Hydroboration of vinyl halides with mesitylborane : a direct access to (mesityl)(alkyl)haloboranes

The straightforward formation of (mesityl)(alkyl)haloboranes from mesitylborane and vinyl halides is a relatively complex process that operates in a hydroboration/rearrangement sequence
 Hydroboration of vinyl halides with mesitylborane : a direct access to (mesityl)(alkyl)haloboranes

The stepwise installation of substituents on a Bsp2 centre while preserving its high Lewis acidity remains an actual challenge driven by the strong interest in boron-containing responsive materials and π systems as well as in frustrated Lewis pairs chemistry.

In line with this, (aryl)haloboranes have proven to be essential synthesis intermediates that are generally obtained by Si/B or Sn/B exchanges or more scarcely by metalation/borylation reactions at a carbon center. Among them and with a limited number of examples, the mixed (aryl)(alkyl)haloboranes [Ar(Alk)BX] represent a very restricted family of compounds.

Today, we report the straightforward synthesis of (mesityl)(alkyl)haloboranes. The methodology is based on the reaction of stable mesitylborane with vinylhalides that operates in a hydroboration/rearrangement sequence leading ultimately to a haloborane product via the transfer of the halogen atom from the carbon of the starting material to the boron.  Its scope and limitation are also explored through the standard reactivities of chosen (mesityl)(alkyl)(bromo)boranes so prepared.

The reaction mechanism was fully apprehended thanks to theoretical calculations carried out at the DFT-B3LYP-D3 level of theory revealing two accessible pathways, one of which being kinetically favoured.

Reference

Marc Devillard*, Marie Cordier, Thierry Roisnel, Chiara Dinoi, Iker Del Rosal, Gilles Alcaraz*
Chem.Commun., 2022, DOI: 10.1039/D1CC06365K

Contacts

  • Marc Devillard, Univ. Rennes, CNRS, ISCR - UMR 6226, F-35000 Rennes, France
    marc [dot] devillardatuniv-rennes1 [dot] fr
     
  • Gilles Alcaraz, Univ. Rennes, CNRS, ISCR - UMR 6226, F-35000 Rennes, France
    gilles [dot] alcarazatuniv-rennes1 [dot] fr

 

Published January 12, 2022