Pyrazinium salts reaction

Pyrido[2,3-b]pyrazinium salts, N-aryl-2,3-dimethyl-nucleophilic attack, 3, 253 Pyrido[2,3-(i]pyrazinium salts reactions... 

No systematic study of the mass spectra of pyridopyrazines has been noted, but those of 2,3-dialkyl and 2,3-diaryl derivatives have been recorded 750MS97), and mass spectrometry has been used in the elucidation of problems in the reactions of pyrido[2,3-f ]pyrazines with amide ion (including use of and derivatives) (79JHC305), and of pyrido[2,3-f ]pyrazinium salts with indoles (78ZOR431). The mass spectra of some 1-deazaflavins have been recorded (74JCS(P1)1965). 

Hydrolytic ring opening of the isomeric [l,2,3]triazolopyrimidinium salt 99 yielded the amide 100. The same team also described <1997T9393> the analogous transformation of the [l,2,3]triazolo[l,5- ]pyrazinium salts 101 reaction of this quaternary salt with a secondary amine (e.g., with pyrrolidine) led to the formation of the azadieneamine 102. For the formation of this product, a similar mechanism to that with 96 was anticipated. 

Methylpyrazine is methylated with methyl iodide in dimethyl sulfoxide at room temperature to give l-methyl-3-methylpyrazinium iodide and i-methyl-2-methyl-pyrazinium iodide, in a ratio of 3.9 I. The rate of methylation relative to pyrazine was 2.06 (666). The reaction of 2,5-dimethylpyrazine with iodo- or bromoacetic acid to give the 1,2,5-trimethylpyrazinium salt has been investigated (3). A kinetic study of the reaction of sodium hydroxide on quaternary pyrazinium salts (667, 668) has been made using a conductivity method to follow the progress of the reaction (11=5 12). In the case of 1,2,5-trimethylpyrazinium hydroxide, equilibrium lies toward (11), which slowly disappears, presumably forming the ether (13) (668). When 1,2,5-trimethylpyrazinium bromide was heated in a sealed tube trimethyl- and tetramethylpyrazine were produced (660). 

The reactions of pyrazine with sodium amide in liquid ammonia to give the anion of 2-amino-1,2-dihydropyrazine (608), and of 3-substituted 1-methylpyrazinium ions with liquid anunonia to give 3(or 5)-substituted 2-amino-1-methyl-1,2-dihydro-pyrazines (609) have been described in Section IV. 1C. Similar reactions of pyrazine with phenyllithium at —45° in tetrahydrofuran (720a) and of 1,2,5-trimethyl-pyrazinium salts in liquid ammonia with nitromethide and ethanethiolate anions (721) have been described in Section IV.2C(8). 

A mixture of the iminochlorosulfide (145), pyrazine, and an isocyanide (R—NC) underwent a three-component cyclocondensation to give the salt (146). Initial reaction gave a A -imidoyl-pyrazinium salt, which was then trapped by the nucleophilic isocyanide to form the desired product <93TL2319>. 

The /V-ethylpyrazinium 36e and 8-ethylpteridinium salts 40d which show, as we have seen (see Tables I and III), some tendency to undergo a diaddition with monofunctional nucleophiles, are also able to react with 1,3-bifunctional nucleophilic reagents to give cyclization products. Thus, reactions of pyrazinium 36e and pteridinium 40d salts with thioureas afford... 

Qualitative data on the cyclizations of pyrazinium 36, quinoxalinium 37, 1,2,4-triazinium 38, and pteridinium 40 salts with CH-active acetamides show that their reactivities follow the same order as has been established for diaddition reactions with simple nucleophiles (Section III,B,1) (86KGS1380). For example, the anilide of acetoacetic acid readily forms cycloadducts with quinoxalinium salts 37, but no cyclization products with pteridinium cations 40. By enhancing the NH-activity of the amide group, the cyclization with pteridinium salts could be achieved. Thus, the N-(pyridin-2-yl)-substituted amide of acetoacetic acid is able to undergo the cyclization reaction with the pteridinium cation 40d to afford pyrrolo [2,3-g] pteridine 62 (Scheme 48) (86KGS420). 

The data on the Sn reactions of phosphorus-centered nucleophiles with electro-phihc nitroarenes and azines are scarcely available in the literature [11, 159] Although a number of o -adducts derived from the addition of P-nucleophiles to isoquinoline [140], phthalazine [160], 4,7-phenanthroline [161, 162], A -alkyl-pyrazinium, and quinoxalinium salts [163] have been isolated and identified by NMR and X-ray crystallography, no attempts to convert these o -adducts into the corresponding Sn products have been done. For instance, Af-ethylpyrazinium tetrafluoroborate reacts with dialkyl and diaryl phosphonates under very mild conditicHis (room temperature, acetonitrile) to give stable dialkyl 3-phenyl-5,6-dicyano-l-ethyl-l,2-dihydropyrazin-2-yl phosphonates in good yields (Scheme 50) [163],... 

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