Chemistry Reference
In-Depth Information
Fig. 13
Structures of 4,5-
dihalophenanthrenes
X
X
47a
:X= F
47b
:X= Cl
47c
:X= Br
47d
:X= I
X
X
X
X
Fig. 14
Structures of
decafluorophenanthrene
(
48a
) and
decachlorophenanthrene
(
48b
)
X
X
X
X
48a
:X=F
48b
:X=Cl
X
X
2
1
10
9
3
8
N
N
Fig. 15
Structure of
1,3,8,10-tetramethyl-4,7-
phenanthroline (
49
)[
54
]
4
7
56
49
diiodide
47d
[
50
]. The X-ray structures of
47a
,
47b
, and
47d
show twisted
structures with torsional angles
y
of 20.1
, 37.7
, and 34.6
, respectively [
6
,
50
].
Decafluorophenanthrene (
48a
)[
51
,
52
] and decachlorophenanthrene (
48b
)[
53
]
(Fig.
14
) have also been synthesized. The X-ray structure of
48b
shows a
pronounced torsional angle
y
of 41.9
[
27
,
53
].
2.4
1,10-Disubstituted 4,7-Phenanthrolines
As in 4,5-disubstituted phenanthrenes, substitutions at the sterically most hindered
C1 and C10 positions of 4,7-phenanthroline as depicted in
49
(Fig.
15
) cause helical
twist of the aromatic structure [
54
]. The first example of such derivatives, 1,10-
dicarboxy-3,8-diphenyl-4,7-phenanthroline (
50
), was reported in 1932 (Scheme
9
)
[
55
]. Condensation of
p
-phenylenediamine with benzaldehyde and then with
pyruvic acid followed by cyclization produced
50
. Oxidation of
50
to tetracarbox-
ydipyridyl
51
provided the supporting evidence for the formation of
50
.
More recently, 13,14-dimethyldibenzo[
b
,
j
][4,7]phenanthroline (
55
) was
synthesized by the copper-catalyzed condensation reactions between 1,4-
diiodobenzene (
52
) and 2-aminoacetophenone (
53
) to give
54
followed by sulfuric
acid-promoted cyclization reactions (Scheme
10
)[
56
]. Alternatively,
55
was also
prepared by a one-pot procedure involving the ZnCl
2
-catalyzed reactions between
N
,
N
0
-diphenyl-
p
-phenylenediamine (
56
) and acetic acid (Scheme
11
)[
57
,
58
]. The
enantiomers of
55
were separated by a chiral HPLC column and were found to
undergo rapid racemization at room temperature. A slower rate of racemization was
observed for the 13,14-diethyl derivative
57
. The X-ray structure of
57
confirmed
the twisted aromatic framework.
