2-Bromo-6- pyrazine

Amino-3-Methoxy-5-Bromo-Pyrazine 7 grams of 2-amino-3,5-dibromo-pyrazine are boiled for 9 hours in a methanolic solution of sodium methylate (obtained from 0.65 gram of Na and 18.5 ml of methanol). By cooling a crystalline product is obtained, filtered and washed once with methanol and 2 to 3 times with water. The yield is 5.4 grams, melting at 138°C. 

Amino-3-Methoxy-Pyrazine 3 grams of 2-amino-3-methoxy-5-bromo-pyrazine are hydrogenated, in methanolic solution at room temperature and at atmospheric pressure, in the presence of 1 gram of palladium over charcoal... 

Bromo derivatives of 2-amino-3-chloro- and 2-amino-3-bromo-pyrazines are obtained by bromination with bromine in 20% hydrobromic acid at 5°. Similar treatment of 2-amino-5-bromopyra-zine-3-carboxylic acid gives 2-amino-3,5-dibromopyrazine.291 292... 

Comparison of the ultraviolet absorption and ionization constants of aminopyrazine, methylaminopyrazine, and dimethylaminopyra-zine indicates that aminopyrazine exists as such and not in the tautomeric imino form.147 Aminopyrazines, like their pyridine analogs, form diazonium salts, which readily decompose to the corresponding pyrazinones. For example, nitrous acid treatment of aminopyrazine318 and 2-aminopyrazine-5-carboxylic acid210 gives the corresponding pyrazinones in 30 and 59% yield, respectively. The diazonium salt from aminopyrazine cannot be converted into bromo-pyrazine under the conditions of the Sandmeyer reaction. 

In a series of reactions with potassium amide in liquid ammonia, 6-chloropyrido[2,3-f)]pyrazine gave reduction and ring contraction (Section 2.15.13.3), the 6-bromo analogue underwent only reduction, whilst the 6-fluoro derivative gave only the 6-amino substitution product (79JHC305). 

Imidazo[ 1,5-a]pyrazine, 1 -bromo-3-methyl-hydrolysis, S, 625 reactivity, 5, 625... 

A mixture of 1- and 3-chloro, 1,3-dichloro, and 1,3,5-trichloro derivatives was obtained on chlorination of imidazo[l, 5-a]pyrazine (172). Bromination gave similar results (75JHC207,75JOC3373 84MI24). The 8-chloro compound is best made from the 8-oxy derivative of 172. When the 1-bromo-3-methyl derivative of 172 was treated in turn with aqueous bromine and excess dilute caustic soda, the pyrazine ring was destroyed to give 4-bromo-2-methylimidazole-5-aldehyde (75JOC3373). 

N,A -bis(2-phyidylmethyl)pyrazine-2,3-dicarboxamide was crystallized in two orthorhombic forms, which differ from each other in the conformational arrangements of the compound [44], A new polymorph of 2-bromo-5-hydroxybenzaldehyde has been reported where a pair of hydrogen bonds linked molecules related by a center of inversion [45], One of the intermediates important in the synthesis of an antituberculosis drug, methyl p-aminobenzoate, was found to crystallize in a new monoclinic polymorph where molecules were arranged in head-to-tail linear ribbon arrays [46]. 

HPA = (4-pyridylthio)aceticacid 2-fur = 2-furoate a-fur = a-furoate = ([Pg.116]

In acidic solution, 7-bromo-2,3-dimethylpyrido[2,3-b] pyrazine (289) is reduced reversibly to the 1,4-dihydro derivative 290 without loss of bromide, whereas in alkaline solution the primarily formed dihydro compound loses hydrogen bromide to the parent pyrido[2,3-fc]pyrazine (291), which may be further reduced350 [Eq. (149)]. 

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