Synthesis of methyl 2-[2-(4-phenyl[1,2,4]triazolo-[4,3-a]quinoxalin-1-ylsulfanyl)acetamido]alkanoates and their N-regioisomeric analogs

Abstract

Methyl 2-[2-(4-phenyl[1,2,4]triazolo[4,3-a]quinoxalin-1-ylsulfanyl)acetamido]alkanoates were formed by the reaction of 2-(4-phenyl-1,2-dihydro[1,2,4]triazolo[4,3-a]quinoxalin-1-ylsulfanyl)acetic acid with a variety of amino acid esters via DCC coupling method in the presence of N-hydroxybenzotriazole in good yields. These amino acid derivatives linked to triazoloquinoxaline moiety were also obtained by the reaction of 2-(4-phenyl[1,2,4]triazolo[4,3-a]quinoxalin-1-ylsulfanyl)acetohydrazide with amino acid ester derivatives via azide coupling method in poor yields due to the competing decomposition of the corresponding azide resulting in the starting 4-phenyl-[1,2,4]triazolo[4,3-a]quinoxaline-1(2H)-thione. The N-regioisomeric methyl 2-[3-(4-phenyl-1-thioxo[1,2,4]triazolo[4,3-a]quinoxalin-2(1H)-yl)propanamido]alkanoates were efficiently produced from the 3-(4-phenyl-1-thioxo[1,2,4]triazolo[4,3-a]quinoxalin-2(1H)-yl)-propanohydrazide and amino acid esters via azide coupling method in good to moderate yields.