Heterogeneous Organo- and Metal Catalysis Using Phosphine Oxide Derivatives Anchored on Multiwalled Carbon Nanotubes

Maria Cristina Ligi,Stefano Cicchi,Giulia Serrano,K Michał Pietrusiewicz,Anna Flis,Giacomo Biagiotti

doi:10.3390/c6030057

Abstract

Oxidized multiwalled carbon nanotubes were modified anchoring phosphine oxides and used as heterogeneous catalysts. A proper substitution of the phosphine oxides allowed the use of the Tour reaction and the nitrene cycloaddition to obtain functionalized carbon nanotubes (CNT) with a loading up to 0.73 mmol/g of material. The catalysts proved efficient in Wittig reactions, Mitsunobu reactions, and Staudinger ligations. Furthermore, the phosphorus decorated CNT were used to produce nanocomposite with Pd nanoparticles able to catalyze Heck reactions.

Highlights

Significant attention in the development of catalytic organophosphorus-based reactions featured last decade [1]
We present examples of heterogeneous phosphorus-organocatalysis for the synthesis of small organic molecules in an attempt to explore the potential scope of this approach rather than study in details each process
In a previous work [23], we have shown how it is possible to covalently functionalize carbon based nanostructured materials using amino substituted and azido substituted phosphine derivatives to prepare new materials that have been preliminarily tested in a Staudinger ligation experiment

Summary

Introduction

Significant attention in the development of catalytic organophosphorus-based reactions featured last decade [1]. Substituted phosphines can catalyze many different kind of reactions, recovering their starting oxidation state as the end of the process, such as when they act as nucleophiles in wide range of transformations ranging from Michael to. There are several examples in which their oxidation state changes from P(III) to P(V). This is the case of Staudinger ligation [3], Mitsunobu [4], Wittig [5], and Appel [6] reactions in which the byproduct is a phosphine oxide, which is often not easy to remove from the reaction mixture. First O’Brien et al published a catalytic version of the Wittig reaction [7,8]. By using a phosphine oxide as pre-catalyst and phenyl silanes as reducing agents, they achieved different alkenes in the presence of either aldehyde or ketone as starting materials

Methods

Results

Conclusion