Pyridine 1-oxide thioalkylation

Pyridine 1-oxide and a series of its methyl analogues undergo thioalkylation at the a-and y-positions when heated with an alkanethiol in acetic anhydride at 95 °C for 3 h (Table 13). Under these conditions, attack by thiol at 2- or 4-methyl groups does not seriously compete with ring substitution. j8 -Substitution does not occur at C-3 in 2-methylpyridine, but it does so at C-5 where the adjacent a-position is vacant. Notice that again a 3-methyl substituent tends to direct substitution to C-2 rather than C-6. This is also true for 3,4-dimethylpyridine. Increasing the size of the 4-substituent does reduce the relative... 

Pyridine 1-oxide and methyl analogues undergo thioalkylation at the a- and y-positions with alkanethiols in acetic anhydride (Scheme 19). Some (3-substitution occurs under these conditions probably via episulfonium intermediates, evidence for which comes from the isolation of tetrahydropyridines, e.g. (267). 

Pyridine A-oxide and methyl analogues undergo thioalkylation at the - and -positions with alkanethiols in acetic anhydride (Scheme 30). 

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