Alkylthiopyrazines

Conversion into C-Amino-, C-Azido-, C-Cyano-, or C-Alkylthiopyrazines... 

Just as pyrazine. V-oxides may be converted into C-halogeno- (Section 4.1.3) or C-acyloxypyrazines (Section 5.5.2.3), so they can afford C-amino-, C-azido-, C-cyano-, or C-alkylthiopyrazines, although such reactions are not well developed yet. The following examples will illustrate such procedures as used in recent literature ... 

Since dipyrazinyl sulfides are simply alkylthiopyrazines in which the alkyl group is replaced with another pyrazinyl group, information on such sulfides is included here. Alkylthiopyrazines are the most frequently encountered thiopyrazines, both as end products and as useful intermediates for other types of pyrazine. 

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 ... 

The dealkylation of alkylthiopyrazines to pyrazinethiones has been covered already (Section 6.1.1). Of the other possible reactions of alkylthiopyrazines, those represented in recent literature are discussed in the following subsections. 

Minor reactions of alkylthiopyrazines are illustrated by the following examples ... 

Halogenopyrazines react with alkylthiolate ions to give alkylthiopyrazines, by replacement of one or, in some cases, two halogeno substituents the reaction is usually carried out at reflux or at elevated temperatures in sealed tubes. The following pyrazines have been prepared by these methods from the chloropyrazines unless otherwise specified 2-ethylthio and 2-isopropylthio (668a) 2-methyl-3-methylthio (735, 844,977) 2-methyl-5(and 6)-methylthio (735) 2,5-dimethyl-3-methyl(ethyl,... 

Alkylthiopyrazines may be prepared from halogenopyrazines by reaction with the appropriate sodium (or potassium) alkylthioiate, usually at elevated temperatures. In this way 2-ethylthio- and 2-isopropylthiopyrazine were prepared from... 

The oxidation of alkylthiopyrazines to alkylsulfonyl- and alkylsulfinylpyrazines (e.g., 11 and 12, respectively) has been described in Section 5A, and cleavage of 2-methyl-6-methylsulfonyl4/f-pyrazino[2,3-d] [1,3]oxazin4-one by guanidine (432)... 

A few such pyrazine derivatives have been made by primary synthesis (see Chapters 1 and 2) but the main preparative route is by oxidation of alkylthiopyrazines, discussed in Section 6.2.2.1. 

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