Coupling reactions, of arenediazonium

The coupling reaction of arenediazonium ions with semidione radicals (12.84, obtainable by reduction of 1,2-diketones, 12.83) is also included here in the discussion of 1,3-dicarbonyl compounds, although it is a coupling with a nucleophilic radical and does not strictly belong in this context. The reaction (Scheme 12-43) was... 

The reactions of arenediazonium ions with 7V-alkyl- or 7V-arylhydroxylamines were investigated by Bamberger (1920b, and earlier papers). Mitsuhashi et al. (1965) showed that the l,3-diaryl-3-hydroxytriazenes are tautomeric with 1,3-diaryltriazene-3-oxides (Scheme 6-16). Oxidation of 1,3-diaryltriazenes with peroxybenzoic acid in ether yields the same product as that from diazonium salts and TV-arylhydroxyl-amine. The infrared spectrum of the product obtained by coupling diazotized relabeled aniline with A/-phenylhydroxylamine indicates that the diaryltriazene-oxide is the preponderant tautomer. 

In the first paper on arenediazonium salt/crown ether complexes, Gokel and Cram (1973) mention that they were not able to synthesize the rotaxane 11.14 by an azo coupling reaction of the complexed diazonium ion with Af,Af-dimethylaniline. 

In organic synthesis, we know only one interesting case where reactions of arenediazonium ions take place in the presence of a crown ether, but not at all without. It is the azo coupling reaction of 4-methoxybenzenediazonium tetrafluoroborate with pyrroles. Butler and Sheppard (1978) reported that the azo derivatives 11.15 and 11.16 were obtained under phase-transfer conditions (CH2C12 or CHC13 + water) in the presence of dicyclohexano-18-crown-6, but not at all by a published procedure (Kreutzberger and Kalter, 1961). 

It has long been known that pyrroles can be used as coupling components (see, for example, Schofield, 1967, p. 76). More recently Butler and coworkers have studied the reactions of arenediazonium ions with pyrroles (Butler et al., 1977 Butler and Shepherd, 1978, 1980). 1-Methyl- and 2,5-dimethylpyrrole react with diazotized sulfanilic acid to give 12.34 and 12.35 respectively. The formation of 12.34 is in accordance with the a-positions in pyrrole being more susceptible to elec-... 

Genkina et al. (1979, 1981, 1985) investigated azo coupling reactions of indoles with fused benzo and benzothiopheno rings, namely 4,5- and 6,7-benzindole, 4,5,6,7-dibenzindole (12.42), indolo[6,5]-, -[4,5]-, and -[5,4]-benzo[Z ]thiophene (12.43 to 12.45). Arenediazonium ions reacted with all these indole derivatives at the 3-position. 

Therefore in this section we will focus first on the reactions of arenediazonium ions with secondary amines such as A-alkylanilines and dialkylamines. Reactions with primary amines will be discussed later in this section. Most diarylamines do not undergo Af-azo coupling to a significant extent, as they are weaker nucleophiles. 

In a very recent work, the Pd-catalysed cross-coupling reactions with arenediazonium salts under aerobic conditions in the presence of a chiral monothiourea ligand were reported (Scheme 25) [106]. Even if this Hgand bears four chiral centres, no test in asymmetric Heck-type reaction has been described so far. 

Palladium catalysts have been found which are effective in the Suzuki coupling reaction of arylboronic acids with aryl chlorides carrying electron-withdrawing groups.73 Biaryls may also be synthesized by cross-coupling of arylboronic acids with arenediazonium salts.74,75 There has been a report of the polymer-bound palladium-catalysed Suzuki coupling of aryl triflates with organoboron compounds.76 Arylbor-onates may themselves be synthesized by the palladium-catalysed reactions of... 

By far the most important azo coupling reaction, i.e. the reaction of arenediazonium ions with aromatic coupling components, has been known for many decades and has been extensively reviewed Therefore, in this section we shall concentrate on reactions of aliphatic diazonium ions, diazoalkanes and diazocarbonyl compounds which have not been known previously as well as on coupling reactions which have gained in importance more recently, specifically those of heterocyclic diazonium ions. 

The fact that adenosine and its derivatives are azo coupling components is used for immobilizing nicotinamide-adenine nucleotide (NAD ) for affinity chromatography purposes. In 87a NAD is bonded to a matrix through an azo bond. 87a is used for the purilication of dehydrogenase enzymes Butler and coworkers have studied the reactions of arenediazonium ions with pyrroles Pyrroles are known to react readily with diazonium ions under... 

A similar case seems to be that of the reactions of arenediazonium ions with phenothiazine describ l by Bisson, Hanson and Slocum Colonna et al. also reported an azo coupling reaction with nine 4-substituted N,N-dimethylanilines (e.g. 141). With X=C0CH3 the substrate was monodemethylated and N-coupling took place. The authors interpreted the result in terms of scheme (66). 

Although these two reactions are similar to the corresponding reactions of arenediazonium salts, aryl radicals are not involved in the reaction of the lead reagents and these reactions are better explained by a ligand coupling mechanism. 

Nucleophilic Displacement. PhTMS-BF3 0Et2 system has been shown to be useful in the transformation of allylic alcohols to allylic sulfides (eq IS). Preparation of unsymmetrical diaryl sulfides can be achieved by reaction of arenediazonium tetraflu-oroborates with PhSTMS (eq 19). In some cases, addition of cupric sulfide increases the yield of the diaryl sulfides. The use of (phenylthio)trimethylsilane as a coupling partner in palladium catalyzed reactions with aUyl carbonates (eq 20) and aryl iodide (eq 21) has been explored. ... 

Arenediazonium salts are also used for the couplina[563], (Z)-Stilbene was obtained unexpectedly by the reaction of the ti-stannylstyrene 694 by addition-elimination. This is a good preparative method for cu-stilbene[564]. The rather inactive aryl chloride 695 can be used for coupling with organostannanes by the coordination of Cr(CO)3 on aromatic rings[3.565]. 

The coupling of arenediazonium compounds 1 to 1,3-dicarbonyl substrates 2 (Z = COR) is known as the Japp-Klingemann reaction As suitable substrates, /3-ketoacids (Z = COOH) and /3-ketoesters (Z = COOR) can be employed. As reaction product an arylhydrazone 4 is obtained. 

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