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Deviation from the anti-Markovnikov rule: a computational study of the regio- and stereoselectivity of diene hydroboration reactions

  • Laurence Hamdan
  • Khaled Abdel-Maksoud
  • Riya Radia
  • Janine Boodram
  • Kwan Y. Man
  • Iain McGregor
  • Catherine Munteanu
  • Kishan Muthu
  • Jannat Poddar
  • Joanna Roberts
  • Stephanie Sadler
  • Nabeela Siddiqi
  • Sianne Tam
  • Anna Andreou
  • Oren A. Scherman
  • Edina RostaEmail author
Chapter
Part of the Highlights in Theoretical Chemistry book series (HITC, volume 12)

Abstract

Hydroboration and subsequent use of boron compounds in novel organic synthesis have been fl ourishing in recent years largely due to its amiability in producing asymmetric stereo- and regioselective products. Direct products of diene hydroboration, however, have received little attention, with most substrates being assumed to produce the anti-Markovnikov product expected from textbook organic chemistry understanding. Previous experimental studies have observed the presence of a plethora of hydroboration products, and a significant progress has been made in assigning species to experimental data—though often with contradicting results. This study has used a computational approach employing quantum chemical calculations to determine atomic charges of cyclic and acyclic dienes and correlate these with calculated activation energy barriers in order to predict the regio- and stereoselective outcome of hydroboration reactions. Results indicated a strong correlation between the most polarized atomic charges of double-bonded carbons and the lowest energy transition states as expected. Intriguingly, we identified 1,3-cyclohexadiene as the main example that does not follow the anti-Markovnikov rule. We proceed to show that in addition to the polarity of the double bonds within a molecule, in this case, the conjugation with the allyl double bond and the specific geometric features of the cyclohexane ring were key stabilizing factors for the unexpected transition state preference, resulting in a regioselectivity that is in quantitative agreement with previous experimental data. Our results further indicated that Re-face attacks and steric factors due to substituents of the substrate infl uenced mainly the stereoselective outcome of the reaction, also affecting the pathways available to proceed through to complete the hydroboration process.

Keywords

Hydroboration Anti-Markovnikov rule Markovnikov rule 11B NMR Lewis acid–base Frustrated Lewis pair 

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Copyright information

© Springer-Verlag Berlin Heidelberg 2016

Authors and Affiliations

  • Laurence Hamdan
    • 1
  • Khaled Abdel-Maksoud
    • 1
  • Riya Radia
    • 1
  • Janine Boodram
    • 1
  • Kwan Y. Man
    • 1
  • Iain McGregor
    • 1
  • Catherine Munteanu
    • 1
  • Kishan Muthu
    • 1
  • Jannat Poddar
    • 1
  • Joanna Roberts
    • 1
  • Stephanie Sadler
    • 1
  • Nabeela Siddiqi
    • 1
  • Sianne Tam
    • 1
  • Anna Andreou
    • 2
  • Oren A. Scherman
    • 2
  • Edina Rosta
    • 1
    Email author
  1. 1.Department of ChemistryKing’s College LondonLondonUK
  2. 2.Melville Laboratory for Polymer Synthesis, Department of ChemistryUniversity of CambridgeCambridgeUK

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