Reactions of Alkoxy- or Aryloxypyrazines

These pyrazine ethers, both nuclear and extranuclear, undergo several useful reactions. Their hydrolysis to tautomeric pyrazinones or hydroxyalkylpyrazines has been covered in Sections 5.1.1 and 5.2.1. Other reactions are illustrated in the following examples  

5-Dimethoxy-3,6-dihydropyrazine (173) gave 2,5-dimethoxypyrazine (174) [dichlorodicyanobenzoquinone, PhMe, reflux, 2 h 43% 70 or BifMe2-SiOCH2CH2C(SiMe3)=CHTs, LiN(C6H )2 (made in situ), HF, -40°C, N2, 2 days 21%].34 

2-Isopropyl-3,6-dimethoxy-2,5-dihydropyrazine (175, R = H) gave 5,5-dideutero-2-isopropyl-3,6-dimethoxy-2,5-dihydropyrazine (175, R = D) (MeOD—D2(), KOH, reflux, 3 h 84% with no upset to chirality).41 

2-Methoxypyrazine gave 3-methoxy-l-methylpyrazinium iodide (176) (Mel, no details but confirmed in structure by 13C- and 15N NMR spectra).1224 Also other examples.367 

5-Diethoxy-3,6-dihydropyrazine (177) gave 2,5-bisdimethylamino-3,6-dihy-dropyrazine (178) (neat Me2NH, 60°C, sealed, 6 h 77%).70 

Ethyl l-benzyl-5-ethoxy-2-piperazinecarboxylate (179) gave ethyl 7-benzyl-3-methyl-5,6,7,8-tetrahydroimidazo [1,2-fl] pyrazine-6-carboxylate (181) (H2N(n[,C=CH, PhMe, 100°C, 7 h %), presumably via the primary aminolytic product (180) analogues likewise. 

---