Synthesis of an ortho-triazacyclophane: N, N ′, N ″-trimethyltribenzo-1,4,7-triazacyclononatriene

Article abstract of DOI:10.1021/jo1017074

N,N′,N″-Trimethyltribenzo-1,4,7-triazacyclononatriene has been synthesized via sequential palladium-catalyzed Buchwald-Hartwig N-arylation reactions affording the 9-membered triaza o-cyclophane in 35% overall yield. An X-ray crystal structure shows the ne

Full text of DOI:10.1021/jo1017074

pubs.acs.org/joc
Synthesis of an ortho-Triazacyclophane: N,N0,N00-Trimethyltribenzo-
1,4,7-triazacyclononatriene
Andria M. Panagopoulos,† Matthias Zeller,‡ and Daniel P. Becker*,†
†Department of Chemistry, Loyola University Chicago, 1032 West Sheridan Road, Chicago, Illinois 60660,
United States, and ‡Department of Chemistry, 1 University Plaza, Youngstown State University,
Youngstown, Ohio 44555-3663, United States
dbecke3@luc.edu
Received September 14, 2010
N,N0,N00-Trimethyltribenzo-1,4,7-triazacyclononatriene has been synthesized via sequential palladium-
catalyzed Buchwald-Hartwig N-arylation reactions affording the 9-membered triaza o-cyclophane
in 35% overall yield. An X-ray crystal structure shows the new cyclophane to have a C2-symmetric
saddle conformation, as compared to the crown conformation exhibited by the related carbocyclic
cyclotriveratrylene (CTV).
Introduction
organometallic guests within its bowl-shaped cleft.7-9 CTV
modification continues to be a significant area of study,10-13
and it has been used as a building block enabling the con-
struction of more complex cryptophanes.14-17 Although CTV
has proven to be quite useful, the molecule suffers from insol-
ubility in aqueous systems and only limited opportunities
for derivatization of the apical methylenes. Most derivatives
of CTV have been prepared by varying the groups on the
phenolic oxygens around the periphery of the molecule;
Collet was among the first to transform CTV into crypto-
phanes in this manner.18 Nierengarten addressed the aque-
ous insolubility of CTV by appending poly(ethylene glycol)
The area of supramolecular chemistry is of continued inter-
est because of a wide variety of applications including materi-
als technology, catalysis, medicine, analytical detection, and
sensing. Cyclophanes, which are supramolecular structures
comprised of aromatic units with bridging chains, have appli-
cations in molecular recognition as synthetic receptors1 and
have been used as building blocks for organic catalysts.2 There
is growing interest in the development of cyclophanes as hosts
for ionic guests.3-5
The archetypal cyclophane cyclotriveratrylene (CTV, 1), a
[1.1.1]orthocyclophane, is a commonly employed scaffold
in supramolecular chemistry6 that is readily prepared from
veratryl alcohol in acid and has been studied extensively for
its capability of binding a number of smaller organic and
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€
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49, 3848–3852.
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1999, 431–432.
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DOI: 10.1021/jo1017074
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Published on Web 10/25/2010
J. Org. Chem. 2010, 75, 7887–7892 7887
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Panagopoulos et al.
JOCArticle
FIGURE 1. Cyclotriveratrylene (CTV) and CTV-oxime derivatives.
units via the peripheral oxygens toward derivatives with biomed-
ical applications, specifically to aid in the biological delivery of
fullerenes, although the derivatives were of high molecular weight
(>3000 to >6000 amu).19 As part of our own exploration of
apex-modified CTV derivatives,20 we have isolated the crown
and saddle conformers of CTV-oxime (2a,b)21 and studied the
kinetics and thermodynamics of their interconversion between
the crown and saddle CTV-oxime derivative 2a,b22 (Figure 1).
CTV exists almost exclusively in its crown conformation (1a),
and the saddle conformer of CTV was only recently isolated and
characterized through high-temperature melt and quench tech-
niques by Zimmermann, who also studied the thermodynamic
and kinetic properties of the interconversion of the crown and
saddle CTV conformers.23 Holman24 as well as Huber25 have
identified topoisomeric cryptophanes containing blended crown
and saddle CTV moieties; Holman’s cryptophane undergoes
a conformational crown to saddle “implosion” upon thermal
liberation of its tetrahydrofuran guest.
Several heteroatom analogues of CTV and the tribenzo-
cyclononene core have been reported in which the methylene
groups have been replaced (3a-c). Trithiacyclotriveratrylene
(3a)26,27 forms complexes with copper(I),28 rhodium(III),29 and
platinum(II),30 and it also exists in a temperature and solvent-
dependent equilibrium of the crown and saddle forms. In
addition, the trioxycyclononene 3b31,32 and trimercury cyclono-
nene 3c,33 which is planar rather than crown-shaped, have also
been described. Recently, the first apical methylene aza-
substituted cyclophane was reported with the synthesis of
FIGURE 2. Analogues of CTV.
monoamine tribenzo-1-azacyclophane 3d34 which was pre-
pared as a potential benzodiazepine receptor ligand, while
Tanaka reported the synthesis of the trimethyl triaza[13]-
metacyclophane 4.35 We envisioned a derivative of the
tribenzotricyclononatriene core of CTV retaining its high
(C3v) symmetry with nitrogen atoms in place of the methy-
lenes to provide a ready handle for apical functionalization
and altering the charge on the scaffold, to enable modulation
of host-guest properties, and to facilitate attachment to sur-
faces. Furthermore, the nitrogen atoms should function as a
ligand for metals as described for the oxa- and thia-analogues
above, ultimately providing a redox-switchable host molecule.
Herein we describe the synthesis of the novel triazaorthocyclo-
phane 5a (Figure 2).
(19) Rio, Y.; Nierengarten, J. Tetrahedron Lett. 2002, 43, 4321–4324.
(20) Lutz, M. R., Jr.; Zeller, M.; Becker, D. P. Tetrahedron Lett. 2008, 49,
5003–5005.
Results and Discussion
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Lett. 2007, 48, 6368–6371.
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J. Phys. Chem. A 2009, 113, 8258.
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J. Phys. Chem. B 2004, 108, 18772–18778.
(24) Mough, S. T.; Goeltz, J. C.; Holman, K. T. Angew. Chem., Int. Ed.
2004, 43, 5631–5635.
(25) Huber, G.; Brotin, T.; Dubois, L.; Desvaux, H.; Dutasta, J.;
Berthault, P. J. Am. Chem. Soc. 2006, 128, 6239–6246.
(26) Weiss, T.; Klar, G. Z. Naturforsch., Teil B: Anorg. Chem., Org.
Chem. 1979, 34B, 448–450.
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1011–1016.
Looking retrosynthetically at the target tribenzo-1,4,7-triaza-
cyclononatriene, we envisioned four unique synthetic approaches
(Figure 3), with N-aryl bonds constructed potentially utilizing
Buchwald-Hartwig,36-39 Ullman,40 or nucleophilic aromatic
substitution (SNAR) methodologies. Route A considers the
direct trimerization of an ortho-substituted aniline. This highly
convergent synthesis has literature precedent in the work of
Tanaka35 and co-workers who synthesized metacyclophane
4 in low yield directly from a meta-substituted aniline. Ap-
proaches B and C consider a diphenlyamine derivative joining
the third ring in a double-coupling. Finally, route D describes a
linear construction of the molecule. The final intramolecular
(30) Von Deuten, K.; Klar, G. Cryst. Struct. Commun. 1981, 10, 757–764.
(31) Weiss, T.; Schulz, P.; Klar, G. Z. Naturforsch., Teil B: Anorg. Chem.,
Org. Chem., Biochem., Biophys., Biol. 1974, 29, 156–158.
(32) Von Deuten, K.; Klar, G. Z. Naturforsch., Teil B: Anorg. Chem.,
Org. Chem. 1981, 36B, 1526–1531.
(35) Ito, A.; Ono, Y.; Tanaka, K. J. Org. Chem. 1999, 64, 8236–8241.
(36) Muci, A. R.; Buchwald, S. L. Top. Curr. Chem. 2002, 219, 131–209.
(37) Wolfe, J. P.; Wagaw, S.; Marcoux, J.; Buchwald, S. L. Acc. Chem.
Res. 1998, 31, 805–818.
(33) Woodard, C. M.; Hughes, G.; Massey, A. G. J. Organomet. Chem.
1976, 112, 9–19.
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Perkin Trans. 1 1996, 741–745.
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(39) Hartwig, J. F. Acc. Chem. Res. 1998, 31, 852–860.
(40) Ley, S. V.; Thomas, A. W. Angew. Chem., Int. Ed. 2003, 42, 5400–
5449.
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FIGURE 3. Retrosynthetic strategies toward the tribenzo-1,4,7-triazacyclononatriene ring system.
SCHEME 1. 1 ꢀ 2 Synthesis Attempt from Bis(2-bromophenyl)-
macrocyclization of the 9-membered ring should be aided by the
limited degrees of freedom imposed by the aryl rings.
amine
For the highly convergent approach (A), we subjected 2-
iodoaniline and 2-bromoaniline to a variety of Buchwald-
Hartwig cross-coupling conditions. Employing Pd(OAc)2,
P(t-Bu)3 as the ligand, and sodium tert-butoxide as the base in
dioxane under reflux as a typical example afforded only phena-
zine in 92% isolated yield via facile air oxidation of the
metastable dihydrophenazine.41 Tanaka was able to synthesize
the triazametacyclophane 4 from the corresponding secondary
N-methyl derivative but not from the unsubstituted (primary)
aniline. Therefore, we attempted the convergent trimerization
employing a secondary aniline utilizing similar Pd-catalyzed
cross-coupling conditions. N-Methyl-2-bromoaniline under
Buchwald-Hartwig conditions produced a complex mixture
from which only dehalogenated dimer and dehalogenated
tetramer were isolated in extremely low yields (0.3% and 2%,
respectively). We were unable to detect the desired product in
any mixture derived from the direct trimerization approach
under a variety of Buchwald-Hartwig conditions, even when
an authentic sample was available for direct comparison from
the linear approach below.
Given the facile formation of phenazine in the trimerization
attempt, we focused on the moderately convergent [2 ꢀ 1]
syntheses (routes B and C). Subjecting bis(2-bromophenyl)-
amine to Buchwald-Hartwig conditions, carbazole 6 was
formed as the major product via a reductive coupling in 65%
yield. In addition, the phenazine derivative 7 was produced in
4% via intramolecular N-arylation involving a 6-membered
ring formation. The monocoupled triaryl product 8 was also
isolated in 4% yield (Scheme 1).
SCHEME 2. 1 ꢀ 2 Synthesis Attempt from N-(2-Aminophenyl)-
1,2-benzenediamine
1,2-dibromobenzene resulted in 5,10-dimethyldihydrophena-
zine (10) as the only isolated product (Scheme 2).
The inability to produce the desired cyclophane utilizing
convergent approaches led us to pursue a linear synthesis
(route D) with sequential protection of the aniline nitrogens
to avoid 6-membered ring formation. Scheme 3 outlines the
successful synthesis of the N,N0,N00-trimethyltriazaorthocyclo-
phane 5a in 35% overall yield. A modification of the Buchwald-
Hartwig N-arylation method used by Tietze42 employing 1,2-
bromochlorobenzene and o-nitroaniline gave 2-chloro-N-(2-
nitrophenyl)benzenamine 11 in 99% yield. The aniline was
protected by methylation using KOH and Me2SO4 in refluxing
acetone45 to give the N-methyldiphenylamine 12 in quantita-
tive yield without the need for further purification. Compound
12 was easily reduced with the general method of Sanz46
using CuCl and KBH4 in dry MeOH at room temperature to
give 13 in quantitative yield, again without further purifica-
tion, whereas more common reduction methods such as Pd/C
and H2NNH2 or hydrogenation gave dehalogenated or
A similar convergent synthesis attempt beginning with
N-(2-aminophenyl)-1,2-benzenediamine42,43 is shown in
Scheme 2. The diamine and the 1,2-dihalide were subjected to
palladium-catalyzed N-arylation producing phenazine (9) in 20%
yield as the only isolated product. When an N-methyl blocking
group was added44 to the central nitrogen, attempted N-arylation
of the N-(2-aminophenyl)-N-methyl-1,2-benzenediamine with
(41) Bidman, T. A. Russ. J. Gen. Chem. (Trans. Zh. Obshch. Khim.) 2004,
74, 1433–1434.
(42) Tietze, M.; Iglesias, A.; Merisor, E.; Conrad, J.; Klaiber, I.; Beifuss,
U. Org. Lett. 2005, 7, 1549–1552.
(43) Black, D. S.; Rothnie, N. E. Aust. J. Chem. 1983, 36, 1141–1147.
(44) Wilshire, J. F. K. Aust. J. Chem. 1988, 41, 995–1001.
(45) Wilshire, J. F. K. Aust. J. Chem. 1988, 41, 995–1001.
(46) Sanz, R.; Fernandez, Y.; Castroviejo, M. P.; Perez, A.; Fananas, F. J.
J. Org. Chem. 2006, 71, 6291–6294.
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SCHEME 3.a Linear Synthesis of N,N0,N00-Trimethyltribenzo-1,4,7-triazacyclononatriene 5a
aReaction conditions: (a) Pd(dba)2, BINAP, tol, 24 h; (b) KOH, Me2SO4, acetone; (c) CuCl, KBH4, MeOH; (d) KH, MeI, DMF; (e) Pd(dba)2,
BINAP, 1:5 t-BuOH/tol.
demethylated reduction products. The aniline 13 was coupled to
iodonitrobenzene using the previously established Buchwald-
Hartwig conditions to produce triarylamine 14 in 80% yield.
Compound 14 was subjected to methylation using KH and MeI
followed by reduction of the nitro group with CuCl and KBH4
to give products 15 and 16, respectively. The triarylaniline was
successfully closed to the 9-membered cyclophane through the
use of Buchwald-Hartwig coupling in a microwave reactor to
afford the N,N0-dimethyltriazaorthocyclophane 5b in 50% iso-
lated yield after purification. The last step is a macrocyclization
with unique steric demands and application of thermal condi-
tions gave significant decomposition, low yields (<5%), poor
conversion and extremely long reaction times (>5 days). How-
ever, we found that application of microwave conditions in this
step gave moderate to good yields. The third apical nitrogen was
methylated employing KH and MeI to give a quantitative yield
FIGURE 4. X-ray structure of compound 5b with atom labels;
of the N,N0,N00-trimethyltriazaorthocyclophane 5a without the
thermal ellipsoids are at the 50% probability level.
need for further purification (Scheme 3).
The structure of the N,N0-dimethyl derivative 5b was
1
assigned on the basis of the equivalent methyls in the H
NMR at δ 2.68 (6H, s) and the appropriate exact mass (MHþ)
observed by mass spectrometry. The structure was ultimately
confirmed by single-crystal X-ray analysis revealing a C2-sym-
metric saddle (Figure 4). The 1H NMR of the N,N0,N00-trimeth-
yl dervative 5a reveals the high C3v symmetry with signals at
δ 6.90 (12H, s) and δ 2.91 (9H, s) and manifesting the similarity
of protons ortho and meta to the nitrogen, leading to a
fortuitous singlet for all 12 aromatic protons.
In conclusion, we have constructed the new triazacyclo-
phane, tribenzo-1,4,7-triazacyclononatriene 5b, in seven
steps via palladium-catalyzed C-N amination, followed by
alkylation and reduction, and reiteration of this sequence in
order to obtain the triaryl precursor to the final palladium-
catalyzed cyclization to the 9-membered cyclophane. Alkylation
of 5b gives the C3v-symmetric N,N0,N00-trimethyltriazaortho-
cyclophane and demonstrates the ability to function-
alize the cyclophane at the apex in order to modulate its
physicochemical properties. We envision that the new tria-
zacyclophane will complement the familiar carbocyclic
framework of CTV with greater versatility, including the
ability to bind cationic species in the apex analogous to metal
complexes of the well-known triazacyclononene (TACN)
derivatives that have utility as MRI contrast agents47,48
and radioimmunotherapy agents.49 These studies are in
progress and will be reported in due course.
Experimental Section
General Experimental Methods. All solvents were distilled
prior to use. All reagents were used without further purification
unless otherwise noted. All Pd- and Cu-catalyzed reactions were
conducted under an inert atmosphere of argon, and all other
reactions were conducted under a nitrogen atmosphere. Sorbent
Technologies silica gel 60A, 40-75 μm (200 ꢀ 400 mesh)
was used for column chromatography. Sorbent Technologies
(47) Chong, H.; Garmestani, K.; Bryant, L. H., Jr.; Milenic, D. E.;
Overstreet, T.; Birch, N.; Le, T.; Brady, E. D.; Brechbiel, M. W. J. Med.
Chem. 2006, 49, 2055–2062.
(48) Levy, S. G.; Jacques, V.; Zhou, K. L.; Kalogeropoulos, S.; Schumacher,
K.;Amedio, J. C.; Scherer, J. E.;Witowski, S. R.; Lombardy, R.; Koppetsch, K.
Org. Process Res. Dev. 2009, 13, 535–542.
(49) Chong, H.; Ma, X.; Le, T.; Kwamena, B.; Milenic, D. E.; Brady,
E. D.; Song, H. A.; Brechbiel, M. W. J. Med. Chem. 2008, 51, 118.
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aluminum-backed silica gel 200 μm plates were used for TLC.
142.2, 136.9, 130.7, 130.68, 127.4, 125.5, 123.6, 121.9, 118.6, 115.8,
41.1; IR (CDCl3) 3440 (NH2), 3351 (NH2); HRMS (MHþ) calcd
for C13H13N2Cl 233.0767, found 233.0791.
1H NMR spectra were obtained utilizing a 300 MHz spectro-
meter with trimethylsilane (TMS) as the internal standard. 13
C
N1-(2-Chlorophenyl)-N1-methyl-N2-(2-nitrophenyl)benzene-1,2-
diamine (14). Compound 13 (0.842 g, 3.62 mmol), o-iodonitro-
benzene (1.35 g, 5.43 mmol), Pd(dba)2 (0.104 g, 5% mol), BINAP
(0.170 g, 7.5%), Cs2CO3 (2.35 g, 7.42 mmol), and12 mLoftoluene
were placed in a pressure tube. The mixture was purged with argon
at rt for 15 min, and the tube was then sealed and placed in a
preheated oil bath at 80-90 °C for 30 h. After TLC showed
consumption of 13, the reaction mixture was filtered through a
pad of silica gel eluting with 90/10 EA/DCM. The solvent was then
removed under vacuum. The crude product was then purified by
column chromatography on silica gel eluting with 1/99 Et2O/
petroleum ether to afford the desired product 14 as a red crystalline
solid (0.785 g, 80%): mp 141-145 °C; 1H NMR (300 MHz,
CDCl3) δ 9.03 (1H, bs), 8.07 (1H, dd, J=8.7, 1.5 Hz), 7.32-7.19
(4H, m), 7.12-6.99 (5H, m), 6.90 (1H, ddd, J=8.0, 6.9, 2.2 Hz),
6.68 (1H, ddd, J=8.4, 6.9, 1.2 Hz), 3.16 (3H, s); 13CNMR(75MHz,
CDCl3) δ 147.2, 145.1, 142.4, 135.2, 131.6, 130.7, 129.5, 127.4,
126.5, 126.5, 126.0, 124.8, 124.0, 123.2, 121.7, 117.0, 115.8, 40.6;
IR (CDCl3) 3344 (NH), 1503 (NO2); HRMS (MHþ) calcd for
C19H16N3O2Cl 354.1009, found 354.0961.
NMR spectra were obtained using a 75 MHz spectrometer. A
CEM Discover Microwave model no. 908005 was used for all
microwave (MW) reactions. Infrared (IR) spectra were deter-
mined as a solution in CHCl3. Single-crystal X-ray diffraction
data were collected on a charge-coupled-device (CCD) dif-
fractometer with a liquid nitrogen vapor cooling device. Data
were collected at 100 K with graphite-monochromated Mo
˚
KR X-ray radiation (λ = 0.71073 A). Data were collected,
reduced, and corrected for absorption using multiscan meth-
ods. The structure was solved by direct methods and refined by
full matrix least-squares against F2 with all reflections. Non
hydrogen atoms were refined anisotropically. C-H hydro-
gen atom positions were idealized. Additional details of the
structure determination can be found in the Supporting
Information.
(20-Chlorophenyl)(2-nitrophenyl)amine (11). Compound 11
was synthesized according to the general procedures outlined
by Tietze et al.42 A pressure tube was charged with o-nitroaniline
(0.690 g, 5 mmol), o-bromochlorobenzene (0.60 mL, 5.00 mmol),
Pd(dba)2 (0.144 g, 5%), BINAP (0.233 g, 7.5%), Cs2CO3 (3.26 g,
10 mmol), and toluene (10 mL). The mixture was purged with
argon for 10 min at rt, and the pressure tube was sealed. The
reaction was sealed and placed in a preheated oil bath. The tempera-
ture was brought to 120 °C and the reaction stirred for 24 h. TLC
showed complete consumption of o-nitroaniline, and the reaction
mixture was filtered through a pad of SiO2 using 5/5/90 EA/DCM/
petroleum ether as the eluent. The solvent was removed under
vacuum and no further purification was needed to give the product
as an orange solid (1.24 g, 100%) which was identical to the material
reported in the literature42 by 1H NMR.
2-Chloro-N-methyl-N-(2-nitrophenyl)aniline (12). Following
the general method of Wilshire,45 compound 11 (1.25 g, 5 mmol)
was stirred at rt in acetone (16 mL), and freshly crushed KOH
(1.23 g, 22.0 mmol) was added to the stirring mixture. After the
reaction was brought to reflux, Me2SO4 (2.18 mL, 23 mmol) was
added dropwise via syringe over 10 min. The mixture was
allowed to stir at reflux for 1 h. The reaction was cooled to rt,
and 20 mL of 10 M NaOH was added to the solution. After 1 h,
the mixture was quenched with 10 mL of H2O and extracted
with 3 ꢀ 10 mL of DCM. The organic layers were combined and
dried over Na2SO4. The solvent was removed under vacuum,
and the mixture was placed in an 80 °C oil bath under vacuum to
remove excess Me2SO4. No further purification was needed to
obtain the desired compound 12 as an off-white solid (1.31 g,
100%): mp 73-75 °C; 1H NMR (300 MHz, CDCl3) δ 7.68 (1H,
dd, J=8.1, 1.5 Hz), 7.54 (1H, ddd, J=8.7, 7.3, 1.7 Hz), 7.42 (1H,
dd, J=7.8, 1.5 Hz), 7.19 (1H, dd, J=7.7, 1.7 Hz), 7.14-7.11 (2H,
m), 7.06 (1H, dd, J=7.7, 1.9 Hz), 7.0 (1H, ddd, J=8.2, 7.3, 1.1
Hz); 13C NMR (75 MHz, CDCl3) δ 145.0, 143.0, 133.2, 131.3,
130.9, 128.7, 127.9, 126.7, 126.2, 125.9, 120.8, 120.6, 41.1; IR
(CDCl3) 1520 (NO2); HRMS (MHþ) calcd for C13H11O2N2Cl
263.0509, found 263.0604.
N1-(2-Chlorophenyl)-N1,N2-dimethyl-N2-(2-nitrophenyl)benzene-
1,2-diamine (15). A solution of compound 14 (0.405 g, 1.14 mmol)
in 4 mL of DMF was added to KH (0.46 g, 3.42 mmol). Upon
addition, the solution turned from orange to deep purple. The mix-
ture was stirred at rt for 10 min, and then MeI (0.4 mL, 5.7 mmol)
was added dropwise via syringe. The reaction was stirred at rt until
the solution returned to a yellow color. The reaction was then
quenched with H2O and extracted with 3 ꢀ 15 mL of EA. The
organic layers were combined and washed with 3 ꢀ 15 mL of H2O,
brine, and then H2O again to remove excess DMF. The organic layer
was then dried over MgSO4, and the solvent was removed under
reduced pressure to give the desired product as a yellow powder with
1
no further purification necessary (0.362 g, 86%): H NMR (300
MHz, CDCl3) δ 7.63 (1H, dd, J = 8.0, 1.7 Hz), 7.36 (1H, ddd,
J=8.8, 7.3, 1.8 Hz), 7.29-7.19 (2H, m), 7.12 (1H, dd, J=8.2,
1.7 Hz), 7.07-6.92 (5H, m), 6.88 (1H, ddd, J=8.2, 7.3, 1.2 Hz), 6.81
(1H, dd, J=7.8, 1.2 Hz), 3.32 (3H, s), 3.27 (3H, s); 13C NMR
(75 MHz, CDCl3) δ 146.5, 143.5, 142.1, 138.8, 132.7, 131.0, 128.7,
127.6, 126.2, 124.2, 124.1, 123.7, 123.1, 120.4, 118.8, 38.5, 38.1; IR
(CDCl3) 1520 (NO2); HRMS (MHþ) calcd for C20H18N3O2Cl
368.1166, found 368.1091.
N1-(2-Aminophenyl)-N2-(2-chlorophenyl)-N1,N2-dimethylbenzene-
1,2-diamine (16). Following the general procedure of Sanz,46 CuCl
(0.460 g, 4.65 mmol) was added to a stirring solution of compound 15
(0.570 g, 1.55 mmol) in MeOH (15.5 mL) at rt. KBH4 (0.836 g,
15.5 mmol) was then added in portions. The reaction stirred at rt until
the solution became clear, 2-4 h. The reaction was then quenched
with H2O and extracted 3 ꢀ 30 mL of 90/10 EA/DCM. The organic
layers were combined and dried over Na2SO4, and the solvent was
removed to give the desired product as a reddish-brown oil (0.450 g,
86%): 1H NMR (300 MHz, CDCl3) δ 7.3 (1H, dd, J=8.0, 1.9 Hz),
7.15 (1H, 8.5, 7.3, 1.7 Hz), 7.06-6.88 (7H, m), 6.83-6.73 (2H, m),
6.60 (1H, dd, J=7.3, 1.5 Hz); 13C NMR (75 MHz, CDCl3) δ 147.0,
143.4, 142.2, 141.1, 136.7, 131.1, 128.2, 127.3, 124.6, 124.4, 124.3,
123.4, 123.4, 123.2, 122.6, 122.5, 118.7, 116.1, 39.4, 38.6; IR (CDCl3)
3441 (NH2), 3368 (NH2); HRMS (MHþ) calcd for C20H20N3Cl
338.1424, found 338.1379.
N-Methyl-2-(10-methylphenazin-5(10H)-yl)aniline (5b). Com-
pound 16 (0.090 g, 0.27 mmol), Pd(dba)2 (0.016 g, 10% mol),
BINAP (0.034 g, 20% mol), and Cs2CO3 (0.132 g, 0.41 mmol) in
3 mL of 1:1 toluene/t-BuOH were added to a 10 mL microwave
tube. The mixturewas purged with Ar for 5 min while stirring at rt.
The MW settings were as follows: P= 250 W, time = 60 min,
temp=130 °C; PSI = 250. The reaction mixture was checked by
TLC after each 60 min run. When TLC showed consumption of
N1-(2-Chlorophenyl)-N1-methylbenzene-1,2-diamine (13). Follow-
ing the general procedure of Sanz,46 CuCl (0.137 g, 1.38 mmol) was
added to a stirring solution of compound 12 (0.121 g, 0.46 mmol) in
MeOH (4.6 mL) at rt. KBH4 (0.174 g, 3.22 mmol) was then added
in portions. The reaction was stirred at rt until the solution became
clear (2-4 h). The reaction was quenched with H2O and extracted
with 3ꢀ15 mL of 90/10 EA/DCM. The organic layers were
combined and dried over Na2SO4, and the solvent was removed to
give the desired product as a brown oil (0.107 g, 100%): 1H NMR
(300 MHz, CDCl3) δ7.32 (1H, dd, J=7.8, 1.4Hz), 7.25(1H, dd, J=
7.3, 1.7 Hz), 7.22 (1H, dd, J=7.1, 1.7 Hz), 7.16 (1H, dd, J=8.0, 1.6
Hz), 7.00-6.95 (2H, m), 6.76 (1H, ddd, J=9.3, 7.7, 1.4 Hz), 6.67
(1H, ddd, J=8.9, 7.6, 1.5 Hz); 13C NMR (75 MHz, CDCl3) δ147.6,
J. Org. Chem. Vol. 75, No. 22, 2010 7891

Panagopoulos et al.
JOCArticle
starting material 16 (240 min total), the mixture was filtered
through a pad of silica gel eluting with 90/10 EA/DCM. The
solvent was removed under reduced pressure. The product was
then purified by column chromatography eluting with DCM/
petroleum ether gradient to give the cyclized product 5b as a white
powder (41 mg, 50%): 1H NMR (300 MHz, CDCl3) δ 7.05-6.95
(6H, m), 6.87 (1H, d, J = 1.1 Hz), 6.84 (1H, d, J = 1.1 Hz),
6.75-6.73 (4H, m), 5.82 (1H, bs), 2.68 (6H, s); 13C NMR (75
MHz, CDCl3) δ 144.2, 141.4, 140.2, 127.8, 126.1, 121.9, 121.1,
118.4, 117.5, 39.9; IR (CDCl3) 3382 (NH), 1499 (CdC); HRMS
(MHþ) calcd for C20H19N3 302.1579, found 302.1573. Single
crystals for X-ray structural analysis were grown by the slow
evaporation of a solution of 5b DCM.
stirred at rt until effervescence ceased (about 5 min), and MeI
(0.022 mL, 0.35 mmol) was added dropwise via syringe. The
reaction was allowed to stir at rt for 2 h, during which time the
solution became faint yellow. The reaction mixture was
quenched with deionized H2O and extracted with EA (3 ꢀ 10
mL). The organic layers were combined and dried over Na2SO4,
and the solvent was removed under reduced pressure to give the
1
product 5a as a pale yellow oil (0.021 g, 95% yield): H NMR
(300 MHz, CDCl3) δ 6.92 (12H, s), 2.93 (9H, s); 13C NMR (75
MHz, CDCl3) δ 144.0, 122.9, 121.0, 40.6; IR (CDCl3) 3052
(CH), 1605 (CdC) HRMS (MHþ) calcd for C21H21N3 316.1808,
found 316.1799.
5,10,15-Trimethyl-10,15-dihydro-5H-tribenzo[b,e,h][1,4,7]tri-
azonine (5a). A solution of N,N0-dimethyl triazacyclophane 5b
(0.018 g, 0.07 mmol) in 0.2 mL of DMF was added to KH (0.028 g,
0.21 mmol). Upon addition, effervescence ensued, and the
solution turned a pale pinkish-purple color. The mixture was
Supporting Information Available: X-ray crystal structure
coordinates and files for compound 5b (CIF). 1H and 13C NMR
spectra are available for all compounds in the eight-step linear
synthesis. This material is available free of charge via the
Internet at http://pubs.acs.org.
7892 J. Org. Chem. Vol. 75, No. 22, 2010