Triaryl phosphine-functionalized N-heterocyclic carbene ligands for Heck reaction

Article abstract of DOI:10.1016/j.tet.2004.10.049

A new type of triaryl phosphine-functionalized imidazolium salts 6 were prepared. Their palladium complexes, generated in situ, were successfully applied in the palladium-catalyzed Heck reaction. Using 1 mol% of Pd(dba) ₂ and 1 mol% 6c in the presence of 2 equiv of K₂CO ₃ in DMAc has proven to be highly efficient for the coupling of a wide array of aryl bromides and iodides with acrylates in excellent yield. The coupling of 4-bromotoluene with various styrene derivatives catalyzed by Pd/6c complex also gave good results. Graphical Abstract.

Full text of DOI:10.1016/j.tet.2004.10.049

Tetrahedron 61 (2005) 259–266
Triaryl phosphine-functionalized N-heterocyclic carbene ligands
for Heck reaction
*
Ai-E Wang, Jian-Hua Xie, Li-Xin Wang and Qi-Lin Zhou
State Key Laboratory, Institute of Elemento-organic Chemistry, Nankai University, Tianjin 300071, China
Received 25 May 2004; revised 30 September 2004; accepted 8 October 2004
Available online 6 November 2004
Abstract—A new type of triaryl phosphine-functionalized imidazolium salts 6 were prepared. Their palladium complexes, generated in situ,
were successfully applied in the palladium-catalyzed Heck reaction. Using 1 mol% of Pd(dba)2 and 1 mol% 6c in the presence of 2 equiv of
K2CO3 in DMAc has proven to be highly efficient for the coupling of a wide array of aryl bromides and iodides with acrylates in excellent
yield. The coupling of 4-bromotoluene with various styrene derivatives catalyzed by Pd/6c complex also gave good results.
q 2004 Elsevier Ltd. All rights reserved.
1. Introduction
application of palladium–NHC complex in Heck reaction in
1995, various palladium complexes with monodente
carbenes, chelating dicarbenes or tridentate pincer bis-
carbenes, and even donor-functionalized NHC’s have been
synthesized and used as catalysts for the Heck reaction.13
Most of the donor-functionalized NHC ligands had a N-
donor, such as pyridine, imine or oxazoline as pendant
groups. However, little attention has been paid to the
synthesis of phosphine-functionalized NHC ligands,14
though the theoretical calculation suggested that the
chelating phosphine–carbene Pd complex might be a
suitable catalyst for the Heck reaction.15 So far as we
know, there was one successful application of phosphine–
NHC ligand in Heck reaction, which was reported by Nolan
and co-workers.14c Herein, we describe the synthesis of a
new type of phosphine-functionalized NHC ligands with
stable triaryl phosphines as pendant functional groups and
their application in palladium-catalyzed Heck reaction. The
results revealed that the palladium-NHC species generated
in situ from phosphine-functionalized imidazolium salts and
Pd(dba)2 in the presence of K2CO3 were highly effective for
the coupling of a wide range of bromides and iodides with
acrylates and the coupling of aryl bromides with styrene
derivatives.
Heck reaction has received intensive studies over the past
several decades.1 Especially the palladium-catalyzed aryla-
tion and vinylation have proven to be one of the most
powerful means for the formation of carbon–carbon bond in
organic synthesis.2 Usually, Heck reaction is carried out in
the presence of phosphine ligands, which stabilize the active
palladium intermediates3 and assist the initial oxidative-
addition of C–X bonds.4 Excellent results have been
reported for the palladium-catalyzed Heck reactions when
sterically bulky monophosphines,5 diphosphines,6 cyclome-
talated phosphines7 or phosphites are used as ligands.8
However, the phosphine ligands and the phosphine–
palladium complexes are liable to air and moisture at
elevated temperature, placing significant limits on their
synthetic application. Therefore, in view of practical use,
the development of more reactive and stable ligands is of
importance for the palladium-catalyzed Heck reaction.
Recently, nucleophilic N-heterocyclic carbenes (NHC’s),9
with a stronger s-donor electronic property than bulky
tertiary phosphines,10 have emerged as a new family of
ligands. In contrast to metal complexes of phosphines, the
metal–NHC complexes appeared to be extraordinarily
stable toward heat, air and moisture due to their high
dissociation energies of the metal–carbon bond.11 This
superiority of NHC’s made them a potential type of ligands
for Heck reaction. Since Herrmann12 reported the first
2. Result and discussion
2.1. Synthesis of phosphine-functionalized imidazolium
salts
Keywords: Carbenes; Heck reaction; Palladium; Phosphine-functionalized.
* Corresponding author. Fax: C86 22 2350 6177;
e-mail: qlzhou@nankai.edu.cn
Initially, we attempted to synthesize triaryl phosphine-
functionalized imidazolium salts 6 via the direct reduction
0040–4020/$ - see front matter q 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2004.10.049

260
A.-E. Wang et al. / Tetrahedron 61 (2005) 259–266
was ortho-metallated by n-BuLi and reacted with Ph2PC1 to
afford 2-(diphenylphosphino)benzyldimethylamine (8). In
the presence of ethyl chloroformate, 8 was converted to the
key intermediate o-(diphenylphosphino)benzyl chloride (9)
at refluxing condition. The yield was 42% for the three
steps. Subsequently, alkylation of 1-arylimidazole with
compound 9 in refluxing ethanol gave triaryl phosphine-
functionalized imidazolium salts 6 in the yields of 46–63%.
By using K2CO3 as the base, tridentate imidazolium salt 10
was obtained from 1H-imidazole and the compound 9 in
32% yield.
2.2. Heck reaction
2.2.1. Arylation of acrylates. Having prepared the new
phosphine-functionalized imidazolium salts 6 and 10, we
firstly tested the catalytic activity of the palladium
complexes 1116 (Scheme 3) for the Heck reaction of
p-tolyl bromide with n-butyl acrylate (Scheme 3). Prelimi-
nary experiment in DMAc in the presence of Cs2CO3 as the
base at 120 8C showed that the catalyst 11a generated in situ
was efficient to yield coupling product (Table 1, entry 1).
Controlled experiment indicated that the coupling reaction
did not take place in the absence of imidazolium salt 6a. A
systematic investigation on the substituent effect in the
imidazolium salts 6 indicated that the introduction of alkyl
groups to the N-phenyl ring of NHC ligands notably
increased the reaction rate and the yield of product, and
imidazolium salt 6c was found to be the most reactive one
(entries 2 and 3). But the tridentate phosphine-functiona-
lized imidazolium salt 10 showed a poor reactivity in this
reaction (entry 4). As a comparison, the phosphinoxide 5b
was also tested for the reaction and poorer catalytic activity
(24 h, 67% yield) was observed, indicating that the pendant
phosphine group in ligands 6 is necessary for having a high
reactivity.
Scheme 1. Reagents and conditions: (i) Mg, THF, reflux; (ii) PPh2Cl,
K78 8C to room temperature; (iii) H2O2, CH2Cl2, room temperature;
(iv) NBS, AIBN, CCl4, reflux; (v) 1-arylimidazole, EtOH (abs), reflux;
(vi) Cl3SiH, EtOH, toluene, 120 8C.
of the phosphinoxide 514d (Scheme 1). Diphenyl-o-tolylphos-
phane (2), prepared from coupling of Ph2PC1 with Grinard
reagent of 2-bromotoluene, was treated with H2O2 to form
the corresponding phosphinoxide 3 in excellent yield (97%
for three steps). Bromination of compound 3 with NBS in
the presence of AIBN provided o-(diphenylphosphinyl)-
benzyl bromide (4) in 65% yield. Then, alkylation of
1-arylimidazole with bromide 4 gave imidazolium salts 5 in
70% yield. However, the direct reduction of compound 5
with Cl3SiH was unsuccessful. Use of other reducing
reagents, such as methyldichlorosilane, also gave disap-
pointing results. It was very likely that the bulky steric effect
around the phosphorus atom in compound 5 hindered its
interaction with the reducing reagent.
Another synthetic route was then designed to make
phosphine-functionalized imidazolium salts 6, which started
from benzaldehyde (Scheme 2). The benzaldehyde was
condensed with dimethylamine, followed by the reduction
with NaBH4 to give benzyldimethylamine (7). Compound 7
Scheme 3.
Various palladium compounds, such as Pd(dba)2, Pd(OAc)2,
[Pd[(h-C3H5)Cl]]2 and Pd2(dba)3$CHCl3, were compared
as catalyst precursors under the same reaction conditions
(1 mol% [Pd], 1 mol% 6c, 1 equiv p-tolyl bromide,
1.5 equiv n-butyl acrylate, 2.0 equiv Cs2CO3 and DMAc
as solvent at 120 8C) (Table 1). The results showed that
Pd(dba)2 was the choice of catalyst precursor, which gave
100% conversion in the shortest reaction time (entry 3). The
ratio of imidazolium salt 6c to palladium precursor was also
studied. The ratio of 1:1 was found to be optimal. When the
ratio of 6c/Pd changed from 1:1 to 2: 1, the coupling product
was obtained in only 29% yield (entry 8). Further increasing
the ratio to 3:1 or 4:1 led a very slow reaction (entries 9 and
10). These results suggested that NHC ligand 6c coordinated
to palladium with two coordinating atoms to form a
chelating complex. When the ratio of 6c/Pd exceeded 2:1,
two bidentate P–C ligands occupied all of the four
Scheme 2. Reagents and conditions: (i) (a) Me2NH2Cl, Ti(Oi-Pr)4, NEt3,
EtOH (abs), room temperature; (b) NaBH4, room temperature; (ii) (a) n-BuLi,
Et2O, room temperature; (b) Ph2PCl, Et2O, K78 8C to room temperature;
(iii) ClCO2Et, benzene, reflux; (iv) 1-arylimidazole, EtOH (abs), reflux;
(v) 1H-imidazole, K2CO3, EtOH (abs), reflux.

A.-E. Wang et al. / Tetrahedron 61 (2005) 259–266
Table 1. Heck reaction of 4-bromotoluene and n-butyl acrylate under various conditionsa
261
Entry
Pd
Ligand
L/Pd
Base
Solvent
Time (h)
Conv. (%)b
Yield (%)c
1
2
3
4
5
6
7
8
Pd(dba)2
Pd(dba)2
Pd(dba)2
Pd(dba)2
Pd(OAc)2
[Pd[(h-C3H5)Cl]]2
Pd2(dba)3$CHCl3
Pd(dba)2
Pd(dba)2
Pd(dba)2
Pd(dba)2
Pd(dba)2
Pd(dba)2
Pd(dba)2
Pd(dba)2
Pd(dba)2
Pd(dba)2
Pd(dba)2
Pd(dba)2
Pd(dba)2
Pd(dba)2
6a
6b
6c
10
6c
6c
6c
6c
6c
6c
6c
6c
6c
6c
6c
6c
6c
6c
6c
6c
6c
1
1
1
1
1
1
1
2
3
4
1
1
1
1
1
1
1
1
1
1
1
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
NEt3
DMAc
DMAc
DMAc
DMAc
DMAc
DMAc
DMAc
DMAc
DMAc
DMAc
DMAc
DMAc
DMAc
DMAc
DMAc
DMAc
DMAc
DMAc
DMF
18
14
12
24
24
24
18
12
24
24
24
24
24
24
24
24
12
11
12
12
24
91
99
100
22
54
88
98
100
18
5
11
45
98
7
14
65
93
99
83
74
56
62
82
85
NDd
28
41
57
29
ND
ND
ND
39
9
10
11
12
13
14
15
16
17
18e
19
20
21
KOAc
K3PO4
KOH
KF
Na2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
65
ND
ND
54
93
99
75
50
39
DMSO
Dioxane
a Reaction conditions: 1 mol% [Pd], 1 mol% 6c, 1 equiv p-tolyl bromide, 1.5 equiv n-butyl acrylate, 2.0 equiv base at 0.5 M at 120 8C.
b Determined by GC.
c Isolated yield.
d Not determined.
e At 140 8C.
coordination sites of palladium, hindering the oxidative
addition of p-tolyl bromide to palladium, and consequently
resulted in a slow or even no reaction. The base was found to
significantly influence both the reaction rate and the yield of
product. The highest yield was achieved by using K2CO3
(entry 17). Other inorganic bases, such as KOH, KF, KOAc,
Na2CO3 and K3PO4, and organic base NEt3 gave the
coupling product in low yields (entries 11–16). The reaction
was also solvent dependent when using K2CO3 as the base.
DMAc was found to be the choice of solvent. Increasing the
temperature from 120 to 140 8C accelerated the reaction rate
and the yield of product (entry 18).
activity, which is superior or comparable to the sterically
demanding ortho-substituted arylphosphines, P(o-tol)3
17
and the monodentate carbenes IMes.18 It was noteworthy
that in the coupling reaction of aryl bromides bearing
another halide group, such as F or Cl, the mono-coupling
products were formed predominantly. The bis-coupling
products were isolated in just 3 and 7% yields in the reaction
of ortho- and para-chlorophenyl bromides (entries 17 and
19). However, the reaction of dibromides, with excess n-
butyl acrylate, produced di-coupling products in quantitat-
ive yields (entries 20 and 21). Bromides bearing carbonyl
groups can couple with n-butyl acrylate leaving carbonyl
group unchanged (entries 22 and 23). The aryl iodides had
higher reactivities than bromides in the coupling reaction
with n-butyl acrylate. The reactions were complete in 2 h at
120 8C and the yields were excellent (entries 24, 25 and 26).
Double arylation products could be obtained in high yields
when excess iodides were used (entries 27–29). However
the reaction of aryl chlorides, such as 1-chloro-4-nitro-
benzene and 2-chlorobenzaldehyde, with n-butyl acrylate
provided very little amount of desired coupling products
using Pd/6c system at the same conditions. Besides n-butyl
acrylate, methyl acrylate and ethyl acrylate can also
efficiently react with p-tolyl bromide providing the
corresponding coupling products in 86 and 99% yields,
respectively.
At the optimal reaction conditions, a wide array of aryl
bromides bearing electron-donating or electron-withdrawing
groups can react with n-butyl acrylate providing coupling
products in excellent yields. As can be seen in the Table 2,
most of the aryl bromides with electron-withdrawing
substituents, such as CF3, CN or NO2, reacted completely
at 120 8C in less than 6 h. While for the aryl bromides with
electron-donating substituents, complete conversions were
achieved only at 140 8C. These results showed that the
electron-deficient bromides were beneficial to the reaction.
The steric effect of substrates was also obvious. For the
sterically congested substrates, such as 1-bromo-3,5-di-tert-
butylbenzene (entry 6) and 1-bromo-3,5-di-tert-butyl-4-
methoxybenzene (entry 9), longer reaction time were
required. 1-Bromo-2-methyl naphthalene, another sterically
congested bromide, could also couple with n-butyl acrylate
using our catalyst system in high yield (entry 10). These
results showed that the carbene ligands generated in situ
from phosphine-functionalized imidazolium salt 6 have an
2.2.2. Arylation of styrenes. Using the same reaction
conditions, we further studied the Heck reaction of
4-bromotoluene with styrene using in situ generated
palladium complexes of phosphine-functionalized NHC
ligands. The results are summarized in Table 3. Arylation

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A.-E. Wang et al. / Tetrahedron 61 (2005) 259–266
Table 2. Heck reaction of aryl bromides and iodides with n-butyl acrylate under optimal reaction conditionsa
Entry
1
Aryl halide
Temperature (8C)
Time (h)
11
Conv. (%)b
99
Product
Yield (%)c
99
Ref.
19
140
2
140
12
100
98
17
3
4
140
140
12
11
100
99
98
99
20
18
5
6
140
140
12
24
100
100
98
18
21
100
7
8
140
140
12
12
100
100
100
96
18
18
9
140
24
100
94
22
10
11
12
140
120
120
24
6
100
100
100
100
99
23
24
25
6
96
13
120
10
97
89
23
14
15
120
120
5
6
100
100
93
85
18
25
16
17
120
120
6
97
96
92
25
26
10
87d

A.-E. Wang et al. / Tetrahedron 61 (2005) 259–266
263
Table 2 (continued)
Entry
Aryl halide
Temperature (8C)
Time (h)
5
Conv. (%)b
100
Product
Yield (%)c
100
Ref.
18
120
27
19
120
120
5
100
99
93e
99
13a
20f
16
28
21f
22
120
120
12
12
100
100
99
83
28
23
23
120
5
100
93
29
24
25
26
120
120
120
2
2
2
100
100
100
97
92
93
19
18
18
27g
140
140
60
100
100
93
99
30
30
28g
140
29g
140
45
100
100
30
a Performed with 1.5 equiv acrylate, L/PdZ1, 2.0 equiv base; 0.5 M.
b Determined by GC.
c Isolated yield.
d 3% Di-coupled product was obtained.
e 7% Di-coupled product was obtained.
f
4.0 equiv acrylate, 5.0 equiv base.
g 4.0 equiv halide, 5.0 equiv base.
of styrene with 4-bromotoluene at 140 8C gave 100%
conversion and offered 96% yield of the coupling product
(entry 1). A variety of styrene derivatives with electron-
donating or electron-withdrawing groups on the phenyl
ring were tested, and 100% conversions with good to
excellent yields were obtained within 12 h. This revealed
that the Pd catalysts bearing a chelating phosphine-
functionalized NHC ligand were comparably good as the
Pd catalysts containing a monodentate NHC ligand and a
triarylphosphine in the arylation reaction of styrenes.31
4-Chlorostyrene was an exception, however, which gave a
lower yield of coupling product (74%, entry 6). In the
reaction of bromo-substituted styrenes, such as 4-bromos-
tyrene and 3-bromostyrene, no cross-coupling products
were isolated. On the contrary, the self-coupling of
bromostyrenes occurred to form polymer PPV.32 The
lower yield in the reaction of 4-chlorostyrene can be also
ascribed to some extent to its polymerization as a
precipitation of a yellow solid was observed at the end
of the reaction.

264
A.-E. Wang et al. / Tetrahedron 61 (2005) 259–266
Table 3. Heck reaction of 4-bromotoluene with styrene derivativesa
Entry
1
Olefin
Product
Yield (%)b
96
Ref.
33
2
3
4
5
6
96
93
34
35
36
37
38
91
91
74c
7
99
39
Polymer
Polymer
9
—
—
32
32
10
a Performed with 1.5 equiv olefin, L/PdZ1, 2.0 equiv base, 0.5 M, 140 8C, 12 h.
b Isolated yield.
c Polymer was observed.
3. Conclusion
derivatives were purchased from Aldrich Co. or Acros Co.
and used as received, with the exception of 2-bromotoluene,
3-bromotoluene and 4-bromotoluene, which were distilled
prior to use. Pd(OAc)2 and [Pd[(h-C3H5)Cl]]2 were
purchased from Acros Co. Pd(dba)2 and Pd2(dba)3$CHCl3
were prepared according to the reported procedures.40
Absolute EtOH was distilled from magnesium ethylate. 1,4-
Dioxane was distilled from sodium benzophenone ketyl.
Anhydrous DMSO, DMF, DMAc were freshly distilled
from calcium hydride. K3PO4 was ground to a fine powder
and dried in a vacuum oven prior to use. Cs2CO3, K2CO3,
Na2CO3, KF, KOAc and KOH were used as received. NEt3
In summary, we have developed a new type of efficient
triaryl phoshphine-funtionalized NHC ligands for the
palladium-catalyzed Heck reactions. These phosphine-
functionalized imidazole carbene ligands were easily
prepared. Their palladium complexes, generated in situ,
were applicable to the coupling reaction of bromides and
iodides with acrylates and the coupling reaction of styrene
derivatives with 4-bromotoluene in high yields. In these
Heck reactions, the bulky substituents on the N-phenyl ring
of the phoshphine-functionalized NHC ligands were found
to be beneficial to the high activity of the catalyst. This
might suggest that the introduction of bulky groups to the
P-phenyl rings of the phoshphine-funtionalized NHC
ligands is also helpful to increase the activity of the Pd
catalyst, which is in progress in our laboratory.
1
was redistilled prior to use. H, 13C and 31P NMR spectra
were recorded in CDCl3 on Varian Mercury Vx-300
spectrometers. HRMS were recorded on APEX II spectro-
meter. GC analyses were performed using a Hewlett
Packard Model HP 6890 Series with HP-5 column.
4.1.1. Synthesis of 3-phenyl-1-(2-diphenylphosphinoben-
zyl)-3H-imidazol-1-ium chloride (6a). Under an atmos-
phere of argon, 8 mL abs. EtOH was added to a Schlenk
tube charged with 1-phenylimidazole (288 mg, 2.0 mmol)
and o-(diphenylphosphino)benzyl chloride (0.64 g,
2.05 mmol). The mixture was allowed to stir at 80 8C for
2 days. The ethanol was then removed under vacuum.
The residue was purified by a flash chromatography
4. Experimental
4.1. General
All reactions and manipulations were performed in an
argon-filled glovebox or using standard Schlenk techniques,
unless otherwise indicated. The aryl halides and styrene

A.-E. Wang et al. / Tetrahedron 61 (2005) 259–266
265
(CH2Cl2/MeOH) to give 6a as a white solid (0.42 g, 46%
yield). 1H NMR d 5.96 (s, 2H, CH2), 6.90 (m, 1H,
NCHCHN), 7.08–7.63 (m, 19H, Ar-H), 8.04 (m, 1H,
NCHCHN), 11.12 (s, 1H, NCHN); 31P NMR d K16.58
(s); 13C NMR d 51.8, 52.1, 119.8, 121.9, 122.7, 122.8,
129.0, 129.1, 129.6, 130.3, 130.7, 130.8, 132.6, 132.7,
133.8, 134.1, 134.6, 134.7, 135.0, 135.1, 136.9, 137.0,
137.4, 137.8; HRMS for C28H24N2PC [MKCl]C, calcd:
419.1672; found: 419.1672.
mixture was stirred for 30 min at 25 8C and then added
1.0 mmol of aryl halide, 1.5 mmol of olefin successively.
The Schlenk tube was placed in a 120 8C or 140 8C oil bath
and the reaction mixture was stirred and monitored by GC.
After the reaction was complete, the reaction mixture was
passed through a short plug of silica gel and washed with
copious amount of Et2O. The washings were concentrated
and purified by flash chromatography on silica gel to offer
1
the product. The products were identified by H NMR.
4.1.2. Synthesis of 3-mesityl-1-(2-diphenylphosphinoben-
zyl)-3H-imidazol-1-ium chloride (6b). The compound 6b
was prepared in 60% yield by the same procedure described
Acknowledgements
1
for 6a using 1-mesitylimidazole. H NMR d 2.02 (s, 6H,
We thank the National Natural Science Foundation of
China, the Major Basic Research Development Program
(Grant G2000077506), the Ministry of Education of China
and the Committee of Science and Technology of Tianjin
for financial support.
CH3), 2.33 (s, 3H, CH3), 6.20 (s, 2H, CH2), 6.95 (s, 1H,
Ar-H), 6.98 (s, 3H, Ar-H), 7.24–7.38 (m, 11H, Ar-H), 7.46
(m, 1H, NCHCHN), 7.59 (s, 1H, Ar-H), 8.11 (m, 1H,
NCHCHN), 10.87 (s, 1H, NCHN); 31P NMR d K14.89 (s);
13C NMR d 17.8, 21.3, 51.1, 51.4, 122.6, 122.7, 129.1,129.2,
129.7, 130.0, 130.3, 131.0, 132.2, 132.3, 133.7, 133.9,
134.2, 134.5, 135.0, 135.1, 136.0, 136.5, 136.7, 136.9,
138.1, 138.5, 139.0, 141.4; HRMS for C31H30N2PC
[MKCl]C, calcd: 461.2141; found: 461.2143.
References and notes
4.1.3. Synthesis of 3-(2,6-diisopropylphenyl)-1-(2-diphe-
nylphosphinobenzyl)-3H-imidazol-1-ium chloride (6c).
The compound 6c was prepared in 63% yield by the same
procedure described for 6a using 1-(2,6-diisopropylphenyl)-
imidazole. 1H NMR d 1.11 (d, JZ7.2 Hz, 6H, CH3), 1.23 (d,
JZ7.2 Hz, 6H, CH3), 2.26 (m, 2H, CH), 6.26 (s, 2H, CH2),
6.98 (m, 1H, NCHCHN), 7.00 (s, 1H, Ar-H), 7.24–7.55 (m,
15H, Ar-H), 7.75 (s, 1H, Ar-H), 8.14 (m, 1H, NCHCHN),
10.84 (s, 1H, NCHN); 31P NMR d K14.48 (s); 13C NMR d
24.4, 24.6, 28.7, 28.9, 51.1, 51.3, 122.7, 122.8, 123.6, 124.9,
129.2, 129.3, 129.7, 130.0, 130.5, 130.9, 132.1, 132.2,
133.9, 134.2, 135.0, 136.5, 136.7, 138.3, 138.6, 139.4,
145.6; HRMS for C34H36N2PC [MKCl]C, calcd: 503.2610;
found: 503.2609.
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1
10 as a white solid (0.62 g, 32% yield). H NMR d 5.58
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7.70 (s, 2H, Ar-H), 7.74 (m, 2H, NCHCHN), 10.39 (s, 1H,
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131.6, 131.7, 133.8, 134.1, 134.7, 134.8, 135.3, 136.8,
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