Palladium-catalyzed regioselective and stereoselective oxidative heck arylation of allylamines with arylboronic acids

Article abstract of DOI:10.1002/adsc.201300225

A general and convenient palladium-catalyzed oxidative Heck arylation of both N-protected and N,N-diprotected allylic amines with arylboronic acids under mild conditions has been developed. The catalyst system, consisting of Pd(OAc)₂ (palladium acetate), AgOAc (silver acetate) and KHF ₂ (potassium hydrogen fluoride), could efficiently catalyze the coupling reaction in acetone without the aid of any ligand, leading exclusively to the γ-arylated allylic amine products in good to excellent yields. This method is highlighted with excellent regio- and stereocontrol and remarkable functional group tolerance. The carbamate moiety in allylic amine substrates is of crucial importance to the catalytic performance, and the chelation between the carbonyl O (oxygen) and Pd (palladium) atoms is believed to be responsible for the high regioselectivity and stereoselectivity observed. Copyright

Full text of DOI:10.1002/adsc.201300225

FULL PAPERS
DOI: 10.1002/adsc.201300225
Palladium-Catalyzed Regioselective and Stereoselective Oxidative
Heck Arylation of Allylamines with Arylboronic Acids
Lingjuan Zhang,a Chaonan Dong,a Chenjun Ding,a Jing Chen,a Weijun Tang,b
Huanrong Li,a Lijin Xu,a,* and Jianliang Xiaob
a
Department of Chemistry, Renmin University of China, Beijing 100872, Peopleꢀs Republic of China
Fax : (+86)-10-6251-6444; phone: (+86)-10-6251-1528; e-mail: xulj@chem.ruc.edu.cn
Liverpool Centre for Materials and Catalysis, Department of Chemistry, University of Liverpool, Liverpool L69 7ZD,
b
U.K.
Received: March 16, 2013; Published online: May 15, 2013
Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/adsc.201300225.
Abstract: A general and convenient palladium-cata- reocontrol and remarkable functional group toler-
lyzed oxidative Heck arylation of both N-protected ance. The carbamate moiety in allylic amine sub-
and N,N-diprotected allylic amines with arylboronic strates is of crucial importance to the catalytic per-
acids under mild conditions has been developed. The formance, and the chelation between the carbonyl O
catalyst system, consisting of PdACTHNURGTNEUNG(OAc)2 (palladium (oxygen) and Pd (palladium) atoms is believed to be
acetate), AgOAc (silver acetate) and KHF2 (potassi- responsible for the high regioselectivity and stereose-
um hydrogen fluoride), could efficiently catalyze the lectivity observed.
coupling reaction in acetone without the aid of any
ligand, leading exclusively to the g-arylated allylic
amine products in good to excellent yields. This Keywords: allylic amines; arylation; oxidative Heck
method is highlighted with excellent regio- and ste- reaction; palladium; regioselectivity
Introduction
noborons with olefins has become a rapidly expanding
area of research and is emerging as a powerful com-
Allylic amine derivatives are structural motifs found plement to the normal Heck reaction, because of its
in many natural and biologically active compounds, mild conditions, low toxicity, high functional group
and they also serve as valuable synthetic intermedi- tolerance and easy availability of organoborons.[6]
ates in various transformations.[1,2] Accordingly, a sig- Considerable advances have been made through the
nificant research effort has been put into the efficient development of more active transition metal catalyst
construction of these compounds, and a number of systems,[7–9] and the contributions from the groups of
methods can now be found in the literature.[3–5] Larhed[8] and Jung[9] are particularly noteworthy. Al-
Among these reported methods, the Pd-catalyzed though a variety of electron-deficient, electron-rich
Heck arylation of allylic amines with aryl halides and and electron-neutral olefins could be successfully ary-
pseudohalides has been extensively investigated, and lated with organoboronic acids and their derivatives
useful strategies have been developed to control the to afford high yields and selectivities, examples of the
product regioselectivity, which arises from the two oxidative Heck arylation of allylic amines are very
competing reaction pathways (Scheme 1).[4,5] In recent rare, with only one report available in the literature.
years, the catalytic oxidative Heck coupling of orga- Sigman et al. revealed that arylboronic esters could
undergo regioselective (linear) coupling reaction with
allylic amines in the presence of a Pd-carbene catalyst
and O2 (Scheme 1, path A),[7l] but only two N,N-di-
protected allylic amines containing a carbamate
moiety were attempted. Therefore, more general and
efficient catalyst systems for oxidative Heck coupling
of allylic amines with organoborons are desirable.
Scheme 1. Two competing pathways.
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Palladium-Catalyzed Regioselective and Stereoselective Oxidative Heck Arylation of Allylamines
Recently, we found that the combination of the reduced steric hindrance.[5e,k,10] The performance
PdACHTUNGTRENNUNG(OAc)2 and dppp [1,3-bis(diphenylphosphino)pro- of copper oxidants was also explored (Table 1, en-
pane] in ethylene glycol constitutes a highly effective tries 9 and 10), but none of them could work as effec-
catalyst system for the internal Heck arylation of N- tively as AgOAc. Increasing the amount of AgOAc to
Boc-allylamine with aryl bromides (Scheme 1, path 2 equivalents could increase the yield to 66%
B),[10a] and Pd
ACHTUNGTRENNUNG(OAc)2 could catalyze the Heck cou- (Table 1, entry 11). Considering the remarkable effect
pling reaction of aryl bromides with bulky N,N-dipro- of fluoride ion on promoting the Suzuki–Miyaura re-
tected allylic amines under ligand-free conditions to action[11]and oxidative Heck reaction,[7j,q] we next in-
give the g-arylated products in a highly regioselective vestigated the effect of fluoride ion in this study. De-
and stereoselective manner (Scheme 1, path A).[10b] lightfully, the reaction finished in 8 h in the presence
More recently, we have developed a mild and efficient of KHF2, exclusively affording the desired product 3a
catalytic method for the highly regioselective and ste- in 95% yield (Table 1, entry 12). The addition of KF
reoselective direct g-arylation of N,N-diprotected al- and CsF could also enable the reaction to go to com-
lylic amines with thiophenes and furans in the pres- pletion (Table 1, entries 13 and 14), but the reaction
ence of Pd
(Scheme 1, path A).[10c] It was found that the use of ed homcoupling product of 1a. In order to further im-
allylic amine substrates containing carbamate prove the efficiency, a survey of solvent effect was
ACHTUNGTRENNUNG(OAc)2 and appropriate oxidants was less efficient due to the formation of the unwant-
a
moiety was crucial to ensure good catalyst perfor- made. Lower yields were achieved in CH3CN and
mance, and the steric properties of these allylic water (Table 1, entries 15 and 16), and the reaction
amines greatly affected the regiocontrol. Encouraged was totally inhibited in DMF, DMSO and NMP
by these results and in continuing our interest in the (Table 1, entries 17–19). Employing PdACHTUNRGTNEUNG(OAc)2 as the
regioselective arylation of olefins, herein, we report source of palladium was important for this transfor-
a general and effective palladium catalyst system con- mation, as catalysts derived from other Pd precursors
sisting of Pd
ACHTUNGTRENNUNG
ficiently catalyzes the highly regioselective and stereo- catalyst system comprising PdAHCUTNGTRENNUNG
selective oxidative Heck reaction of organoboronic KHF2, which has been shown to efficiently catalyze
acids with both N-protected allylic amines and N,N- the oxidative Heck arylation of allyl esters with aryl-
diprotected allylic amines under ligand-free condi- boronic acids in a highly regio- and stereoselective
tions. The catalyst system displays broad functional manner,[7j] could also work well in our case (Table 1,
group tolerance at both coupling partners, and pro- entry 23). However, the necessity of two equivalents
vides a robust, complementary approach to existing of CuF2 and KHF2 made this chemistry less attractive.
methods.
Further study revealed that the reaction with the
Pd
AHCTUNGTRENNUNG
external oxidant, that is, under an N2 atmosphere,
proved to be ineffective as no product formation was
observed (Table 1, entry 24). Whiteꢀs protocol, report-
Results and Discussion
With p-tolylboronic acid 1a as the model substrate ed to be highly effective for the selective oxidative
and N-Boc-allylamine 2a as the model olefin, we Heck reaction of arylboronic acids with olefins,[7g] was
started our screening studies for the establishment of also tested, but it only afforded an inferior yield of
suitable reaction conditions. Initially, the coupling re- 30% (Table 1, entry 25). Thus the optimal reaction
action was carried out in acetone at 608C in the pres- conditions were finally determined as follows:
ence of a catalytic amount of PdACTHNUTRGENN(UG OAc)2 with O2 as PdAHCUTNGTREN(NUNG OAc)2 (5 mol%), AgOAc (2 equiv.) and KHF2
the oxidant under ligandless conditions, but no reac- (1 equiv.) in acetone at 608C. It should be stressed
tion occurred (Table 1, entry1). Replacing O2 with that in all cases no observation of allylic migration or
BQ (1,4-benzoquinone) still did not result in any dis- partial deprotection was made.
cernible reaction (Table 1, entry 2). Several silver salts
Having the optimal reaction conditions in hand, we
were then examined (Table 1, entries 3–8), and the next examined the reaction of 2a with a range of aryl-
best yield of 46% was obtained in the case of AgOAc boronic acids. As shown in Table 2, all of the reac-
(Table 1, entry 5). It is notable that only linear g-ary- tions proceeded efficiently, providing the expected g-
lated (E)-allylic amine 3aa was produced in all these arylated linear (E)-allylic amine products in good to
cases without the Z stereoisomer and the branched excellent yields. It is worth noting that excellent re-
isomer 4aa being detected. This is remarkable since gioselectivivites (terminal/internal >99:1) and stereo-
the previous observations show that the bulkiness of selectivities (E/Z>99:1) were observed in these trans-
the substituent on the allylic amine nitrogen has a de- formations, and no regioisomer and stereoisomer
cisive effect on the regiocontrol, and the arylation of could be detected. Notably, this catalyst system toler-
2a under ligand-free conditions generally leads to ated not only functional groups with varying electron-
a mixture of g- and b-arylated allylic amines due to ic properties, but at different substitution positions as
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Table 1. Screening conditions for oxidative Heck arylation of p-tolylboronic acid (1a) with N-Boc-allylamine (2a).[a]
FULL PAPERS
Entry
Solvent
Oxidant (equiv.)
Additive (equiv.)
Yield [%][b]
1
2
3
4
5
6
7
8
acetone
acetone
acetone
acetone
acetone
acetone
acetone
acetone
acetone
acetone
acetone
acetone
acetone
acetone
CH3CN
H2O
DMF
DMSO
NMP
acetone
acetone
acetone
acetone
acetone
dioxane
O2
BQ (1)
none
none
none
none
none
none
none
none
nd
nd
12
28
46
30
9
Ag2SO4 (1)
AgNO3 (1)
AgOAc (1)
Ag2CO3 (1)
AgOTf (1)
Ag2O (1)
40
nd
nd
66
95
86
76
68
61
nd
nd
nd
80
60
80
92
nd
30
9
Cu
CuF2 (1)
(OAc)2 (1)
none
none
none
10
11
12
13
14
15
16
17
18
19
20[c]
21[d]
22[e]
23[f]
24[g]
25[h]
AgOAc (2)
AgOAc (2)
AgOAc (2)
AgOAc (2)
AgOAc (2)
AgOAc (2)
AgOAc (2)
AgOAc (2)
AgOAc (2)
AgOAc (2)
AgOAc (2)
AgOAc (2)
AgOAc (2)/CuF2 (1)
none
KHF2 (1)
KF (1)
CsF (1)
KHF2 (1)
KHF2 (1)
KHF2 (1)
KHF2 (1)
KHF2 (1)
KHF2 (1)
KHF2 (1)
KHF2 (1)
KHF2 (2)
none
BQ (2)
AcOH (4)
[a]
Reaction conditions: 1a (0.5 mmol), 2a (1.0 mmol), PdACTHNUGTRNEUNG(OAc)2 (0.025 mmol), oxidant, additive, solvent (2.5 mL), 608C, 8 h.
No 4aa was detected in all reactions. nd: not detected. Boc=tert-butyloxycarbonyl.
Isolated yield.
[b]
[c]
[d]
[e]
[f]
PdCl2 was used to replace Pd
ACHTUNGTRENNUNG
Pd
Pd
C
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
Reaction temperature 858C, 5 h.
1a (1.0 mmol), 2a (2.0 mmol), PdCATHNUGTRNE(NGU OAc)2 (2 mol%), dppp (3 mol%), acetone (3 mL), 708C, 20 h, N2.
1a (1.5 mmol), 2a (1.0 mmol), Pd(II)/phenyl bis-sulfoxide (10 mol%), BQ (2.0 mmol), AcOH (4.0 mmol), dioxane
[g]
[h]
(3.0 mL), room temperature, 24 h.
well. Of particulate note is that the sensitive halogen afford the corresponding allylic amines in good yields
substituent (Br and Cl) in the aromatic ring of aryl- (Table 2, entries 22 and 23). The catalyst system also
boronic acids did not affect the yields of the desired worked effectively for the highly selective olefination
products (Table 2, entries 7 and 8), and the obtained of other organoborons. It was found that arylboronic
products can serve as useful starting materials for fur- esters and potassium aryl trifluoroborates[8i] (Table 2,
ther elaboration. Of further interest is that hydroxy- entries 24 and 25) displayed similar reactivity to their
methyl group could well survive the reaction condi- boronic acid analogues. Noteworthy is that all the
tions, giving the corresponding product in good yield substrates underwent clean conversions without for-
(Table 2, entry 13). Steric effects appear to have little mation of the allylic migration products or homocou-
influence on the reaction efficiency, as evidenced by pling products.
the fact that we encountered no problem in the olefi-
Encouraged by the successful arylation of 2a, we
nation of arylboronic acids bearing ortho-substitutents then extended our research to other allylic amine de-
(Table 2, entries 2, 5, 10). The reaction is not limited rivatives, and the results are shown in Table 3. For N-
to arylboronic acids only; heteroarylboronic acid and protected allylic amines 2b and 2c, high yields of the
alkenylboronic acid participated equally well to expected products were obtained under the conditions
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Palladium-Catalyzed Regioselective and Stereoselective Oxidative Heck Arylation of Allylamines
Table 2. Oxidative Heck arylation of 2a with arylboronic
Table 2. (Continued)
acids.[a]
Entry
Arylboronic Acid 1
Yield [%][b] (Product)
24
1y
1z
95 (3ba)
25
93 (3ba)
[a]
Reaction conditions:
1 (0.5 mmol.), 2a (1.0 mmol),
Entry
Arylboronic Acid 1
Yield [%][b] (Product)
96 (3ba)
Pd(OAc)2 (5 mol%), AgOAc (1.0 mmol), KHF2
AHCTUNGTRENNUNG
(0.5 mmol), acetone (2.5 mL), 608C, 8 h.
Isolated yield.
1
2
3
4
5
1b
1c
1d
1e
1f
[b]
90 (3ca)
established for 2a regardless of the nature of the sub-
stituents on the aryl ring and allylic amine nitrogen,
and the regioselectivity and stereoselectivity are simi-
lar to that observed in the arylation of 2a (Table 3,
entries 1–8). Similarly, arylation of N,N-diprotected
allylic amines with various arylboronic acids proceed-
ed smoothly to exclusively afford g-arylated linear
(E)-allylic amines in good to excellent yields, and
a range of functional groups in both coupling partners
were well tolerated (Table 3, entries 9–24). It is nota-
ble that the allylamine 2f, which was previously
shown to be less reactive,[7l] could be readily arylated
91 (3da)
90 (3ea)
90 (3fa)
6
1g
1h
1i
90 (3ga)
91 (3ha)
90 (3ia)
88 (3ja)
90 (3ka)
83 (3la)
7
8
to furnish the expected products (Table 3, enACHTUNGTRENNUNGtries 15
and 16). The viability of the current catalyst system
was further demonstrated in the highly regioselective
and stereoselective arylation of a-substituted allylic
amine 2j (Table 3, entries 25 and 26). The frequently
encountered partial deprotection in the arylation of
N,N-diprotected allylic amines did not take place in
our case.[5j,10b,c]
9
1j
10
11
1k
1l
12
1m
84 (3ma)
We also explored the reaction of b-arylated allylic
amines 2k and 2l with arylboronic acids, and the de-
sired products were isolated in satisfactory yields
(Table 4). It is worth noting that these highly substi-
tuted allylic amines have been confirmed to be of Z
configuration by NMR spectroscopy. However, no re-
action was observed in the reaction of electron-rich
N,N-diethylallylic amine (2m). It is believed that the
strong coordination of the nitrogen atom of allylic
amine 2m to Pd could cause catalyst poisoning, there-
by inhibiting the arylation. Similar poor performance
of N,N-dialkylallylic amines has been reported
recently.[4b,5k,10b,c] It appears that the presence of a car-
bamate group in allylic amine substrates is necessary
for high catalytic activity.
Taking all the data presented in Table 2, Table 3
and Table 4 into account, it is evident that the aryla-
tion shows almost negligible sensitivity to the steric
characteristics of the substituent on the allylic amine
nitrogen, but the electronic properties of the sub-
strates has a significant impact on the catalytic activi-
ty and selectivity. Recently Jiao and his co-workers
reported high levels of regio-, and stereocontrol ex-
13
14
1n
1o
82 (3na)
75 (3oa)
15
16
17
18
1p
1q
1r
1s
73 (3pa)
81 (3qa)
80 (3ra)
87 (3sa)
19
20
21
1t
87 (3ta)
90 (3ua)
90 (3va)
1u
1v
22
23
1w
1x
75 (3wa)
83 (3xa)
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Table 3. Oxidative Heck arylation of allylic amines 2b–i with arylboronic acids.[a]
Entry
Arylboronic Acid 1
Allylic amine 2
Yield [%][b] (Product)
90 (3bb)
1
2
3
1b
1c
1d
2b
2b
2b
91 (3cb)
89 (3db)
4
5
6
7
1v
1a
1e
1h
2b
2c
2c
2c
85 (3vb)
90 (3ac)
89 (3ec)
90 (3hc)
8
1v
1a
1i
2c
2d
2d
82 (3vc)
83 (3ad)
81 (3id)
9
10
11
1m
2d
80 (3md)
12
13
14
1t
2d
2e
2e
82 (3td)
80 (3ae)
81 (3be)
1a
1b
15
1d
2f
85 (3df)
16
17
18
19
20
21
22
1v
1a
1v
1p
1v
1a
1f
2f
2g
2g
2h
2h
2i
87 (3vf)
82 (3ag)
90 (3vg)
75 (3ph)
85 (3vh)
89 (3ai)
81 (3fi)
2i
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Palladium-Catalyzed Regioselective and Stereoselective Oxidative Heck Arylation of Allylamines
Table 3. (Continued)
Entry
Arylboronic Acid 1
Allylic amine 2
Yield [%][b] (Product)
83 (3ii)
23
1i
2i
2i
2j
2j
24
1v
1b
1v
93 (3vi)
25
79 (3bj)
26
80 (3vj)
[a]
Reaction conditions: 1 (0.5 mmol.), 2 (1.0 mmol), PdACTHNUGTRENUNG(OAc)2 (5 mol%), AgOAc (1.0 mmol), KHF2 (0.5 mmol), acetone
(2.5 mL), 608C, 8 h.
Isolated yield.
[b]
Table 4. Oxidative Heck arylation of allylic amines 2k and 2l with arylboronic acids.[a]
Entry
Arylboronic Acid 1
Allylic amine 2
Yield [%][b] (Product)
70 (3ak)
1
2
3
4
5
1a
1b
1h
1y
1a
1b
2k
2k
2k
2k
2l
73 (3bk)
69 (3hk)
74 (3bk)
67 (3al)
6
2l
65 (3bl)
[a]
Reaction conditions: 1 (0.5 mmol.), 2 (1.0 mmol), PdACTHNUGTRENUNG(OAc)2 (5 mol%), AgOAc (1.0 mmol), KHF2 (0.5 mmol), acetone
(2.5 mL), 608C, 8 h.
Isolated yield.
[b]
hibited in Pd-catalyzed arylation of allylic esters
which were ascribed to the coordination of the car-
bonyl O to palladium.[7j,12] In our current investiga-
tion, this chelation effect may contribute similarly to
the excellent regioselectivity and stereoselectivity ob-
served. Accordingly, a plausible mechanism is suggest-
ed in Scheme 2. The palladium intermediate A gener-
ated by transmetallation of the aryl group from boron
to palladium reacts with the allylic amine to form the
neutral intermediate B. The coordination between the
carbonyl O atom and Pd atom facilitates a highly re-
gioselective migration of the aryl moiety to give inter-
mediate C, in which Ha is ideally positioned, following
À
rotation around the C C bond, in a syn relationship
with Pd to undergo regio- and stereoselective b-H tion of allylic amines with arylboronic acids.
Scheme 2. Proposed mechanism for oxidative Heck aryla-
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Lingjuan Zhang et al.
FULL PAPERS
matography on silica gel using a mixture of ethyl acetate
and hexane (10/90 to 15/85) to give the pure product.
elimination to furnish the expected product. Finally,
oxidation of the Pd(0) species by AgOAc regenerates
the Pd(II) to complete the catalytic cycle. Similar che-
lation-assisted regio- and stereocontrol has also been
reported in the arylation of allyl derivatives and vinyl
derivatives.[4b,5k,7g,j,8e,f,13,14]
(E)-tert-Butyl 3-p-tolylallylcarbamate (3aa): white solid;
mp 878C. 1H NMR (400 MHz, CDCl3): d=7.28 (d, J=
7.92 Hz, 2H), 7.13 (d, J=7.96 Hz, 2H), 6.49 (d, J=15.84 Hz,
1H), 6.16 (dt, J=6.12, 15.60 Hz, 1H), 4.70 (br, 1H), 3.92 (s,
2H), 2.35 (s, 3H), 1.49 (s, 9H); 13C NMR (100.6 MHz,
CDCl3): d=155.8, 137.4, 133.9, 131.4, 129.3, 126.3, 125.3,
79.4, 42.8, 28.4, 21.2; HR-MS (ESI): m/z=270.1461, calcd.
for C15H21NNaO2 [M+Na]+: 270.1465.
Conclusions
(E)-tert-Butyl 3-(3-methoxyphenyl)allylcarbamate (3ea):
colorless oil. 1H NMR (400 MHz, CDCl3): d=7.23 (t, J=
7.92 Hz, 1H), 6.96 (d, J=7.68 Hz, 1H), 6.90 (t, J=2.2 Hz,
1H), 6.80 (dd, J=2.12, 8.16 Hz, 1H), 6.48 (d, J=15.84 Hz,
1H), 6.20 (dt, J=6.04, 15.60 Hz, 1H), 4.81 (br, 1H), 3.92 (s,
2H), 3.82 (s, 3H), 1.49 (s, 9H); 13C NMR (100.6 MHz,
CDCl3): d=159.8, 155.8, 138.2, 131.3, 129.5, 126.8, 119.8,
113.3, 111.7, 79.5, 55.2, 42.7, 28.4; HR-MS (ESI): m/z=
286.1412, calcd. for C15H21NNaO3 [M+Na]+: 286.1414.
In summary, we have developed an efficient palladi-
um catalyst system for oxidative Heck reactions of
both N-protected and N,N-diprotected allylic amine
derivatives with a wide range of arylboronic acids to
give the g-arylated allylic amines in good to excellent
yields. The reaction proceeded highly regio- and ste-
reoselectively under mild conditions in the absence of
ligand, and a wide range of functionalities in both
coupling partners could be well tolerated. Many fac-
tors, such as solvent, allylic amine derivative, oxidants
and additives, influenced the catalytic efficacy, and
the allylic amine substrates containing a carbamate
moiety were found to be essential for securing high
regioselectivity and stereoselectivity due to carbonyl
coordination to Pd. This approach provides a simple
and efficient pathway to access various synthetically
useful g-arylated allylic amines. Efforts focusing on
the synthetic application and the mechanism of this
coupling reaction are currently being made in our lab,
and will be reported in due course.
(E)-Benzyl
3-(4-cyanophenyl)allylACTHUGNETRNNU(G methyl)carbamate
(3vf): yellow oil. 1H NMR (400 MHz, CDCl3): d=7.60 (d,
J=8.24 Hz, 2H), 7.44 (m, 7H), 6.45 (m, 1H), 6.32 (m, 1H),
5.19 (s, 2H), 4.11 (m, 2H), 2.98 (s, 3H); 13C NMR
(100.6 MHz, CDCl3): d=141.0, 136.7, 132.4, 130.6, 130.1,
129.0, 128.5, 128.1, 128.0, 126.9, 118.9, 110.9, 67.3, 51.0, 50.6,
34.7, 33.9; HR-MS (ESI): m/z=329.1258, calcd. for
C19H18N2NaO2 [M+Na]+: 329.1260.
(Z)-2-(2-Phenyl-3-p-tolylallyl)isoindoline-1,3-dione (3al):
white solid, mp 83.68C. 1H NMR (400 MHz, CDCl3): d=
7.71 (m, 2H), 7.61 (m, 2H), 7.50 (t, J=8.1 Hz, 4H), 7.28 (d,
J=7.8 Hz, 2H), 7.22 (d, J=7.9 Hz, 3H), 6.91 (s, 1H), 4.99
(s, 2H), 2.38 (s, 3H); 13C NMR (100.6 MHz, CDCl3): d=
168.1, 139.9, 136.8, 136.5, 134.2, 133.9, 133.7, 131.8, 129.1,
129.0, 128.3, 127.5, 127.0, 123.1, 37.9, 21.3; HR-MS (ESI):
m/z=376.1311, calcd. for C24H19NNaO2 [M+Na]+: 376.1308.
Experimental Section
General Methods
Acknowledgements
Unless otherwise noted, all experiments were carried out in
air. 1H NMR and 13C NMR spectra were recorded on
a Bruker Model Avance DMX 400 Spectrometer (1H
400 MHz and 13C 106 MHz, respectively). Chemical shifts
(d) are given in ppm and are referenced to residual solvent
peaks, and coupling constants (J) are reported in Hertz. The
arylboronic acids and their derivatives, catalysts and other
common materials and solvents are commercially available,
and were used as received without further purification.
Financial support from the National Natural Science Founda-
tion of China (21072225, 21172258 and 91127039), the Fun-
damental Research Funds for the Central Universities, and
the Research funds of Renmin University of China
(11XNL011) is greatly acknowledged.
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