Pd2dba3/P(i-BuNCH2CH2) 3N: A highly efficient catalyst for the one-pot synthesis of trans-4-N,N-diarylaminostilbenes and N,N-diarylaminostyrenes

Article abstract of DOI:10.1016/j.tet.2005.06.117

A Pd₂dba₃/P(i-BuNCH₂CH₂) ₃N catalyzed one-pot synthesis of unsymmetrically substituted trans-4-N,N-diarylaminostilbenes and both symmetrically and unsymmetrically substituted N,N-diarylaminostyrene derivatives is reported. The procedure involves two or more palladium catalyzed sequential coupling reactions (an amination and an inter-molecular Heck reaction) in one-pot using the same catalyst system with two different aryl halides, including aryl chlorides and hetero aryl halides as the coupling partners.

Full text of DOI:10.1016/j.tet.2005.06.117

Tetrahedron 61 (2005) 9775–9782
Pd2dba3/P(i-BuNCH2CH2)3N: a highly efficient catalyst for the
one-pot synthesis of trans-4-N,N-diarylaminostilbenes and
N,N-diarylaminostyrenes
*
Mecheril V. Nandakumar and John G. Verkade
Department of Chemistry, 1275 Gilman Hall, Iowa State University, Ames, Iowa 50011, USA
Received 1 May 2005; revised 23 June 2005; accepted 24 June 2005
Available online 25 August 2005
Abstract—A Pd2dba3/P(i-BuNCH2CH2)3N catalyzed one-pot synthesis of unsymmetrically substituted trans-4-N,N-diarylaminostilbenes
and both symmetrically and unsymmetrically substituted N,N-diarylaminostyrene derivatives is reported. The procedure involves two or
more palladium catalyzed sequential coupling reactions (an amination and an inter-molecular Heck reaction) in one-pot using the same
catalyst system with two different aryl halides, including aryl chlorides and hetero aryl halides as the coupling partners.
q 2005 Elsevier Ltd. All rights reserved.
1. Introduction
Palladium catalyzed C–C and C-hetero-atom bond forming
reactions represent one of the most powerful methods for
the synthesis of several complex molecular structures such
as gilvocarcines and pradimicines.1 The scope of these
methods has been enhanced by the discovery of new ligands
N,N-Diarylaminostilbenes are versatile compounds that
have found interesting applications in the field of
that facilitate coupling reactions more efficiently under mild
reaction conditions. In recent years our explorations of the
photochemistry as electro photographic photoconductors
chemistry of commercially available proazaphosphatranes
and photoreceptors.9 A series of recent reports showed that
the fluorescence enhancement of N,N-diarylaminostilbenes
such as 1, first synthesized in our laboratories,2 have shown
them to be efficient ligands in palladium-catalyzed
has been achieved by N-phenyl substitution10 and also their
N-arylation,3 Suzuki4 and Stille5 couplings, including
use as new ionophores for transition metals.11 The
those of neutral as well as electron-rich and electron-
deficient aryl chlorides. Moreover, proazaphosphatranes can
traditional approaches to the synthesis of these compounds
begin from aniline and the corresponding aryl halides via a
also function as strong non-ionic stoichiometric bases that
facilitate a variety of useful organic transformations.6
multi step process.12 Recently, the synthesis of trans-4-N,N-
diarylaminostilbenes from the corresponding halostilbenes
Recently, palladium-catalyzed sequential coupling
or aminostilbenes, using palladium catalyzed amination
reactions, has also been reported.10,11
reactions have emerged as a powerful tool for the synthesis
of complex organic molecules from readily available
starting materials in a single pot reaction.7 Among them,
Very recently, we disclosed in preliminary form an efficient
the palladium-catalyzed synthesis of N-aryl-2-benzylindo-
one-pot procedure for the synthesis of trans-4-N,N-
lines via a sequential N-arylation/cyclization/C-arylation
reaction between 2-allylaniline and aryl halides demon-
diarylaminostilbenes via a sequential double amination/
arylation protocol using Pd2dba3/1 as the catalyst.13 In this
strated the importance of such reactions in modern synthetic
chemistry.8
full paper we report the results of our detailed investigation
of the one-pot synthesis of unsymmetrically substituted
trans-4-N,N-diarylaminostilbenes and both symmetrically
and unsymmetrically substituted N,N-diarylaminostyrenes.
Furthermore, we report the synthesis of dibenz[b,d]azepine
via a palladium-catalyzed one-pot amination/Suzuki
reaction.
Keywords: Proazaphosphatranes; Palladium; Amination; C–C Coupling;
trans-4-N,N,-Diarylaminostilbenes; Heck reaction.
*
Corresponding author. Tel.: C1 515 294 5023; fax: C1 515 294 0105;
e-mail: jverkade@iastate.edu
0040–4020/$ - see front matter q 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2005.06.117

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M. V. Nandakumar, J. G. Verkade / Tetrahedron 61 (2005) 9775–9782
2. Results and discussion
The products in entries 5 and 7 are novel and their structures
1
were confirmed on the basis of their H and 13C NMR and
2.1. One-pot synthesis of unsymmetrically substituted
trans-4-N,N-diarylaminostilbenes (identical aryl groups
on the nitrogen)
their high-resolution mass spectra. The yield for 5a (86%) is
comparable to that reported in a patented procedure (89%)
involving the single-step reaction of 4-methyldiethylbenzyl-
phosphonate with 4-N,N-diphenylaminobenzaldehyde.14
However, the yield of 5a is substantially better than that
attained in the same patent via the Wittig reaction of
4-methylbenzyltriphenylphosphonium chloride with the
aforementioned aldehyde (72%) and also to the overall yield
(46%) reported for an earlier three-step synthesis.14 Although
the remaining compounds in entries 2, 3, 4, 6, and 8 were
reported earlier,9,15 no yields were provided. The difference in
reactivity of 4-aminostyrene at different temperatures under
our reaction conditions allowed us to couple a variety of aryl
halides at the nitrogen and the double bond to synthesize
unsymmetrically substituted title compounds.
The optimized reaction conditions for the one-pot synthesis
of symmetrically and unsymmetrically substituted trans-4-
N,N-diarylaminostilbenes have previously been reported.13
From these experiments, it is evident that the title
compounds were formed via a double amination, followed
by an inter-molecular Heck reaction. Thus, the reaction of 2
with 2 equiv of the first aryl halide 3 completed the double
amination as judged by TLC (Scheme 1). The subsequent
Heck reaction was initiated by adding 1.2 equiv of the
second aryl halide 4 followed by increasing the temperature
to 110 8C for an additional 16 h (see Table 1 for details).
Scheme 1.
Table 1. One-pot synthesis of unsymmetrically substituted trans-4-N,N-diarylaminostilbenes
Entry
Aryl halide (3)
Time (h)
Temperature T
(8C)
Aryl halide (4)
Yield (%)a,b
1
2
3
3
60
60
86 (46)c
60c
3
4
5
6
7
8
2
2
2
3
3
3
85
85
85
60
60
60
83
91
75
44
43
81
a Isolated yield, average of two runs.
b Reaction conditions: Pd2(dba)3 (2 mol%), 1 (4 mol%), NaO-t-Bu (3.5 equiv), aryl halide 3 (2 equiv), aryl halide 4 (1.2 equiv), 10 mL of dry toluene, argon
atmosphere.
c Literature yield.

M. V. Nandakumar, J. G. Verkade / Tetrahedron 61 (2005) 9775–9782
9777
2.2. One-pot synthesis of unsymmetrically substituted
trans-4-N,N-diarylaminostilbenes (different aryl groups
on nitrogen)
Encouraged by the results obtained via Scheme 1, we
investigated the reaction of 2 with different aryl halides by
changing the mode of coupling, namely, by carrying out
mono-amination using the first aryl halide followed by the
second amination and inter-molecular Heck reaction, by
addition of the second aryl halide and heating at 110 8C for
an additional 16 h (Scheme 2). This reaction was also found
to be quite general, allowing the synthesis of a variety of the
title compounds using the same protocol.
Scheme 3.
literature for the synthesis of N,N-diarylaminostyrenes
possessing identical aryl groups on the nitrogen, but most
of these approaches are multi-step procedures.17b It is
evident from the literature that a simple, mild, and efficient
one-pot procedure for the synthesis of these compounds
would be very useful. Herein, we report such a protocol
using the same catalyst system employed earlier in this
paper and the results are collected in Scheme 3 (Table 2).
Our yield of 78% for 6a is lower than that reported in a
patent,9 which involved the reaction of 4-[N-(4-methylphe-
nyl)-N-phenylamino]benzaldehyde with diethylbenzylphos-
phonate (91%). It should be noted that the higher literature
yield9 for 6a was achieved in a single reaction involving two
reactants, one of which required prior synthesis. When this
requirement is taken into account, the overall literature yield
is 50%16 compared with our one-pot yield of 78%. The
compounds in entries 6 and 10 are novel, while the products
in entries 4 and 9 were reported previously,15 although no
yield was given. It is also worthy of note that although when
the less reactive aryl chlorides were used as the first aryl
halide (entries 7, 8, and 9), the yields for the target
compounds were still excellent although a higher tempera-
ture and longer reaction time was required. It may be noted
that while the application of less expensive aryl chlorides
further reduces the cost of the total procedure, additional
energy costs would be incurred.
The compounds in entries 5 and 6 are novel and the
structures of the products were confirmed on the basis of
their spectral data. The yields of N,N-diarylaminostyrenes
obtained in entries 1, 2, and 8 using our protocol are better
than the two step procedure reported in a patent, which
involve a palladium-catalyzed amination to synthesize the
corresponding 4-chlorotriphenylamine followed by a
Grignard reaction with vinyl chloride.17b The products in
entries 3 and 7 were reported in patents,19 but no yields were
given. The reaction of less reactive 4-chlorotoluene also
afforded 7 in 78% yield, using the same amount of catalyst
loading, but an elevated temperature and a longer reaction
time was required (Table 3, entry 8).
2.3. One-pot synthesis of diarylaminostyrenes with
identical aryl groups on the nitrogen
2.4. One-pot double amination for the synthesis of
unsymmetrically substituted N,N-diarylaminostyrenes
As with N,N-diarylaminostilbenes, N,N-diarylaminostyrenes
have also been used as hole-transport materials for organic
electroluminescent devices and electrophotographic photo-
receptors.17 Moreover, this class of compounds serves as a
precursor for the synthesis of a variety of photo chemically
valuable target molecules such as N,N-diarylaminostil-
benes, which are building blocks for the synthesis of
oligo(phenylenevinylene) (OPV) dyes containing diphenyl-
amino substituents.18 Several methods are available in the
Unlike symmetrically substituted N,N-diarylaminostyrenes,
a general procedure for the synthesis of unsymmetrically
substituted N,N-diarylaminostyrenes is not known in the
literature, owing primarily to the difficulty in controlling the
mono-amination step in known procedures such as Ullmann
coupling followed by a Vilsmeir and Wittig reaction
sequence.
Scheme 2.

9778
M. V. Nandakumar, J. G. Verkade / Tetrahedron 61 (2005) 9775–9782
Table 2. One-pot synthesis of unsymmetrically substituted trans-4-N,N-diarylaminostilbenes
Entry
Aryl halide (3)
Time (h)
Temperature T
(8C)
Aryl halide (4)
Yield (%)a,b
1
2
3
4
5
3
3
3
3
3
60
60
60
60
85
78 (50)c
79
52
81
50
6
3
85
71
7
8
12
12
110
110
44
71
9
12
110
110
65
74
10
0.5
a Isolated yield, average of two runs.
b Reaction conditions: Pd2(dba)3 (2 mol%), 1 (4 mol%), NaO-t-Bu (3.5 equiv), aryl halide 3 (2 equiv), aryl halide 4 (1.2 equiv), 10 mL of dry toluene, argon
atmosphere.
c Literature yield.
We were able to synthesize several derivatives of 8 with two
different aryl groups on nitrogen in a one-pot multi-
component reaction using the Pd2dba3/1 as catalyst system,
and aryl bromides and aryl chlorides as the two coupling
Table 3. One-pot synthesis of symmetrically substituted N,N-diarylami-
nostyrenes
substrates. The success of this reaction relies on the fact that
the amination using an aryl bromide was completed in 2–3 h
at 60–80 8C, whereas the aryl chlorides required a minimum
of 110 8C to couple. In a typical procedure, the reaction of
4-aminostyrene with 1-bromo-4-tert-butyl benzene and
4-chlorotoluene afforded product 8a. The reaction mixture
was heated at 85 8C for 2 h, during which time mono-
amination was completed as judged by TLC. Raising the
temperature to 110 8C for another 16 h completed the
synthesis of 8a in 80% yield (entry 1 in Table 4).
Entry
Aryl halide
Time
(h)
Temperature Yield
(%)a,b
T (8C)
1
2
3
3
60
90 (78)c
85
85
86 (77)c
86c
3
4
3
3
All the products in Table 4 are novel and their structures
85
81
1
were assigned on the basis of their H and 13C NMR, and
their HRMS spectra. As with other aryl chlorides, sterically
hindered examples such as 2-chlorotoluene and 2-chloro-p-
xylene were equally reactive, affording the coupled products
in moderate to good yields (Table 4, entries 3–5) (Scheme 4).
5
6
3
3
85
85
91
78
7
8
12
16
100
110
86
78
a Isolated yield, average of two runs.
b Reaction conditions: Pd2(dba)3 (2 mol%), 1 (4 mol%), NaO-t-Bu
(2.5 equiv), aryl halide 3 (2.1 equiv), 10 mL of dry toluene, argon
atmosphere.
c Literature yield.
Scheme 4.

M. V. Nandakumar, J. G. Verkade / Tetrahedron 61 (2005) 9775–9782
Table 4. One-pot synthesis of unsymmetrically substituted N,N-diarylaminostyrenes
9779
Entry
1
Aryl halide (3)
Aryl halide (4)
Yield (%)a,b
80
2
3
4
5
81
66
53
73
68
6
a Isolated yield, average of two runs.
b Reaction conditions: Pd2(dba)3 (2 mol%), 1 (4 mol%), NaO-t-Bu (2.5 equiv), aryl halide 3 (1 equiv), aryl halide 4 (1.2 equiv), 10 mL of dry toluene, 2 h at
85 8C and then the temperature was raised to 110 8C for 16 h, argon atmosphere.
2.5. Synthesis of 5,6-dihydro-7H-dibenz[b,d]azepine
3. Conclusion
The Pd2dba3/1 ligand system has been shown to be useful
for the one-pot synthesis of a variety of symmetrically and
unsymmetrically substituted trans-4-N,N-diarylaminostil-
benes and for N,N-diarylaminostyrenes. Interestingly, the
same catalyst system is used for both the amination and the
inter-molecular Heck coupling with a catalyst loading that is
relatively low (2 mol% of Pd2(dba)3 and 4 mol% of the
ligand). Using 4 mol% of Pd(OAc)2 and 8 mol% of 1, 5,6-
dihydro-7H-dibenz[b,d]azepine was synthesized in moder-
ate yield in a one-pot amination/Suzuki reaction.
To test a different application of proazaphosphatranes as
ligands in one-pot multi-component reactions, we tried a
one-pot amination/Suzuki sequence for the synthesis of 5,6-
dihydro-7H-dibenz[b,d]azepine (11). Apart from an isolated
literature report for the synthesis of 11 in 48% yield, via a
trifluoromethanesulfonic acid-catalyzed cyclization of N-
aminophenethylaniline,20 no other descriptions for the
synthesis of this compound were found in the literature.
Although a single report of a one-pot amination/Suzuki
reaction was found for the synthesis of 1,3-diphenylinda-
zoles; this protocol required a bi-catalytic system.21
4. Experimental
The reaction of 2-bromophenethylamine with 2-bromo-
phenylboronic acid in the presence of 4 mol% of Pd(OAc)2
and 8 mol% of 1 at 110 8C for 24 h afforded 11 in 53%
isolated yield (Scheme 5).
4.1. General considerations
All reactions were performed under an atmosphere of argon
in oven dried glassware. Toluene was collected from a
Grubbs type solvent purification system (Innovative
Although, possible side reactions such as inter and intra
molecular amination22 and Suzuki coupling could be
expected under our experimental conditions, we were able
to isolate the expected product in somewhat better yield than
that reported earlier.20 The product was characterized by its
1H and 13C NMR and high-resolution mass spectra. Further
elaboration of the methodology depicted in Scheme 5 to
synthesize more complex molecules using one-pot sequen-
tial reactions is underway.
1
˚
Technologies) and stored over 4 A molecular sieves. H
and 13C NMR spectra were recorded on Varian VXR
300 MHz and Bruker 400 MHz NMR spectrometers. NMR
spectra were obtained using CHCl3-d as solvent. Chemical
shifts are given as d values with tetramethylsilane or the
CHCl3 proton at 7.27 as the internal standard. Mass spectra
were recorded on a Kratos MS-50 mass spectrometer.
4.2. General procedure for the synthesis of symmetri-
cally substituted N,N-diarylaminostyrenes
An oven dried Schlenk tube equipped with a magnetic
stirring bar was charged with Pd2dba3 (2 mol%) and
NaOtBu (1.75 mmol). The tube was capped with a rubber
septum, evacuated and then flushed with argon three times.
Ligand 1 (4 mol%), 4-aminostyrene (0.5 mmol), arylhalide
3 (1 mmol) and toluene (10 mL) were successively added
Scheme 5.

9780
M. V. Nandakumar, J. G. Verkade / Tetrahedron 61 (2005) 9775–9782
via syringe. The tube was heated at the temperature and for
the time specified in Table 1, all the starting material was
converted in to the corresponding N,N-dirylaminostyrenes
as judged by TLC. To this reaction mixture, aryl halide 4
(0.6 mmol) was added and the temperature was raised to
110 8C. After heating for another 16 h, the reaction mixture
was cooled to room temperature. The reaction mixture was
filtered through a short column of silica gel to remove the
solid impurities and the filtrate was concentrated in vacuo.
The crude products were purified by column chromato-
graphy using 0.5–2% EtOAc/hexane mixtures as eluants to
afford the coupled products.
(224.4 mg, 1.099 mmol) was added and heated at 110 8C for
16 h afforded the coupled product 6f (143 mg, 71%) as a
yellow solid after chromatography with 1% EtOAc/hexane
mixtures as eluant.
1H NMR (300 MHz, CDCl3): d 1.22 (s, 9H), 6.90–7.02 (m,
9H), 7.12–7.28 (m, 9H), 7.37 (d, JZ7.52 Hz, 2H). 13C NMR
(75 MHz, CDCl3): d 31.66, 34.54, 122.90, 123.41, 124.40,
124.47, 126.31, 126.46, 126.99, 127.39, 127.47, 128.43,
128.82, 129.37, 131.30, 137.85, 144.88, 146.29, 147.69,
147.83. HRMS: calcd for C30H29N (MC) 403.23000, found:
403.23052.
4.2.1. N,N-Diphenyl-4-[2-(4-methylphenyl)ethenyl]ben-
zenamine. See Table 1, entry 1.15
4.2.12. N-(3-Methoxyphenyl)-N-(phenyl)-4-[2-phenyl-
ethenyl]benzenamine. See Table 2, entry 9.15
4.2.2. N,N-Bis(4-methoxyphenyl)-4-[2-phenylethenyl]
benzenamine. See Table 1, entry 2.15
4.2.13. N-(3-Pyridyl)-N-(phenyl)-4-[2-phenylethenyl]
benzenamine. See Table 2, entry 10. Chromatography
with 20–50% EtOAc/hexane mixture as eluants. H NMR
1
4.2.3. N,N-Bis(3-methylphenyl)-4-[2-phenylethenyl]ben-
zenamine. See Table 1, entry 3.15
(300 MHz, CDCl3): d 6.94–7.03 (m, 8H), 7.18–7.33 (m,
8H), 7.39 (d, JZ7.56 Hz, 2H), 8.13–8.14 (m, 1H), 8.31 (s,
1H). 13C NMR (75 MHz, CDCl3): d 124.12, 124.80, 126.51,
127.77, 128.82, 129.78, 132.72, 137.53, 143.34, 144.22,
145.44, 146.38, 146.71. HRMS: calcd for C25H20N2 (MC)
348.16265, found: 348.16317.
4.2.4. N,N-Bis(4-methylphenyl)-4-[2-phenylethenyl]ben-
zenamine. See Table 1, entries 4 and 8.15
4.2.5. N,N-Bis(3-methoxyphenyl)-4-[2-phenylethenyl]
benzenamine. See Table 1, entry 5. H NMR (300 MHz,
1
4.3. General procedure for the synthesis of
unsymmetrically substituted trans-4-N,N-diaryl-
aminostilbenes (different aryl groups on nitrogen)
CDCl3): d 3.74 (s, 6H), 6.59–6.72 (m, 6H), 7.04–7.27 (m,
7H), 7.34–7.42 (m, 4H), 7.50 (d, JZ7.32 Hz, 2H). 13C NMR
(75 MHz, CDCl3): d 55.48, 108.72, 110.42, 117.16, 124.24,
126.49, 127.32, 127.49, 128.31, 128.84, 130.03, 131.92,
137.75, 147.23, 148.81, 160.60. HRMS: calcd for
C28H25NO2 (MC) 407.18853, found: 407.18903.
An oven dried Schlenk tube equipped with a magnetic
stirring bar was charged with Pd2dba3 (2 mol%) and
NaOtBu (1.75 mmol). The tube was capped with a rubber
septum, evacuated and then flushed with argon three times.
Ligand 1 (4 mol%), 4-aminostyrene (0.5 mmol), arylhalide
3 (1.1 mmol) and toluene (10 mL) were successively added
via syringe. The tube was heated at the temperature and for
the time specified in Table 1, the reaction mixture was
cooled to room temperature. The reaction mixture was
filtered through a short column of silica gel to remove the
solid impurities and the filtrate was concentrated in vacuo.
The crude products were purified by column chromato-
graphy using 0.5–2% EtOAc/hexane mixtures as eluant to
afford the coupled products.
4.2.6. N,N-Bis(4-methoxyphenyl)-4-[2-(4-methylphenyl)
ethenyl]benzenamine. See Table 1, entry 6.15
4.2.7. N,N-Bis(4-methoxyphenyl)-4-[2-(3-methylphenyl)
ethenyl]benzenamine. See Table 1, entry 7. 1H NMR
(300 MHz, CDCl3): d 2.38 (s, 3H), 3.81 (s, 6H), 6.84–6.96
(m, 7H), 7.02–7.10 (m, 6H), 7.24–7.35 (m, 5H). 13C NMR
(75 MHz, CDCl3): d 21.68, 55.67, 114.84, 120.64, 123.54,
126.26, 126.76, 127.04, 127.33, 128.06, 128.28, 128.68,
129.78, 137.88, 138.28, 140.89, 148.39, 156.03. HRMS:
calcd for C29H27NO2 (MC) 421.20418, found:421.20489.
4.3.1. 4-Ethenyl-N,N-diphenylbenzenamine. See Table 3,
entry 1.17b
4.2.8. N-(4-Methylphenyl)-N-(phenyl)-4-[2-phenylethe-
nyl]benzenamine. See Table 2, entries 1, 3, 5, and 7.16
4.3.2. 4-Ethenyl-N,N-bis(4-methylphenyl)benzenamine.
See Table 3, entries 2 and 8.17b
4.2.9. N-(4-Methoxyphenyl)-N-(phenyl)-4-[2-phenylethe-
nyl]benzenamine. See Table 2, entries 2 and 8.9
4.3.3. 4-Ethenyl-N,N-bis(3-methylphenyl)benzenamine.
See Table 3, entry 3.19
4.2.10. N-(4-Methoxyphenyl)-N-(4-methylphenyl)-4-[2-
(4-methylphenyl)ethenyl]benzenamine. See Table 2,
entry 4.16
4.3.4. 4-Ethenyl-N,N-bis(3,5-dimethylphenyl)benzena-
mine. See Table 3, entry 4.13
4.2.11. N-(4-tert-Butyl-phenyl)-N-(phenyl)-4-[2-phenyl-
ethenyl]benzenamine. See Table 2, entry 6. Pd2dba3
(9.2 mg, 2.0 mol%), NaOtBu (168 mg, 1.75 mmol), ligand
4.3.5. 4-Ethenyl-N,N-bis(4-tert-butylphenyl)benzena-
mine. See Table 3, entry 5. H NMR (300 MHz, CDCl3):
1
1
(6.8 mg, 4.0 mol%), 4-aminostyrene (59.5 mg,
d 1.31 (s, 18H), 5.10 (d, JZ10.89 Hz, 1H), 5.58 (d, JZ
17.58 Hz, 1H), 6.60 (dd, J1Z10.86 Hz, J2Z17.58 Hz, 1H),
6.99–7.03 (m, 6H), 7.24–7.27 (m, 6H). 13C NMR (75 MHz,
CDCl3): d 31.66, 34.50, 111.81, 122.96, 124.19, 126.22,
0.499 mmol), 1-bromo-4-tert-butyl benzene (106.5 mg,
0.4997 mmol), and 10 mL of dry toluene was heated at
85 8C for 3 h and to the same reaction mixture iodobenzene

M. V. Nandakumar, J. G. Verkade / Tetrahedron 61 (2005) 9775–9782
9781
127.10, 131.27, 136.55, 145.10, 145.92, 148.04. HRMS:
calcd for C28H33N (MC) 383.26130, found: 383.26190.
122.72, 127.05, 127.09, 129.87, 130.12, 130.15, 131.65,
133.36, 136.57, 137.23, 144.83, 145.18, 147.74. HRMS:
calcd for C23H23N (MC) 313.18305, found: 313.18347.
4.3.6. 4-Ethenyl-N,N-bis(4-chlorophenyl)benzenamine.
See Table 3, entry 6. H NMR (300 MHz, CDCl3): d 5.15
1
4.4.4. 4-Ethenyl-N-(4-tert-butylphenyl)-N-(2-methylphe-
nyl)benzenamine. See Table 4, entry 4. 1H NMR
(300 MHz, CDCl3): d 1.32 (s, 9H), 2.05 (s, 3H), 5.09 (d,
JZ10.89 Hz, 1H), 5.57 (d, JZ17.61 Hz, 1H), 6.60 (dd, J1Z
10.89 Hz, J2Z17.58 Hz, 1H), 6.87–6.97 (m, 4H), 7.13–7.27
(m, 8H). 13C NMR (75 MHz, CDCl3): d 18.80, 31.65, 34.41,
111.36, 120.48, 122.04, 126.06, 126.22, 127.09, 127.54,
129.79, 130.29, 131.87, 136.55, 136.73, 144.59, 144.96,
145.42, 147.56. HRMS: calcd for C25H27N (MC)
341.21435, found: 341.21499.
(d, JZ10.86 Hz, 1H), 5.61 (d, JZ17.58 Hz, 1H), 6.59 (dd,
J1Z10.86 Hz, J2Z17.58 Hz, 1H), 6.96–6.99 (m, 6H), 7.15–
7.17 (m, 4H), 7.19–7.29 (m, 2H). 13C NMR (75 MHz,
CDCl3): d 113.04, 124.16, 125.42, 127.49, 128.30, 129.64,
133.01, 136.18, 146.07, 146.81. HRMS: calcd for
C20H15NCl2 (MC) 339.05816, found: 339.05855.
4.3.7. 4-Ethenyl-N,N-bis(1-naphthyl)benzenamine. See
Table 3, entry 7.19
4.4. General procedure for the synthesis of unsymme-
trically substituted N,N-diarylaminostyrenes
4.4.5. 4-Ethenyl-N-(4-methylphenyl)-N-(4-methoxyphe-
nyl)benzenamine. See Table 4, entry 6. 1H NMR
(300 MHz, CDCl3): d 2.21 (s, 3H), 3.69 (s, 3H), 5.00 (d,
JZ8.10 Hz, 1H), 5.48 (d, JZ13.17 Hz, 1H), 6.50 (dd, J1Z
8.16 Hz, J2Z13.00 Hz, 1H), 6.72–6.74 (m, 2H), 6.83–6.97
(m, 8H), 7.13–7.15 (m, 2H). 13C NMR (75 MHz, CDCl3): d
21.00, 55.65, 111.54, 114.86, 121.67, 124.22, 127.05,
127.16, 129.99, 130.64, 132.38, 136.46, 140.86, 145.43,
148.26, 156.18. HRMS: calcd for C22H21NO (MC)
315.16231, found: 315.16277.
An oven dried Schlenk tube equipped with a magnetic
stirring bar was charged with Pd2dba3 (2 mol%) and
NaOtBu (1.75 mmol). The tube was capped with a rubber
septum, evacuated and then flushed with argon three times.
Ligand 1 (4 mol%), 4-aminostyrene (0.5 mmol), arylbro-
mide (0.5 mmol), aryl chloride (0.6 mmol) and toluene
(10 mL) were successively added via syringe. The tube was
heated at 85 8C for 2 h and then the temperature was raised
to 110 8C for an additional 16 h. The reaction mixture was
cooled to room temperature and filtered through a short
column of silica gel to remove the solid impurities and the
filtrate was concentrated in vacuo. The crude products were
purified by column chromatography using hexane—1%
EtOAc/hexane mixtures as eluant to afford the coupled
products.
4.4.6. 5,6-Dihydro-7H-dibenz[b,d]azepine (11). An oven
dried Schlenk tube equipped with a magnetic stirring bar
was charged with Pd(OAc)2 (4.48 mg, 3.99 mol%), Cs2CO3
(652 mg, 2.00 mmol) and 2-bromophenylboronic acid
(100 mg, 0.497 mmol). The tube was capped with a rubber
septum, evacuated and then flushed with argon three times.
Ligand 1 (13.68 mg, 7.988 mol%), 2-bromophenethylamine
(100 mg, 0.499 mmol) and toluene (10 mL) were succes-
sively added via syringe. The tube was heated at 110 8C for
24 h. Then the reaction mixture was cooled to room
temperature and filtered through a short column of silica
gel to remove the solid impurities and then the filtrate was
concentrated in vacuo. The crude product was purified by
column chromatography using hexanes as eluant to afford
the 11 (51 mg, 53%) as a colorless solid.
4.4.1. 4-Ethenyl-N-(4-methylphenyl)-N-(4-tert-butylphe-
nyl)benzenamine. See Table 4, entry 1. 1H NMR
(300 MHz, CDCl3): d 1.30 (s, 9H), 2.31 (s, 3H), 5.10 (d,
JZ10.98 Hz, 1H), 5.58 (d, JZ17.58 Hz, 1H), 6.60 (dd, J1Z
11.01 Hz, J2Z17.58 Hz, 1H), 6.98–7.05 (m, 8H), 7.22–7.27
(m, 4H). 13C NMR (75 MHz, CDCl3): d 21.07, 31.66, 34.50,
111.80, 122.76, 123.89, 124.17, 125.07, 126.19, 127.08,
130.06, 131.19, 132.87, 136.50, 145.10, 145.28, 145.79,
148.04. HRMS: calcd for C25H27N (MC) 341.21435, found:
341.21500.
1H NMR (400 MHz, CDCl3): d 3.13 (t, JZ8.4 Hz, 2H), 3.95
(t, JZ8.4 Hz, 2H), 6.75 (t, JZ7.32 Hz, 1H), 6.96–7.00 (m,
1H), 7.09–7.11 (m, 1H), 7.16 (t, JZ8.6 Hz, 2H), 7.24–7.27
(m, 2H), 7.34–7.38 (m, 2H). 13C NMR (100 MHz, CDCl3):
d 28.37, 52.27, 108.27, 117.80, 118.98, 121.06, 125.20,
127.22, 129.31, 131.42, 144.28. HRMS: calcd for C14H13N
(MC) 195.10480, found: 195.10506.
4.4.2. 4-Ethenyl-N-(4-methylphenyl)-N-(3-methylphe-
nyl)benzenamine. See Table 4, entry 2. 1H NMR
(300 MHz, CDCl3): d 2.27 (s, 3H), 2.34 (s, 3H), 5.13 (d,
JZ10.98 Hz, 1H), 5.61 (d, JZ17.70 Hz, 1H), 6.62 (dd, J1Z
10.89 Hz, J2Z17.58 Hz, 1H), 6.82–6.92 (m, 3H), 6.99–7.16
(m, 7H), 7.27–7.29 (m, 2H). 13C NMR (75 MHz, CDCl3): d
21.06, 21.62, 111.98, 121.47, 123.16, 123.74, 124.89,
125.19, 127.14, 129.18, 130.11, 131.45, 133.00, 136.49,
139.22, 145.28, 147.89, 148.00. HRMS: calcd for C22H21N
(MC) 299.16740, found: 299.16778.
Acknowledgements
We thank the National Science Foundation for support of this
work in the form of a grant, and Aldrich for research samples.
4.4.3. 4-Ethenyl-N-(4-methylphenyl)-N-(2,5-dimethyl-
phenyl)benzenamine. See Table 4, entries 3 and 5. H
1
References and notes
NMR (300 MHz, CDCl3): d 2.00 (s, 3H), 2.28 (s, 3H), 2.32
(s, 3H), 5.10 (d, JZ10.86 Hz, 1H), 5.58 (d, JZ17.58 Hz,
1H), 6.61 (dd, J1Z10.86 Hz, J2Z17.58 Hz, 1H), 6.85–7.07
(m, 8H), 7.12–7.15 (m, 1H), 7.24–7.27 (m, 2H). 13C NMR
(75 MHz, CDCl3): d 18.33, 20.96, 21.06, 111.27, 120.36,
1. For general references see; (a) Tsuji, J. Palladium Reagents
and Catalysis: Innovations In Organic Synthesis; Wiley:
Chichester, England, 1995. (b) Negishi, E. I. In Handbook of
Organopalladium Chemistry for Organic Synthesis, Vol. 1–2;

9782
M. V. Nandakumar, J. G. Verkade / Tetrahedron 61 (2005) 9775–9782
10. Yang, J. S.; Chiou, S. Y.; Lia, K. L. J. Am. Chem. Soc. 2002,
124, 2518–2527.
Wiley: New York, 2002. (c) Deshpande, P. P.; Martin, O. R.
Tetrahedron Lett. 1990, 31, 6313–6316. (d) Matsumoto, T.;
Hosoya, T.; Suzuki, K. J. Am. Chem. Soc. 1992, 114, 3568–
3570. (e) Kitamura, M.; Ohmori, K.; Kawase, T.; Suzuki, K.
Angew. Chem., Int. Ed. 1999, 38, 1229–1232.
11. Yang, J. S.; Lin, Y. H.; Yang, C. S. Org. Lett. 2002, 4,
777–780.
12. (a) Cao, X. D.; Zhou, X. Q.; Dong, Q. M.; He, Q.; Liu, D. Z.
Jingxi Huagong 2003, 20, 452–454. (b) Sengupta, S.;
Sadhukaran, S. K.; Muhuri, S. Tetrahedron Lett. 2002, 43,
3521–3524. (c) Lin, T. C.; He, G. S.; Prasad, P. N.; Tan, L. S.
J. Mater. Chem. 2004, 14, 982–991.
2. Proazaphosphatranes such as 1 are commercially available
(Aldrich, Strem and Digital Specialty Chemicals).(b) Kisanga,
P. B.; Verkade, J. G. Tetrahedron 2001, 57, 467–475.
3. (a) Urgaonkar, S.; Nagarajan, M.; Verkade, J. G. J. Org. Chem.
2003, 68, 452–459. (b) Urgaonkar, S.; Nagarajan, M.;
Verkade, J. G. Org. Lett. 2003, 5, 815–818.
13. Nandakumar, M. V.; Verkade, J. G. Angew. Chem., Int. Ed.
2005, 44, 3115–3118.
14. (a) Sasaki, M. Ger. Offen. Patent Application. DE 3342724A1-
19840530, 1984, Chem. Abstr. No. 101, 219792. (b) Gajare,
A. S.; Toyota, K.; Yoshifuji, M.; Ozawa, F. Chem. Commun.
2004, 17, 1994–1995. (c) Lee, H. J.; Sohn, J.; Hwang, J.; Park,
S. Y.; Choi, H.; Cha, M. Chem. Mater. 2004, 3, 456–465.
15. (a) Fujimaki, Y.; Suzuki, Y.; Takei, Y.; Nomori, H.
(Konishiroku Photo Industry Co. Ltd Japan). Jpn. Kokai
Tokkyo Application JP 84-69481 19840407, 1985; Chem.
Abstr. No. 104, 159589. (b) Borsenberger, P. M.; Cowdery-
Corvan, J. R.; Magin, E. H.; Sinicropi, J. A. Thin Solid Films
1997, 307, 215–220.
4. Urgaonkar, S.; Nagarajan, M.; Verkade, J. G. Tetrahedron
Lett. 2002, 43, 8921–8924.
5. (a) Su, W.; Urgaonkar, S.; Verkade, J. G. Org. Lett. 2004, 6,
1421–1424. (b) Su, W.; Urgaonkar, S.; Verkade, J. G. J. Am.
Chem. Soc. 2004, 126, 16433–16439.
6. For recent reviews, see: (a) Verkade, J. G. Top. Curr. Chem.
2002, 233, 1. (b) Verkade, J. G.; Kisanga, P. B. Aldrichim.
Acta 2004, 37, 3–14. (c) Verkade, J. G.; Kisanga, P. B.
Tetrahedron 2003, 59, 7819–7853.
7. (a) Edmondson, S. D.; Mastraechio, A.; Parmee, E. R. Org.
Lett. 2000, 2, 1109–1112. (b) Matyus, P.; Maes, B. U. W.;
Riedl, Z.; Hajos, G.; Lemiere, L. F.; Tapolcsanyi, P.;
Monsieurs, K.; Elias, O.; Dommisse, R. A.; Krajsovszky, G.
Synlett 2004, 7, 1123–1139. (c) Cuny, G.; Choussy, M. B.;
Zgu, J. Angew. Chem., Int. Ed. 2003, 42, 4774–4777. (d)
Khedkar, V.; Tillack, A.; Michalik, M.; Beller, M. Tetra-
hedron Lett. 2004, 45, 3123–3126. (e) Siebeneicher, H.;
Bytschkov, I.; Doye, S. Angew. Chem., Int. Ed. 2003, 42,
3042–3044. (f) Yamazaki, K.; Nakamura, Y.; Kondo, Y.
J. Chem. Soc., Perkin Trans. 1 2002, 2137–2138.
16. Behl, M.; Hattemer, E.; Brehmer, M. Macrmol. Chem. Phys.
2002, 203, 503–510.
17. (a) Lindner, S. M.; Thelakkat, M. Macromolecules 2004, 37,
8832–8835. (b) Shoichi, N.; Hisao, E. (Tosoh Corpn., Japan)
Jpn. Kokai Tokkyo Patent No. JP 2002-80870 20020322,
2003, Chem. Abstr. No. 139 276694.
18. Li, C. L.; Shieh, S. J.; Lin, S. C.; Liu, R. S. Org. Lett. 2003, 5,
1131–1134.
19. (a) Sato, Y.; Okata, T.; Ichinosawa, A. (Mitsubishi Chemical
Industries Ltd, Japan). Jpn. Kokai Tokkyo Koho Patent No.
2000150169, 2000, Chem. Abstr. No.133, 10852. (b) Sage, I.
C.; Wood, E. L.; Feast, W. J.; Peace, R. J. Crit. UK Pat. Appl
Patent No. GB 2334959, 1999, Abstr. No.132, 23286.
20. Ohta, T.; Miyake, S.; Shudo, K. Tetrahedron Lett. 1985, 26,
5811–5814.
8. Lira, R.; Wolfe, J. P. J. Am. Chem. Soc. 2004, 126,
13906–13907.
9. (a) Sasaki, M. (Ricoh Co., Ltd Japan). Ger. Offen. Patent
Application DE 83-3315437 19830428, 1983, 97; Chem.
Abstr. No. 100, 112236.(b) Oda, Y.; Homma, T.; Yoshihide, F.
Denshi Shashin Gakkaishi 1990, 29, 250–258. (c) Fujimaki,
Y.; Tadokoro, H.; Oda, Y.; Yoshioka, H.; Homma, T.;
Moriguchi, H.; Watanabe, K.; Konishita, A.; Hirose, N.
J. Imaging Technol. 1991, 17, 202–206.
21. Collot, V.; Bovy, P. R.; Rault, S. Tetrahedron Lett. 2000, 41,
9053–9057.
22. Wolfe, J. P.; Rennels, R. A.; Buchwald, S. L. Tetrahedron
1996, 52, 7525–7546.