2- vinyl 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). 

Vinyl pyrazines (44) have been shown to react with benzene in the presence of CF3S03H to afford anti-Markovnikov-type addition products (45). This unusual outcome suggests that acid-catalysed addition reactions can give anti-Markovnikov-type products when a multiply charged (i.e. superelectrophilic) group is adjacent to the... 

Dimethylpyrazine (48) and the cationic bis(cyclopentadienyl) zirconium complex (49) gave an isolable intermediate formulated as the complex (50) and thence 2,5-dimethyl-3-(pent-l-enyl) pyrazine (51) [one pot procedure complex (49), CH2C12, 23°C, 15 min then HC=CPr J, 23°C, 2.5 h 88%] 868 several analogues, like 2,5-dimethyl-3,6-bis[l-methyl-2-(trimethylsilyl)-vinyl] pyrazine (51a) (61%), were made similarly.868... 

Photoisomerization. Studies have been reported for the photoisomerization of cis- to tra y-2,3-diphenylpiperazine,250 cis- to trails-1,4-dimethyl -2,3-diphenylpiperazine,250 and between possible geometric forms of 2-[2-(naph-thalen-2-yl)vinyl]pyrazine (240)66 or related compounds.1236... 

Methylpyrazine 1,4-dioxide (297) gave 2-[2-(pyridin-2-yl)vinyl]pyrazine 1,4-dioxide (298) [2-pyridinecarbaldehyde, NaOH, MeOH—H20, N2, 80°C, 5 min 96%] isomers and analogues likewise.81... 

Methylpyrazine (300) gave 2-[2-(l-methylpyrrol-2-yl)vinyl]pyrazine (299) [NaH, Me2NCHO, 60°C, N2, 1 h then l-methyl-2-pyrrolecarbaldehyde J, 50°C, 5 h 40% compare conditions with those required for alkylidenation of the more activated methyl group in substrate (297)].1485... 

Methylpyrazine gave 2-[2-(pyridin-3-yl)vinyl]pyrazine (303) [3-pyridinecar-baldehyde, Bz20 (neat), no details].756... 

CIC the earthy odour of fresh potatoes is represented by 2-isopropyl-3-methoxy pyrazine. This earthy note is supported by the mushroom character of l-octen-3-ol. The key component of boiled potatoes is 3-(methylthio)-propanal, balanced with dimethyl sulphide. The high reaction temperatures in baked and fried potatoes start the Maillard reaction to form mainly heterocyclic components 2-ethyl-3,5-dimethyl pyrazine, 2-ethyl-6-vinyl pyrazine, 5-methyl-6,7-dihydro-(5H)cyclopenta-pyrazine, 2-acetyl-l,4,5,6-tetrahydro-pyridine are responsible for the roasted, nutty cracker-like flavour. The heat-induced degradation of the potato lipids and the frying oil imparts a fatty, tallowy character to the french fried potatoes. (E,E)-2,4-Decadienal, 2-octenal, octanoic acid and decanoic acid are main contributors to this fatty note. 

Ozonolysis of vinylpyrazine in methanol at — 30° furnishes pyrazine aldehyde in 73% yield.196 Vinylpyrazine undergoes a variety of addition reactions and pyrazylethyl derivatives of amines, ketones, ethyl phenyl acetate, phenylacetonitrile, and acetamide have been obtained.197-199 2-(2-Pyrazylethyl)cyclohexanone (42) has been prepared both by the condensation of vinylpyrazine with cyclohexanone in the presence of sodium metal and by interaction of vinyl-pyrazine with the pyrrolidine enamine of cyclohexanone followed by hydrolysis.200... 

Pyrazine, tetrahydro-, 3, 177, 178 Pyrazine, 1,2,3,4-tetrahydro-synthesis, 3, 177 Pyrazine, 2,3,5-tri-t-butyl-synthesis, 3, 185 Pyrazine, 2,3,5-trichloro-nucleophilic substitution, 3, 176 Pyrazine, 2-vinyl-polymers, 1, 290-291 Pyrazine-3-carboxylic acid, 2-amino-methyl ester... 

Aldehydes and the corresponding 2-aminopyridine, pyrazine, or pyrimidine are admixed in presence of a catalytic amount of clay (50 mg) to generate iminium intermediate. Isocyanides are subsequently added to the same container and the reactants are further exposed to MW to afford the corresponding imidazo[l,2-a]pyridines, imi-dazo[l,2-a]pyrazines and imidazo[l,2-a]pyrimidines (Scheme 6.48). The process is general for all the three components, e. g. aldehydes (aliphatic, aromatic and vinylic), isocyanides (aliphatic, aromatic and cyclic) and amines (2-aminopyridine, 2-amino-pyrazine and 2-aminopyrimidine). A library of imidazo[l,2-a]pyridines, imidazo[l,2-ajpyrazines and imidazo[l,2-a]pyrimidines can be readily obtained by varying the three components [151]. 

The vinyl triflate of Komfeld s ketone has been subjected to Heck reactions with methyl acrylate, methyl methacrylate, and methyl 3-(Af-rerf-butoxycarbonyl-lV-methyl)amino-2-methylenepropionate leading to a formal synthesis of lysergic acid [259]. A similar Heck reaction between l-(phenylsulfonyl)indol-5-yl triflate and dehydroalanine methyl ester was described by this research group [260]. Chloropyrazines undergo Heck couplings with both indole and 1-tosylindole, and these reactions are discussed in the pyrazine Chapter [261], Rajeswaran and Srinivasan described an interesting arylation of bromomethyl indole 229 with arenes [262]. Subsequent desulfurization and hydrolysis furnishes 2-arylmethylindoles 230. Bis-indole 231 was also prepared in this study. 

Even reactions which are thermodynamically unfavoured, e.g. with Kaq as low as 5 x 10-6, may be electrocatalytically mediated. For example, rotating platinum electrodes covered with polymerized [Ru(4-vinyl-4 -methyl-2,2 -bipyridyl)3]2+wiil electrocatalytically mediate the oxidation96 of such species as [Ru(bipy)3]2+, [Ru(bipy)2(4,4 -bipy)2]2+, [Ru(bipy)2(py)(MeCN)]2+, [Ru(bipy)2-(MeCN)J2+ and [Ru(bipy)2(pyrazine)2]2+. 

Reaction of cis-6H,9aH-2-(ferf-butoxycarbonyl)perhydropyrido[l,2-fl] pyrazine-6-aldehyde with ylide, formed from (3-chlorobenzyl)(triphe-nyl)phosphonium bromide with BuLi, furnished 6-[(E)-2-(3-chlorophe-nyl)vinyl] derivative (07USA2007/037817). The treatment of cis-6H,9aH-... 

Propynyl vinyl sulfide, 1877 Pyrazine, 1428b Pyridazine, 1428c... 

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