Pyrazine Chemistry. IV. Bromination of 2-Amino-3-carbomethoxypyrazine

Abstract

ethanol containing hydrogen chloride, dissolving the separated hydrochloride (m. p. 163-165°) in warm 95% ethanol and pouring the solution slowly into cold water, yielded the pure base of m. p. 72-73°.Ultraviolet Spectra.-The apparatus used was a Beckman Model DU Quartz Spectrophotometer. The solvents were:for I, 95% ethanol; for II purified dioxane" finally redistilled through a 15-ball Snyder column with rejection of the fore-run; for III, pyridine dried over solid potassium hydroxide and distilled, only the middle fraction being used. The samples were purified as follows.Compound I was obtained from the hydrochloride (crystallized from 1 N hydrochloric acid) by action of warm aqueous ammonium hydroxide, and was then crystallized from 50% ethanol. Compound II was obtained pure from I by twice crystallizing from anhydrous dioxane. Compound III was obtained from I by two crystallizations from pyridine, and was freed of adhering solvent as described above. The ultraviolet spectra are shown in Fig. 1.Infrared Spectra.-Samples of I, II and III, purified as outlined, were suspended in "Nujol" and examined in a double-beam infrared spectrophotometer. 23 The plotted results appear in Figs. 2 and 3. Molecular Weight Determinations.-The Cottrell ebulliometer,24 enclosed to exclude drafts, was swept out with dry nitrogen before each determination. About 65 ml. of solvent (dried and fractionally distilled) was used, and in each case several values were obtained at increasing concentrations. At higher concentrations some difficulty was encountered owing to irregular splashing and foaming. The results, calculated in terms of extents of association, are shown graphically in Fig. 4. (22) Fieser, "Experiments in Organic Chemistry," D. C. Heath and Co., N. Y., 2nd ed" 1941, p. 369.(23) The spectra were determined by Samuel Sadtler and Son, Analytic and Consulting Chemists, Philadelphia, using an instrument made by Baird Associates, Inc.(24) The low solubilities of the compounds in permissible solvents near their freezing points made the freezing point method inapplicable.

RuII Multinuclear Metallosupramolecular Rack‐Type Architectures of Polytopic Hydrazone‐Based Ligands: Synthesis, Structural Features, Absorption Spectra, Redox Behavior, and Near‐Infrared Luminescence

“…[8] Reaction of aminopyrazine 20 with N-bromosuccinimide led to 2-amino-5-bromo-pyrazine [9] (19), which, on treatment with Br 2 , HBr, and NaNO 2 , yielded 2,5-dibromopyrazine [10] (18), the reaction of which with methylhydrazine led to 2,5-bis(1-methylhydrazino)pyrazine (17). Reaction of 17 with two equivalents of 2-pyridinecarboxaldehyde (25) led to ligand 8 (Scheme 1).…”

“…Materials and general methods: The following compounds were prepared as previously described: 21 (from 22) and 26, [6] 19, [9] 18, [10] 24, [8] 14,…”

TMP-cadmiate: A Base for Efficient and Chemoselective Deprotonative Metallation Reactions of Aromatic Compounds

“…Similar compounds such as 2-bromo-5-iodopyrazine [62] and 2,5-dibromopyrazine [63] have previously been prepared by diazotization of 5-bromopyrazinamine (41% and 66% yield, respectively), the latter being accessible by bromination of pyrazinamine (75% yield) [64]. Such compounds could find applications as substrates for the synthesis of molecules endowed with biological [65] or photophysical [66] properties.…”

Modulation ofπ-Electron Conjugation in Oligo(triacetylene) Chromophores by Incorporation of a Central Spacer

“…All spacers were commercially available with the exception of 2,5-dibromopyrazine and naphthalene-2,6-diyl bis(trifluoromethanesulfonate), which were synthesized according to published procedures. The former was obtained in two steps by bromination of pyrazine-2-amine with N-bromosuccinimide (71%) [21] and subsequent diazotization of the NH 2 group (66%) [22]. The latter was prepared in 72% yield by esterification of naphthalene-2,6-diol with (CF 3 SO 2 ) 2 O [23].…”

“…The overall shape of the c ) Prepared according to [23]. d ) Prepared according to [21] and [22]. spectrum is more characteristic of an anthracene than an oligomeric DEE chromophore; however, the two transitions with maxima at 495 and 335 nm are bathochromically shifted by nearly 100 nm compared to the two longest-wavelength absorptions of the pure aromatic hydrocarbon [30].…”