title: Tandem β-elimination/hetero-michael addition rearrangement of an N-alkylated pyridinium oxime to an O-alkylated pyridine oxime ether: an experimental and computational study.
abstract: A novel OH(-)-promoted tandem reaction involving C(β)-N(+)(pyridinium) cleavage and ether C(β)-O(oxime) bond formation in aqueous media has been presented. The study fully elucidates the fascinating reaction behavior of N-benzoylethylpyridinium-4-oxime chloride in aqueous media under mild reaction conditions. The reaction journey begins with the exclusive β-elimination and formation of pyridine-4-oxime and phenyl vinyl ketone and ends with the formation of O-alkylated pyridine oxime ether. A combination of experimental and computational studies enabled the introduction of a new type of rearrangement process that involves a unique tandem reaction sequence. We showed that (E)-O-benzoylethylpyridine-4-oxime is formed in aqueous solution by a base-induced tandem β-elimination/hetero-Michael addition rearrangement of (E)-N-benzoylethylpyridinium-4-oximate, the novel synthetic route to this engaging target class of compounds. The complete mechanistic picture of this rearrangement process was presented and discussed in terms of the E1cb reaction scheme within the rate-limiting β-elimination step.
authors.affiliation: Department of Chemistry and Biochemistry, University of Zagreb, School of Medicine , Šalata 3, HR-10000 Zagreb, Croatia.
authors.forename: Igor
authors.initials: I
authors.lastname: Picek
authors.forename: Robert
authors.initials: R
authors.lastname: Vianello
authors.forename: Primož
authors.initials: P
authors.lastname: Šket
authors.forename: Janez
authors.initials: J
authors.lastname: Plavec
authors.forename: Blaženka
authors.initials: B
authors.lastname: Foretić
mesh_terms: D000478:Alkylation; D004987:Ethers / Q000138:chemical synthesis* / Q000737:chemistry; D015394:Molecular Structure; D010091:Oximes / Q000138:chemical synthesis* / Q000737:chemistry; D011725:Pyridines / Q000138:chemical synthesis* / Q000737:chemistry; D011726:Pyridinium Compounds / Q000737:chemistry*; D011789:Quantum Theory; D013816:Thermodynamics
chemical_list: D004987:Ethers; D010091:Oximes; D011725:Pyridines; D011726:Pyridinium Compounds