Diazonium salts adducts

Other limitations of the reaction are related to the regioselectivity of the aryl radical addition to double bond, which is mainly determined by steric and radical delocalization effects. Thus, methyl vinyl ketone gives the best results, and lower yields are observed when bulky substituents are present in the e-position of the alkene. However, the method represents complete positional selectivity because only the g-adduct radicals give reductive arylation products whereas the a-adduct radicals add to diazonium salts, because of the different nucleophilic character of the alkyl radical adduct. ... 

Methylnitramine/reacts with diazonium salts to form ArN NNMeN02 which are yellow solids that ignite below their mp and decomp on standing at room temp (Ref 1). It reacts with activated olefins to form adducts of the type XCH2CH2NMeN02 where X is an activating group (Ref 2)... 

The arenediazocyanides have been known since 1879. They played an important role in the Hantzsch-Bamberger debate on the (Z)/( ,)-isomerism of diazo compounds (see Sec. 7.1). When an aqueous solution of a diazonium salt is added to a solution of sodium or potassium cyanide, both in relatively high concentration, at a temperature below 0°C, a yellow to red (Z)-arenediazocyanide starts to crystallize. Hantzsch and Schulze (1895 a) found that these compounds rearrange into the (ii)-isomers, which have a bathochromically shifted visible absorption (see Sec. 7.1). Under strongly alkaline conditions a 1 2 adduct is formed, to which Stephenson and Waters (1939) assigned the structure 6.36. It was never corroborated, however, by modern instrumental analysis. 

The first diazonium-salt-crown-ether adduct was isolated and identified as a 1 1 complex by Haymore et al. (1975). Unfortunately Haymore never published the X-ray structural analysis of benzenediazonium hexafluorophosphate with 18-crown-6 which he performed in 1980. ORTEP drawings with measured bond angles and lengths from Haymore s investigation can be found in a review chapter by Bartsch (1983, p. 893). A few data from Haymore s work (e.g., R = 0.064) were also mentioned by Cram and Doxsee (1986, footnote 7). Groth (1981) published the results of his X-ray investigation of 4-methoxybenzenediazonium tetrafluoroborate and 21-crown-7 (R = 0.042) and Xu et al. (1986) those of 4-methoxybenzenediazonium tetrafluoroborate and dibenzo-24-crown-8 (R = 0.086). 

A completely different method of synthesis of azo compounds from diazonium salts involving radical intermediates was found by Citterio et al. (1980, 1982 c), Cit-terio and Minisci (1982), and Fontana et al. (1988). It is a new general synthesis of arylazoalkanes based on the addition of an alkyl radical to an arenediazonium ion followed by reduction of the intermediate azo radical cation adduct by a metal salt (Scheme 12-80). The preferred source for the alkyl radical R in this reaction is an alkyl iodide, which gives rise to alkyl radicals cleanly in the presence of an arenediazonium salt and a Ti3+ or Fe2+ salt as in Scheme 12-81. The overall stoichiometric equation is therefore as given in Scheme 12-82. The yields vary between 36% and 79% (with respect to alkyl iodide). 

Introduction of Other Nucleophiles Using Diazonium Ion Intermediates. Cyano and azido groups are also readily introduced via diazonium intermediates. The former involves a copper-catalyzed reaction analogous to the Sandmeyer reaction. Reaction of diazonium salts with azide ion gives adducts that smoothly decompose to nitrogen and the aryl azide.56... 

The trapping of hydroxyl radicals has also been of interest in connection with electrochemistry. Bard et al. (1974) initiated electrochemical applications of spin trapping and showed, for example, that the cathodic reduction of diazonium salts in the presence of PBN gives aryl-radical spin adducts. A route... 

Diazene, furan ozonide decomposition, 730 Diazo compounds, ozone adducts, 734 Diazonium salts, TEARS assay, 667 Dibenzoyl peroxide, determination, 698 Z-Dibenzoylstilbene, tetracyclone bleaching, 734-5... 

Other classical synthetic approaches to 2-furanamine have failed, including the Curtius method and Beckmann rearrangement of 2-benzoylfuran oxime. However, hydrazinolysis of AT-(2-furyl)phthalimide, obtained from phthalimide and 2,5-dimethoxy-2,5-dihy-drofuran, gives 2-furanamine which was not isolated but detected by GLC-MS and H NMR spectroscopy. The latter reveals the absence of imino tautomers (75AP713). The chemistry of 2-dialkylamino-5-phenylfurans is typical of enamines protonation occurs on carbon to produce iminium salts. They are stable to base but afford 5-phenylfuran-2(3//)-one on hydrolysis with dilute acid. 2-Morpholino-5-phenylfuran couples with diazonium salts and affords Diels-Alder adducts with maleic anhydride and IV-phenylmaleimide (73JCS(P1)2523). 

The Meerwein arylation is at least formally related to the atom transfer method because a net introduction of an aromatic ring and a chlorine across a double bond is accomplished (Scheme 62). Facile elimination of HC1 provides an efficient route to the kinds of substituted styrenes that are frequently prepared by Heck arylations. Standard protocol calls for the generation of an arene diazonium chloride in situ, followed by addition of an alkene (often electron deficient because aryl radicals are nucleophilic) and a catalytic quantity of copper(II) chloride. It is usually suggested that the copper salt operates in a catalytic redox cycle, reducing the diazonium salt to the aryl radical as Cu1 and trapping the adduct radical as Cu11. 

In contrast to classical Meerwein arylations, non-activated alkenes are well suited for this reaction type for two reasons. First, due to the relatively slow formation of azo compounds by addition of aryl radical 49 to 48, this undesired pathway cannot compete successfully with the attack of 49 on the alkene to give radical adduct 50. Second, a nucleophilic alkyl radical 50 arises from the addition step, which is effectively trapped by electrophilic salt 48 to give azo compound 51. As a result of several improvements, the methodology is now applicable for a wide range of polar to non-polar alkenes with almost no restrictions on the substitution pattern of the diazonium salt [101, 102]. Moderate diastereoselectivities have been obtained in first attempts with chiral auxiliaries [103]. The azo compounds accessible, such as 51, can be converted to carboamination products 52 by hydrogenation and to various other heterocycles. 

Codeine, dihydrocodeinone, and 14-hydroxydihydrocodeinone couple with the diazonium salt of 4-aminoacetophenone at C-8, giving the corresponding azo adduct.(168)... 

Another diazonium salt (241) reacts with 3-chloropentane-2,4-dione, or 3-chloroacetoacetic ester, with loss of two carbon atoms to give (242) which hydrolyzes and cyclizes under carefully controlled conditions to the hydroxypyrazolotriazine (243). The free diazo compound (244) gives the adduct (245) with dimethyl acetylenedicarboxylate (Scheme 76) (77JHC227). 

It forms a complex with dioxane contg 2 moles of TNMe to one of dioxane, mp 44—4.5°, bp at 8mm, 61—2° (Ref 19a, p 33). It reacts with aromatic diazonium salts to give compds of the type ArN NC(N02)3. The compds are relatively unstable and their expl props have not been examined (Ref 12). It reacts with N-hydroxymethyl compds to form adducts of the type RNHCH2C(N02)3- The same compds are formed from TNMe, formaldehyde, and the amine or from trinitroethanol and the amine (Ref 31). It forms complexes with N-contg heterocyclics whose expl props have not been examined (Ref 42). It forms complexes with benzene and methylbenzenes. The formation constants for these complexes vary from 8.46 for the benzene complex to 279.4 for the hexa-methylbenzene complex (Ref 49)... 

The CH2 group of co-imidazol-l-yl)acetophenone 1004 is sufficiently activated by the carbonyl and the imidazole group that it readily reacts with aldehydes, aromatic diazonium salts (to form diazo compounds) and acrylonitrile. The reaction of 1004 with phenyl isothiocyanate in the presenceof KOH results in the formation of adduct 1005 that is not isolated but further condensed with phenacyl bromide to afford thienylimidazole 1006 in 87% yield (Scheme 241) <2003SC153>. In the presence of a 2-sulfanyl group 1007, the enolate of ot-imidazolyl acetophenone 1008 no longer reacts with aldehydes or even alkyl halides except for Mel 1009 <200282691 >. 

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... 

The preparation and amphiphilic properties of a new class of surfactants, N-(fatty acyl)-iV -P-D-glucopyranosyl or P-maltosyl-hydrazines, has been described. l-Glycosyl-3-methylpyrazol-5-ones such as 82, formed by acid-catalysed reaction of aldose hydrazones with 2,2,2-trifluoroethyl acetoacetate, were sensitive to oxidation. Coupling with a diazonium salt prevented degradation and provided highly coloured adducts such as 83, suitable as derivatives for... 

Aromatic diazonium salts instead of the aryl halides also undergo Pd-catalyzed coupling of organotins, but they are less used. Aryl triflates are more popular.t The reaction of the triflate required LiCl as an additive. It was explained that triflate ligand of the oxidative adduct has to be replaced by chloride ligand before the transmetallation step. The system composed of AsPhj as ligand and NMP as solvent seems so far to be the most efficient for cross-coupling with aryl triflates. It does not require LiCl as an additive. The tolerance of heteroaryl halides and triflates is also noteworthy. Some examples are shown in Schemes 22-28. 

Diazoalkanes react to form phosphinazines (7.382) which, in some cases, are decomposed by heat (6.107). Phenyl diazonium salts react with triphenylphosphine to form coloured adducts which decompose rapidly in aqueous solution to give phosphine oxide and benzene (6.108). 

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