The Mechanism of the Reaction of Nicotinic Acid 1-Oxide with Acetic Anhydride(Organic,Chemical)

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In order to elucidate the mechanism of the 2-acetylation in the reaction of nicotinic acid 1-oxide (2a) with boiling acetic anhydride, thermal,reactions and reactions with hot acetic anhydride have been explored with 3-X-pyridine 1-oxides (2). The former reactions of 2d(X=CONHAc), 2f(X=CONMeAc), 2h(X=CH_2OAc) and 2j[X=CH(OAc)_2] result in recovery or decomposition. The latter reactions of 2c(X=CONH_2), 2d, 2e(X=CONHMe), 2h and 2j bring about mainly deoxygenative α-acetoxylation, no 2-acetylation being noticed. However, the reaction of 2f with acetic anhydride affords 6,7-dihydro-6-methyl-7-methylene-5H-pyrrolo[3,4-b]pyridin-5-one 1-oxide (7) as an initial product, which further undergoes deoxygenative β-acetoxylation to give 7-acetoxy-7-acetoxymethyl-6,7-dihydro-6-methyl-5H-pyrrolo[3,4-b]pyridin-5-one (8) and 7-acetoxymethylene-6,7-dihydro-6-methyl-5H-pyrrolo[3,4-b]pyridin-5-one (9). On the basis of these results we propose a new electrophilic pathway for the 2-acetylation of 2a and 2f.
公益社団法人日本薬学会の論文
1987-10-25