title: Synthesis of 2,3-Dihydro-1H-azepine and 1H-Azepin-2(3H)-one Derivatives From Intramolecular Condensation between Stable Tertiary Enamides and Aldehydes.
abstract: A new strategy to construct 2,3-dihydro-1H-azepine and 1H-azepin-2(3H)-one heterocyclic rings is reported based on emerging tertiary enamide synthons. Under very mild conditions employing BBr3 as a Lewis acid catalyst and P2O5 as an additive, tertiary enamides that contain a formyl group underwent highly efficient and scalable intramolecular cyclic condensation to afford diverse 2,3-dihydro-1H-azepine and 1H-azepin-2(3H)-one derivatives in 71-96% yields. The reaction proceeded most probably through a nucleophilic addition of enamides to aldehyde, deprotonation, and dehydration cascade. Application of the method in the synthesis of dihydro-azepino[2,1-a]isoindol-5-ones, the core structure of naturally occurring lennoxamine, was also demonstrated.
authors.affiliation: MOE Key Laboratory of Bioorganic Phosphorus Chemistry and Chemical Biology, Department of Chemistry, Tsinghua University , Beijing, 100084, China.
authors.forename: Wenju
authors.initials: W
authors.lastname: Zhu
authors.affiliation: MOE Key Laboratory of Bioorganic Phosphorus Chemistry and Chemical Biology, Department of Chemistry, Tsinghua University , Beijing, 100084, China.
authors.forename: Liang
authors.initials: L
authors.lastname: Zhao
authors.affiliation: MOE Key Laboratory of Bioorganic Phosphorus Chemistry and Chemical Biology, Department of Chemistry, Tsinghua University , Beijing, 100084, China.
authors.forename: Mei-Xiang
authors.initials: MX
authors.lastname: Wang