Total Syntheses of Vicinal Dichloride Monoterpenes Enabled by Aza-Belluš–Claisen Rearrangement
作者:Jiangqun Cheng、Yuan-He Li、Jun Huang、Zhen Yang
DOI:10.1021/acs.orglett.1c03187
日期:2021.11.5
were achieved via an aza-Belluš–Claisen rearrangement, which involved the reaction of an α-chloro carboxylic acidchloride with halogen-substituted trans-allyl morpholines in the presence of Lewis acids. The developed method was used for the total synthesis of a group of monoterpene natural products bearing vicinal dichloride subunits.
Z-allylic dibromides regio- and stereoselectively prepared were reacted with the sodium enolate of ethyl acetoacetate or di(α-ethoxyvinyl)cuprate to yield, after hydrolysis, and decarboxylation in the case where the enolate of ethylacetoacetate was the nucleophile, the corresponding ketones. After reduction and bromination, the products were converted into the appropriate organometallic compounds and
Asymmetric Synthesis of a Bicyclo[4.3.0]nonene Derivative Bearing a Quaternary Carbon Stereocenter: Desymmetrization of σ-Symmetrical Diketones through Intramolecular Addition of an Alkenyl Anion
作者:Tomoyuki Yoshimura、Yuki Enami、Jun-ichi Matsuo
DOI:10.1055/s-0040-1706421
日期:2020.12
strategy involving an intramolecular addition. The intramolecularnucleophilic addition of a highly reactive carbanion generated from an alkenyl iodide in the presence of a chiral ligand occurs with discrimination of two keto carbonyl groups to give the corresponding bicyclic compound in 81% yield and 39% ee. Asymmetric synthesis via an intramolecular desymmetrization strategy using a chiral ligand–carbanion
obtained in good yields from pentynoic acids 3- or 5-substituted with an iodo-aryl moiety by palladium-catalyzed cyclization of their potassium carboxylates. Using this approach, an efficient newroute to U-68,215 is described.