Chemistry Reference
In-Depth Information
FIGURE 2.6
Orthogonal synthesis of dendrimer.
individual building blockwill react only with the periphery of the other building block
(A reacts only with D, and C only with B). Therefore, the total number of reactions is
decreased to half of that for a conventional method. However, this strategy generally
requires complicated reaction systems to perform the quantitative coupling in the
presence of different types of functional groups, especially for dendrimers having the
same repeat unit of the linkage.
2.3 RAPID SYNTHESIS OF DENDRIMERS
There are other several recent reports that appear to be particularly noteworthy in the
area of rapid synthesis of dendrimers.
Rannard and Davis [14] reported a one-pot multiple-addition convergent synthesis
of polycarbonate dendrimers, in which the second-generation dendrimer was ob-
tained by sequential activation of an alcohol unit with 1,1-carbonyl diimidazole
followed by addition of an unprotected AB
2
triol (Scheme 2.1).
Majoral and coworkers [15] reported the one-pot synthesis of a fourth-generation
dendrimer via divergent strategy using two different unprotectedAB
2
-building blocks
(Scheme 2.2). In this method, to obtain phosphorus-containing dendrimers, they
demonstrated that the condensation reaction between phophorhydrazides and alde-
hydes on one side, and the Staudinger reaction between phosphines and azides on the
other side. This sequence of reactions does not require any isolation, since the only by-
products are H
2
O and N
2
. Although this method has poor versatility because the
