Organophosphorus chemistry for the synthesis of dendrimers

Abstract

Dendrimers are multifunctional, hyperbranched and perfectly defined macromolecules, synthesized layer after layer in an iterative manner. Besides the nature of the terminal groups responsible for most of the properties, the nature of the internal structure, and more precisely of the branching points, is also of crucial importance. For more than 15 years, we have demonstrated that the presence of phosphorus atom(s) at each branching point of the dendrimeric structure is particularly important and highly valuable for three main reasons: (i) the versatility of phosphorus chemistry that allows diversified organochemistry for the synthesis of dendrimers; (ii) the use of 31P-NMR, which is a highly valuable tool for the characterization of dendrimers; (iii) some properties (in the fields of catalysis, materials, and especially biology), that are directly connected to the nature of the internal structure and of the branching points. This review will give an overview of the methods of synthesis of phosphorus-containing dendrimers, as well on the ways to graft phosphorus derivatives as terminal groups, with emphasis on the various roles played by the chemistry of phosphorus.

Scheme 1

The principle of the divergent synthesis of dendrimers.

Scheme 2

The most important method of synthesis of phosphorus dendrimers.

Figure 1

Functionalized phenols that have been grafted to dendrimers ended by P(S)Cl₂ functions.

Figure 2

Some phenol aldehydes used instead of HOC₆H₄CHO for the synthesis of dendrimers.

Scheme 3

Synthesis of a small dendrimer via substitutions with methylhydrazine.

Figure 3

Functionalization of the surface of dendrimers by amino derivatives (only one function is shown, representative of all the terminal groups).

Figure 4

Multifunctionalization of the surface of dendrimers, and of the internal structure.

Scheme 4

Functionalization of terminal groups by direct reaction of phosphorus derivatives.

Scheme 5

Other types of reactions for the grafting of phosphorus derivatives as terminal groups.

Scheme 6

Two methods of synthesis of dendrimers by Staudinger reactions.

Scheme 7

Reactivity of the P=N-P=S linkages and growing of new branches inside the dendrimer.

Scheme 8

Example of synthesis of a Janus dendrimer, thanks to the presence of P=N-P=S linkages.

Scheme 9

Use of the Wittig reaction for the functionalization of the surface of dendrimers.

Scheme 10

Horner-Wadsworth-Emmons reaction for the grafting of aminoacids.

Scheme 11

Cleavage of P-OR bonds in catalysis conditions.

Scheme 12

Cleavage of P-OMe bonds while preserving P-OAr bonds.