Pyrazino benzimidazol

Alen J, Robeyns K, Borggraeve WMD, Meervelt LV et al (2008) Synthesis of pyrazino[l, 2-a]benzimidazol-l(2H)ones via a microwave assisted Buchwald-Hartwig type reaction. Tetrahedron 64 8128-8133... 

Pyrazino[2,3-Z ]pyrazines are reduced in aqueous alcoholic solution to the l,4-(5,8)-dihy-dro derivatives [359] in acidic medium the two-electron wave is followed by a four-electron reduction to a hexahydro derivative. The benzo and dibenzo derivatives are similarly reduced primarily in a reversible two-electron reduction [370] the further reduction of 5,12-dihydroquinoxalino[2,3-Z7]quinoxaline yields 2-(o-aminoanilinomethyl)benzimidazole [371]. 

Thiazolo[3, 4 -l,2]pyrazino[7,8-a]benzimidazoles.—[C3NS-C3N2-C4Ng-C6]. In connection with their more detailed work on thiazolodiazepino-benzimidazoles (see p. 714), Maynard et al. have condensed 2-(4 -thiazolyl)benzimidazole and 1,2-dibromoethane to produce 5,6-dihydro-thiazolio[3, 4 -l,2]pyrazino[7,8- ]benzimidazole bromide, and described several of its reactions, notably the cleaving of its thiazolium ring. ... 

Alen et al. (2008) reported a reaction of 3,5-dichloropyrazinones with 2-bro-mo-4,6-disubstituted aniline to give 3-anilino-pyrazinones. A microwave-assisted Buchwald-Hartwig type cyclization converted various 3-anilino-pyrazinones easily to the substituted pyrazino[l,2-a]benzimidazol-l(2/0ones (tricyclic stmctures) using palladium as catalyst with moderate to good yield (27-78%). 

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