| Abstract: | Reaction of α-bromoisobutyrophenone on pyridine l-oxide and γ and β-picoline l-oxide, in the prosence of silver nitrate, leads to N-alkoxypyridinium and picolinium salts, bearring a keto group on their alkoxyl chain. On treatment with pyrrolidine, these salts, are converted to 4-ω-pyrrolidinobutadienyl-3-isoxzolinols, substituted or not by a methylgroup in their chain. The reaction proceeds according to the PARC-ANRO mechanism(Poton Abstraction, Ring Closure-Addition of a Nucleopile, Ring Opening), as demonstrated by isolation of the bicyclic isoxazolino pyridinium intermediates which result form the first phase of this process, In addition, steric hindrance towards ring opening caused by the methyl group in the adduct derived from β-picoline N-oxide, allow observation of a competiting novel mode of fragmentation alkoxylogous of Katritxky's mode A of decmposition of N0-alkoxypyridinium salts. |
