1.2.4- Triazine 3-methylthio-, nucleophilic addition

Another example of a nucleophilic addition at C-3 is provided by the reaction of the quaternary salt 20 with sodium methoxide yielding the relatively stable adduct 33, (Scheme 24) (74BSF999). The C-3 adducts 35 and 36 have been suggested as intermediates in the conversion of 2-meth-yl-3-methylthio-l,2,4-triazin-5-ones 34 into the corresponding 3-methoxy derivatives however, no spectroscopic evidence for adduct formation has been presented (Scheme 24) (72BSF1511). 

Ring-degenerate transformations initiated by the nucleophilic addition at C-5 of the 1,2,4-triazine ring have also been reported to occur in reactions of 4-aryl-substituted 3-methylthio-l,2,4-triazine-3,5-diones with hydrazine hydrate (Scheme 80). This ANRORC mechanism involves the open-chain compound 138 as intermediate (80JHC1733 81JHC953). 

The easy addition at C-5 of 1,2,4-triazines is shown by the VNS (3.3.3) reaction of the 3-methylthio derivatives in the absence of activating groups a closely related addition of nitro-alkanes represents a very useful nucleophilic acylation. The ready displacement of methylthio from the same compound is also significant. ... 

The easy addition at C-5 of 1,2,4-triazines is shown by the VNS (section 2.3.3) reaction of the 3-methylthio-derivatives in the absence of activating groups a closely related addition of nitroalkanes represents a very useful nucleophilic acylation. The ready displacement of methylthio from the same compound is also indicative. " Nucleophilic displacement of methylthio in 1,2,4-triazines and 1,2,4,5-tetrazines by alkoxide and amines is very easy. Mono-displacement can be carried out on 3,6-bis(methylthio)-1,2,4,5-tetrazine but the reaction using methoxide requires careful control of reaction conditions to avoid formation of the dimethoxy derivative. However, reaction of the bis(methylthio) compound with methyllithium resulted in nucleophilic attack at nitrogen ... 

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