title: Gold-catalyzed oxidative ring expansion of 2-alkynyl-1,2-dihydropyridines or -quinolines: highly efficient synthesis of functionalized azepine or benzazepine scaffolds.
abstract: A gold-catalyzed highly regio- and chemoselective oxidative ring expansion of 2-alkynyl-1,2-dihydropyridines and its analogues using pyridine-N-oxide as the oxidant has been developed. Ring expansion proceeds through exclusive 1,2-migration of a vinyl or phenyl group, whereas no 1,2-H and 1,2-N migration take place. The reaction provides an efficient and attractive route to various types of medium-sized azepine derivatives in generally high to excellent yields with a broad functional group tolerance. DFT studies indicate that the reaction proceeds through the formation of a cyclopropyl gold intermediate, and no gold carbene species is involved.
authors.affiliation: State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 345 Lingling Lu, Shanghai 200032 (P. R. China).
authors.forename: Ming
authors.initials: M
authors.lastname: Chen
authors.forename: Yifeng
authors.initials: Y
authors.lastname: Chen
authors.forename: Ning
authors.initials: N
authors.lastname: Sun
authors.forename: Jidong
authors.initials: J
authors.lastname: Zhao
authors.forename: Yuanhong
authors.initials: Y
authors.lastname: Liu
authors.forename: Yuxue
authors.initials: Y
authors.lastname: Li
mesh_terms: D001381:Azepines / Q000138:chemical synthesis* / Q000737:chemistry; D001552:Benzazepines / Q000138:chemical synthesis* / Q000737:chemistry; D002384:Catalysis; D004095:Dihydropyridines / Q000737:chemistry*; D006046:Gold / Q000737:chemistry*; D010084:Oxidation-Reduction; D011804:Quinolines / Q000737:chemistry*; D013237:Stereoisomerism; D013816:Thermodynamics
chemical_list: D001381:Azepines; D001552:Benzazepines; D004095:Dihydropyridines; D011804:Quinolines; D006046:Gold
keywords: azepines; dihydropyridines; gold; homogeneous catalysis; ring expansion