Furazan ring opening upon treatment of benzofurazan with ethanolamine to yield quinoxalines

Abstract

Heating of benzofurazans with ethanolamine in the presence of catalytic amount of p toluenesulfonic acid leads to quinoxalines.Study of chemical properties of benzofurazans showed that the heating of compounds 1a-g with ethanolamine at 150-170 °C in the presence of catalytic amount of p toluenesulfonic acid unexpectedly leads to quinoxalines 2a-g (Scheme 1).It should be noted that the reaction of ben zo[1,2 c:3,4 c´]difurazan 1e proceeds with generation of Scheme 1 1, 2: R 1 = H, R 2 = H (a), Me (b), MeO (c); R 1 = NH 2 , R 2 = H (d); R 1 + R 2 = (e), N N N Ph (f), -CH=CH-CH=CH-(g) Scheme 2 Scheme 3heat and leads to furazano[4,5 f]quinoxaline 2e in 76% yield. Upon further heating of compound 2e with ethanol amine at 150 °C, a reduction of its furazan ring takes place to form 5,6 diaminoquinoxaline 3 (Scheme 2).

Palladium‐Catalyzed Regioselective Direct Arylation of Benzofurazans at the C‐4 Position

“…It is known that furazan unit of benzofurazans can easily undergo a ring opening in the presence of ethanolamines under acidic conditions to yield quinoxaline derivatives. [17] Quinoxaline is an important motif, which is present in many pharmaceuticals. [18] Therefore, we investigated the synthesis of some quinoxalines from arylated benzofurazans.…”

“…Therefore, we investigated the synthesis of some quinoxalines from arylated benzofurazans. Using the Samsonov conditions, namely, 10 mol% para ‐toluenesulfonic acid in the presence of 1‐aminoethanol, the arylated benzofurazans 6 , 15 and 25 were converted into 5‐arylquinoxalines 27 – 29 in 82–87% yields (Scheme ).…”

Funcionalização dirigida de quinoxalinas substituídas visando a obtenção de substâncias bioativas

“…Esquema 9 -Preparação do núcleo quinoxalínico utilizando a hidrazona 31. Samsonov (2007) demonstrou a preparação do núcleo quinoxalínico através de benzofurazanos (32) e o aminoálcool 26 (Esquema 10). Essa reação passa por uma abertura do anel furazano e heterociclização, semelhante à reação de Davis-Beirut (SAMSONOV, 2007).…”