Synthesis 2007(22): 3431-3446  
DOI: 10.1055/s-2007-990854
REVIEW
© Georg Thieme Verlag Stuttgart · New York

Hexadecyltributylphosphonium Azide - A Highly Potent Reagent for the Synthesis of Unusual Azides

Klaus Banert*
Institut für Chemie, Technische Universität Chemnitz, Straße der Nationen 62, 09111 Chemnitz, Germany
Fax: +49(371)53121229; e-Mail: klaus.banert@chemie.tu-chemnitz.de;
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Publikationsverlauf

Received 2 May 2007
Publikationsdatum:
29. Oktober 2007 (online)

Abstract

Hexadecyltributylphosphonium azide (QN3) is easily accessible and highly lipophilic, resulting in good solubility in nonpolar solvents like cyclohexane. The low melting point of this reagent allows convenient usage as a (supercooled) melt. Thus, extremely rapid nucleophilic substitution reactions and isolation of unstable products by simple re-condensation are possible. Utilizing these properties, the application of QN3 in the synthesis of organic azides is successful even in cases in which classical methods have failed. This is demonstrated in this review by several examples, including unstable starting materials and substrates with steric hindrance or i-strain, or dealing with rapid subsequent reactions, either desired or not, of the generated azides.

1 Introduction

2 Synthesis and Properties of Hexadecyltributylphosphonium Azide (QN3)

3 SN2 Reactions

3.1 With Steric Hindrance

3.2 With Internal Strain

4 Other Nucleophilic Substitutions

5 Nucleophilic Substitution with Rapid Subsequent Reactions of the Azides

5.1 Rapid Sigmatropic Rearrangements

5.2 Rapid Electrocyclic Ring Opening

6 Conclusion

43

Banert, K.; Joo, Y.-H. unpublished results.

64

Banert, K.; Hagedorn, M. unpublished results.

66

These experiments were performed in collaboration with Dr. Hans Peter Reisenauer and Prof. Günther Maier at the Justus-Liebig-Universität Gießen.

72

Banert, K.; Kuhtz, A. unpublished results.