2- pyrazine iodide

Triisobutyl-6-methylpyrazine 2-[2-(Trimethylammonio)ethyl] pyrazine iodide... 

Dimethylaminoethyl)pyrazine was quaternized by methyl iodide to give 2-(2 -trimethylammonioethyl)pyrazine iodide (48) (which with aqueous sodium hydroxide gave 2-vinylpyrazine) (657) and 2-hydroxy-3-nitro-5,6-diphenylpyrazine... 

Figure 5.1 Principal inertial axes of (a) hydrogen cyanide, (b) methyl iodide, (c) benzene, (d) methane, (e) sulphur hexafluoride, (f) formaldehyde, (g) s-lraws-acrolein and (h) pyrazine...

A study of the a-arylation of diazine mono iV-oxides, under Heck-like conditions, also gave emphasis to pyrazines but a number of examples using pyrimidines and pyridazines were also described (Scheme 1). A wide range of aryl chlorides, bromides and iodides was used and the products were easily deoxygenated by catalytic reduction. An interesting feature was the use of a copper additive, which was only required for the pyrimidine reactions, to give a very substantial improvement in yield <06AG(I)7781>. 

As with other haloaromatic systems, Barbier reactions are also suitable for heterocyclic systems. For example, the lithio derivatives formed in situ from iodide 187 upon sonication reacted immediately with electrophiles such as benzaldehyde, hexanal and diphenyl disulfide, to give good yields of 188 <00T3709>. Similar chemistry was also successful with pyrazines, pyrimidines, and pyridazines. 

By comparison with an octadecyloxy stilbazium iodide monolayer (x<2> = 0.51 x 10"6 esu) [15], the value of the effective second-order susceptibility x r at 45° incidence was estimated to be 1.0 x 10"7 esu. The value is fairly large, in comparison with those of the conventional nonlinear optical materials (e.g. LiNbOs). Other pyrazine derivatives (C120PPy and C12SPPy) also gave thick noncentrosymmetric LB films with fairly large second-order nonlinearity by the alternating deposition with arachidic acid. The estimated Xeff values of the pyrazine LB films are listed in Table 3. 

Qudguiner s group lithiated a sym-disubstituted pyrazine, 2,6-dimethoxypyrazine (43), with lithium 2,2,6,6-tetramethylpiperidine (LTMP). The resulting lithiated intermediate was quenched with h to give 3-iodo-2,6-dimethoxypyrazine (44) and 3,5-diiodo-2,6-dimethoxypyrazine (45) [35]. Iodide 44 was then coupled with phenylacetylene to provide adduct 46. 

The same authors reported in a later study <2000H(3)69> that pyrazinone 340 is also a suitable starting material for a such transformation. The reaction proceeds in two steps the starting pyrazinone 340 when treated with benzonitrile oxide yields an addition product 341 which undergoes oxidative cyclization in the presence of iodine-potassium iodide to the ring-closed [l,2,4]oxadiazolo[4,5-tf]pyrazines 342. 

Ring nitrogens in pyrazines and the benzo derivatives react with electrophiles to form quaternary ammonium species such as iV-alkylpyrazinium salts and pyrazine iV-oxides. N-Alkylation has generally been performed by treatment with a reactive alkyl iodide. The N-1 nitrogen in 2(l//)-pyrazinone 5 is methylated using chloro(chloromethyl)dimethyl-silane followed by desilylation with cesium fluoride to yield l-methyl-2(l//)-pyrazinone <2000TL4933>. 

The direct alkylation of aminopyrazines is usually unsatisfactory as a synthetic method because it mainly takes place at the most basic ring nitrogen. However, 3,6-diamino-2,5-dicyanopyrazines are successfully alkylated by treatment with alkyl iodide or bromide in protic solvent in the presence of alkali such as NaOH in dimethylacetamide (DMA) to form bis(dialkylamino)pyrazines <1998DP(39)49>. Reaction of 2,6-diamino-3,5-diarylpyrazine with methylglyoxal in aqueous HCl-ethanol led to -alkylation but no formation of the expected bicyclic imidazolo[l,2- z]pyrazine <2001S768>. 

Pyrazine 168 underwent cross-coupling with propyne in the tri-o-tolylphosphine, and copper(l) iodide to provide 170. The isocyanate or methyl chloroformate and sodium hydride to give An isolated example of the synthesis of chiral pteridines from a (Scheme 33). 2-Isothiocyanatopyrazine-3-carboxylates have been isothiocyanatopyrazine-2-carboxylate 172 reacted with R)- —) provided the pteridine derivative 173 and uncyclized pyrazine with pyridine precursors afforded pyrido[2,3 Pytitnidines. 

In the present study, [N-Alk-Pz](TCNQ)m and [N-Alk-Pz](MTCNQ)m salts have been synthesized, with Aik for CnH2n+i n = 1, 2,...5 m 1,2. Aldrich- KodxLCQ pyrazine was used without any additional purification, while TCNQ and MTCNQ were refined by vacuum zone sublimation. Iodide alkyls were synthesized by the reaction of corresponding alcohols with phosphate tri-iodide followed by a distillation in inert atmosphere. To obtain alkylpyrazinium iodides, the quatemization reaction was used ... 

A Diels-Alder approach to varenicline was recently published by Dr. Reddy s Laboratories. Entry to a key bicyclic intermediate is achieved by an iodide-catalyzed Diels-Alder reaction of tetrabromo dimethyl pyrazine (47) with excess norbomadiene. Dihydroxylation of 48, oxidative cleavage, and reductive amination prepares N-p-methoxybenzyl varenicline (50), which is deprotected under transfer hydrogenation conditions to give varenicline (1) in 10% yield for the sequence.47 This approach continues the theme of building the piperidine of 1 through olefin oxidative cleavage and reductive amination, but by doing so late in the sequence however, the approach... 

It has been reported earlier that ketones on treatment with nitrogen iodide and aqueous ammonia yield pyrazines.142 Recently electrolysis of ketones in aqueous ammoniacal solution containing potassium iodide was also found to yield pyrazines. Thus, 2,5-dimethylpyrazine was isolated in 7% yield after electrolysis of an aqueous medium containing acetone, potassium iodide, and ammonia using a platinum anode and a nickel cathode. The mechanism proposed for this reaction is in situ formation of nitrogen iodide followed by reaction with the ketone in several steps to give dihydropyrazine and then pyrazine. In support of this proposal is the observation that electrolysis of potassium iodide in aqueous ammonia under similar conditions, but in the absence of ketones, produces nitrogen iodide.143... 

Reduction of 5-methyl-l-oxo-2,3,4,6,7,8-hexahydro-l//-pyrido[l,2-ajpyrazinium iodide, its 2-benzyl derivative and cis- and trans-5-methylperhydropyrido[l,2-a]pyrazin-l-ones with Li in liquid NH3 gave 1-methyldecahydro-l,5-diazecin-5-one (73CPB1248). Under the same conditions, 2-benzoyl-5-methylperhydro-pyrido[l,2-a]pyrazinium iodide afforded 2-benzylperhydropyrido[l,2-a]pyrazine. The 10-membered l-methyldecahydro-l,5-diazecin-5-one was also obtained from trans-5-methylperhydropyrido[l,2-fl]pyrazin-l-one by treatment with sodium amalgam in aqueous EtOH. 

The 7-oxo group of perhydropyrido[l,2-a]pyrazine-l,4,7-trione 130 was converted into an epoxide group with trimethylsulfonium iodide in the presence of rert-BuOK in DMSO, and the separated epoxides 131 and 132... 

Ionization. Ionization constants for pyrazine and several C-methylated derivatives have been redetermined for possible correlation with the polarographic half-wave potentials of the same compounds and their 1-alkyl iodides.1373... 

Pyrazine gave 1-dodecylpyrazinium iodide (6) (Ci2H23I, AcMe, reflux, 8 h 4%, owing to losses in purification)1475 or 1,4-diethylpyrazinediium bistetrafluo-roborate (Et3OBF4, C1CH2CH2C1, reflux, N2,45 min 75%).1667... 

Mel, AcMe, or EtOH , sealed, 100°C, 4 h 95%) 286 homologues were made likewise 286 and similar treatment of pyrazine 1,4-dioxide gave a separable ( ) mixture of 1-methylpyrazinium iodide and its 4-oxide in approximately equal amounts.286... 

Pyrazine (367) was converted into 1,4-diethylpyrazinediium bis(tetrafluorobo-rate) (368), the 1,4-diethylpyrazine radical cation iodide (369, X = I) (electrolytic reduction Nal J,), and finally the corresponding tetraphenylborate (369, X = BPh4) (NaBPh4 18%) which was sufficiently stable for elemental and X-ray analysis.548... 

Quaternary salts of l,2-bis(pyrazin-2-yl)ethylene (372) underwent (E — Z) photoisomerization the quantum yield for the chloride salt was better than that for the iodide salt.1165... 

The displacement of a nuclear halogeno substituent by a cyano group can be done fairly readily in the pyrazine series, usually by treatment with cuprous cyanide, potassium cyanide plus cuprous iodide, or potassium cyanide in the presence of a palladium catalyst. The following examples illustrate these procedures ... 

Radical nucleophile oxidation based on one-electron oxidation, known as the Minisci reaction, is employed for the functionalization of /V-heterocycles with acidic hydrogen peroxide in the presence of iron(II) salts (Figure 3.112).472 A range of A-heterocycles (pyridines, pyrazines, quinolines, etc.) which are activated towards attack by nucleophilic radicals when protonated are suited to this chemistry. The Minisci reaction is suitable for the preparation of carboxylic amides (from formamide), carboxylic esters (from pyruvic esters via a hydroxyhydroperoxide), aldehydes (from 1,3,5-trioxane) and alkylated pyridines (either from carboxylic acids or from alkyl iodides in dimethyl sulfoxide).473 The latter reaction uses dimethyl sulfoxide as the source of methyl radical (Figure 3.112). 

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