Aryldiazonium acetate

Reaction of melatonin with various aryldiazonium chlorides in ethanolic sodium acetate solution afforded arylazo-melatonin derivatives. Reactions of these products with either malonitrile or ethyl cyanoacetate formed the corresponding ary lam inotriazino[4,3-/z indole scaffolds 60-63 <2005BMC1847>. 

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. 

Aryldiazonium salts react with bis(dibenzylideneacetone)palladium to form arylpalladium salts and nitrogen. Therefore, diazonium salts may be employed to catalytically arylate alkenes under mild conditions. Since many aryl halides are made from diazonium salts this variation could even be more convenient than using aryl halides. The reaction proceeds in good to excellent yields in nonaqueous solvents, using sodium acetate as the base at room temperature with terminal alkenes and cyclopentene." Internal alkenes usually give poor yields, however. 

Malonyl-a-aminopyridine (37) reacted with aryldiazonium chloride in ethanol in the presence of sodium acetate to give 3-arylhydrazono-2,4-dioxopyrido[ 1,2-a]pyrimidines (89MI6). Heating compound 37 in for-... 

Reaction of aryldiazonium chlorides with sodium 6,9-dimethyl-6,7,8,9-tetrahydro- and 1,6-dimethyl-l, 6,7,8-tetrahydro-4-oxo-4//-pyrido[l, 2-u]pyrimidine-3-carboxylates 582 and 17 in water in the presence of sodium acetate at 5°C gave 9-(aryldiazo) derivatives 583 and 584 (83JMC1126). 

In place of sodium hydroxide, sodium acetate may be added to the mixture of diazonium salt solution and the aromatic liquid.6 Another variation, introduced by Hodgson and Marsden,6 consists in converting the aryldiazonium chloride to a stabilized diazonium salt by treatment wi,th naphthalene-l-sulfonic acid, naphthalene-1,5-disulfonic acid, or zinc chloride the dried salt is then suspended in an aromatic liquid and treated with sodium acetate and acetic anhydride. 

When sodium acetate is added to aryldiazonium salts, aryldiazo acetates, R—N=N—OCOCH3, are probably formed through rearrangement of the aryldiazonium salts initially produced, and they react in the same manner as the aryldiazo hydroxides. The aryldiazo acetates are probably the reactive intermediates also in the procedure in which a stabilized diazonium salt is treated with sodium acetate and acetic anhydride in the presence of an aromatic compound. 

Aryl-4,6-dinitroindazoles are obtained by treatment with alkaline metal carbonates of the corresponding hydrazones [302-304], The latter are formed from picryl acetal aldehydes with aryldiazonium salts. Scheme 2.28 demonstrates that... 

The free radical arylation of thiazole (391) has been performed either by the Gomberg-Bachmann (392) decomposition of aryldiazonium chlorides (119,393), by the thermal decomposition of benzoyl peroxide (394-397) or N-nitrosoacetanilide (398), or by the photolysis of benzoyl peroxide or iodobenzene (398). The three monophenylthiazoles are obtained in the practically constant proportions 2-phenyl, 60% 5-phenyl, 30% 4-phenyl, 10%, giving the order, 2>5>4, of decreasing reactivity of the three positions of thiazole toward phenyl radicals (398). Competition reactions with nitrobenzene (397) gave an estimation of the globed reactivity of thiazole relative to benzene of 0.75 with the partial rate factors f2 = 2.2, /s=1.9, /4 = 0.5. When the thermolysis of benzoyl peroxide is performed in acetic acid solution, the substrate in reaction is the conjugate acid of thiazole the global reactivity is enhanced to 1.25,... 

In a similar fashion ethers, acetals and formic acid may serve as efficient hydride donors towards carbonium ions, aryldiazonium salts (reduction with loss of nitrogen occurs) and pyrylium salts. A review of this chemistry is available. ... 

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>. 

In the reactions between the halogenated dialkyl (2-oxoethyl)phosphonates (216 X = halogen) and aryldiazonium salts in aqueous sodium acetate, loss of the CHO group occurs when X = Cl... 

Diazonium Salts. Diazonium salts are potentially explosive. See the cautionary note in Experimental Conditions. Aryldiazonium salts 26 react with alkyl- and arylmagnesium reagents,184-191 arylzinc,190,192,193 and aryltin reagents194 to give azo compounds. Yields vary considerably the best are achieved with the diazonium salt 26e191 (see Eq. 48). Aryldiazonium salts also react with enolates, enol derivatives, or enamines of aldehydes (see Eq. 85),195 ketones (see Eq. 95),185 and with silyl ketene acetals (see Eq. 121).196,197... 

Reaction of silyl ketene acetals with aryldiazonium salts produces a-keto ester hydrazones196197 by rearrangement of the initially formed azo compounds (Eq. 121). The latter are obtained with disubstituted ketene acetals.197... 

The diazonium salt procedure consists in a reaction between a dry aryldiazonium tetra-fluoroborate with PCI3 in a solvent, generally an acetic acid ester, and in the presence of a copper(I) salt. Very rarely, aryldizaonium hexafluorosilicates have been employed but appear to offer no particular advantages. The procedure involves the conversion of the diazonium tetrafluoroborate into the diazonium adduct (283) followed by liberation of nitrogen and generation of the aryltrichlorophosphonium salt which is hydrolysed. A wide... 

Aryl halides are frequently prepared from the corresponding aryldiazonium salts by diazotation procedures. However, diazonium salts can be subjected directly to very mild Heck arylation conditions, which deliver coupled products (entry 19). Preferably, the reaction is executed in nonaqueous solvents such as acetonitrile, acetone, or methylene chloride with sodium acetate as base and with palladiumbis(dibenzylideneacetone) as catalyst. Alternatively, a combination of the amine and f-butyl nitrite, in a mixture of acetic acid and monochloroacetic acid, can provide the desired product directly, which makes the isolation of a diazonium salt unnecessary (entry 20). " It is also possible to use aromatic acid anhydrides as oxidative addition precursors (entry 21). Clearly, anhydrides are very interesting starting materials for a number of Heck reactions due to price and absence of halide salt formation. 

Fluoroboric acid (tetrafluoroboric acid, fluoboric acid) [16872-11-0] M 87.8, b 130°(dec), pK -4.9. Crystallise fluoroboric acid several times from conductivity water. It can be stored in a glass vessel at room temperature. It is available conunercially as 48% aqueous solution. It is most usefiil for preparing tetrafluoroborate salts which are generally insoluble. For example, addition of the acid to aryldiazonium salt solutions precipitates the more stable aryldiazonium tetrafluoroborate salts which can be washed with H2O to remove impirrities, followed by EtOH and Et20, and stored for short periods of time before further use. It is a catalyst for preparing acetals. [Mathers et al. J Am Chem Soc 37 1516 1915, Wamser Christian JAm Chem... 

The modem methods for performing the GBH reaction are based on the thermal decomposition of certain aryltriazenes in the presence of trifluoroacetic acid [66,67], or on the phase transfer catalysed reaction of aryldiazonium tetrafluoroborate in the presence of potassium acetate [61], both methods in an excess of arene as the reactant and reaction solvent. The first method requires previous preparation of the aiyltriazene (VII) by diazotation of an aromatic amine in hydrochloric acid followed by addition of piperidine [66], other dialkylamine or 5-aminotetrazole [67]. For example, from the diazotized aniline solution 43, by addition of an equimolar amount of piperidine, the yellow-orange 1-phenyl-3,3-(pentanediyl)triazene (48) readily crystallize in 81% overall yield [66], Scheme 17. 

The aryldiazonium salts are definitely the most reactive SM electrophilic reactants [46,47], They are able to cross-couple with arylboronic acids in lower alcohols as solvents employing palladium(ll) acetate, with [47] or without [46] any palladium(O)-stabilizing ligand in good to excellent yields. Table 3. 

---