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Synfacts 2013; 9(1): 0104
DOI: 10.1055/s-0032-1317902
Organo- and Biocatalysis
© Georg Thieme Verlag Stuttgart · New York

NHC-Catalyzed Annulation of Isatin N-Boc Ketimines and Enals

Authors

    Rezensent(en):

  • Benjamin List

  • Qinggang Wang

Lv H, Tiwari B, Mo J, Xing C, Chi YR * Nanyang Technological University, Singapore
Highly Enantioselective Addition of Enals to Isatin-Derived Ketimines Catalyzed by N-Heterocyclic Carbenes: Synthesis of Spirocyclic γ-Lactams.

Org. Lett. 2012;
14: 5412-5415
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Publikationsverlauf

Publikationsdatum:
17. Dezember 2012 (online)

 
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Key words

enals - ketimines - NHCs - γ-lactams

Significance

Chi and co-workers report an N-heterocyclic carbene (NHC)-catalyzed annulation of isatin N-Boc imines with enals, which affords spirocyclic oxindole-γ-lactams bearing one quaternary chiral center in good diastereo- and excellent stereoselectivities (dr up to >20:1 and er > 99.5:0.5). Ketimines and γ-aryl enals with electron-donating substituents lead to better yield and selectivity compared to electron-withdrawing substituents. The presence of a trace of water is beneficial for the conversion of the reaction. The resulting products can be easily deprotected to free γ-lactams in high yield.


 

Comment

γ-Lactams are privileged scaffolds found in naturally occurring and synthetic biologically active compounds. Herein, the authors have developed a novel NHC-catalyzed annulation methodology, which allows for a rapid construction of spirocyclic oxindole-γ-lactams with high ­diastereoselectivity and enantioselectivity. More efficient catalysts and the application to more challenging substrates are expected.


 

 


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