Pyrazine 2- ethyl-3-methyl

Pyrazine, 2-ethyl-3-methyl Sd (roasted) ° Pyrazine, 2-ethyl-5-methyl Sd (roasted) ° Pyrazine, 2-ethyl-6-methyl Sd (roasted) ° Pyrazine, 3-5-dimethyl-2-(2 -furyl) Sd Pyrazine, 3-5-dimethyl-2-acetyl Sd Pyrazine, 3-6-dimethyl-2-(2 -furyl) Sd Pyrazine, 3-6-dimethyl-2-acetyl Sd Pyrazine, 3-ethyl-2-5-dimethyl Sd (roasted) " ... 

Pyrazine, 2-ethyl-3-methyl-, 2-ethyl-3-methylpyrazine [15707-23-0] FEMA 3155... 

The alkylation of pyrazine at a nuclear carbon atom has been discussed in detail in Section 1C (612-615, 617, 634). For example, 2-butylpyrazine was prepared from pyrazine and butyllithium in ether at —20 (612), 2-s-butylpyrazine was prepared from pyrazine, ethyl methyl ketone, and alkali or alkaline earth metals in liquid ammonia (614) the effect of temperature on the products, specificity, and yields from the alkylation of pyrazine by ethyllithium (and other alkyllithiums) in ether or hexane solutions between — 25° and 34° has been examined (615). 

Table II lists the major volatile compounds from baked blanched and fried blanched shallot slices generated from thermal degradation of nonvolatile flavor precursors of shallot were methyl propyl trisulfide, dimeihylthiophencs, methyf propyl disulfide, and dipropy trisulfide. The major volatile compounds that were probably generated from ihemia imeractiuns of nonvolatile flavor precursors of shallot and sugars were pyrazines, especially ethyl dimethyl pyrazines, dimethyl-pyrazines, ethyl methyl pyrazines, and trimethylpyrazine.

Pyrazine, 3-ethyl-2-6-dimethyl Sd (roasted) ° Pyrazine, 3-ethyl-2-methyl Sd Pyrazine, 3-methyl-2-(2 -furyl-4 -methyl) ... 

Pyrazine, 2-ethyl-6-methyl Cured Lf Pyrazine, 2-methyl Cured Lf smoke Pyrazine, butyl Cured Lf smoke ... 

Bourguignon and coworkers in their preparation of thieno[2,3-6]pyrazine used methyl-pyrazine (364 Scheme 107) (80JHC257) as starting material. The chlorination of (364) yields 2-chloro-3-methyl- and 2-chloro-6-methyl-pyrazine in a ratio of 80 20. Without separation this mixture is treated with ethyl mercaptoacetate in the presence of sodium ethoxide to give (365) in 91% yield (based on 2-chloro-3-methylpyrazine). Oxidation of the methyl group to an aldehyde function and subsequent base catalyzed ring closure yields (366), which is transformed to (363) by the method depicted already in Scheme 106. 

In Figure 3, as in Figure 2, samples isolated from oats with 7.4% and 8.3% lipid content were different with regard to chemical composition. Since the oil itself may play several roles, for example as generator of aroma compounds as well as solvent for other volatile compounds, it is of interest to follow the aroma pattern in the abovementioned samples. The amount of heterocycles decreased in most cases when the initial oat lipid content increased. Compounds such as pyrazine derivatives (methyl, 2,5-dimethyl, 2,6-dimethyl, 2-ethyl-5-methyl, trimethyl, 2,5-methyl-3-ethyl), furfural, 5-... 

N-Heterocycles Pyridine Pyrazines Unsubstituted, 2,3-Dimethyl, MARM ++ 2,5-Dimethyl-3-ethyl, Methyl, 2-Ethyl-6-methyl, 2,5-Dimethyl, 2-Ethyl-5-methyl, 2,6-Dimethyl, Acetylmethyl, 2-(2-Furyl), Ethyl, 2-Methyl-5-(methylethyl), Trimethyl Pyrroles 2-Acetyl, N-Methyl-2-furyl, 1-Formyl, 1-Furfury 1-2-formyl, 5-Methvl-2-formvl Trimethylpyrazine (TMPy) (RV = 0.989)... 

Maltol Isobutyrate 2-Methoxy 3-(or 5- or 6-) Isopropyl Pyrazine 5H-5-Methyl-6,7 -dihydrocyclopenta[b]pyrazine 5-Methyl Furfural Methyl Furoate Methyl Hexanoate Methyl Isovalerate 5-Methyl 2-Phenyl 2-Hexenal Methyl Thiobutyrate Methyl Valerate P-Naphthyl Ethyl Ether Phenyl Ethyl Cinnamate Phenyl Ethyl Propionate Propyl Formate Propyl Mercaptan Salicylaldehyde 8-T etradecalactone 2-Tridecanone... 

Alkylation of pyrazine has been achieved under a variety of conditions. Treatment of pyrazine in ether at — 20° with butyllithium gave a 10% yield of 2-butyl-pyrazine but with phenyllithium only polymeric material or unchanged starting material was obtained (612). Pyrazine is alkylated at the 2-position by the radical MeNHCO(CH2)4CH2 generated from 2-methyl-3,3-pentamethyleneoxazirane and ferrous sulfate (613). Aldehydes and ketones in the presence of a solution of an alkali or alkaline earth metal in liquid ammonia (or a suspension of these metals in other solvents) can be made to alkylate the pyrazine ring in moderate to good yields. Thus from pyrazine and ethyl methyl ketone, a 60% yield of 2-s-butylpyrazine was obtained (614). 

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). 

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. 

The carbonyls are represented by peaks 4, 6, 7, 11 and 16 on Figure 3. They were identified as isobutyraldehyde, isovaler-aldehyde, 2-methyl butanal, pentanal cUid hexanal. The pyrazines are represented by peaks 13, 18, 20, 25 cind 26. They were identified as pyrazine, 2-methyl pyrazine, 2,5-dimethyl pyrazine, 2-ethy1-5-methyl pyrazine and 2-ethyl-3-methyl pyrazine. The authors observed a decrease in carbonyls (which are responsible for harsh green flavor notes) euid increase in pyrazines (which are responsible for roasted notes) with longer roasting time. 

Our results showed that the flavour profile of peas was affected by market class, cultivar location, and crop year. The highest total volatile compound (TVC) was observed in cultivars from marrowfat-market class. Crops grown in Meath Park location had the highest TVC. Furthermore, different volatile compounds were identified in pea cultivars. In both crop years, cultivars from the green-market class had the highest mean values of esters and hydrocarbons, whereas the highest value of alcohols was observed for the marrowfat-market class, and the dun-market class had the highest mean values of ketones and pyrazine. 3-Methyl-butanol, 1-propanol, 2-ethyl-hexanol, 3-methyl-butanal, trichloromethane, 2-butanone, dimethyl sulfide, ethyl acetate and 2,3-diethyl-5-methyl pyrazine were the most abundant volatile compounds observed in the pea cultivars. 

Elemental composition analysis (and some idea of the volatile composition of colfee) strongly suggested that this ion corresponded to a pyrazine. It did not, however, allow us to distinguish between trimethyl pyrazine and ethyl methyl pyrazine, isomers that consequently have the same molecular weight. Accurate mass may therefore allow us to discriminate between some molecules or molecular classes but will be of little value in the analysis of mixtures of isomers, such as systems containing a wide range of terpenes. 

Both 2- and 3-methyl groups in pyrido[2,3-Z ]pyrazines are acylated by ethyl oxalate (71TH21500). They give (preferentially 3-) styryl derivatives with aromatic aldehydes and oximes with pentyl nitrite. 

Because silylation with HMDS 2/TCS 14 in acetonitrile at ambient temperature converts the unreactive a-chloroketone moiety of 743 into an /Z-mixture of reactive alkyl 4-chloro-3-trimethylsilyloxycrotonates 746a, b [230, 231] which can be isolated and distilled, if humidity is excluded, silylation of 743a, b in the presence of ami dine salts such as 745 gives the desired ethyl or methyl imidazole(4,5)-acetates 748a, b via IMz and 747b. The reaction of formamidine acetate with 746a,b affords 745 (with R=H) in up to 70% yield [232, 233] (Scheme 5.79). As side reactions one must, e.g., take into account the reaction of 746 with ammonia to give 755 which subsequently dimerizes to the pyrazine 756, as discussed in Section 5.5.3. 

Fluorobenzene to fluorodihydrocatechol and fluorocatechol Conversion of 2,5-dimethyl pyrazine to 5-metyl pyrazine-2-carboxylic acid, conversion of 5-ethyl-2-methyl pyridine to... 

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>. 

Perhydropyrido[l,2- ]pyrazin-l-one was prepared in the reaction of methyl pipecolinate and ethylene imine in boiling EtOH <19951JSP5461047>. Cyclocondensation of ethyl 2-amino-2-(2-pyridyl)acetate with DMAD, followed by treatment of reaction mixture with NaOMe, gave the 2-(l-methoxycarbonyl)-4-oxo-47/-pyrido[l,2- ]pyrazin-3-yl)acetate <1996JHC639>. 

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