Preparation of Alkylthiopyrazines

All the important routes to alkylthiopyrazines have been discussed already by primary synthesis (Chapters 1 and 2), by alkanethiolysis of halogenopyrazines (Sections 4.2.5 and 4.4), or by S-alkylation of pyrazinethiones (Section 6.1.2). The remaining minor routes are either unrepresented in recent literature or are illustrated in the following examples  

2-Isopropyl-3,6-dimethoxy-5-methyl-2,5-dihydropyrazine (44) gave 2-(2-ben-zylthioethyl)-5-isopropyl-3,6-dimethoxy-2-methyl-2,5-dihydropyrazine (45) (lithiation in situ, THF then ICH2CH2SCH2Ph [, -70°C, 24 h 80%).198 

2-Cyclohexylsulfinylpyrazine gave 2-(cyclohex-l-enylthio)pyrazine [(F3CC0)20, MeCN, 20°C, 12 h 74%] 318 see also Section 6.2.2.1 

5-Bismethylthio-3,6-dihydropyrazine gave 2,5-bismethylthiopyrazine (ClCO2Me, CH2CI2, 0 20°C, 12 h 65%). 4 

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