5-Hydroxy-3-methyl-2- pyrazine

A patent (726) has described the preparation of 2methyl-pyrazine by reaction with ammonia and air at 350° over a catalyst containing vanadium pentoxide and potassium sulfate a series of cyanomethylpyrazines has been prepared from the corresponding methylpyrazines by reaction with sodium amide in liquid ammonia followed by Af-methyl-A -phenylcyanamide in dioxane (644). 2-Hydroxyiminomethylpyrazine has been prepared from 2-methylpyrazine, sodium amide, and liquid ammonia with butyl nitrite (727, 728), and 2-hydroxy-iminomethyl-3,6-dimethyI-5-pentylpyrazine similarly from 2,3,5-trimethyl-6-pentylpyrazine (648). Nitrones (28) have been prepared from 23-and 2,5-dimethyl-and tetramethylpyrazine through the substituted methylpyridinium (perchlorates) (27) by reaction with p-nitroso-A, fV-dimethylaniline (729). Dehydrogenation of ethylpyrazine at 600° over a calcium cobaltous phosphate catalyst gives 2-vinyl-pyrazine (658). 

Chloro-5-hydroxy-3,6-dimethylpyrazine with phosphoryl chloride gave a low yield of 2,5-dichloro-3,6-dimethylpyrazine (312) 3-chloro-5-hydroxy-2-methyl-pyrazine gave 3,5-dichloro-2-methylpyrazine (535) and 2-chloro-5-hydroxy-3,6-diisobutylpyrazine with phosphoryl chloride at 150° for 5 hours gave 2,5-dichloro-3,6-diisobutylpyrazine (101). 

The first lithiopyrazine derivative was prepared by Hirschberg et al. (1015) from 3-iodo-2,5-dimethylpyrazine and butyllithium in ether subsequent reaction with (a) carbon dioxide gave 3-carboxy-2,5-dimethylpyrazine, and (b) several aromatic aldehydes gave the carbinols (62, R = H, p-methoxy, m-nitro) (1015). Similar reactions were observed when 2-formylpyridine and 2-acetylpyridine (1016) were used as the carbonyl compounds, but with acetaldehyde attempted reactions were unsuccessful (1015). A patent also describes the preparation of many carbinols from 2,5-disubstituted 3-iodopyrazines (164). The lithio reagent derived from 3-iodo-2,5-dimethylpyrazine (with butyllithium in hexane) with 2-nitrobenzaldehyde gave 2,5-dimethyl-3[ 1 -hydroxy-1 (2"-nitrophenyl)methyl] pyrazine (1017). 

The reaction of an aqueous solution of sucrose with glycinamide at 140° has been reported to give a mixture which contains 2,5-bis(I> fl o-tetrahydroxybutyl)-pyrazine and 2-(D-iiraf>o-tetrahydroxybutyl)-5-hydroxypyrazine (1073) and molasses inverted with 30% sidfuric acid and treated with ammonia under pressure produced a mixture containing 2-hydroxymethylpyrazine, 5-hydroxy-2-methyl-pyrazine, and 2-ara6o-tetrahydroxybutyl-6-methylpyrazine (47). 

Typical preparations have been described for 2-(r-hydroxyiminomethyl)pyrazine (138) 2-(4 -dimethylamino-T-hydroxyiminobutyl)pyrazine (1186) 2-(2 -hydroxy-iminopentyl)-6-methylpyrazine (645) 2-(2 -hydroxyimino-3, 3 -dimethylbutyl)-6-methylpyrazine (645) 2-[r-hydroxyimino-2-(pyridin-2"-yl) (hyl]pyrazine (642) 2-[2 -hydroxyimino-2 -(pyridin-2"-yl, pyrazin-2"-yl, or pyrimidin-4 -yl)ethyl]pyrazine (642) 2-[l, 2 -bishydroxyimino-2 -(pyridin-2"-yl)ethyl]pyrazine (642) 2-12 -(2",4"-dinitrophenylhydrazono)-3 -methylbutyl]-6-methylpyrazine (645) 2-[ 1-(substituted hydrazono)ethyl]pyrazine (1196) 2-[l -phenyl-1 -(substituted hydrazono)methyl]-pyrazine (1196) 2-(r-thiosemicarbazonoethyl)pyrazine (138) 2-(2 -chloro-l -thiosemicarbazonoethyOpyrazine (138) and 2,5-dimethyl-3,6-bis(r-semicarbazono-ethyl)pyrazine (1196). 

Pyrido[2,3-6]pyrazine, 8-hydroxy-tautomerism, 3, 250 Pyrido[2,3-h]pyrazine, methyl-acylation, 3, 253 Pyrido[2,3-6]pyrazine, 2-oxo-oxidation, 3, 250-251... 

Pyrido[3,4-b]pyrazine, 2-hydroxy-IR spectra, 3, 249 Pyrido[3,4-b]pyrazine, 3-hydroxy-IR spectra, 3, 249 structure, 3, 254 Pyrido[3,4-6]pyrazine, methyl-... 

Thieno[3,4-d]oxazole-3a(4H)-carboxylic acid, dihydro-2-methyl-synthesis, 6, 1020 Thieno[2,3-d Joxazoles synthesis, 6, 990 Thieno[3,2-g]pteridine structure, 3, 284 lH-Thieno[3,4-c]pyran-2-ones synthesis, 4, 1032 Thienopyrazines synthesis, 4, 1022-1024 Thieno[2,3-6]pyrazines, 4, 1023 electrophilic substitution, 4, 1024 Thieno[3,4-6]pyrazines, 4, 1024 Thieno[3,4-c]pyrazole, 4,6-dihydro-3-hydroxy-carbamates... 

Hydroxy group of rru -7,9u-H-7-(prepared from 7-formyl-2-(2-pyrimidyl)perhydropyrido[l,2-u]pyrazine by the treatment with MeOCH2P(Ph)3Cl in the presence of -Pr2NH in THF at 0°C, than with BuLi at room temperature (99MIP6). 

Stereostructures of a co-crystal of (li )-l- 4-[(9aA)-perhydropyrido[l,2- ]pyrazin-2-yl]phenyl -2-phenyl-7-hydroxy-l, 2,3,4-tetrahydroisoquinoline with ERa-LBD301-553/C — S triple mutant <2005JME364> and iV-[2-(4-hydroxyphenyl)ethyl]-a-propyl-3-[(4-hydroxyphenyl)methyl]-l,4-dioxo-l,2,3,4,ll,l la-hexahydro-67/-pyrazino[l,2- ]isoquinoline-3-acetamide with fructose-1,6-biphosphatase <2003JBC51176> were determined by X-ray crystallography. The structure of a complex formed from 3-[( -methylphenyl)amino]-4-[(4-methylphenyl)imino]-4//-pyrido[l,2-tf]pyrazine with sodium bis(trimethylsilyl)amide and (norbornadiene)Mo(CO)4 in THF was characterized by single crystal X-ray diffraction <1995JPR38>. 

Partly saturated pyrazino[l,2-r-]pyrimidines were prepared by formation of the pyrazine ring. 2-Substituted-8-hydroxy-3,4-dihydro-177,277-pyrazino[l,2-r-]pyrimidin-l-ones were prepared by a [6+0] synthesis involving cyclization of 6-hydroxy-pyrimidine-4-(fV-hydroxyethyl)carboxamides <2005W02005/087766>. The 2/7-pyra-zino[l,2-c]pyrimidine-3-carboxamide 164 (Y = NH) was formed from [5+1] atom fragments via the uracil derivative 163 (Y = NH) and DMF-dimethyl acetal. Compounds 163 were prepared from 6-chloromethyluracil and glycine methyl ester 162 (Y = NH) (Scheme 20) <2004W02004/014354>. 

Kinetic parameters k, often also and AS, occasionally AV ) for formation and dissociation of several pentacyanoferrate(II) complexes [Fe(CN)5L]" have been established. Ligands L include several S- and A-donor heterocycles,4-methyl- and 4-amino-pyridines, a series of alkylamines, 3- and 4-hydroxy- and 3- and 4-methoxy-pyridines, several amino acids, nicotinamide, " 4-pyridine aldoxime, 3-Me and 3-Ph sydnones, several bis-pyridine ligands,neutral, protonated, and methylated 4,4 -bipyridyl, 1,2-bis(4-pyridyl)ethane and traTO-l,2-bis0-pyridyl)ethene, pyrazine- 4,4 -bipyridyl- and bis(4-pyridyl)ethyne-pentaammine-cobalt(III), edta-ruthenium(III), and pentaammineruthenium-(II)and-(III) complexes of... 

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