Pyrazino pyrazines, reduction

Reduction of a 7-(2-oxoethyl) derivative with NaBH4 in EtOH at room temperature gave 7-(2-hydroxyethyl)-2-(2-pyrimidinyl)perhydropyrido[l, 2-u]pyrazine (99MIP6). Reduction of 7-formyl-8-[(4-cyanophenyl)methoxy]-1,3,4,6,11,1 lu-hexahydro-2//-pyrazino[l,2-A]isoquinoline-l,4-dione with NaBH4 yielded a 7-hydroxymethyl derivative (98MIP7). 

Pyrazino[l,2-tf]pyrazines 245 (Y = NH) were prepared from [6+0] fragments by bond formation a to the ring junction nitrogen atom in the reductive cyclization of the N-protected piperazine derivative 244 (Scheme 44) <2002W0055518>. 

Reduction of 2-benzyl-2,3,4,6,7,8-hexahydro-l//-pyrido[l,2-a]pyrazin-l-one (73CPB1248) and l-oxo-l,2,3,4-tetrahydropyrazino[l,2-b]isoquinolinium bromide (73CPB2039) with NaBH4 yielded perhydropyrido[l,2-fl] pyrazin-1-one and l,3,4,6-tetrahydro-2//-pyrazino[l,2-6]isoquinolin-l- one, respectively. 

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]. 

Good yields of pyrazino[2,3-rf]pyridazine-5,8-diol (2) are obtained when pyrazine-2,3-dicarb-oxylic add esters such as 1 are reacted with hydrazine.32,86,88 Detailed studies on the pathway of this reaction have shown that reduction of the products during the course of the reaction (where the reducing species is thought to be diimide) is substantially diminished in an inert atmosphere.89... 

The electrochemical reduction of pyrazino[2,3-(t]pyrazines has also been studied... 

The ESR spectra of the radical anions of pyrazino[2,3-b]pyrazine obtained by electrolytic and by chemical reduction have been examined. 

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