Methyl diazonium ion

In Eq. (3), the unstable methyl diazonium ion decomposes by S l reaction into nitrogen and a methyl cation w hich combines with the anion Z to give CH3—Z. In Eq. (4) an Sk2 reaction occurs. The loss of the nitrogen from CH3—here takes place only wdth the participation of the anion as nucleophile. 

Metabolism is required for both the carcinogenicity and direct cytotoxicity of dimethylnitrosamine. The metabolism of dimethylnitrosamine produces methyl diazonium ion which can fragment into a methyl carbonium ion which is believed to be the ultimate carcinogen and responsible for the liver necrosis. 

Procarbazine is rapidly and completely absorbed following oral administration. It readily decomposes by chemical and metabolic routes, with a half life of 7 to 10 minutes, to produce highly reactive. species including methyl diazonium ion, methyl radicals, hydrogen peroxide, formaldehyde, and hydroxyl radicals. ... 

Alkyl diazonium ions are very reactive intermediates, but have none the less been observed in superacid solution. Dissolving diazomethane in fluorosulphonic acid at -120 °C yielded the methyl diazonium ion (177) and the methylene diazenium ion (178) in the ratio 4 to 1. 

Jensen et al. [87] provided evidence that the in vitro methylation of DNA was carried out by microsomally-activated DMNA and that the methylation was correlated with formaldehyde production. Sagelsdorff et al. [88] showed DNA methylation in rat liver by daminozide, 1, 1-dimethylhydrazine, and DMNA. Studies with other nitroso compounds also confirmed the formation of hydros derivatives, aldehydes, and nitrite by rat liver microsomes and by purified cytochrome P-450 IlBl [84]. The sequence of specific methylation of DNA by N-nitix>so compounds shares a common intermediate, methyl diazonium ion [89]. 

Two methods for converting carboxylic acids to esters fall into the mechanistic group under discussion. One of these methods is the reaction of carboxylic acids with diazo compounds, especially diazomethane. The second is alkylation of car-boxylate anions by halides or sulfonates. The esterification of carboxylic acids with diazomethane is a very quick and clean reaction. The alkylating agent is the extremely reactive methyl diazonium ion, which is generated by proton transfer from the carboxylic acid to diazomethane. The collapse of the resulting ion pair with loss of nitrogen is extremely rapid ... 

The mechanism of the reaction of diazomethane with a carboxylic acid shows why diazomethane must be handled with great care. The methylene group of diazomethane reacts with the proton of the carboxyhc acid to give a methyl diazonium ion. This ion reacts rapidly with carboxylates to give an ester, but the nitrogen gas that is released is very stable, and is therefore an excellent, neutral leaving group. 

A related reaction, in which deuterium increases reaction rate, is the decomposition of p-methyl diazonium ion ... 

The diazonium ion from 2 2 dimethylpropylamine rearranges via a methyl shift on loss of nitrogen to give 1 1 dimethylpropyl cation... 

Purines, N-alkyl-N-phenyl-synthesis, 5, 576 Purines, alkylthio-hydrolysis, 5, 560 Mannich reaction, 5, 536 Michael addition reactions, 5, 536 Purines, S-alkylthio-hydrolysis, 5, 560 Purines, amino-alkylation, 5, 530, 551 IR spectra, 5, 518 reactions, 5, 551-553 with diazonium ions, 5, 538 reduction, 5, 541 UV spectra, 5, 517 Purines, N-amino-synthesis, 5, 595 Purines, aminohydroxy-hydrogenation, 5, 555 reactions, 5, 555 Purines, aminooxo-reactions, 5, 557 thiation, 5, 557 Purines, bromo-synthesis, 5, 557 Purines, chloro-synthesis, 5, 573 Purines, cyano-reactions, 5, 550 Purines, dialkoxy-rearrangement, 5, 558 Purines, diazoreactions, 5, 96 Purines, dioxo-alkylation, 5, 532 Purines, N-glycosyl-, 5, 536 Purines, halo-N-alkylation, 5, 529 hydrogenolysis, 5, 562 reactions, 5, 561-562, 564 with alkoxides, 5, 563 synthesis, 5, 556 Purines, hydrazino-reactions, 5, 553 Purines, hydroxyamino-reactions, 5, 556 Purines, 8-lithiotrimethylsilyl-nucleosides alkylation, 5, 537 Purines, N-methyl-magnetic circular dichroism, 5, 523 Purines, methylthio-bromination, 5, 559 Purines, nitro-reactions, 5, 550, 551 Purines, oxo-alkylation, 5, 532 amination, 5, 557 dipole moments, 5, 522 H NMR, 5, 512 pJfa, 5, 524 reactions, 5, 556-557 with diazonium ions, 5, 538 reduction, 5, 541 thiation, 5, 557 Purines, oxohydro-IR spectra, 5, 518 Purines, selenoxo-synthesis, 5, 597 Purines, thio-acylation, 5, 559 alkylation, 5, 559 Purines, thioxo-acetylation, 5, 559... 

Examine the geometries (in particular, CN bond distances) of methyl diazonium, tert-butyl diazonium and phenyl diazonium ions. Which, if any, of these ions is best described as a weak complex between a cation and N2 Which is furthest away from this description Is your result consistent with the observed reactivity patterns Explain. 

The high reactivity of heterocyclic diazonium ions in azo coupling reactions is the reason why in some cases the primary diazotization products cannot be isolated. For example, diazotization of 2-methyl-5-aminotetrazole (2.14) directly yields the triazene 2.15, i. e., the N-coupling product, since the intermediate diazonium ion is reactive enough to give the N-coupling product with the parent amine even under strongly acidic conditions (Scheme 2-8 Butler and Scott, 1967). 

Semiquantitatively, the reaction of an aromatic diazonium ion with the methoxide ion occurs in three phases. The first is the extremely rapid formation of the (Z)-diazo methyl ether. This is followed by a second, partitioning, phase which in the case of the 4-nitrobenzenediazonium ion at 30 °C is completed in 60 s (Boyle et al., 1971). During this phase, some of the (Z)-diazo ether decomposes to form dediazoniation products (mainly nitrobenzene via the hydro-de-diazoniation reaction) and the rest is converted into the (Zi)-diazo ether. 

The conductometric results of Meerwein et al. (1957 b) mentioned above demonstrate that, in contrast to other products of the coupling of nucleophiles to arenediazonium ions, the diazosulfones are characterized by a relatively weak and polarized covalent bond between the p-nitrogen and the nucleophilic atom of the nucleophile. This also becomes evident in the ambidentate solvent effects found in the thermal decomposition of methyl benzenediazosulfone by Kice and Gabrielson (1970). In apolar solvents such as benzene or diphenylmethane, they were able to isolate decomposition products arising via a mechanism involving homolytic dissociation of the N — S bond. In a polar, aprotic solvent (acetonitrile), however, the primary product was acetanilide. The latter is thought to arise via an initial hetero-lytic dissociation and reaction of the diazonium ion with the solvent (Scheme 6-11). 

All these results are consistent with the hypothesis that aryl cations react in aqueous media at diffusion-controlled rates with all nucleophiles that are available in the immediate neighbourhood of the diazonium ion. On this basis Romsted and coworkers (Chaudhuri et al., 1993a, 1993b) used dediazoniation reactions as probes of the interfacial composition of association colloids. These authors determined product yields from dediazoniation of two arenediazonium tetrafluoroborates containing ft-hexadecyl residues (8.15 and 8.16) and the corresponding diazonium salts with methyl groups instead of Ci6H33 chains. ... 

First of all, there are the two products of O-coupling addition of methoxide ion to the diazonium ion, the (Z)- and (jE)-diazo methyl ethers. As discussed in Section 6.2, they are formed in reversible reactions with half-lives of the order of a fraction of a second (Z) to a minute (E). The two diazo ethers are, however, decomposed rapidly to the final dediazoniation products. We show in Scheme 8-47 the products obtained by Broxton and McLeish (1983 b) in the dediazoniation of 4-chloro-3-nitrobenzenedi-azonium ion (8.64) with methoxide ion in CH3OH. The products are 4-chloro-3-nitro-anisole (8.65, 49 9o), 2-chloro-nitrobenzene (8.66, 449o), and 2-nitroanisole (8.67). 

Kochi (1956a, 1956b) and Dickerman et al. (1958, 1959) studied the kinetics of the Meerwein reaction of arenediazonium salts with acrylonitrile, styrene, and other alkenes, based on initial studies on the Sandmeyer reaction. The reactions were found to be first-order in diazonium ion and in cuprous ion. The relative rates of the addition to four alkenes (acrylonitrile, styrene, methyl acrylate, and methyl methacrylate) vary by a factor of only 1.55 (Dickerman et al., 1959). This result indicates that the aryl radical has a low selectivity. The kinetic data are consistent with the mechanism of Schemes 10-52 to 10-56, 10-58 and 10-59. This mechanism was strongly corroborated by Galli s work on the Sandmeyer reaction more than twenty years later (1981-89). 

The photolysis of arenediazonium salts has been widely used for intramolecular cyclizations in the synthesis of 1-phenylethylisoquinoline alkaloids by Kametani and Fukumoto (review 1972). An example is the photolysis of the diazonium ion 10.73, which resulted in the formation of O-benzylandrocymbine (10.74) (Kametani et al., 1971). The mechanism of this cyclization is obviously quite complex, since the carbon (as cation or radical ) to which the diazonio group is attached in 10.73 does not react with the aromatic CH group, but with the tertiary carbon (dot in 10.73), forming a quinone-like ring (10.74). In our opinion the methyl cation released is likely to react with the counter-ion X- or the solvent. 

In 1988 Masoud and Ishak demonstrated that ( -arenediazo methyl ethers do not react with 2-naphthol in dry organic solvents such as dioxan, ethanol, 2-propanol, but only in the presence of water. The reactions are catalyzed by hydrochloric acid (even in the absence of water). Under such conditions almost quantitative yields of azo compounds were obtained. A careful and extensive kinetic investigation of the HCl-catalyzed dediazoniation of substituted benzenediazo methyl ethers, varying the HC1 concentration and the diazo ether/2-naphthol ratio (the latter either absent or in large excess), and comparing the observed rate constants with Hammett s acidity functions for dioxane and ethanol (see Rochester, 1970) indicated the mechanism shown in Schemes 12-8 to 12-10 (DE = diazo methyl ether, D+ = diazonium ion). 

The first step was found to be a fast pre-equilibrium (Scheme 12-8). The dependence of the measured azo coupling rate constants on the acidity function and the effect of electron-withdrawing substituents in the benzenediazo methyl ether resulting in reduced rate constants are consistent with a mechanism in which the slow step is a first-order dissociation of the protonated diazo ether to give the diazonium ion (Scheme 12-9). The azo coupling proper (Scheme 12-10) is faster than the dissociation, since the overall rate constant is found to be independent of the naphthol con-... 

A novel result of azo coupling was observed by Bagal et al. (1992 a) when they reacted 4-phenylazophenol and its 2-methyl derivative with an excess of 4-nitroben-zenediazonium salt. They obtained a compound whose elemental analysis and H NMR, UV, and IR spectra are consistent with 4,4-bis(4 -nitrophenylazo)-cyclohexa-2,5-dienone (12.14). The replacement of an arylazo group by a more electrophilic diazonium ion had occasionally been observed before this, but the double azo coupling in the 4-position is new. 

Other compounds with reactive methylene and methyl groups are completely analogous to the nitroalkanes. Compounds with ketonic carbonyl groups are the most important. Their simplest representatives, formaldehyde and acetone, were considered for many decades to be unreactive with diazonium ions until Allan and Podstata (1960) demonstrated that acetone does react. Its reactivity is much lower, however, than that of 2-nitropropane, as seen from the extremely low enolization equilibrium constant of acetone ( E = 0.9 x 10-7, Guthrie and Cullimore, 1979 Guthrie, 1979) and its low CH acidity (pK = 19.1 0.5, Guthrie et al., 1982). ... 

As the reaction sequence of Scheme 12-38 can be stopped at the stage of the oo-methylglyoxal phenylhydrazone (12.78), it is possible to synthesize asymmetrically substituted formazanes (12.80, Ar = Ar ) by reacting acetone with one equivalent of a diazonium ion ArNJ under acidic conditions and then coupling the co-methyl-glyoxal phenylhydrazone with Ar NJ in alkaline solution. 

Penton and Zollinger (1979, 1981 b) reported that this could indeed be the case. The coupling reactions of 3-methylaniline and A,7V-dimethylaniline with 4-methoxy-benzenediazonium tetrafluoroborate in dry acetonitrile showed a number of unusual characteristics, in particular an increase in the kinetic deuterium isotope effect with temperature. C-coupling occurs predominantly (>86% for 3-methylaniline), but on addition of tert-butylammonium chloride the rate became much faster, and triazenes were predominantly formed (with loss of a methyl group in the case of A V-di-methylaniline). Therefore, the initial attack of the diazonium ion is probably at the amine N-atom, and aminoazo formation occurs via rearrangement. 

A number of miscellaneous reactions involving diazonium ions and possible vinyl cations have been reported. Treatment of amine 138 with sodium nitrite in 20% aqueous acetic acid is reported to give methyl cyclopropyl ketone as one of four products (116). The reaction has been postulated to involve a vinyl cation, presumably by the following sequence of reactions (116) ... 

The reaction can be carried out efficiently using aryl diazonium tetrafluoroborates with crown ethers, polyethers, or phase transfer catalysts.103 In solvents that can act as halogen atom donors, the radicals react to give aryl halides. Bromotrichloromethane gives aryl bromides, whereas methyl iodide and diiodomethane give iodides.104 The diazonium ions can also be generated by in situ methods. Under these conditions bromoform and bromotrichloromethane have been used as bromine donors and carbon tetrachloride is the best chlorine donor.105 This method was used successfully for a challenging chlorodeamination in the vancomycin system. 

This reactivity enables t/tro-substitution to be carried out at a specific position in the ring, irrespective of the presence of other contra-directing groups, and it allows the reaction to be carried out under mild conditions, or with weak electrophiles such as diazonium ions.2 Recent additions to the extensive list of electrophiles that have been used are toluene />-sulfonylisocyanate and ethoxycarbonyl isocyanate (Equation (53)),176 sulfonyl chloride,177 arene178 and silane sulfonyl chlorides,179 and dichloromethyl methyl ether (Equation (54)).1... 

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