Highly enantioselective [4 + 2] cyclization of chloroaldehydes and 1-azadienes catalyzed by N-heterocyclic carbenes
作者:Teng-Yue Jian、Li-Hui Sun、Song Ye
DOI:10.1039/c2cc35273g
日期:——
Highly functionalized dihydropyridinones were synthesized via the N-heterocyclic carbene-catalyzed enantioselective [4 + 2] annulation of alpha-chloroaldehydes and azadienes. Hydrogenation of the resulted dihydropyridinones afforded the corresponding piperidinones with high enantiopurity.
A highly enantioselective construction of δ- and γ-lactone[2,3-b]piperidine skeletons was accomplished by tandem aza-Diels–Alder reaction–hemiacetal formation–oxidation from N-Tos-1-aza-1,3-butadienes and aliphatic dialdehydes.
δ-和的高度对映选择性 γ-内酯[2,3- b ]哌啶通过串联氮杂-狄尔斯-阿尔德反应-半缩醛形成-N -Tos-1-氮杂-1,3-丁二烯和脂肪族二醛的氧化来完成骨架。
NaOH-Promoted Chemoselective Cascade Cyclization of Cyclopropyl Esters with Unsaturated Imines: Access to Bioactive Cyclopenta[c]pyridine Derivatives
作者:Dingwu Pan、Chengli Mou、Ningning Zan、Ya Lv、Bao-An Song、Yonggui Robin Chi、Zhichao Jin
DOI:10.1021/acs.orglett.9b02088
日期:2019.9.6
A chemoselective cascade cycloaddition reaction is developed for green and efficient access to cyclopenta[c]pyridine derivatives. Simple and inexpensive NaOH is used as the sole catalyst for this process. The δ-carbon of cyclopropyl ester is activated as a nucleophilic carbon to initiate highly chemoselective cascade reactions. Cyclopenta[c]pyridines bearing various substituents are afforded in excellent
chemoselective dienophiles in normal-electron-demand Diels–Alderreactions with HOMO-raised trienamines, rather than typical 4π-participation in inverse-electron-demand versions. The enantioenriched cycloadducts could be efficiently converted to spiro or fused frameworks with high structural and stereogenic complexity by a sequential aza-benzoin reaction or other transformations.