Synthesis and Application of Organoboron Compounds

Table of Contents

1. Frontmatter

2. Boryl Anions

   Makoto Yamashita, Kyoko Nozaki

   Abstract

   This chapter focuses on the chemistry of boryl anions. The first section gives a brief history of boryl anion before the first isolated boryl anion equivalent, boryllithium, emerged. Synthesis and properties of all existing boryl anions are summarized in the second section. In the third section, examples of boryl–transition metal complexes synthesized from boryl anion reagents are presented. The following fourth section describes chemistry of boryl-substituted main group element compounds made from boryl anions. At the end of this chapter, the authors provide a summary and their perspective for related fields.

3. Fundamental and Applied Properties of Borocations

   Michael J. Ingleson

   Abstract

   The past 5 years has witnessed considerable growth in the field of borocation chemistry with a multitude of new cations containing 2, 3 and 4 coordinate boron centres reported. Perhaps more significant has been the expansion in the synthetic utility of borocations as stoichiometric reagents and catalysts. It is these new applications of borocations that are the primary focus of this article which concentrates on reports from 2009 to the end of June 2014. The correlation between structure and reactivity in these recent studies will be emphasised to aid in the future design of new borocations for specific targeted outcomes.

4. Asymmetric Catalytic Borylation of α,β-Unsaturated Acceptors

   Sumin Lee, Jaesook Yun

   Abstract

   Asymmetric β-borylation (conjugate borylation) of α,β-unsaturated acceptors allows the efficient synthesis of chiral organoboron compounds bearing extra functional groups. In the last 8 years, impressive progress has been made regarding this reaction since the first asymmetric report. While copper catalysis has dominated the field of asymmetric borylation due to its high reactivity and selectivity, various metal-catalyzed and metal-free methods have also been developed. The present chapter covers recent developments in asymmetric borylation of α,β-unsaturated compounds while focusing on the substrate scope and enantioselectivity of each catalytic system. In addition, recent achievements of asymmetric borylation conducted in water are briefly presented.

5. Reactions of Alkynylboron Compounds

   Naoki Ishida, Masahiro Murakami

   Abstract

   This chapter overviews reactions of alkynylboron compounds, in which the carbon–carbon triple bond is transformed into a different form, with the boryl group remaining in the product. Most of the reactions produce multiply substituted alkenyl- and aryl-boron compounds.

6. Improving Transformations Through Organotrifluoroborates

   Kaitlin M. Traister, Gary A. Molander

   Abstract

   Organotrifluoroborates have emerged as choice reagents for a number of diverse transformations, providing reactivity patterns that complement those of other available organoboron reagents. Over the last several years, numerous potassium organotrifluoroborates have become commercially available owing to their long shelf-lives. As a result of this and their unique reactivity patterns, a significant amount of progress has been made in the synthesis and utilization of organotrifluoroborate salts in organic transformations.

7. The Catalytic Dehydrocoupling of Amine–Boranes and Phosphine–Boranes

   Heather C. Johnson, Thomas N. Hooper, Andrew S. Weller

   Abstract

   Mechanistic studies into the catalysed dehydrocoupling of amine–boranes and phosphine–boranes have seen a rapid development over the last 5 years. The primary driver for this intense research effort has been the development of catalysts that might offer significant benefits with regard to the kinetics of hydrogen release, for potential use when linked with a fuel cell. Secondary to this, although becoming increasingly important, is the use of dehydrocoupling approaches to afford well-defined polymeric materials with B–N or B–P backbones that offer potential as high-performance polymers, as pre-ceramic materials and as precursors to white graphene. There have been many systems studied using catalysts incorporating metals from across the periodic table. This review attempts to bring together the insight revealed from these studies, which shows a rich and complex mechanistic landscape for the dehydrocoupling of phosphine–boranes and amine–boranes.

8. At the Forefront of the Suzuki–Miyaura Reaction: Advances in Stereoselective Cross-Couplings

   Ho-Yan Sun, Dennis G. Hall

   Abstract

   The synthesis of optically enriched compounds is a continuing challenge in organic synthesis. While the Suzuki–Miyaura cross-coupling has been used extensively in the construction of sp²–sp² bonds, only recently has it come to prominence as a useful means to construct stereogenic centres. This chapter describes the latest achievements in the development of stereoselective Suzuki–Miyaura cross-coupling reactions, including advances made both in atroposelective couplings as well as stereoselective C(sp³) couplings. Focus is also given to the mechanistic details of these cross-coupling processes.

9. Boronic Acid-Catalyzed Reactions of Carboxylic Acids

   Kazuaki Ishihara

   Abstract

   Although boric acid (B(OH)₃) and boronic acids (RB(OH)₂) behave as oligomeric mixtures, these boron compounds, as well as borane, electrophilically activate carboxylic acids as a mixed anhydride under equilibrium. In particular, electron-deficient arylboronic acids are useful as Lewis or Brønsted acid catalysts. The pK _a of boronic acids is in the range of 5–9, which is significantly higher than that of the strong protic acids. However, diortho-substituted arylboronic acids with electron-withdrawing groups are unstable and are easily decomposed by base-promoted protodeboronation. In this chapter, the main emphasis is upon the recent progress on boronic acid-catalyzed reactions of carboxylic acids, as well as a few other reactions which can be catalyzed by boronic acids.

10. Reagent-Controlled Lithiation–Borylation

    Daniele Leonori, Varinder K. Aggarwal

    Abstract

    This chapter focuses on the stereo-controlled homologation of chiral boronic esters with chiral lithium carbenoid (lithiation–borylation) as a powerful method for the asymmetric synthesis of many complex molecules. It is highlighted that the potential methodology to create multiple contiguous stereogenic centers on “growing” carbon chains.

11. Recent Advances in the Synthesis and Applications of Organoborane Polymers

    Frieder Jäkle

    Abstract

    Recent advances in the synthesis of organoborane polymers are reviewed in this chapter. The last decade has witnessed new approaches for the direct polymerization of functional borane monomers as well as the use of innovative polymer modification techniques. Powerful new methods that allow for positioning of functional borane moieties at well-defined positions in the polymer chain have also been developed. The resulting organoborane polymers have been investigated as luminescent and electro-active materials, electrolytes for batteries, supported Lewis acid catalysts, sensors for anions and biologically relevant molecules, building blocks of stimuli-responsive and dynamic (supramolecular) materials, and for biomedical applications.

12. Backmatter