Synthesis and Characterization of Novel Bis-Triazenes
J . Org. Chem., Vol. 63, No. 21, 1998 7441
1
3
C NMR. 13C NMR spectroscopy supported the con-
clusions from the 1H NMR data. The aromatic reso-
nances of para-substituted compounds 6a -f were ob-
served as four signals that were found between δ 154.77
and δ 118.70. The ortho-substituted compounds 6g and
6
h produced four aromatic resonances between δ 132.17
and 118.92 which represented the hydrogen-bearing
aromatic carbons. The signals for the ipso carbons of the
aromatic ring are believed not to be detected due to a
nuclear Overhauser enhancement observed in the proton-
decoupled spectrum. As the signal intensities for the
carbons bearing hydrogens in compounds 6g and 6h
increase, the ipso carbons of the aromatic ring which bear
no hydrogens do not experience a nuclear Overhauser
enhancement. This leads to the drowning out of the ipso
carbon’s signal in the background noise of the spectrum.
The methyl carbon bonded to the oxygen atom in methyl
ester 6d had a signal of δ 51.90. The ethyl ester
substituent 6e created two signals within the proton-
F igu r e 1. Proton and carbon labels for the bicyclic basket
structure of 3,8-di[2-aryl-1-azenyl]-1,3,6,8-tetraazabicyclo-
[4.4.1]undecane (6).
which integrate in the ratio 6:2. The two proton mul-
tiplet in the range δ 4.63-4.17 is assigned to the proton
h h
labeled H in Figure 1. The chemical shift of H is more
than a full ppm downfield from the other three protons,
, H , and H , observed in a 6-proton multiplet in the
range δ 3.22-3.59. The explanation for the downfield
shift of the protons H is that somehow the H protons
H
e
f
g
h
h
are in an entirely different chemical environment in
which they are deshielded. A close inspection of many
of these low-field multiplets reveals eight lines suggesting
the signal is a doublet of a doublet of doublets (see inset
in Figure 2). This pattern can be explained if H and H
g h
are diastereotropic and experience geminal coupling to
one another as well as different couplings to their two
decoupled 13C NMR spectra at δ 60.65 (CH
(CH ). The acetyl group in compound 6c had two
) and δ 14.37
2
3
resonances, one for the carbonyl carbon (δ 197.44) and
one for the methyl group (δ 26.51). The cyano substituted
compounds 6b and 6h gave cyano-carbon resonances at
δ 108.10-108.14. The carbonyl carbon of esters 6d and
6e and the acetyl group of 6c gave resonances at δ
197.44-166.51.
Carbon atoms C1 and C5 of the bicyclotetraamine
basket (Figure 1), which are equivalent carbons of the
ethyl linkages closest to the triazene moiety, were found
to resonate in the range δ 47.06-46.51. C2 and C4,
which are equivalent carbons of the ethylene moiety
farthest from the triazene moiety, resonate in the range
δ 47.43-46.92. The resonance for the methylene bridg-
ing carbon C3 had signals from δ 73.84 to 73.40. The
resonances of the equivalent methylene groups which are
nonbridging, C6 and C7, had signals from δ 71.12 to
71.01. These assignments were confirmed by the follow-
ing DEPT experiments.
neighboring diastereotopic protons H
e
and H
f
.
An
example of this multiplet can be observed at δ 4.33-4.17
1
in the H NMR spectrum of the p-CO
2
CH
3
derivative 6d ,
Figure 2, which is a typical 250-MHz H NMR spectrum
of 6. In the case of 6e, the signal for H at δ 4.39-4.31
is overlapped by the quartet of the CH group of the ethyl
1
h
2
ester which has the same chemical shift to give a signal
with an integration of six rather than two.
The second 6-proton multiplet caused by the remaining
protons of the ethylene bridges is a more complex
6
-proton multiplet found in the range δ 3.59-3.22 of the
1
H NMR of 6. This more complex multiplet is assigned
to the H , H , and H protons of the ethylene bridge and
is the result of the overlapping and second-order spectral
e
f
g
effects of three nonequivalent protons, H
with different but almost identical chemical shifts (H
and H
tiplet varies from 14 to 24 uneven and disproportioned
lines (see inset Figure 2). Slight variations in the
chemical shifts of these three protons determine the
degree of overlap and second-order spectra of the mul-
tiplet and therefore the size and number of lines of the
multiplet. In Figure 2 this complex multiplet can be
observed in the range δ 3.47-3.29.
g
, H
e
, and H
f
,
e
DEP T Exp er im en t. DEPT experiments were run on
1
3
compounds 6d , 6c, and 6f in order to confirm the
C
f
are diastereotopic). The line count of this mul-
NMR assignments. The DEPT spectrum for the para-
methyl ester compound 6d had positive peaks at δ 51.90,
120.32, and 130.23, indicating a methine or methyl
groups. The positive signal at δ 51.90 was assigned to
the methyl group on the methyl ester substituent. The
two remaining positive signals in the DEPT spectrum of
6d , δ 120.32 and 130.23, were assigned to the meta and
ortho methine groups of the aromatic rings. The DEPT
spectrum of 6d also gave inverse peaks at δ 46.99 and
46.92, which were assigned to carbons C1/C5 and C2/C4
(Figure 1), respectively, confirming these carbons as
methylene carbons. The inverse peaks at δ 73.42 and
71.11 of 6d ’s DEPT spectrum were assigned to C6/C7 and
C3, respectively, and confirmed their identity as meth-
ylene carbons. The DEPT spectrum for the para bromo
compound 6f revealed positive peaks at δ 122.12 and
118.74, which were assigned to the aromatic meta and
ortho methine carbons. Inverse peaks at δ 46.98 and
46.55 of the DEPT spectrum of 6f were assigned to the
methylene carbons of C1/C5 and C2/C4, respectively,
while the inverse peaks at δ 73.26 and 71.06 were
assigned to the methylene carbons of C6/C7 and C3,
respectively. For the DEPT spectrum of the para methyl
ketone compound 6c, there were three positive peaks
observed. The first of these positive peaks, observed at
The bicyclic basket portion of 6, Figure 1, also contains
three single-carbon methylene linkages, two of which are
nonbridging (C6 and C7) and one which is bridging (C3);
these are the original formaldehyde carbon atoms. Pro-
tons H
a b
and H of the bridging methylene (C3) are
enantiotopic and give rise to a singlet in the range δ
4
2
.22-4.15 with an integration of two protons. In Figure
this singlet can be observed at δ 4.15. On the other
hand, protons H
methylene groups C6 and C7 are diastereotopic. The
chemical shift values of H and H turn out to be close to
one another, giving rise to a second-order spectra AB
system of doublets resulting in H and H being observed
c d
and H of the equivalent nonbridging
c
d
c
d
as a quartet-like signal in the proton NMR in the range
δ 5.01-4.77, depending on the substituent. In Figure 2
this four- line AB system is observed at δ 4.99, 4.93, 4.88,
and 4.82.