Efficient Halogenation of 2-Aminopyrazine

Abstract

2-Aminopyrazine was halogenated with NIS, NCS, and NBS under different reaction conditions. Chlorination and bromination were achieved with good yields by using acetonitrile as the solvent. However, iodination was only obtained in poor yields. Undoubtedly, the best conditions for both mono- and dihalogenation were the use of NBS, acetonitrile, and microwave assistance for short periods. 3,5-Dibromo-2-aminopyrazine is an excellent functionalized starting material for the synthesis of nitrogen heterocycles.

Peripheral engineering of Ir(iii) emitters with imidazo[4,5-b]pyrazin-2-ylidene cyclometalates for blue organic light emitting diodes

“…We started from commercially available pyrazin-2-amine, from which the addition of N -bromosuccinimide afforded 5-bromopyrazin-2-amine in high yield. 22 Next, the 2,6-dimethylphenyl substituent was introduced by Suzuki cross coupling, and the second bromination afforded the desired 3-bromo-5-(2,6-dimethylphenyl)pyrazin-2-amine. Next, it was transformed into the imidazole intermediate using a three-steps-in-one approach: 23 i.e.…”

“…We started from commercially available pyrazin-2-amine, from which the addition of N-bromosuccinimide afforded 5-bromopyrazin-2-amine in high yield. 22 Next, the 2,6dimethylphenyl substituent was introduced by Suzuki cross coupling, and the second bromination afforded the desired 3-bromo-5-(2,6-dimethylphenyl)pyrazin-2-amine. Next, it was transformed into the imidazole intermediate using a threesteps-in-one approach: 23 i.e., (i) treatment with triethyl orthoformate to afford an ethyl N-arylformimidate, 24 and (ii) direct condensation with 4-tert-butlyaniline in giving asymmetric N,N 0diarylformamidine, 25 (iii) followed by copper-catalyzed intramolecular C-N bond formation to yield the demanded 1-(4-(tbutyl)phenyl)-6-(2,6-dimethylphenyl)-1H-imidazo [4,5-b]pyrazine.…”