The synthesis of dendrimers including PN−PS linkages specifically placed at some generations
within the dendrimeric architecture allows the grafting of several types of functional groups at site- and depth-specific locations in the internal layers. The synthesis is carried out up to the fourth generation starting from
a difunctional core, or up to the third generation starting from a hexafunctional core. These dendrimers include
2, 6, or 18 PN−PS groups, depending on the type of core and the generation considered. The functional
groups are introduced by several types of reactions. First, the strong polarization of the PN−PS linkage
induces a facile reactivity with various alkyl triflates such as methyl, allyl, and propargyl triflates, leading to
the formation of functionalized phosphonium salts [PNP−S−R]+. The alkylation induces a weakening of
the P−S bond which is cleaved with P(NMe2)3, leading to the formation of internal aminophosphite groups
[PN−P:]. These highly reactive tricoordinated phosphorus atoms are alkylated by methyl or allyl iodide,
leading to a second series of functionalized dendrimers including phosphonium salts at some precise internal
layers. A third series of internally functionalized dendrimers is obtained by the Staudinger reaction of
functionalized azides with the aminophosphite internal groups. Isothiocyanate, aldehyde, and primary amine
derivatives have been grafted regiospecifically in this way [PN−PN−R]. The reactivity of the aldehyde
internal functions leading to the grafting of azides or crown-ethers is also described.
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