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Phosphine-Catalyzed [4+1] Cycloadditions of Allenes with Methyl Ketimines, Enamines, and a Primary Amine.

Ze-Hun CaoYu-Hao WangSubarna Jyoti KalitaUwe SchneiderYi-Yong Huang
Published in: Angewandte Chemie (International ed. in English) (2019)
Unprecedented phosphine-catalyzed [4+1] cycloadditions of allenyl imides have been discovered using various N-based substrates including methyl ketimines, enamines, and a primary amine. These transformations provide a one-pot access to cyclopentenoyl enamines and imines, or (chiral) γ-lactams through two geminal C-C bond or two C-N bond formations, respectively. Several P-based key intermediates including a 1,4-(bis)electrophilic α,β-unsaturated ketenyl phosphonium species have been detected by 31 P NMR and HRMS analyses, which shed light on the postulated catalytic cycle. The synthetic utility of this new chemistry has been demonstrated through a gram-scaling up of the catalytic reaction as well as regioselective hydrogenation and double condensation to form cyclopentanoyl enamines and fused pyrazole building blocks, respectively.
Keyphrases
  • ionic liquid
  • room temperature
  • magnetic resonance
  • high resolution
  • gram negative
  • crystal structure
  • capillary electrophoresis
  • solid state
  • mass spectrometry