N-(Alkyl)-2-amino-1,4-pyrazine Derivatives: Synthesis and Antioxidative Properties of 3- and 3,5-p-Hydroxyphenyl-Substituted Compounds

Abstract

2-Amino-5-(p-hydroxyphenyl)-1,4-pyrazine and 2-amino-3,5-bis(p-hydroxyphenyl)-1,4-pyrazine are endowed with excellent antioxidative properties. For a possible development in medicinal chemistry, the lipophilicity of these lead compounds has to be increased. Therefore various methods of N-alkylation were systematically explored. The best results were obtained by quenching aminopyrazinyl anion with alkyl iodides, and by coupling aldehydes (reductive amination) in the presence of phenylsilane and tin catalyst. Aminopyrazines equipped with linear alkyl side-chains of at least six carbons showed improved radical-scavenging properties in lipidic media.

Gold catalysis in the synthesis of azaindoles: pyrrolo[2,3-b]pyridines and pyrrolo[2,3-b]pyrazines

“…Under these conditions amines 10 were obtained as the main product (52-75%, see Table 1) but some debromination was observed and the corresponding N-benzyl-N-(5-arylpyrazin-2-yl)amines 11 were detected ( Figure 2). In addition, when chromatographic purification was performed to separate the amines 10, in the reduction of salt 9a the N-benzyl-N-(3-bromopyrazin-2-yl)amine 12 was detected in trace amounts, and, in the case of 9d, a small amount of 3-bromo-5-(4-methoxyphenyl)pyrazin-2-yl amine 13 35 was also obtained with 11d 36 in an inseparable mixture (13:11d ≈ 4:6 by NMR spectroscopy) ( Figure 2). Table 2.…”