Boron-Containing Chiral Auxiliaries
Organoboron chemistry has proven its general versatility over the last century. In this chapter, the focus is on boron-containing auxiliaries. First, a short overview of commonly used cyclic compounds is provided, followed by their diastereoselective synt
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Boron-Containing Chiral Auxiliaries Marvin Mantel, Marcus Brauns, and J€ org Pietruszka
Abstract Organoboron chemistry has proven its general versatility over the last century. In this chapter, the focus is on boron-containing auxiliaries. First, a short overview of commonly used cyclic compounds is provided, followed by their diastereoselective synthesis in the main part. In six subsections, from cycloadditions to remote-controlled reactions are discussed in detail. Finally, arguably the most prominent transformation of one group of synthesized reagents – the allyl addition – is used to exemplify the broad applicability in asymmetric synthesis and in natural product synthesis in particular. Keywords Allyl addition • Boron • Diastereoselective synthesis • Natural products Contents 1 Introduction 2 Overview 3 Diastereoselective Synthesis 3.1 Cycloadditions 3.2 Matteson Homologations 3.3 SN2’ Reactions 3.4 Carbonyl Allylation 3.5 [3,3]-Sigmatropic Rearrangement 3.6 Remote-Controlled Reactions
M. Mantel and M. Brauns Institut für Bioorganische Chemie, Heinrich-Heine-Universita¨t Düsseldorf im Forschungszentrum Jülich Stetternicher Forst, 52426 Jülich, Germany J. Pietruszka (*) Institut für Bioorganische Chemie, Heinrich-Heine-Universita¨t Düsseldorf im Forschungszentrum Jülich Stetternicher Forst, 52426 Jülich, Germany Institute for Bio- and Geosciences 1 (IBG-1): Biotechnology, Forschungszentrum Jülich, 52428 Jülich, Germany e-mail: [email protected]
M. Mantel et al. 4 Applications in Asymmetric Synthesis References
1 Introduction Among the chemical elements utilized in organic chemistry, boron has proven to be the dexterous answer to a large number of challenging synthetic problems. Thus, last decades’ Nobel Prizes for boron-based works in 1976, 1979, and 2010 underline with undoubtable convincement the early recognized importance of substances employing the versatile element [1–4]. Not only a broad variety of reagents but also the excellent synthetic properties, embodied, for example, by high stereoselectivities in allylic addition reactions, have made boron-bearing compounds an indispensable part of modern organic synthesis [5–9]. In this article it is intended to show how boron auxiliary reagents have been utilized during the last decades addressing several synthetic problems by a more than sufficient reactivity paired with excellent stereoselectivity. However, over the bygone half-century relentlessly conducted research on boron chemistry has spawn a sheer endless variety of reagents and applications, making it impossible to give a complete treatise of the topic within the following pages. Thus, the compounds dealt with in this article were needed to be edged suiting the book series’ title. All reagents mentioned are united by a heterocyclic character with a boron atom and chirality located within the ring system. Also, the elaborated moieties are categorized as auxiliaries, which is why further chemistry takes place on another residue attached to the boron exclusively. An overview of chiral auxili
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