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Enantioselective Addition-Alkylation of α,β-Unsaturated Carbonyls via Bisguanidinium Silicate Ion Pair Catalysis

Journal Article


Abstract


  • © 2020 American Chemical Society. Silicon hydrides, alkynylsilanes, and alkoxylsilanes were activated by fluoride in the presence of bisguanidinium catalyst to form hypervalent silicate ion pairs. These activated silicates undergo 1,4-additions with chromones, coumarins, and α-cyanocinnamic esters generating enolsilicate intermediates, for a consequent stereoselective alkylation reaction. The reduction-alkylation reaction proceeded under mild conditions using polymethylhydrosiloxane, a cheap and environmentally friendly hydride source. The addition-alkylation reactions with alkynylsilanes and alkoxylsilanes resulted in the construction of two vicinal chiral carbon centers with excellent enantioselectivities and diastereoselectivities (up to 99% ee, >99:1 dr). Density functional theory calculations and experimental NMR studies revealed that penta-coordinated silicates are crucial intermediates.

UOW Authors


  •   Chen, Wenchao (external author)
  •   Ang, Esther (external author)
  •   Tan, Siu (external author)
  •   Chua, Zhijie (external author)
  •   Ren, Jingyun (external author)
  •   Yang, Ziqi (external author)
  •   Teng, Bo (external author)
  •   Lee, Richmond
  •   Lu, Haihua (external author)
  •   Tan, Choon (external author)

Publication Date


  • 2020

Citation


  • Chen, W., Ang, E., Tan, S., Chua, Z., Ren, J., Yang, Z., Teng, B., Lee, R., Lu, H. & Tan, C. (2020). Enantioselective Addition-Alkylation of α,β-Unsaturated Carbonyls via Bisguanidinium Silicate Ion Pair Catalysis. Journal of the American Chemical Society,

Scopus Eid


  • 2-s2.0-85095813670

Place Of Publication


  • United States

Abstract


  • © 2020 American Chemical Society. Silicon hydrides, alkynylsilanes, and alkoxylsilanes were activated by fluoride in the presence of bisguanidinium catalyst to form hypervalent silicate ion pairs. These activated silicates undergo 1,4-additions with chromones, coumarins, and α-cyanocinnamic esters generating enolsilicate intermediates, for a consequent stereoselective alkylation reaction. The reduction-alkylation reaction proceeded under mild conditions using polymethylhydrosiloxane, a cheap and environmentally friendly hydride source. The addition-alkylation reactions with alkynylsilanes and alkoxylsilanes resulted in the construction of two vicinal chiral carbon centers with excellent enantioselectivities and diastereoselectivities (up to 99% ee, >99:1 dr). Density functional theory calculations and experimental NMR studies revealed that penta-coordinated silicates are crucial intermediates.

UOW Authors


  •   Chen, Wenchao (external author)
  •   Ang, Esther (external author)
  •   Tan, Siu (external author)
  •   Chua, Zhijie (external author)
  •   Ren, Jingyun (external author)
  •   Yang, Ziqi (external author)
  •   Teng, Bo (external author)
  •   Lee, Richmond
  •   Lu, Haihua (external author)
  •   Tan, Choon (external author)

Publication Date


  • 2020

Citation


  • Chen, W., Ang, E., Tan, S., Chua, Z., Ren, J., Yang, Z., Teng, B., Lee, R., Lu, H. & Tan, C. (2020). Enantioselective Addition-Alkylation of α,β-Unsaturated Carbonyls via Bisguanidinium Silicate Ion Pair Catalysis. Journal of the American Chemical Society,

Scopus Eid


  • 2-s2.0-85095813670

Place Of Publication


  • United States