Metal-halogen exchange between hydrazine polyanions and α,α′-dibromo-o-xylene

Article abstract of DOI:10.1021/om4009394

Aromatic-bridged bis(hydrazines) were found to be the main products in the reaction of hydrazine polyanions with α,α′-dibromo-o-xylene. It was confirmed that the reaction is driven by a metal-halogen exchange process. A three-step reaction mechanism is suggested.

Full text of DOI:10.1021/om4009394

Article
pubs.acs.org/Organometallics
Metal−Halogen Exchange between Hydrazine Polyanions and α,α′-
Dibromo‑o‑xylene
Oleg Lebedev and Uno Maeorg*
̈
Institute of Chemistry, University of Tartu, Ravila 14a, 50411 Tartu, Estonia
S
* Supporting Information
ABSTRACT: Aromatic-bridged bis(hydrazines) were found to
be the main products in the reaction of hydrazine polyanions
with α,α′-dibromo-o-xylene. It was confirmed that the reaction is
driven by a metal−halogen exchange process. A three-step
reaction mechanism is suggested.
Scheme 1. Synthesis of an Aromatic-Bridged Bis(hydrazine)
INTRODUCTION
■
Hydrazine derivatives are currently of great importance, finding
application as dyes, pesticides, drugs, and building blocks in
organic synthesis. Some of them have been proven to be active
against tuberculosis, hypertension, and Parkinson’s disease.1 In
addition, certain hydrazines show remarkable neuroprotective
activity and are used for the treatment of psychiatric disorders.
Many of the hydrazine-based antidepressants are molecules
where a hydrazine moiety is bonded to an aromatic core
through one or several methylene groups: e.g., phenelzine
(Figure 1).2
monosubstituted hydrazines with dihalides leads to the
corresponding heterocycles.3 In our case steric hindrance
cannot be a reason for the formation of the noncyclic product,
as even bulkier heterocycles have been prepared utilizing similar
aromatic dihalides.5 In the obtained compound two methylene
groups are bonded to equivalent nitrogens, but of different
hydrazine molecules. Understanding that there is not an
objective reason for this behavior of α,α′-dibromo-o-xylene, we
assumed that the reaction pathway should include the
formation of an intermediate bearing two different substituents
on the aromatic ring. According to the proposed mechanism
the trianion 1a and α,α′-dibromo-o-xylene (6) generate the
intermediates 2a and 3 via metal−halogen exchange (Scheme
2). In the next step 3 may interact with the trianion 1a,
affording the intermediate 4a which, in turn, can react either
with the intermediate 2a or its azo form 5a, finally completing
the structure. In the current work we present an experimental
confirmation of our hypothesis that the reaction is driven by a
metal−halogen exchange process.6
Figure 1. Hydrazine-based antidepressants phenelzine and isocarbox-
azid.
Previously we reported that the reaction of BocNHNH2
treated with 3 equiv of BuLi and α,α′-dibromo-o-xylene
unexpectedly afforded a product with two hydrazine fragments
attached to the aromatic ring (Scheme 1).3 Such aromatic-
bridged bis(hydrazines) may be considered as close analogues
of phenelzine; however, only a limited number of examples
have been synthesized so far. Similar compounds with a
carbonyl group have been prepared by the reaction of
hydrazines with aromatic esters or acyl halides.4
A surprising result inspired us to start searching for an
explanation of the phenomenon, because generally alkylation of
Received: September 20, 2013
Published: December 11, 2013
© 2013 American Chemical Society
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Scheme 2. Proposed Reaction Pathway
RESULTS AND DISCUSSION
■
We started with screening the hydrazine dianions in the
reaction with the dibromide 6. The dianions 1b,c were
generated from the corresponding hydrazines by treatment
with 2 equiv of BuLi in THF at −78 °C prior to the addition of
the dihalide. In compliance with the proposed mechanism,
hydrazine dianions may be able to react similarly to the
trianion. Indeed, it was found that BocNHNH2 dianion
furnished the same product 9 (Figure 2) with no impact on
the yield and the reaction time (Table 1, entry 2). The dianion
generated from PhNHNHBoc reacted in the same manner,
giving the noncyclic bis(hydrazine) 11 in good yield (entry 3).
These experiments confirmed that the method has a broader
scope and is not limited to monosubstituted hydrazines.
Nevertheless, the experiment with BocNHNHBoc dianion
revealed that the presence of two strongly electron withdrawing
groups on both nitrogens totally blocks the metal−halogen
interconversion (entry 13).
To prove the metal−halogen exchange process, similar
reactions have been carried out with 2,2′-bis(bromomethyl)-
1,1′-biphenyl (7). This halide is similar to 6, and it is expected
to give the analogue of the intermediate 3 if the metal−halogen
exchange is taking place. However, the intermediate 3′
generated from 7 was supposed to undergo self-cyclization
via fast intramolecular alkylation to build a favorable six-
membered-ring system; this is in contrast to its analogue 3
obtained from the dihalide 6, for which this way is undesirable,
as it would produce a strained four-membered cycle (Scheme
3). The desired carbocycle 12 was found in both reactions with
BocNHNH2 and PhNHNHBoc (entries 4 and 5). Some similar
examples of a bromine−lithium interconversion with sub-
sequent intramolecular cyclization may be also found in the
literature.7
The next step of our work was to confirm that hydrazine
polyanions act as metal donors in the process. The measured
pKa values of mono- and disubstituted hydrazines indicate that
the existence of the corresponding dianions is definitely
possible.8 In our recent works we assumed that the trianion
may be likewise obtained by the treatment of BocNHNH2 with
3 equiv of BuLi and used for selective alkylation.3,9 Despite the
successful results obtained, full deprotonation of BocNHNH2
has not been proven so far, thus making the existence of the
trianion still questionable.
Figure 2. Compounds 6−19.
Our idea was to demonstrate the absence of free BuLi in the
reaction mixture after 3 equiv of BuLi is added to BocNHNH2
and the possibility to trap the excess BuLi if a greater amount
was employed. At first we designed a model system adding 3
equiv of BuLi to PhNHNHBoc to produce the dianion 1c with
a fixed excess of BuLi. There are two theoretical possibilities for
further metal−halogen exchange with the dihalides 6 or 7. The
first option is participation of the dianion 1c, which should
afford the intermediate 2c or its azo analogue 5c, which would
likely react with BuLi. Alternatively, the process may take place
between BuLi and the dihalide, providing BuBr, which can
alkylate the dianion. This means that in both cases the
hydrazine derivative 16 is expected to form (Scheme 4). This
hypothesis was successfully confirmed (entries 6 and 7). As
may be seen from Table 1, the yield of 16 is higher if the
dihalide 7 is employed. This result is consistent with the
inference that the intermediate 3′ is being constantly removed
from the reaction mixture via self-cyclization, thus suppressing
possible side reactions with BuLi or BuBr. The analogous
experiments with BocNHNH2 and 3 equiv of BuLi revealed no
N-butyl derivatives, pointing out full deprotonation of the
starting material (entries 1 and 4). In contrast, the use of 4
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Table 1. Summarized Results of the Experiments
Scheme 4. Two Possible Ways of the Formation of 16 in
Entry 6 of Table 1
isolated
products
(yield, %)
reaction
entry starting material
conditions
time
1
2
3
4
5
6
7
8
9
BocNHNH2
BocNHNH2
PhNHNHBoc
BocNHNH2
PhNHNHBoc
PhNHNHBoc
PhNHNHBoc
BocNHNH2
BocNHNH2
BocNHNH2
BocNHNH2
PhNHNHBoc
3 equiv of BuLi, 1
10 min 9 (44), 10 (4)
10 min 9 (42), 10 (4)
30 min 11 (65)
equiv of 6
2 equiv of BuLi, 1
equiv of 6
2 equiv of BuLi, 1
equiv of 6
a
3 equiv of BuLi, 1
equiv of 7
1 h
12 (58), 13
(30)
2 equiv of BuLi, 1
equiv of 7
1 day
1 day
1 h
12 (26), 14
(34), 15 (17)
3 equiv of BuLi, 1
equiv of 6
11 (18), 16
(27)
a
a
a
3 equiv of BuLi, 1
equiv of 7
12 (61), 16
(52)
b
17 (18), 18
b
4 equiv of BuLi, 1
equiv of 6
2 h
(21)
3 equiv of BuLi, 0.5 1 day
equiv of 6
complex mixture
c
10
11
12
13
14
15
3 equiv of BuLi, 2
equiv of 6
10 min 9 (40)
equiv of BuLi and 6 as a halide afforded the desired species 17
and 18 in 39% total yield, whereas the formation of 9 was
totally suppressed (entry 8). This experiment finally verified
that free BuLi is observed only if more than 3 equiv is added to
BocNHNH2.
2 equiv of BuLi, 0.5 10 min 9 (62)
equiv of 6
2 equiv of BuLi, 0.5 2 h
equiv of 6
11 (60)
a
a
BocNHNHBoc 2 equiv of BuLi, 1
2 days
1 day
1 h
19 (60)
equiv of 6
Next we studied the reactions of hydrazine polyanions with
0.5 equiv of α,α′-dibromo-o-xylene, which is the stoichiometric
quantity for 9 and 11. As we know from previous experience,
BocNHNH2 trianion failed the test to yield the desired product
9 at these conditions (entry 9). Amazingly, BocNHNH2
dianion afforded 9 in 62% yield which is the best known
result for this compound (entry 11). The reason for such
different actions for these two species is still unclear. Probably,
BocNHNH2 trianion has some specific feature requiring
dihalide in 2-fold stoichiometric quantity. However, it was
demonstrated that there is no positive impact on the yield of 9
if more than 1 equiv of 6 is added to the trianion, as the
additional quantity of the dihalide remains unconsumed (entry
10). PhNHNHBoc dianion was proven to have almost no
difference reacting with either 0.5 or 1 equiv of 6, as very similar
yield values for 11 were found (entry 12).
BocNHNH2
3 equiv of BuLi, 1
equiv of 8
9 (8), 10 (30)
PhNHNHBoc
2 equiv of BuLi, 1
equiv of 8
11 (70)
a
b
Full conversion of the starting material was not observed. The yield
c
is based on the excess of BuLi. 0.76 equiv of 6 was recovered.
Scheme 3. Illustration of the Different Behavior of the
Intermediates 3 and 3′ Generated from the Dihalides 6 and
7
Finally we tested the reactions of hydrazine polyanions with
α,α′-dichloro-o-xylene (8). It is known that the rates of metal
interconversion in chlorides are significantly lower in
comparison with bromides.10 Indeed, the experiment with
BocNHNH2 trianion afforded the bis(hydrazine) 9 only in 8%
yield, whereas the main isolated component was the
heterocyclic product 10 as a result of competing direct
alkylation of the trianion (entry 14). The reaction of
PhNHNHBoc dianion with the dichloride 8 required
significantly more time than the analogous reaction with the
dibromide 6; however, it was surprisingly discovered that the
yield of 11 was almost the same (entry 15).
The obtained results encouraged us to make additional
suggestions regarding the mechanism of the reaction. As has
been shown, the first step of the reaction was proven to be
metal−halogen exchange between a dianion or the trianion and
α,α′-dibromo-o-xylene. We anticipate that it is an equilibrium
process shifted to the left. We propose that if the equilibrium
were shifted to the intermediates 2 and 3, these species would
likely interact with each other, giving heterocycles as main
products. Nevertheless, 10 was isolated as only a minor
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component in entries 1 and 2. Our hypothesis is also supported
by entry 4, where two competing reactionsintramolecular
cyclization of the aromatic intermediate 3′ and intermolecular
alkylation of the trianionare taking place. Though the
intramolecular process is much faster, there is still a comparable
amount of the heterocycle 13 formed (Scheme 5).
reaction mixture, the intermediates 2a and 5a are inappropriate,
as they would more likely afford the heterocycle 10, which was
found only as a minor component. Therefore, the most
probable step is the interaction of the intermediate 3 with the
trianion 1a, furnishing the trianion 4a.
Considering the structure of 9, the third step of the
mechanism should include the reaction of the intermediate 4
with either 2 or 5, as the polyanion 1 is not able to contribute
due to the absence of possible reaction centers. It is still
unknown whether 2 is stable enough to function itself or
transforms to the azo form 5; therefore, we consider both
options. An absolutely analogous reaction of unsymmetrical azo
compounds with alkyllithium reagents under very similar
conditions has been previously reported by our research
group, and it was confirmed to be a very fast and selective
process.13 Apparently, the selectivity of the alkylation of
BocNNR1 with R2Li is achieved due to the greater stability
of the anion BocN−−NR1R2, thus being controlled thermody-
namically.
Scheme 5. Formation of 12 and 13 in Entry 4 of Table 1
The stability of the key intermediates 3 and 5a−c is an
important point that shall be discussed. We suppose that the
intermediate 3 is a stable molecule which does not undergo
intramolecular ring closure at low temperatures. Our expect-
ations are in good accord with Parham’s report, where a very
similar intermediate has been described.14 The stability of the
intermediates RNNBoc (5a−c) strongly depends on the
nature of the R group. If R has an aromatic origin, the stability
of 5 is assured, as such compounds are well-known synthetic
reagents.13 The diazene HNNBoc is still an unknown
substance; however, a similar analogue has been recently
described to be a stable intermediate even at 70 °C.15 Diazene
anions, like LiNNBoc that is thought to be generated in the
reaction of BocNHNH2 trianion, are also known from the
literature to be trapped as intermediates.16
An equilibrium of metal−halogen exchange may be imagined
as a reflective measure of relative anion stability.11 If the
equilibrium is shifted to the left, it may be suggested that
BocNHNH2 trianion is a weaker base than the intermediate 3,
which is an analogue of benzyllithium. Understanding that the
pKa value of toluene is at least several units lower than the pKa
value of butane,12 it is obvious that BuLi should fully
deprotonate BocNHNH2, which has been experimentally
confirmed.
In the case of PhNHNHBoc dianion the equilibrium has to
be shifted to the left even more strongly than in the case of
BocNHNH2 trianion. Analogously with the previous situation
described above, it was also confirmed by an experiment with
the dihalide 7. It was found that the total yield of the products
of dianion alkylation with the dihalide 7 is twice as high as the
yield of the carbocycle 12, despite the fact that the latter species
is expected to form much more quickly (entry 5). A special case
is BocNHNHBoc dianion, where the equilibrium is shifted to
the left so strongly that the metal−halogen interconversion is
not actually taking place (entry 13). Obviously, the strong
electron-withdrawing properties of the Boc group make the N−
Li bond more covalent, eliminating the possibility for
interchange of the metal.
The second step of the mechanism includes an interaction
between the intermediate 3 and the polyanion 1. Our
confidence is based on a comparison of the reactions of
BocNHNH2 trianion 1a with the dihalides 6 and 7 (entries 1
and 4). The only difference in actions of these two dihalides lies
in the failure of 7 to provide the intermediate 3′ in sufficient
quantity, as it is rapidly converting to the carbocycle 12
(Scheme 3). As can be observed, knocking out this
intermediate is sufficient to terminate the process of the
formation of the bis(hydrazine) at step 1, hence giving a green
light for direct alkylation of the trianion 1a (Scheme 5). This
allows us to conclude that the next step of the formation of the
bis(hydrazine) 9 has to include the interaction of 3 with a
hydrazine derivative. Among all three candidates present in the
CONCLUSION
■
In conclusion, we have confirmed that the reaction of hydrazine
polyanions with α,α′-dibromo-o-xylene goes through a metal−
halogen exchange, which is the first step of the proposed
mechanism. Lithium−halogen interconversion is a known
reaction; however, to the best of our knowledge we are the
first to report the process at a nitrogen atom. Our method is a
good synthetic tool, giving access to aromatic-bridged bis-
(hydrazines) in one step.
EXPERIMENTAL SECTION
■
General Considerations. All reactions were performed under an
argon atmosphere in oven-dried glassware. THF was freshly distilled
from Na/benzophenone. PhNHNHBoc and BocNHNHBoc were
prepared by known methods.17 All other reagents were obtained from
commercial sources and used without further purification. TLC was
performed using Macherey-Nagel silica gel TLC plates (Alugram SIL
G/UV 254). Spots were visualized by UV light at 254 nm or by a ∼1%
ethanolic solution of phosphomolybdic acid with subsequent heating.
Column chromatography was carried out on 70−230 mesh Merck
1
Kieselgel. H and 13C spectra were recorded at 200 and 50 MHz,
respectively, on an AVANCE II 200 spectrometer (Spektrospin AG,
Switzerland). Deuteroform was used as a solvent. The chemical shifts
are reported on the ppm scale relative to the singlet (7.26 ppm for 1H)
and triplet (77.0 ppm for 13C). Coupling constants are reported in Hz.
IR spectra were measured on a PerkinElmer Spectrum BXII FTIR
spectrometer using the ATR technique with ZnSe. Melting points
were determined on a Stuart SMP10 melting point apparatus. HRMS
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1
spectra were acquired using direct nano-ESI infusion on a Q Exactive
mass spectrometer (Thermo Fischer Scientific).
solid. Mp: 120−122 °C. H NMR (200 MHz, CDCl3): δ 7.35−6.90
(m/broad s, 6H), 4.92 (broad s, 2H), 4.09 (s, 4H), 1.48 (s, 18H). 13C
NMR (50 MHz, CDCl3): δ 156.6, 136.6, 131.3, 128.0, 80.2, 54.2, 28.3.
FTIR ν (cm−1): 3336, 3307, 3226, 2977, 2934, 2867, 1698, 1552,
1482, 1454, 1367, 1271, 1251, 1152, 1007, 854, 844, 739.
Typical Procedure for Alkylation of BocNHNH2 Trianion with
1 Equiv of Dihalide. An oven-dried flask was charged with
BocNHNH2 (2.00 mmol, 264 mg), evacuated, and back-filled with
argon. Thereafter THF (12 mL) was added to dissolve the solid. The
reaction mixture was cooled to −78 °C, and a 1.6 M BuLi solution in
hexane (6.00 mmol, 3.75 mL) was added dropwise. The reaction
mixture was warmed to −45 °C for 15 min, and a solution of α,α′-
dibromo-o-xylene (2.00 mmol, 528 mg) in THF (2 mL) was added.
The reaction progress was monitored by TLC (petroleum ether/
EtOAc 1/1). After 10 min the reaction was complete. The reaction
mixture was quenched by addition of 0.1 mL of H2O, and the solvent
was evaporated under reduced pressure. To the residue were added 15
mL of chloroform and anhydrous MgSO4. The mixture was filtered,
and MgSO4 was washed with chloroform (3 × 2 mL). The volatiles
were removed under reduced pressure. The residue was purified by
column chromatography on silica (petroleum ether/EtOAc 1/1),
resulting in 9 (161 mg, 44%) as a yellowish solid and 10 (21 mg, 4%)
as a white solid.
Typical Procedure for Alkylation of BocNHNH2 Dianion with
1 Equiv of Dihalide. An oven-dried flask was charged with
BocNHNH2 (2.00 mmol, 264 mg), evacuated, and back-filled with
argon. Thereafter THF (12 mL) was added to dissolve the solid. The
reaction mixture was cooled to −78 °C, and a 1.6 M BuLi solution in
hexane (4.00 mmol, 2.50 mL) was added dropwise. The reaction
mixture was warmed to −45 °C for 15 min, and a solution of α,α′-
dibromo-o-xylene (2.00 mmol, 528 mg) in THF (2 mL) was added.
The reaction progress was monitored by TLC (petroleum ether/
EtOAc 1/1). After 10 min the reaction was complete. The reaction
mixture was quenched by addition of 0.1 mL of H2O, and the solvent
was evaporated under reduced pressure. To the residue were added 15
mL of chloroform and anhydrous MgSO4. The mixture was filtered,
and MgSO4 was washed with chloroform (3 × 2 mL). The volatiles
were removed under reduced pressure. The residue was purified by
column chromatography on silica (petroleum ether/EtOAc 1/1),
resulting in 9 (146 mg, 42%) as a yellowish solid and 10 (20 mg, 4%)
as a white solid.
Typical Procedure for Alkylation of PhNHNHBoc Dianion
with 1 Equiv of Dihalide. An oven-dried flask was charged with
PhNHNHBoc (1.00 mmol, 208 mg), evacuated, and back-filled with
argon. Thereafter THF (5 mL) was added to dissolve the solid. The
reaction mixture was cooled to −78 °C, and a 1.6 M BuLi solution in
hexane (2.08 mmol, 1.30 mL) was added dropwise (a lemon yellow
solution of the dianion was obtained). The reaction mixture was
warmed to −45 °C for 15 min, and a solution of α,α′-dibromo-o-
xylene (1.00 mmol, 264 mg) in THF (1 mL) was added. The reaction
progress was monitored by TLC (petroleum ether/EtOAc 5/1). After
30 min the reaction was complete. The reaction mixture was quenched
by addition of 0.1 mL of H2O, and the volatiles were evaporated under
reduced pressure. The residue was purified by column chromatog-
raphy on silica (petroleum ether/EtOAc 5/1), resulting in 11 (168 mg,
65%) as a white solid.
Typical Procedure for Alkylation of BocNHNHBoc Dianion
with 1 Equiv of Dihalide. An oven-dried flask was charged with
BocNHNHBoc (1.00 mmol, 232 mg), evacuated, and back-filled with
argon. Thereafter THF (5 mL) was added to dissolve the solid. The
reaction mixture was cooled to −78 °C, and a 1.6 M BuLi solution in
hexane (2.08 mmol, 1.30 mL) was added dropwise. The reaction
mixture was warmed to −45 °C for 15 min, and a solution of α,α′-
dibromo-o-xylene (1.00 mmol, 264 mg) in THF (1 mL) was added.
The reaction mixture was warmed to room temperature for 1 h and
stirred at room temperature for 2 days. The reaction progress was
monitored by TLC (petroleum ether/EtOAc 5/1). The reaction
mixture was quenched by addition of 0.1 mL of H2O, and the volatiles
were evaporated under reduced pressure. The residue was purified by
column chromatography on silica (petroleum ether/EtOAc 10/1 → 5/
1), resulting in 19 (199 mg, 60%) as a white solid.
tert-Butyl Isoindolin-2-ylcarbamate (10). White solid. Mp: 79−81
1
°C. H NMR (200 MHz, CDCl3): δ 7.25−7.16 (m, 4H), 6.26 (broad
s, 1H), 4.35 (s, 4H), 1.52/1.50 (s/s, 9H). 13C NMR (50 MHz,
CDCl3): δ 154.9, 138.0, 126.9, 122.2, 80.2, 60.0, 28.3. FTIR ν (cm−1):
3253, 3046, 3027, 2977, 2930, 1700, 1520, 1477, 1463, 1391, 1366,
1274, 1250, 1157, 1049, 910, 738. HRMS (ESI): m/z calcd for
C13H18N2O2 (MH+) 235.1441, found 235.1443.
tert-Butyl 2,2′-(1,2-Phenylenebis(methylene))bis(2-phenyl-
hydrazinecarboxylate) (11). White solid. Mp: 178−179 °C. 1H
NMR (200 MHz, CDCl3): δ 7.41−7.10 (m, 8H), 6.90−6.80 (m, 7H),
6.46/6.21 (broad s/broad s, 1H), 4.69 (s, 4H), 1.37 (s, 18H). 13C
NMR (50 MHz, CDCl3): δ 155.0, 149.6, 135.4, 130.9, 129.0, 127.8,
120.0, 113.8, 80.5, 54.0, 28.2. FTIR ν (cm−1): 3294, 3062, 3029, 2978,
2930, 1700, 1598, 1497, 1456, 1391, 1366, 1248, 1155, 1050, 736, 690.
HRMS (ESI): m/z calcd for C30H38N4O4 (MH+) 519.2966, found
519.2969.
9,10-Dihydrophenanthrene (12).18 Colorless oil. H NMR (200
1
MHz, CDCl3): δ 7.86 (d, J = 7.3 Hz, 2H), 7.45−7.30 (m, 6H), 2.99−
2.97 (m, 4H). 13C NMR (50 MHz, CDCl3): δ 137.4, 134.5, 128.1,
127.4, 126.9, 123.7, 29.0. FTIR ν (cm−1): 3064, 3016, 2931, 2891,
2834, 1485, 1454, 1443, 771, 743, 725.
tert-Butyl 5H-Dibenzo[c,e]azepin-6(7H)-ylcarbamate (13). Yel-
1
lowish oil. H NMR (200 MHz, CDCl3): δ 7.52−7.36 (m, 8H), 5.70
(broad s, 1H), 3.65 (s, 4H), 1.49/1.45 (s/s, 9H). 13C NMR (50 MHz,
CDCl3): δ 154.4, 141.0, 133.2, 132.8, 128.6, 127.9, 127.8, 80.2, 58.8,
28.3. FTIR ν (cm−1): 3242, 3062, 2976, 2933, 1725, 1492, 1481, 1451,
1391, 1366, 1244, 1159, 1098, 1051, 910, 753, 731. HRMS (ESI): m/z
calcd for C19H22N2O2 (MH+) 311.1754, found 311.1755.
tert-Butyl 2,2′-(Biphenyl-2,2′-diylbis(methylene))bis(2-phenyl-
1
hydrazinecarboxylate) (14). White solid. Mp: 76−77 °C. H NMR
(200 MHz, CDCl3): δ 7.60−7.26 (m, 8H), 7.16 (t, J = 7.8 Hz, 4H),
6.81 (t, J = 7.1 Hz, 2H), 6.57 (d, J = 7.0 Hz, 4H), 6.02/5.76 (broad s/
broad s, 2H), 4.47 (s, 4H), 1.48/1.31 (s/s, 18H). 13C NMR (50 MHz,
CDCl3): δ 154.5, 148.9, 140.4, 135.4, 129.8, 129.3, 129.0, 127.7, 127.4,
119.2, 112.5, 80.8, 54.9, 28.2. FTIR ν (cm−1): 3318, 3060, 3023, 2977,
2929, 1703, 1598, 1498, 1476, 1454, 1391, 1366, 1246, 1155, 1050,
1008, 909, 747, 729, 690. HRMS (ESI): m/z calcd for C36H42N4O4
(MH+) 595.3279, found 595.3281.
tert-Butyl 7-Phenyl-7,8-dihydrodibenzo[d,f ][1,2]diazocine-6(5H)-
carboxylate (15). Colorless oil. 1H NMR (200 MHz, CDCl3): δ
7.43−7.12 (m, 10H), 6.76 (t, J = 6.8 Hz, 1H), 6.63−6.56 (m, 2H),
4.78−4.28 (m, 4H), 1.31/1.25 (s/s, 9H). 13C NMR (50 MHz,
CDCl3): δ 155.1, 148.3, 142.1, 141.6, 134.2, 130.4, 129.7, 129.4, 129.3,
129.1, 128.9, 128.5, 127.8, 127.7, 127.5, 118.3, 111.2, 80.4, 55.5, 53.2,
28.2. FTIR ν (cm−1): 3062, 2973, 2931, 2870, 1700, 1597, 1498, 1479,
1454, 1384, 1365, 1320, 1167, 1136, 1089, 910, 747, 691. HRMS
(ESI): m/z calcd for C25H26N2O2 (MH+) 387.2067, found 387.2065.
tert-Butyl 2-Butyl-2-phenylhydrazinecarboxylate (16). Yellowish
1
oil. H NMR (200 MHz, CDCl3): δ 7.28−7.20 (m, 2H), 6.84−6.78
(m, 3H), 6.35/6.15 (broad s/broad s, 1H), 3.50−3.43 (m, 2H), 1.64
(quin, J = 7.4 Hz, 2H), 1.50−1.26 (m, 11H), 0.96 (t, J = 7.2 Hz, 3H).
13C NMR (50 MHz, CDCl3): δ 154.9, 149.3, 129.1, 119.0, 112.7, 80.7,
52.3, 28.5, 28.0, 20.3, 13.9. FTIR ν (cm−1): 3292, 3062, 3027, 2959,
2931, 2871, 1704, 1599, 1499, 1455, 1391, 1366, 1248, 1162, 1140,
1058, 747, 691. HRMS (ESI): m/z calcd for C15H24N2O2 (MH+)
265.1911, found 265.1911.
tert-Butyl 2-Butylhydrazinecarboxylate (17). Brownish oil. 1H
NMR (200 MHz, CDCl3): δ 5.93/4.57 (broad s/broad s, 2H), 2.80 (t,
J = 7.0 Hz, 2H), 1.46−1.33 (m, 13H), 0.87 (t, J = 6.9 Hz, 3H). 13C
NMR (50 MHz, CDCl3): δ 156.7, 80.3, 51.7, 29.8, 28.3, 20.2, 13.9.
FTIR ν(cm−1): 3306, 2960, 2932, 2871, 1704, 1476, 1456, 1392, 1366,
1280, 1253, 1165, 1045, 1019. HRMS (ESI): m/z calcd for
C9H20N2O2 (MH+) 189.1598, found 189.1598.
tert-Butyl 2,2-Dibutylhydrazinecarboxylate (18). White solid. Mp:
Compound Characterization Data. tert-Butyl 2,2′-(1,2-
Phenylenebis(methylene))bis(hydrazinecarboxylate) (9).3 Yellowish
53−55 °C. 1H NMR (200 MHz, CDCl3): δ 5.45/4.90 (broad s/broad
192
dx.doi.org/10.1021/om4009394 | Organometallics 2014, 33, 188−193

Organometallics
Article
s, 1H), 2.69 (broad s, 4H), 1.50−1.25 (m, 17H), 0.89 (t, J = 7.1 Hz,
6H). 13C NMR (50 MHz, CDCl3): δ 79.9, 58.1, 29.9, 28.1, 20.3, 13.9.
FTIR ν (cm−1): 3278, 2957, 2932, 2870, 1713, 1697, 1492, 1457,
1390, 1366, 1247, 1171, 1114, 1080, 1044, 1014. HRMS (ESI): m/z
calcd for C13H28N2O2 (MH+) 245.2224, found 245.2222.
(16) Shapiro, R. H.; Lipton, M. F.; Kolonko, K. J.; Buswell, R. L.;
Capuano, L. A. Tetrahedron Lett. 1975, 16, 1811−1814.
(17) Bredihhin, A.; Maeorg, U. Tetrahedron 2008, 64, 6788−6793.
̈
(18) Sun, C.-L.; Gu, Y.-F.; Huang, W.-P.; Shi, Z.-J. Chem. Commun.
2011, 47, 9813−9815.
Di-tert-butyl Phthalazine-2,3(1H,4H)-dicarboxylate (19).19 White
(19) Carpino, L. A. J. Am. Chem. Soc. 1963, 85, 2144−2149.
1
solid. Mp: 112−113 °C. H NMR (200 MHz, CDCl3): δ 7.26−7.11
(m, 4H), 5.12−4.87 (m, 2H), 4.60−4.32 (m, 2H), 1.53/1.51 (s/s,
18H). 13C NMR (50 MHz, CDCl3): δ 154.3, 131.7, 126.7, 126.3, 81.1,
44.9, 28.2. FTIR ν (cm−1): 3068, 2977, 2931, 2854, 1704, 1477, 1454,
1391, 1366, 1294, 1280, 1236, 1223, 1164, 1148, 1122, 1111, 1043,
1027, 857, 747, 729.
ASSOCIATED CONTENT
■
S
* Supporting Information
Figures giving 1H and 13C NMR spectra for all isolated
compounds. This material is available free of charge via the
Internet at http://pubs.acs.org.
AUTHOR INFORMATION
Corresponding Author
*E-mail for U.M.: uno.maeorg@ut.ee.
■
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This work was supported by the Estonian Science Foundation
(Grant No. 8794), the European Regional Development Fund
(Center of Excellence “Mesosystems: Theory and Applica-
tions”, No. TK114), and the Estonian Science Targeted Project
No. SF0180032s12.
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