Pyrazinones thiation

This conversion is often done indirectly via an halogenopyrazine although direct thiation of pyrazinones has usually been successful when Lawesson s reagent (43) or good quality phosphorus pentasulfide has been employed. The following examples indicate typical conditions used and yields to be expected ... 

Note Like tautomeric pyrazinones (Section 5.1.2.1), nontautomeric pyrazinones undergo thiation easily. 

Most tautomeric pyrazinethiones have been made by primary synthesis (see Chapters 1 and 2), thiolysis of halogenopyrazines (see Section 4.2.4), or thiation of tautomeric pyrazinones (see Section 5.1.2.1) a few nontautomeric pyrazinethiones by primary synthesis (see Chapters 1 and 2) or thiation of nontautomeric pyrazinones (see Section 5.4.2) and nearly all extranuclear pyrazinethiols by thiolysis of extranuclear halogenopyrazines (see Section 4.4). Other routes to such pyrazinethiones and pyrazinethiols are illustrated in the following examples ... 

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