Alkanethiolysis or Arenethiolysis of Nuclear Halogenopyrazines

Like alcoholysis, alkanethiolysis of halogenopyrazines occurs readily but it is usually possible to achieve regioselectivity from di- or polyhalogenopyrazines. The following examples illustrate typical conditions employed and yields to be expected in the presence of various types of passenger groups  

2-Chloropyrazine (149) gave 2-(pyridin-2-ylthio)pyrazine (150) [2(1 H)-pyridinethione, K2C03, Me2NCHO, reflux, 4 h 60%] 126 several other (het-eroarylthio)pyrazines were made by essentially similar reactions.111,684,698,871 

3-Dichloropyrazine gave 2-( 9-aminophenylseleno)-3-chloropyrazine (151) [(o-H2NC6H4Se)2Zn, HC11 to pH 3, EtOH, reflux, 5 min %],351 2,3-bis(2-dimethylaminoethylthio)pyrazine (152) (Me2NCH2CH2SH.HCl, Bu OK, Bu OI I, reflux, 22 h —6% as dihydrobromide, after purification),1033 or other such products.600 

5-Trichloropyrazine gave 2-chloro-5,6-bis(4,6-diaminopyrimidin-5-ylthio)-pyrazine (153) [4,6-diamino-5-pyrimidinethiol, KOH, AcNMe2—H20, reflux, 4 h 93% (based on the pyrimidinethiol )].1312 Also other examples,1602 including use of K-Selectride + alkanethiol.1738 

2-Chloro-3-methylpyrazine (154, R = Cl) gave 2-methyl-3-methylthiopyrazine (154, R = SMe) MeSNa, EtOH, 20°C reflux, 2 h 92%), 2-ethoxycar-bonylmethylthio-3-methylpyrazine (154, R = SCH2C02Et) [NaSCH2C02Et (made in situ), likewise 91%), or analogues.1126 

Also other examples, including use of K-Selectride + alkanelhiol.  

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