SEARCH Articles Figures Tables 2,3-Dimethyl-1,4,5,6-tetrahydropyrazine 4-Cyclohexylcarbonyl-l-phenethyl-2-oxo1,2,3,4-tetrahydropyrazine Dioxo-5,6-dicyano-l,2,3,4-tetrahydropyrazine Tetrahydropyrazine Tetrahydropyrazine Tetrahydropyrazines preparation Tetrahydropyrazines reactions