Chemistry Reference
In-Depth Information
FIGURE 6.19
Preparation of fullerodendrons
46
-
49
. Reagents and conditions: (i)
45
, DCC,
DMAP, HOBt, CH
2
Cl
2
; (ii) TFA, CH
2
Cl
2
.
is depicted in Figure 6.19. The starting fullerene derivative
is easily obtained on a
multigram scale and is highly soluble in common organic solvents owing to the
presence of the four long alkyl chains. The iterative reaction sequence used for the
preparation of the subsequent dendrimer generations relies upon successive DCC-
mediated esterification reaction with the A
2
B-building block
13
possessing two
benzylic alcohol functions and a protected carboxylic acid group followed by
cleavage of a t-butyl ester moiety under acidic conditions [67].
Reaction of diol
45
under esterification conditions using
DCC, DMAP, and 1-hydroxybenzotriazole (HOBt) in CH
2
Cl
2
gave the protected
dendron of second generation
45
with carboxylic acid
13
in 90% yield. Hydrolysis of the t-butyl ester moiety
under acidic conditions then afforded the corresponding carboxylic acid
46
47
in a
quantitative yield. Esterification of
47
with diol
45
(DCC, HOBt, DMAP) afforded
the t-butyl-protected fullerodendron
in 95%yield. Selective hydrolysis of the t-butyl
ester under acidic conditions afforded acid
48
are
easilypreparedonamultigramscaleandarehighlysoluble incommonorganicsolvents.
Following this first successful preparation of dendritic branches with peripheral
C
60
subunits, Nierengarten and coworkers have reported several synthesis of full-
erodendrons having either peripheral C
60
subunits (
7
in 97%yield. Dendrons
13
,
47
,and
49
50
) or containing C
60
groups at
