which is beyond the scope of this section, is Meerwein-type arylations in which aryldiazonium salts undergo usually copper(I)- or palladium-catalyzed couplings with electron deficient alkenes, indicating a radical-based mechanism.The method is so useful for the synthesis of stilbenes from unsubstituted styrenes 92 or p>silylstyrenes. 93... 

A synthesis of diethyl 1-ethoxycarbony 1-2-aryIvinyIphosphonates based on the Pd-catalyzed Heck reaction of aryldiazonium salts with diethyl l-(ethoxycarbonyl)vinylphosphonate has recently been reported. ... 

Synthesis of benzotriazines from pyruvic acid hydrazone 2 and aryldiazonium salts 1 (see 1st edition). 

When reviewed in CHEC-I some examples of cyclization y to the heteroatom had been described for the synthesis of pyridazines, but the method was of most importance in the synthesis of cinnolines. Examples of pyridazine syntheses included cyclization of ketazines with EDA, and intramolecular Wittig reactions of phosphoranes derived from phosphacumuleneneylides and the hydrazones produced from 1,3-dicarbonyl compounds and aryldiazonium salts. Synthetically useful approaches to cinnolines given include the intramolecular Friedel-Crafts acylation of the diacid chlorides derived from the condensation products of aryldiazonium salts and diethyl malonate to give 4(l//)-cinnolinones, and thermal cyclization of iminium hydrazones obtained from enamine esters and aryldiazonium salts. 

A practical synthesis of 2//-pyrimido[4,5-e]ll,2,4]triazin-3-ylidenecyanamides 106 has been developed. The key step is the coupling reaction of an aryldiazonium salt with l-cyano-3-(2,6-dioxo-l,2,3,6-tetrahydropyrimidin-4-ylamino)-2-methylisothiourea 105, obtained from uracil 104, followed by an intramolecular cyclization <04TL931ft>. 

Cinnolines are prepared by an intramolecular cyclization of o-alkenyl or o-alkynyl aryldiazonium salts. For instance, (o-aminophenyl)alkynes 6 or alkyl(o-aminophenyl)ketones 8 (via the enol form) yield 4-hydroxycinnolines 7 (the v. Richter and Borsche syntheses, respectively), o-Aminostyrenes 10 afford 3,4-disubstituted cinnolines 11 (Widman-Stoermer synthesis) ... 

Serotonin has been synthesised by several routes the method shown relies on a Fischer indole synthesis, the requisite phenylhydrazone being constructed by a process known as the Japp-Klingemann reaction in which the enol of a 1,3-dicarbonyl compound is reacted with an aryldiazonium salt, with subsequent cleavage of the 1,3-dicarbonyl unit. 

The arylation of aromatic compounds with aryldiazonium salts (III) in the presence of base affording biaiyls (II) is called the Gomberg-Bachmann-Hey (GBH) reaction [46]. First observations were published by Bamberger [47] and Kuhling [48] more than a century ago. However, the first practical synthesis of biaryls was discovered by the former authors, and was further developed by Hey. The original... 

The intramolecular coupling reaction between an aryldiazonium salt (III) with an arene subunit to form five- or six-membered ring by the influence of copper or an acid, is called the Pschorr cyclization reaction [85]. In historical examples the Pschorr cyclization was used in the synthesis of phenanthrene and its derivatives. For example, c -stilbene derivative 49 is diazotized to give 50, and subsequently treated with the activated copper to obtain phenanthrene (51) in 34% yield [86], Scheme 21. 

Closely related arylation to Pschorr reaction is the Gatterman synthesis of biaryls (II) which involves the coupling reaction of two aryldiazonium salts (III) by the influence of copper or copper(I) salts [97,98], Scheme 24. 

Selvakumar, K., Zapf, A., Spannenberg, A. and Beller, M. (2002) Synthesis of monocarbenepal-ladium(O) complexes and their catal5dic behavior in cross-couphng reactions of aryldiazonium salts. Chem. Eur. J., 8, 3901-6. 

There are three t)q)es of eompositions that eure by eationie meehanism. One of them uses aryldiazonium salts to initiate the reaetion. The seeond one utilizes onium salts and the third one organometallie eomplexes. The most prominent ones are those that eure with the aid of onium salt photoinitiators. Many cationic curable compositions consist of mixtures of compounds with oxirane rings. They may also be mixtures of vinyl ether. In addition, some compositions contain both, epoxides and vinyl ethers. More recent compositions might also include silicone based monomers with epoxide groups. Thus, Crivello and Lee described a synthesis of a series of silicon-epoxy monomers that undergo rapid and efficient photoinitiated cationic polymerizations. Such compounds can be prepared by direct hydrosilylation of olefmic epoxides. 

Using this methodology in 1896, Pschorr first reported the synthesis of phenanthrenes from the corresponding (Z)-2-styiylbenzenediazonium salts promoted by Cu+ [10]. Later, in 1924, Gomberg and Bachmann showed that biaryls could be prepared by intermolecular HAS from aryldiazonium salts and benzene [11]. However, yields were generally low (<40%), and many side reactions of diazonium salts were observed. 

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