Azinium

The exclusion of nitrogen-bridged bicyclic azines is purely arbitrary since the work on such azinoazines with a 10 7r-electron system (and the necessarily accompanying quaternary nitrogen-bridgehead atom) shows the activation expected of other aromatic azinium... 

Heterocyclic structures analogous to the intermediate complex result from azinium derivatives and amines, hydroxide or alkoxides, or Grignard reagents from quinazoline and orgahometallics, cyanide, bisulfite, etc. from various heterocycles with amide ion, metal hydrides,or lithium alkyls from A-acylazinium compounds and cyanide ion (Reissert compounds) many other examples are known. Factors favorable to nucleophilic addition rather than substitution reactions have been discussed by Albert, who has studied examples of easy covalent hydration of heterocycles. 

Irreversible cationization of the azine-nitrogen will increase the reactivity of anionic nucleophiles at the position adjacent to the azinium moiety (71 relative to 70), in the absence of substantial... 

Reactions of iV -alkylated or arylated azinium compounds with nucleophiles proceed more readily than those of the parent, uncation-ized azines, and the ring tends to open. The iV -substituent may bring into play an accelerative effect from the London forces of attraction. Increased displaceability of the substituent in iV -alkyl-azinium compounds has been noted for 2-halopyridinium (87) 1-haloisoquinolinium, 4-halopyrimidinium, 4-methoxypyrid-inium (88), 4-phenoxy- and 4-acetamido-quinazolinium (89), 3-methylthiopyridazinium, and 2-car boxymethylthiopyrimidi-nium salts (90). The latter was prepared in situ from the iV -alkyl-pyrimidine-2-thione. The activation can be effectively transmitted to... 

A special type of ammonio group is represented by 4-( 1 -pyridinium)-pyridine and other azinium analogs. Such products often result from self-quaternization of highly reactive derivatives. A -(4-Pyridyl)-and A -(3-nitro-4-pyridyl)-pyridinium chloride hydrochlorides (121) react with aniline, chloride ion, and water to give 4-substituted pyridines plus pyridine. l-(2-Quinolyl)- and l-(4-quinolyl)-pyridinium salts undergo 2- and 4-substitution, respectively, with amines, anilines, hydroxylamine, phenols, alkoxides, mercaptans, and chloride... 

The general principle that activation of para substitution is greater than of ortho substitution holds true also for an azinium moiety in the one instance studied. Thus, the activation energy for the 4-chloropyridine quaternary salt 280 (Table II, line 9) is 1 kcal lower than that for the 2-isomer (line 5). The rate relation (2- > 4-isomer) is controlled by the entropies of activation in this reaction due to electrostatic attraction in the transition state (281). The reverse rate relation (4- > 2-position) is predicted for aminations of such quaternary compounds due to electrostatic repulsion (282) plus the difference in E. A kinetic study of the 2- and 4-pyridine quaternary salts... 

Tire and NMR parameters of some 1-alkyl-4-benzimidazolyl-2-idene- (type 72) and l-alkyl-4-(5-methylpyrazolyl-3-idene)-l,4-dihydro pyridines (type 73) were discussed in 89CC1086 and 91JOC4223. Comparison of the shifts for DMSO-dg and CDCI3 solutions with data reported for quaternary pyridinium compounds as well as anionic species in the azole series and data obtained for mesoionic betaines of the azinium azolate class left no doubt that these heterofulvalenes have a betaine character and, therefore, the NMR signals correspond to their dipolar resonance form. 

An interesting extrapolation of this synthesis deals with the preparation of the bispyridinium salt 62 from 1,2-phthalic dicarboxaldehyde and its subsequent reaction with primary amines (92BSB509).Tlie expected diimines 63 readily cyclize so that 2-aryl-l-arylimino-2,3-dihydro-l//-isoindoles 64 can be isolated in excellent yields (90-95%). Contrary to the reactions performed by employing the dialdehyde and amines directly, the syntheses involving the azinium salts do not produce those typical dark-colored complex mixtures of products (77JOC4217 85JHC449) (Scheme 20). 

Tliere are few examples for the preparation of imines from A-(l-haloalkyl)azinium halides and primary diamines. Among those reaetions reported, A-(ehlorophenylmethyl)pyridinium ehloride (33k), whieh has not been isolated, reaets with ethane-1,2-diamine and propane-1,3-diamine to afford the eorresponding diimines 72 (Seheme 22, 45-80%) (89JOC4808, 92BSB233). 

A series of new iV-(pyridylmethyl)azinium salts were synthesized fi om 2,4,6-triphenylpyrylium tetrafluoroborate <95T(51)12425>. 

This synthetic strategy also proved to be also suitable for the ring closure to the related [l,3,4]triazolo[2,3-a][l,3,5]tri-azinium salts, as shown in Scheme 33 <1994JHC535, 1995JHC1833> reaction of 169 with l-chloro-l,3-bis(dimethyl-amino)-3-phenyl-2-azaprop-2-enylium perchlorate gave the quaternary salt 170 in 37% yield. 

Methylation of pyrido[l,2-6]cinnolinium-ll-olate (17, R = H) with the soft dimethyl sulfate gave only the A -methyl derivative 43 (74JHC125), whereas the harder trimethyloxonium tetrafluoroborate yielded the 11-methoxy derivative 77 (92CB929). Methylation of pyrido[2,l-a]phthal-azinium-7-olate (20) with methyl iodide afforded a 1 9 mixture of the... 

N-Amination of 2-[o-(l,3-dioxolan-l-yl)phenyl]pyridine (121) with O-tosylhydroxylamine gave an A-amino derivative, which underwent ring closure on the action of 70% perchloric acid to yield a pyrido[2,l-a]phthal-azinium salt (122, R = H) (92JHC1049). The 7-hydroxy derivative of a pyrido[2,l-fl]phthalalzinium salt (122, R = OH) was prepared similarly by cyclization of l-amino-2-(o-methoxycarbonylphenyl)pyridinium salt, ob-... 

Aus 2-Chlor-benzimidazolen konnen durch Substitution die Chloride von 2-Azolium- und 2-Azinium-benzimidazolen erhalten werden. Ihre Anionisierung zu hoch dipolaren Betainen ge-lingt besonders leicht (bereits mit Kaliumcarbonat oder besser mit basischen Ionenaustau-schern) z. B.403 ... 

Tab.27 2-Azolium- bzw. 2-Azinium-t-dehydro-bcnzimidazolernum-Verbindungen durch Deprotonie-rung von 2-Azolium- bzw. 2-Azinium-benzimidazol-halogeniden...

Cycl[2,2,2]azinium salts7 (5) have not been reported so far. Hiickel molecular orbital (HMO)-calculations of the isoelectronic acepentylene (6) lead to two singly occupied degenerate HOMO s.8,9 Since there is no contribution in both the HOMO s and the LUMO from atom 6b this situation does not change in going from 6 to the 5-ion,10 which can be represented as an annulenone derivative of the (4n + 1) rc-type. 

Cycl[3,3,2]azinium salts 43, which should be potentially capable of being aromatic,lb have hitherto not been available for study.598... 

Derivatives containing a pyrrole or thiophene-type heteroatom in the periphery may be looked at only formally as cycl[3,3,2]azines since they are isoelectronic with the cycl[3,3,3]azines described in Section V. 4,5-Dihydro-3//-2a-azacycl[3,3,2]azinium iodide (46) has been prepared, but could not be converted into 2a-azacycl[3,3,2]azine (47).62... 

As a consequence, the properties of the ions 73 and 74 should differ much more than those of the known isoconjugates 71101 and 72.102 The cycl[4,2,2]azinium salts (73) presumably will be diatropic stable compounds. 

Hydrogen exchange at ring carbon in azinium cations... 

Dipolar cycloaddition of anhydro pyrido[2,l-b][l,3]thiazinium hydroxides (128) with aryl isocyanates and dimethyl acetylenedicarboxylate gave pyrido[l,2]pyrimidines (129) and quinolizine-l,2-dicarboxylates (130), respectively (76CB3668). 1,4-Dipolar cycloaddition of pyrido[2,l-h][l,3]thi-azinium betaine (131, R = Me) with 1-diethylamino-l-propyne afforded cycloadduct 132, from which quinolizin-4-one 133 formed by a rapid cheletropic extrusion of carbonyl sulfide (93TL5405 95T6651). 1,4-Dipolar cycloaddition of anhydro 4-hydroxyl-2-oxo-6,7,8,9-tetrahydro-2//-pyrido-[2,l-b][l,3]thiazinium hydroxides (131) and 4-phenyl-l,2,4-triazoline-3,5-dione yielded 135 via 134 [94H(39)219 95H(41)1631] and 136 (95T6651). 

Hydrazotc acid, HN,. ply.. = 4.72, and most of its covalent compounds (including its heavy metal salts) are explosive. It is formed (1) in 90% yield by reaction of sodium amide with nitrous oxide, (2) by reaction of hydraztntum ion with nitrous acid, (3) by oxidation of hydrazimum salts, (4) by reactio n of hydt azinium hydrate with nitrogen trichloride tin benzene solution). Hvdrazoic acid forms metal azides with the corresponding hydroxides and carbonates. It reacts with HC1 to give ammonium chlonde and nitrogen, with H2SO4 to form hydrazinium acid solfate, with benzene to form aniline, and it enters into a number of oxidation-reduction reactions. 

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