The Chemistry of P=N-P=X (X=S, O, NR) Linkages for the Synthesis of Dendritic Structures

The Staudinger reaction between a phosphine and an azide, applied to phosphorus azides, has been used for the synthesis of a large variety of dendritic structures, incorporating P=N-P=X moieties (X = mainly S, but also O and N-R). Conjugation of the P=N bond with the P=X bond greatly stabilizes the P=N bond. Highly branched structures such as dendrons, dendrimers, Janus dendrimers, layered dendrimers, surface-block dendrimers, and diverse other dendritic structures incorporating such linkage have been elaborated. Accelerated methods of synthesis of dendrimers are also based on the Staudinger reaction. A versatile reactivity was observed exclusively on the sulfur atom of P=N-P=S linkages, such as alkylation or complexation. Alkylation on S induces a weakening of the strength of the P=S bond, which can be easily cleaved to generate phosphines able to react in Staudinger reactions inside the structure of dendrimers, thus affording highly sophisticated dendritic structures.

Automated summary

The Staudinger reaction is used for the synthesis of phosphorus azides and dendritic structures containing P=N-P=X moieties. The conjugation of P=N bond with P=X bond stabilizes the P=N bond. Various dendritic structures such as dendrons, dendrimers, Janus dendrimers, layered dendrimers, surface-block dendrimers, etc. have been synthesized using this reaction. Alkylation or complexation exclusively occurs on the sulfur atom of P=N-P=S linkages, weakening the strength of P=S bond and allowing the formation of highly sophisticated dendritic structures.