Chemistry Reference
In-Depth Information
H
H R
H
H
R
R
H
N
N
N
H
H
R
1
R
1
=Me
R
1
=H
2
3
1
Scheme 1 Fullerenynes (1) bearing an alkyne unit give rise to cyclobutene derivatives
(2) regioselectively, and allenic structures (3)
Scheme 2 Fullerene-carbene Lewis acid-base adducts
The addition also occurs onto C
70
with the regioselective formation of a new
bond between the carbene and the carbon atom C-25 of [70]fullerene [
27
].
Among the numerous methods for chemical functionalization of fullerenes
reported during the last decade, some important trends have been outlined for
achieving new properties or major control over factors like reactivity, selectivity,
and compatibility with a wider range of functional groups.
2.1 New Reactions on Fullerenes Involving Metals
The nucleophilic addition of organometallic reagents, such as organolithium [
28
]or
Grignard salts [
29
], is one of the classical methods for fullerene functionalization.
[
30
-
32
]. More recently, the use of transition metals has expanded the arsenal of
chemical tools, achieving new structures with better control of reactivity and
selectivity. Thus, fullerenes' double bonds, despite their electron-poor character,
are able to act as the alkene component in a Pauson-Khand (PK) reaction. There-
fore, when a 1,6-fullerenyne is treated with Co
2
(CO)
8
, highly efficient and
regioselective intramolecular PK products showing three [
33
] (or five [
34
]) fused
pentagonal rings on the same hexagon of the fullerene surface were formed
(Scheme
3
).
