Enantioselective Electrophilic Cyanation of Boron Enolates: Scope and Mechanistic Studies

Takaya Nagata, Atsuko Tamaki, Kensuke Kiyokawa, Ryosuke Tsutsumi, Masahiro Yamanaka, Satoshi Minakata

Research output: Contribution to journalArticlepeer-review

10 Citations (Scopus)

Abstract

Chiral β-ketonitriles bearing a stereogenic carbon center at the α-position are an important class of compounds, many of which serve as useful synthetic intermediates for the preparation of chiral 1,3-aminoalcohols, β-hydroxy nitriles, and related derivatives. Although the enantioselective electrophilic cyanation of enolate equivalents is one of the most promising approaches for the synthesis of chiral β-ketonitriles, the available methods are largely limited to reactions of 1,3-dicarbonyl compounds. Herein, we report on enantioselective electrophilic cyanation of boron enolates, which are readily prepared from α,β-unsaturated ketones and diisopinocampheylborane (Ipc2BH) to afford chiral β-ketonitriles with a high level of enantioselectivity. The present method is scalable and provides facile access to both enantiomers of chiral β-ketonitriles. Analysis of the in situ generated boron enolates by NMR revealed that hydroboration proceeds in a stereospecific manner, providing α,α-disubstituted boron enolates in the form of single isomers. Furthermore, the results of DFT calculations suggest that the cyanation of the boron enolates with p-toluenesulfonyl cyanide (TsCN) proceeds in a highly enantioselective manner through a unique six-membered ring transition state.

Original languageEnglish
Pages (from-to)17027-17032
Number of pages6
JournalChemistry - A European Journal
Volume24
Issue number64
DOIs
Publication statusPublished - 2018 Nov 16
Externally publishedYes

Keywords

  • boron
  • cyanation
  • enantioselectivity
  • enolates
  • synthetic methods

ASJC Scopus subject areas

  • Catalysis
  • Organic Chemistry

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