Diazonium ions, alkyl rearrangement

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... 

The very unstable hydroxy nitrosamine then loses formaldehyde to form the primary alkynitrosamine, which rapidly rearranges to the alkyl diazonium ion. The latter, being a powerful electrophile, alkylates various cellular nucleophiles, including the nucleic acids. 

Despite many attempts it has not been possible to oxidize 2-substituted 1,2,3-triazoles 382 to the corresponding 1-oxides 326. Peracetic acid, 3-chloroperbenzoic acid, dichloropermaleic acid, trifluoroperacetic acid, peroxydisulfuric acid, and f-pentyl hydrogen peroxide in the presence of molybdenum pentachloride all failed to oxidize 382 (1981JCS(P1)503). Alkylation of 1-hydroxytriazoles 443 invariantly produced the isomeric 3-substituted 1,2,3-triazole 1-oxides 448 (see Scheme 132). However, the 2-substituted 1,2,3-triazole 1-oxides 326 can be prepared by oxidative cyclization of 2-hydroxyiminohydrazones (1,2-hydrazonooximes, a-hydrazonooximes) 345 or by cyclization of azoxyoximes 169. Additional methods of more limited scope are reaction of nitroisoxazoles 353 with aryl-diazonium ion and base, and reaction of nitroimidazoles 355 with hydroxy-amine- or amine-induced rearrangement of nitro-substituted furoxanes 357. 

Penton and Zollinger 233.238) reported recently that this could indeed be the case. The coupling reaction of m-toluidine and N,N-dimethylaniline with 4-methoxy-benzenediazonium tetrafluoroborate in dry acetonitrile showed a number of unusual characteristics, in particular an increase in kinetic deuterium isotope effect with temperature. Predominant C-coupling occurs ( 86% for m-toluidine). but on addition of a tert.-alkyl ammonium chloride the rate became much faster, and predominantly diazoamino compounds (with loss of a methyl group from N,N-dimethylaniline) were formed. Therefore, initial attack of the diazonium ion is probably at the amine N-atom and aminoazo formation occurs via rearrangement. 

The rearrangement of N-alkyl-N-nitrosoamides has contributed much to the delineation of scheme 5. The reaction has been shown to proceed with the formation of a diazoester intermediate which fragments to a diazonium ion pair as shown below (White, 1955 White and Aufder-marsh, 1961b Huisgen and Reimlinger, 1956a and b). 

The reaction is especially suited to the generation of optically active diazonium ions with specifically oriented counter-ions. In this respect it has possibilities which are absent for the reaction of diazoalkanes with acids and the deamination of aliphatic amines. However, in carrying out stereochemical studies, great care must be exercised to avoid spurious results, since the transient formation of a diazoalkane, either by loss of a proton from the diazonium ion or by what is probably a concerted elimination reaction of the diazoester, can lead to racemisation of the alkyl function and loss of asymmetry in the anion. Moreover, the diazoester is liable to nucleophilic displacement, for example by an acid molecule formed from already rearranged nitrosoamide, and this can lead to inverted product. 

The reaction of a-ketodiazonium ions is of interest because there is considerable evidence that loss of nitrogen can occur by an 8 2 mechanism (p. 337-347). If this is generally true, the possibility arises of a comparison between the reactions of diazonium ions and those of alkyl halides and tosylates under conditions that do not lead to the formation of carbonium ion intermediates. In the discussion of the molecularity of the rate-determining step, the reaction of ketodiazonium ions was supposed to proceed with simple substitution by an external nucleophile. Product analyses, on the reactions of diazoketones with acids and the deamination of aminoketones, show, however, that extensive rearrangement and molecular fragmentation can occur in suitable alkyl structures. The simplest of these reactions have the following stoichiometric form (Baumgarten and Anderson, 1961) ... 

See Chapter 2 for a discussion of anti- and synperiplanar requirements in E2 elimination reactions.) In each diastereomeric diazonium ion in the example, the bond that is antiperiplanar to the C—N2 bond migrates selectively. (Draw a Newman projection or make a model if you have trouble seeing this.) The same phenomenon is observed in the Beckmann rearrangement, in which an oxime is converted into an amide after a 1,2-alkyl shift and addition of H2O. The group that is trans to the OH group (i.e., antiperiplanar) shifts selectively. 

On the basis of theoretical studies, it has been suggested that alkyl diazonium ions should undergo a rearrangement similar to the cyanide-isocyanide interconversion this reaction, which could only be detected by shift of labelled nitrogen, has not been observed. Reaction of a diazonium ion proceeds usually by one of four routes. 

Reviews this year include the collation of evidence in favour of the o-bridged 2-norbornyl cation,the use of aliphatic diazonium ions as means for the production of carbocations, terpene rearrangements in superacid media,and the formation of carbocations by the silver-assisted reactions of chloroformates. A convenient procedure, using syringe techniques, has been described for the preparation of ca. IM solutions of alkyl cations in SbF5-S02ClF from suitable precursors that are soluble in SO2CIF at —78 Since conversions are essentially quantitative, the... 

Research into the mechanism of diazotization was based on Bamberger s supposition (1894 b) that the reaction corresponds to the formation of A-nitroso-A-alkyl-arylamines. The TV-nitrosation of secondary amines finishes at the nitrosoamine stage (because protolysis is not possible), but primary nitrosoamines are quickly transformed into diazo compounds in a moderately to strongly acidic medium. The process probably takes place by a prototropic rearrangement to the diazohydroxide, which is then attacked by a hydroxonium ion to yield the diazonium salt (Scheme 3-1 see also Sec. 3.4). 

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