1- Methyl-3-methylpyrazinium iodide

Methyl pterin, AK40 6-Methyl purine, AG96 2-Methylpyraz 3 ne, AE22 1-Methylpyrazinium iodide, AE32... 

Cyano-5-(3,4-dimethoxyphenyl)-l-methylpyrazinium iodide (356) gave 6-(3,4-dimethoxyphenyl)-4-methyl-4,5-dihydro-2-pyrazinecarbonitrile (357) [ Hantzsch ester (diethyl 2,6-dimethyl-l,4-dihydro-3,5-pyridinedicar-boxylate) (1 mol), MeCN, 20°C, 3 h 80% or NaBH4, MeCN, 20°C, 30 min 83%], and thence 6-(3,4-dimethoxyphenyl)-4-methyl-l,4,5,6-tetrahydro-2-pyrazinocarbonitrile (357a) (repeat procedures for 24 and 3 h, respectively, both affording 72%).1262... 

Amino-6-methyl-2(l//)-pyrazinethione l-Amino-3-methylpyrazinium iodide 3-Amino-l-methyl-2(l//)-pyrazinone 3-Amino-5-methyl-2(l//)-pyrazinone 3-Amino-6-methyl-2(l//)-pyrazinone... 

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). 

Methylation (666, 912) of 2-methoxypyrazine with methyl iodide in dimethyl sulfoxide at room temperature gave 3-methoxy-l-methylpyrazinium iodide with a rate of methylation relative to pyrazine of 1.05 (666). 2-Methoxypyrazine with tetracyanoethylene oxide gave a small yield of 3 ethoxypyrazinium dicyano-methylide (53) (1094). Alkylation of 2-methoxypyrazine with ethyl methyl ketone in the presence of sodium in liquid ammonia to give 2-s-butyl-6-methoxypyrazine (17%) has been described (614). The reactions of 3-hydroxy-2,5-dimethylpyrazine and alkylhalides have been examined (1095). 

Proton magnetic resonance measurements in dimethyl sulfoxide indicate that 2-aminopyrazine and its 3-methyl derivative exist predominantly in the amino form (979, 1086), in agreement with theoretical and experimental electronic spectra (1083). Proton magnetic resonance analysis of the methylation of 2-aminopyrazine with methyl iodide in dimethyl sulfoxide at room temperature showed it to be methylated 8.8 times as fast as pyrazine to give both 3-amino-l-methyl- and 2-amino-l -methylpyrazinium iodides in the ratio 2.9 I (666). Proton magnetic resonance spectra of ionized 2-aminopyrazine in liquid ammonia have also been reported (665). 

Carbamoylpyrazine was methylated to 3-carbamoyl-l -methylpyrazinium iodide by methyl iodide in methanol at reflux (138) and by methyl iodide in dimethyl sulfoxide at room temperature (666) under the latter conditions the rate of methylation relative to pyrazine was 0.53 (666). 3-Carbamoyl-l-methylpyrazinium iodide reacted with liquid ammonia at — 40° to give 2-amino-5-carbamoyl-l-methyl-1,2-dihydropyrazine (46) (609). With nitromethide ions in liquid ammonia, none of the carbon addition reaction was found (721), but with ethanethiolate ion in liquid ammonia it gave 5-carbamoyl-2-ethylthio-l-methyl-1,2-dihydropyrazine (721). 2-(4 -Morpholino)carbonylpyrazine with methyl iodide gave 3-(4 -morpholino)-carbonyl-1-methylpyrazinium iodide (870). 

Dimethyl 2,3-pyrazinedicarboxylate gave l-ethyl-2,3-dimethoxycarbonylpyrazinium tetrafluoroborate (347) (1 11 )liD. CICH2CH2CI, reflux, 2 h SO Fi methyl 2-pyrazinecarboxylate gave 3-methoxycarbonyl-l-methylpyrazinium iodide (348)... 

Most such pyrazinones have been made by primary synthesis (Chapters 1 and 2) or N-alkylation of tautomeric pyrazinones (Section 5.1.2.2). The minor route by rearrangement of alkoxypyrazines (H 184) appears to be unpresented in recent literature, but there are examples of the hydrolysis of nontautomeric iminopyrazines to corresponding pyrazinones. Thus 3-imino-4-methyl-3, 4-dihy-dro-2-pyrazinamine hydriodide (191, R = H) (i.e., 2,3-diamino-1-methylpyrazinium iodide) underwent hydrolysis in 2 M sodium hydroxide during 1 h at 100°C to afford 3-amino-l-methyl-2(l//)-pyrazinone (192, R = H) ( 40%) without any evidence of Dimroth rearrangement to 3-methylamino-2-pyrazinamine l-methyl-3-methylamino-2(l//)-pyrazinimine (191, R = Me) likewise gave 1-methyl-3-methylamino-2(l//)-pyrazinone (192, R = Me) ( 50%) and other examples have been reported. ... 

Quaternization of the four dimethylpyrazine A(-oxides and 2,3-diphenylpyrazine 1-oxide with methyl iodide in a sealed tube at 80 gave the 4-methylpyrazinium 1-oxide iodides, but 3-phenyl-, 2,5-diphenyl- and 3,5-diphenylpyrazine 1 -oxides and dimethylpyrazine 1,4-dioxides could not be quaternized. The quaternary salts were reduced by sodium borohydride to A -hydroxypiperazines (766). 

Methylation of 2-amino-3-hydroxypyrazine (62) with methyl iodide and sodium methoxide afforded 3-amino-l-methyl-2-oxo-1,2-dihydropyrazine (63), and when an excess of methyl iodide was used, a mixture of compound (63) and its methio-dide (64) was isolated. Reaction with dimethyl sulfate and alkaU gave compound (63) and l,4-dimethyl-2,3-dioxo-l,2,3,4-tetrahydropyrazine (66) the latter was presumed to be formed by hydrolysis of an intermediate quaternary salt since it was also obtained by treatment of the methiodide (64) with aqueous sodium hydroxide. Reaction of 2-amino-3-hydroxypyrazine with ethereal diazomethane produced a mixture of N- and 0-methyl derivatives, (63) and 2-amino-3-methoxy-pyrazine (65). With methyl toluene-p-sulfonate the quaternary salt 2-amino-3-hydroxy-1-methylpyrazinium toluenesulfonate (67) was obtained on alkaline hydrolysis it gave 3-hydroxy-l-methyl-2-oxo-l,2-dihydropyrazine (68) (832). Pulcherriminic acid with diazomethane gave a dimethyl derivative (99). 

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See also in sourсe #XX -- [ ]

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