One-step route to fluorinated furo[2,3-b]quinoxalines

Synthesis of fused quinoxalines

“…The idea to use tandem nucleophilic addition reactions at two neighbouring C=N bonds of an azine ring for construction of condensed aza heterocycles has been successfully applied to pyrazines and their aza and benzo analogues. [1][2][3][4][5] Indeed, the orthocyclization of 1-alkyl-1,4-diazinium salts with bifunctional nucleophiles is an efficient synthetic approach to condensed pyrazines, quinoxalines, pyrido [2,3-b]pyrazines and pteridines in which the pyrazine ring is fused with five-and six-membered heterocycles (Scheme 1). 1,2 Another approach to condensed aza heterocycles is based on a nucleophilic reaction at the C=N bond of an azine ring in combination with a nucleophilic attack at the exo-cyclic electrophilic centre (Scheme 2).…”

“…[1][2][3][4][5] Indeed, the orthocyclization of 1-alkyl-1,4-diazinium salts with bifunctional nucleophiles is an efficient synthetic approach to condensed pyrazines, quinoxalines, pyrido [2,3-b]pyrazines and pteridines in which the pyrazine ring is fused with five-and six-membered heterocycles (Scheme 1). 1,2 Another approach to condensed aza heterocycles is based on a nucleophilic reaction at the C=N bond of an azine ring in combination with a nucleophilic attack at the exo-cyclic electrophilic centre (Scheme 2). This approach was illustrated by the reaction of 6-carbonyl-substituted 1,2,4-triazines with hydrazines.…”

Use of tandem AN-AN reactions for the synthesis of thiazolo[4,5-e]-1,2,4-triazines

“…with bifunctional nucleophiles are of interest as an effective methodology for the synthesis of condensed heterocyclic systems. [1][2][3][4][5][6][7] A general scheme for the synthesis of condensed tetrahydropyrazines from pyrazinium cations is given below.…”

2,3-Dichloro-1-alkylpyrazinium tetrafluoroborates: the synthesis and reactions with nucleophiles

“…§ § Contrary to that, 6,7-difluoro substituted 1-ethylquinoxalinium salts were found to react with bifunctional nucleophiles to give fused quinoxalines through the diaddition reaction at C-2 and C-3 carbons of the pyrazine ring instead of the replacement of two fluorine atoms. 10 This work was supported in part by the US Civilian Research and Development Foundation (award no. REC-005).…”