Magnesium catalysis for the hydroboration of carbodiimides

Catherine Weetman, Michael S. Hill, Mary F. Mahon

Research output: Contribution to journalArticle

  • 16 Citations

Abstract

A β-diketiminato magnesium alkyl complex, [CH{C(Me)NDipp}2}MgnBu] (Dipp=2,6-iPr2C6H3), was shown to be an effective pre-catalyst for the first reported catalytic hydroboration of alkyl- and aryl-substituted carbodiimides with pinacol borane (HBpin). The catalytic reactions proceed under mild conditions to afford the corresponding N-borylated formamidine compounds in good yields. The reactions were observed to proceed through the intermediacy of magnesium amidinate and formamidinatoborate intermediates and an example of one of these latter species has been structurally characterised by an X-ray diffraction analysis. Crucially, no formation of the N-boryl formamidine products was observed in the absence of additional equivalents of the carbodiimide and HBpin substrates. This observation, supported by the evolution of a sigmoidal kinetic profile for the hydroboration of dicyclohexylcarbodiimide, has been rationalised as the consequence of an allosteric effect of the pinacol borane and carbodiimide on the magnesium formamidinatoborate intermediates.

LanguageEnglish
Pages7158-7162
Number of pages5
JournalChemistry - A European Journal
Volume22
Issue number21
Early online date11 May 2016
DOIs
StatusPublished - 17 May 2016

Fingerprint

Carbodiimides
Boranes
Magnesium
Catalysis
Dicyclohexylcarbodiimide
X ray diffraction analysis
Catalysts
Kinetics
Substrates
formamidine

Keywords

  • allosterism
  • hydroboration
  • magnesium
  • synthetic methods

Cite this

Magnesium catalysis for the hydroboration of carbodiimides. / Weetman, Catherine; Hill, Michael S.; Mahon, Mary F.

In: Chemistry - A European Journal, Vol. 22, No. 21, 17.05.2016, p. 7158-7162.

Research output: Contribution to journalArticle

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N2 - A β-diketiminato magnesium alkyl complex, [CH{C(Me)NDipp}2}MgnBu] (Dipp=2,6-iPr2C6H3), was shown to be an effective pre-catalyst for the first reported catalytic hydroboration of alkyl- and aryl-substituted carbodiimides with pinacol borane (HBpin). The catalytic reactions proceed under mild conditions to afford the corresponding N-borylated formamidine compounds in good yields. The reactions were observed to proceed through the intermediacy of magnesium amidinate and formamidinatoborate intermediates and an example of one of these latter species has been structurally characterised by an X-ray diffraction analysis. Crucially, no formation of the N-boryl formamidine products was observed in the absence of additional equivalents of the carbodiimide and HBpin substrates. This observation, supported by the evolution of a sigmoidal kinetic profile for the hydroboration of dicyclohexylcarbodiimide, has been rationalised as the consequence of an allosteric effect of the pinacol borane and carbodiimide on the magnesium formamidinatoborate intermediates.

AB - A β-diketiminato magnesium alkyl complex, [CH{C(Me)NDipp}2}MgnBu] (Dipp=2,6-iPr2C6H3), was shown to be an effective pre-catalyst for the first reported catalytic hydroboration of alkyl- and aryl-substituted carbodiimides with pinacol borane (HBpin). The catalytic reactions proceed under mild conditions to afford the corresponding N-borylated formamidine compounds in good yields. The reactions were observed to proceed through the intermediacy of magnesium amidinate and formamidinatoborate intermediates and an example of one of these latter species has been structurally characterised by an X-ray diffraction analysis. Crucially, no formation of the N-boryl formamidine products was observed in the absence of additional equivalents of the carbodiimide and HBpin substrates. This observation, supported by the evolution of a sigmoidal kinetic profile for the hydroboration of dicyclohexylcarbodiimide, has been rationalised as the consequence of an allosteric effect of the pinacol borane and carbodiimide on the magnesium formamidinatoborate intermediates.

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