Synthesis of polyfunctionalized pyrido[1,2-a]pyrazines and pyrazino[1,2-a]quinolines via one-pot multicomponent reactions

An efficient, straightforward, and general method for the synthesis of pyrido[1,2-a]pyrazine and pyrazino[1,2-a]quinoline derivatives via a one-pot three-component reaction between cyclic enamineones, aromatic aldehydes, and 1,3-dicarbonyl compound is reported. On our knowledge, this is the first reported one-pot multicomponent reaction for synthesis of pyrido[1,2-a]pyrazine and pyrazino[1,2-a]quinoline derivatives. A proposed reaction pathway for the synthesis has been proved experimentally, consisting in addition of 3-(alkoxycarbonylmethylidene)piperazine-2-ones to the products of condensation of aromatic aldehydes and 1,3-dicarbonyl compounds, followed by further cyclocondensation Michael addition. The structure of the thirteen new compounds was proven by elemental and spectral analysis (H-1 and C-13 NMR, HPLC/MS, and FT-IR).