title: Type II intramolecular [5+2] cycloaddition: facile synthesis of highly functionalized bridged ring systems.
abstract: A type II intramolecular oxidopyrylium-mediated [5+2] cycloaddition reaction allows the efficient and diastereoselective formation of various highly functionalized and synthetically challenging bridged seven-membered ring systems (such as bicyclo[4.4.1]undecane, bicyclo[4.3.1]decane, bicyclo[5.4.1]dodecane, and bicyclo[6.4.1]]tridecane). This simple, thermal, direct transformation has a broad substrate scope and is high yielding, with high functional-group tolerance and unique endo selectivity. The highly strained tricyclic cores of ingenol mebutate (picato) and cyclocitrinol are synthesized efficiently and diastereoselectively using this methodology.
authors.affiliation: Laboratory of Chemical Genomics, School of Chemical Biology and Biotechnology, Peking University Shenzhen Graduate School, Shenzhen 518055 (China).
authors.forename: Guangjian
authors.initials: G
authors.lastname: Mei
authors.forename: Xin
authors.initials: X
authors.lastname: Liu
authors.forename: Chuang
authors.initials: C
authors.lastname: Qiao
authors.forename: Wei
authors.initials: W
authors.lastname: Chen
authors.forename: Chuang-chuang
authors.initials: CC
authors.lastname: Li
mesh_terms: D001643:Bridged Bicyclo Compounds / Q000138:chemical synthesis*; D061565:Cycloaddition Reaction
chemical_list: D001643:Bridged Bicyclo Compounds
keywords: bridged ring systems; cycloaddition; diastereoselectivity; endo selectivity; natural products