Palladium-catalyzed carbonylation of amines: Switchable approaches to carbamates and N,N′-disubstituted ureas

Article abstract of DOI:10.1002/adsc.201100545

Switchable access to carbamates and ureas has been developed by solvent control palladium-catalyzed carbonylation of aromatic amines under an atmosphere of carbon monoxide. A variety of N-phenylcarbamates and N,N′- diphenylureas was easily synthesized in good to excellent yields from readily available aromatic amines under mild conditions. Copyright

Full text of DOI:10.1002/adsc.201100545

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DOI: 10.1002/adsc.201100545
Palladium-Catalyzed Carbonylation of Amines: Switchable
Approaches to Carbamates and N,N’-Disubstituted Ureas
Zheng-Hui Guan,a,* Hao Lei,a Ming Chen,a Zhi-Hui Ren,a Yinjuan Bai,a
and Yao-Yu Wanga
a
Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of Ministry of Education, Department of
Chemistry & Materials Science, Northwest University, Xi’an 710069, Peopleꢀs Republic of China
E-mail: guanzhh@nwu.edu.cn
Received: July 13, 2011; Revised: September 14, 2011; Published online: January 19, 2012
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/adsc.201100545.
Abstract: Switchable access to carbamates and ureas synthesized in good to excellent yields from readily
has been developed by solvent control palladium-cat- available aromatic amines under mild conditions.
alyzed carbonylation of aromatic amines under an
atmosphere of carbon monoxide. A variety of N-phe- Keywords: amines; carbamates; carbonylation reac-
nylcarbamates and N,N’-diphenylureas was easily tions; palladium-catalyzed reactions; ureas
Introduction
bonylation of aromatic amines for the preparation of
carbamates and N,N’-diarylureas under an atmos-
Carbamates and N,N’-disubstituted ureas are com- phere of CO.
monly encountered in the structures of biologically
active compounds. Carbamates are pivotal precursors
for the synthesis of pesticides, fungicides, herbicides Results and Discussion
and drugs.[1] N,N’-Disubstituted ureas are widely used
as agrochemicals, dyes, antioxidants and HIV inhibi- Our investigation was initially initiated by a study of
tors.[2] In addition, they are also widely applied as key the reactions of aniline 1a and methanol 2a, and rep-
intermediates in organic synthesis.[3] Efficient ap- resentative data using Pd
ACTHNUTRGNEUNG(OAc)2 as the catalyst are
proaches to carbamates and ureas were achieved by listed in Table 1. Pleasingly, the carbamate 3a was ob-
coupling of amines with phosgene and its deriva- tained in 65% yield along with N,N’-diphenylurea 4a
tives.[4,5] However, the extensive application of these in 15% yield when Cu
ACTHNUTRGENUN(G OAc)2 was employed as oxi-
highly toxic reagents would make serious environ- dant in HMPA (Table 1, entry 1). Thus, we expected
mental problems and equipment corrosion. Therefore, that a switchable access to N-phenylcarbamate 3a and
intense effort has been focused on the development N,N’-diphenylurea 4a might be achieved by reagent
of non-phosgene processes for the synthesis of carba- control. Different solvents were screened to improve
mates and N,N’-disubstituted ureas.[6]
the reaction selectivity, and DMSO was proved to be
The transition metal-catalyzed carbonylation reac- the best for the formation of 3a (Table 1, entries 2–5).
tion of amines has attracted considerable attention as Other oxidants, such as CuO and CuCl2, were inferior
a powerful method for the construction of carbamates to CuACTHNUTRGENUN(G OAc)2 (Table 1, entries 6 and 7). In order to
and N,N’-disubstituted ureas.[7] Perhaps the most further improve the yield of 3a the additives which
widely applicable metal-catalyzed method developed used to enhance the efficiency in Pd-catalyzed car-
to date is the palladium-catalyzed carbonylation reac- bonylation reactions were screened (Table 1, en-
tion.[8] However, the present palladium-catalyzed sys- tries 8–11).[10] Among these additives, KI[11] was found
tems are limited to aliphatic amines, high pressure of to be most effective for the reaction and afforded the
CO and high temperature.[9] The efforts to find new desired product 3a up to 80% yield along with 4a in
catalytic systems for a wide range of aromatic amines 12% yield (Table 1, entry 9). To our delight, when 1,4-
under mild conditions are still desirable. Herein, we dioxane was used as solvent, the yield of 4a was re-
wish to report a facile and efficient Pd-catalyzed car- markably improved to 85% (Table 1, entry 12). Final-
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Table 1. Optimization of reaction conditions for Pd-catalyzed carbonylation.[a]
Entry
Oxidant
Additive
Solvent
Yield of 3a [%][b]
Yield of 4a [%][b]
1
2
3
4
5
6
7
8
Cu
Cu
Cu
Cu
Cu
N
HMPA
DMF
DMA
65
55
30
Trace
70
10
Trace
72
80
75
75
10
–
15
38
25
5
25
7
Trace
24
12
21
19
85
93
79
75
79
MeOH
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
1,4-dioxane
1,4-dioxane
DMSO
DMF
CuO
CuCl2
Cu
Cu
Cu
Cu
Cu
Cu
Cu
Cu
Cu
LiCl
KI
NaI
9
10
11
12
13[c]
14[c]
15[c]
16[c]
(Bu)4NI
–
–
–
toluene
[a]
Reaction conditions: 1a (0.2 mmol) and 2a (10 equiv., 2.0 mmol), CO (1 atm), Pd
(1.5 equiv., 0.3 mmol), additive (0.2 equiv., 0.04 mmol), solvent (2 mL), 1208C.
Isolated yields.
ACHTUNGERTN(NUNG OAc)2 (5 mol%, 0.01 mmol), oxidant
[b]
[c]
The reaction was carried out with 1.1 equiv. of CuACHTNUTRGNEUNG(OAc)2 (0.22 mmol) in the absence of MeOH.
ly, we were pleased to observe that 4a was obtained examined. Although tert-butyl alcohol appeared to be
in 93% yield in 1,4-dioxane in the absence of MeOH unsuitable in this process (3t), the desired carbamates
(Table 1, entry 13). Other solvents were found to be 3p–3s were obtained in moderate yields when ethanol,
less effective than 1,4-dioxane toward N,N’-diphenyl- 2-propanol, benzyl alcohol, or allyl alcohol were em-
A
ployed (Table 2, entries 16–20).
The generality of this carbonylation reaction of ani-
lines was examined to establish the substrates gener- lines to construct N,N’-diphenylureas was also evalu-
ality, and the corresponding N-phenylcarbamates ated under the optimized conditions (Table 3). As for
were obtained in good to excellent yields (Table 2). the electronic effects of the transformation, we found
This catalytic system was tolerant to a number of that electron-rich anilines showed better reactivity
functional groups. Generally, anilines possessing elec- and higher yields of N,N’-diphenylureas than elec-
tron-withdrawing groups gave the products in higher tron-deficient ones (Table 3, entries 2–6). The N,N’-di-
yields than those with electron-donating groups phenylureas 4g–4i which with a Cl, NO2, or Me substi-
(Table 2, entries 2–6). When 3-chloroaniline and 3-ni- tutent at the meta-position were also obtained in good
troaniline were employed, the corresponding products yields (Table 3, entries 7–9). Excellent yields of N,N’-
3g and 3h were obtained up to 95% and 92% yields, diphenylureas 4k and 4l indicated that the reaction
respectively (Table 2, entries 7 and 8). ortho-Substitut- was insensitive to steric hindrance of the anilines
ed anilines also afforded the desired products in good (Table 3, entries 11 and 12). Additionally, an aliphatic
yields which indicated that steric effects had little in- amine, such as benzylamine 1o, showed excellent re-
fluence on this transformation (Table 2, entries 10– activity under these conditions, and gave the corre-
12). Notablely, 2-aminopyridine and 1-naphthylamine sponding
N,N’-dibenzylurea
4m
quantitatively
were also tolerable in this process to give desired car- (Table 3, entry 13).
bamates 3m and 3n in 90% and 58% yields, respec-
tively (Table 2, entries 13 and 14). Moreover, when
2,4-dinitroaniline was employed as a multisubstituted Conclusions
substrate, the reaction also proceeded smoothly to
give the corresponding carbamate 3o in moderate In summary, we have developed a switchable access
yield (Table 2, entry 15). Next, the carbonylation reac- to N-phenylcarbamates and N,N’-diphenylureas by
tions of p-toluidine 1e with other alcohols were also the Pd-catalyzed carbonylation of anilines under an
490
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Palladium-Catalyzed Carbonylation of Amines: Switchable Approaches to Carbamates
Table 2. Pd-catalyzed carbonylation of anilines for synthesis of carbamates.[a]
Entry
1
1
2
Product
Yield [%][b]
80
1a
1b
1c
MeOH
3a
3b
3c
2
3
MeOH
MeOH
89
89
4
1d
MeOH
3d
73
5
6
1e
1f
MeOH
MeOH
3e
3f
76
47
7
8
9
1g
1h
1i
MeOH
MeOH
MeOH
3g
3h
3i
95
92
76
10
11
1j
MeOH
MeOH
3j
78
85
1k
3k
12
13
14
1l
MeOH
MeOH
MeOH
3l
75
90
58
1m
1n
3m
3n
15
1o
1e
1e
MeOH
EtOH
3o
3p
3q
46
64
47
16[c]
17[c]
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Table 2. (Continued)
Entry
1
2
Product
Yield [%][b]
63
18[c]
19[c]
1e
1e
3r
3s
55
0
20[c]
1e
3t
[a]
Reaction conditions: 1 (0.2 mmol) and 2 (10 equiv., 2.0 mmol), CO (1 atm), Pd
(1.5 equiv., 0.3 mmol), KI (0.2 equiv., 0.04 mmol), DMSO (2 mL), at 1208C;
Isolated yields.
ACHUTGTNERN(NGU OAc)2 (5 mol%, 0.01 mmol), CuACHTUNGTRENNUNG(OAc)2
[b]
[c]
5 equiv. of alcohol (1.0 mmol) were used and HMPA (2 mL) was employed as solvent.
atmosphere of CO. This general protocol presents an
intriguing example of solvent control of product selec-
tivity and shows good functional group tolerance. A
wide variety of N-phenylcarbamates and N,N’-diphe-
nylureas was synthesized in good to excellent yields
under mild reaction conditions.
Typical Procedure for the Synthesis of N,N’-Diphen-
ylureas
A 10-mL round flask was charged with amine (0.2 mmol),
CuACHTNUGTRENNUG(OAc)2 (40 mg, 0.22 mmol), and PdACHTUNTGERN(NUGN OAc)2 (2.2 mg,
5 mol%) in 2.0 mL 1,4-dioxane. The flask was evacuated
and back-filled with CO (5 times, balloon) and heated to
reflux under vigorous stirring. Upon completion (detected
by TLC), the reaction mixture was cooled to room tempera-
ture. The solution was subjected to a short column of silica
gel to remove the solids and concentrated under reduced
pressure. The residue was purified by chromatography on
silica gel to afford corresponding products.
Experimental Section
General Information
Column chromatography was performed by employing silica
3a: mp 40–428C (lit.[12] 40–428C); 1H NMR (400 MHz,
CDCl3): d=7.41–7.39 (d, J=7.6 Hz, 2H), 7.33–7.29 (t, J=
8.0 Hz, 2H), 7.09–7.05 (t, J=7.2 Hz, 1H), 6.89 (s, 1H) 3.78
(s, 3H); 13C NMR (100 MHz, CDCl3): d=154.1, 137.8, 128.9,
123.3, 118.6, 52.2; HR-MS (ESI): m/z=174.0533, calcd. for
C8H9NO2 (M+Na+): 174.0525.
1
gel. H NMR spectra were recorded at 400 MHz in DMSO-
d6 or CDCl3 and 13C NMR spectra were recorded at
100 MHz in DMSO-d6 or CDCl3. All new products were fur-
1
ther characterized by HR-MS; copies of their H NMR and
13C NMR spectra are provided in the Supporting Informa-
tion. Unless otherwise stated, all amines and solvents were
purchased from commercial suppliers and used without fur-
ther purification.
3b: mp 114–1158C (lit.[12] 114–1158C); 1H NMR
(400 MHz, CDCl3): d=7.34–7.32 (d, J=7.2 Hz, 2H), 7.25–
7.23 (d, J=8.4 Hz, 2H), 6.90 (s, 1H), 3.76 (s, 1H); 13C NMR
(100 MHz, CDCl3): d=154.0, 136.4, 128.9, 128.4, 119.9, 52.4;
HR-MS (ESI): m/z=208.0140, calcd. for C8H8ClNO2 (M+
Na+): 208.0136.
Typical Procedure for the Synthesis of Carbamates
A 10-mL round flask was charged with amine (0.2 mmol),
1
alcohol (2 mmol), KI (6.6 mg, 0.04 mmol), Cu
ACHTUNGERTN(NUNG OAc)2
3c: mp 117–1188C; H NMR (400 MHz, CDCl3): d=7.40–
(55 mg, 0.3 mmol), Pd(OAc)2 (2.2 mg, 5 mol%) in 2.0 mL
AHCTUNGTRENNUNG
7.38 (d, J=8.8 Hz, 2H), 7.29–7.27 (d, J=9.2 Hz, 2H), 6.96
(s, 1H), 3.76 (s, 3H); 13C NMR (100 MHz, CDCl3): d=
153.9, 136.9, 131.8, 120.2, 115.9, 52.4; HR-MS (ESI): m/z=
251.9634, calcd. for C8H8BrNO2 (M+Na+): 251.9631.
3d: mp 162–1638C (lit.[3] 1648C); 1H NMR (400 MHz,
DMSO-d6): d=10.04 (s, 1H), 7.87–7.85 (d, J=9.2 Hz, 2H),
7.56–7.54 (d, J=8.8 Hz, 2H), 3.66 (s, 3H), 2.47 (s, 3H);
13C NMR (100 MHz, DMSO-d6): d=201.6, 158.9, 148.7,
136.0, 134.6, 122.3, 56.9, 31.4; HR-MS (ESI): m/z=216.0642,
calcd. for C10H11NO3 (M+Na+): 216.0631.
DMSO. The flask was evacuated and back-filled with CO (5
times, balloon) and heated to 1208C under vigorous stirring.
Upon completion (detected by TLC), the reaction mixture
was cooled to room temperature. The resulting mixture was
diluted with EtOAc and then washed with water (15 mL)
and 10% aqueous ammonia (10 mL). The aqueous phase
was extracted with EtOAc (10 mL, 2 times). The combined
organic layer was washed with brine, and dried over MgSO4,
then filtered and concentrated under vacuum. The residue
was purified by column chromatography on silica gel to
afford corresponding products.
3e: mp 96–978C (lit.[12] 97–988C); 1H NMR (400 MHz,
CDCl3): d=7.29–7.27 (d, J=7.2 Hz, 2H), 7.13–7.11 (d, J=
8.0 Hz, 2H), 6.80 (s, 1H), 3.78 (s, 3H), 2.32 (s, 3H);
13C NMR (100 MHz, CDCl3): d=154.2, 135.1, 132.9, 129.4,
118.7, 52.1, 20.6; HR-MS (ESI): m/z=188.0683, calcd. for
C9H11NO2 (M+Na+): 188.0682.
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Palladium-Catalyzed Carbonylation of Amines: Switchable Approaches to Carbamates
Table 3. Pd-catalyzed carbonylation of anilines for synthesis of N,N’-diphenylureas.[a]
Entry
1
1
Product
Yield [%][b]
93
1a
1b
1c
4a
4b
4c
2
3
76
65
4
5
6
1d
1e
1f
4d
4e
4f
61
96
74
7
8
9
1g
1h
1i
4g
4h
4i
71
64
75
10
11
12
1j
1k
1l
4j
4k
4l
57
94
93
13
1p
4m
96
[a]
Reaction conditions: 1 (0.2 mmol), CO (1 atm), Pd
N
ACHTUNGRTEN(NUNG OAc)2 (1.1 equiv., 0.22 mmol), 1,4-di-
oxane (2 mL), reflux.
Isolated yields.
[b]
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3f: mp 85–868C (lit.[14] 88–898C); 1H NMR (400 MHz,
CDCl3): d=7.29–7.27 (d, J=9.6 Hz, 2H), 6.85–6.83 (d, J=
9.2 Hz, 2H), 6.68 (s, 1H), 3.78 (s, 3H), 3.75 (s, 3H);
13C NMR (100 MHz, CDCl3): d=156.2, 154.7, 131.1, 120.9,
114.4, 55.7, 52.5; HR-MS (ESI): m/z=204.0635, calcd. for
C9H11NO3 (M+Na+): 204.0631.
53.4; HR-MS (ESI): m/z=248.0276, calcd. for C8H7N3O5
(M+Na+): 248.0278.
3p: oil; H NMR (400 MHz, CDCl3): d=7.28–7.26 (d, J=
1
7.2 Hz, 2H), 7.08–7.06 (d, J=8.4 Hz, 2H), 6.89 (s, 1H),
4.22–4.17 (m, 2H), 2.28 (s, 3H), 1.29–1.26 (t, J=9.6 Hz,
3H); 13C NMR (100 MHz, CDCl3): d=153.9, 135.4, 132.8,
129.4, 118.8, 61.0, 20.7, 14.5; HR-MS (ESI): m/z=202.0838,
calcd. for C10H13NO2 (M+Na+): 202.0838.
3g: mp 80–818C (lit.[15] 818C); 1H NMR (400 MHz,
CDCl3): d=7.51 (s, 1H), 7.22–7.17 (m, 2H), 7.08 (s, 1H),
7.03–7.01 (d, J=7.2 Hz, 2H), 3.77 (s, 3H); 13C NMR
(100 MHz, CDCl3): d=154.0, 139.1, 134.6, 129.9, 123.4,
118.7, 116.7, 52.5; HR-MS (ESI): m/z=208.0136, calcd. for
C8H8ClNO2 (M+Na+): 208.0136.
1
3q: oil; H NMR (400 MHz, CDCl3): d=7.27–7.25 (d, J=
4.4 Hz, 2H), 7.11–7.09 (d, J=7.6 Hz, 2H), 6.51 (s, 1H),
5.03–5.00 (m, 1H), 2.30 (s, 3H), 1.30 (s, 3H) 1.29 (s, 3H);
13C NMR (100 MHz, CDCl3): d=153.3, 135.4, 132.7, 129.4,
118.7, 68.5, 22.0, 20.7; HR-MS (ESI): m/z=216.1002, calcd.
for C11H15NO2 (M+Na+): 216.0995.
1
3h: mp 147–1488C; H NMR (400 MHz, DMSO-d6): d=
10.15 (s, 1H), 8.40 (s, 1H), 7.81–7.75 (m, 2H), 7.54–7.50 (t,
J=8.0 Hz, 1H), 3.68 (s, 3H); 13C NMR (100 MHz, DMSO-
d6): d=159.0, 153.1, 145.5, 135.2, 129.1, 121.9, 117.0, 57.1;
HR-MS (ESI): m/z=219.0378, calcd. for C8H8N2O4 (M+
Na+): 219.0376.
3r: mp 79–808C (lit.[17] 82–848C); 1H NMR (400 MHz,
CDCl3): d=7.38–7.30 (m, 5H), 7.26–7.24 (d, J=6.0 Hz, 2H),
7.08–7.06 (d, J=8.4 Hz, 2H), 6.76 (s, 1H), 5.16 (s, 2H), 2.28
(s, 3H); 13C NMR (100 MHz, CDCl3): d=153.4, 136.1, 135.1,
132.9, 129.4, 128.5, 128.2, 118.7, 66.8, 29.6, 20.7; HR-MS
(ESI): m/z=264.0999, calcd. for C15H15NO2 (M+Na+):
264.0995.
3i: mp 65–668C (lit.[12] 638C); 1H NMR (400 MHz,
CDCl3): d=7.24 (s, 1H), 7.19–7.18 (d, J=4.0 Hz, 2H), 6.70–
6.88 (t, J=4.0 Hz, 1H), 6.82 (s, 1H), 3.77 (s, 3H), 2.33 (s,
3H); 13C NMR (100 MHz, CDCl3): d=154.1, 138.9, 137.7,
128.8, 124.2, 119.4, 115.8, 52.2, 21.4; HR-MS (ESI): m/z=
188.0679, calcd. for C9H11NO2 (M+Na+): 188.0682.
1
3s: oil; H NMR (400 MHz, CDCl3): d=7.27–7.25 (d, J=
8.8 Hz, 2H), 7.11–7.09 (d, J=8.0 Hz, 2H), 6.70 (s, 1H),
5.99–5.92 (m, 1H), 5.37–5.33 (d, J=16.8 Hz, 1H), 5.26–5.23
(d, J=10.4 Hz, 1H), 4.66–4.65 (d, J=5.0 Hz, 2H), 2.30 (s,
3H); 13C NMR (100 MHz, CDCl3): d=153.3, 135.1, 133.0,
132.4, 129.4, 118.7, 118.1, 65.7, 20.7; HR-MS (ESI): m/z=
214.0843, calcd. for C11H13NO2 (M+Na+): 214.0838.
4a: mp 240–2418C (lit.[18] 2428C); 1H NMR (400 MHz,
DMSO-d6): d=8.68 (s, 2H), 7.48–7.46 (d, J=7.6 Hz, 4H),
7.30–7.26 (t, J=7.2 Hz, 4H), 6.98–6.95 (t, J=7.6 Hz, 2H);
13C NMR (100 MHz, DMSO-d6): d=157.7, 144.8, 134.0,
127.0, 123.3; HR-MS (ESI): m/z=235.0837, calcd. for
C13H12N2O (M+Na+): 235.0842.
1
3j: oil; H NMR (400 MHz, CDCl3): d=8.17–8.15 (d, J=
8.0 Hz, 1H), 7.35–7.33 (d, J=8.0 Hz, 1H), 7.28–7.25 (t, J=
7.6 Hz, 1H), 7.16 (s, 1H), 7.01–7.97 (t, J=8.0 Hz, 1H), 3.80
(s, 3H); 13C NMR (100 MHz, CDCl3): d=153.9, 134.9, 129.3,
128.0, 123.9, 122.3, 120.1, 52.8; HR-MS (ESI): m/z=
208.0313, calcd. for C8H8ClNO2 (M+Na+): 208.0316.
3k: mp 58–598C (lit.[12] 60–618C); 1H NMR (400 MHz,
CDCl3): d=7.76 (s, 1H), 7.23–7.16 (m, 2H), 7.06–7.02 (t, J=
8.0 Hz, 1H), 6.50 (s, 1H), 3.78 (s, 1H), 2.25 (s, 1H);
13C NMR (100 MHz, CDCl3): d=154.7, 136.0, 130.6, 127.1,
124.5, 121.5, 52.6, 17.8; HR-MS (ESI): m/z=188.0677, calcd.
for C9H11NO2 (M+Na+): 188.0682.
4b: mp 301–3028C (lit.[18] 3028C); 1H NMR (400 MHz,
DMSO-d6): d=8.87 (s, 2H), 7.48–7.46 (d, J=8.8 Hz, 4H),
7.32–7.30(d, J=8.8 Hz, 4H); 13C NMR (100 MHz, DMSO-
d6): d=157.5, 143.7, 133.8, 130.6, 125.0; HR-MS (ESI): m/
z=303.0049, calcd. for C13H10Cl2N2O (M+Na+): 303.0062.
4c: mp 292–2938C (lit.[18] 2958C); 1H NMR (400 MHz,
DMSO-d6): d=8.86 (s, 2H), 7.43 (s, 8H); 13C NMR
(100 MHz, DMSO-d6): d=157.4, 144.1, 136.7, 125.4, 118.6;
HR-MS (ESI): m/z=390.9042, calcd. for C13H10Br2N2O
(M+Na+): 390.9052.
1
3l: oil; H NMR (400 MHz, CDCl3): d=8.09 (s, 1H), 7.27
(s, 1H), 7.00–6.95 (m, 2H), 6.87–6.85 (d, J=8.8 Hz, 1H),
3.86 (s, 3H), 3.78 (s, 3H); 13C NMR (100 MHz, CDCl3): d=
153.9, 147.5, 127.5, 122.7, 121.0, 118.1, 109.9, 55.6, 52.2; HR-
MS (ESI): m/z=204.0641, calcd. for C9H11NO3 (M+Na+):
204.0631.
3m: mp 129–1308C (lit.[14] 128–1298C); 1H NMR
(400 MHz, CDCl3): d=10.36 (s, 1H), 8.36–8.35 (d, J=
4.0 Hz, 1H), 8.06–8.04 (d, J=8.0 Hz, 1H), 7.71–7.67 (t, J=
7.2 Hz, 1H), 7.00–6.97 (t, J=6.4 Hz, 1H), 3.83 (s, 3H);
13C NMR (100 MHz, CDCl3): d=154.1, 152.4, 147.4, 138.5,
118.4, 112.5, 52.2; HR-MS (ESI): m/z=175.0475, calcd. for
C7H8N2O2 (M+Na+): 175.0478.
4d: mp 260–2618C (lit.[19] 263–265.58C); 1H NMR
(400 MHz, DMSO-d6): d=9.22 (s, 2H), 7.91–7.89 (d, J=
8.4 Hz, 4H), 7.59–7.57(d, J=8.4 Hz, 4H), 2.50 (s, 6H);
13C NMR (100 MHz, DMSO-d6): d=201.5, 157.0, 149.1,
135.8, 134.8, 122.5, 31.5; HR-MS (ESI): m/z=319.1043,
calcd. for C17H16N2O3 (M+Na+): 319.1053.
3n: mp 123–1258C (lit.[16] 121–1238C); 1H NMR
(400 MHz, DMSO-d6): d=9.55 (s, 1H), 8.05–8.03 (t, J=
4.0 Hz, 1H), 7.91–7.89 (t, J=4.8 Hz, 1H), 7.73–7.01 (d, J=
8.0 Hz, 1H), 7.60–7.58 (d, J=7.2 Hz, 1H), 7.53–7.44 (m,
3H), 3.68 (s, 3H); 13C NMR (100 MHz, DMSO-d6): d=
160.5, 138.8, 133.1, 132.9, 131.1, 130.9, 130.7, 130.0, 127.7,
126.1, 56.9; HR-MS (ESI): m/z=224.0680, calcd. for
C12H11NO2 (M+Na+): 224.0682.
4e: mp 268–2698C (lit.[18] 2698C); 1H NMR (400 MHz,
DMSO-d6): d=8.49 (s, 2H), 7.32–7.30 (d, J=8.0 Hz, 4H),
7.06–7.04 (d, J=8.4 Hz, 4H), 2.21 (s, 6H); 13C NMR
(100 MHz, DMSO-d6): d=157.8, 142.3, 135.7, 134.3, 123.4,
25.5; HR-MS (ESI): m/z=263.1148, calcd. for C15H16N2O
(M+Na+): 263.1155.
4f: mp 241–2428C (lit.[18] 2408C); 1H NMR (400 MHz,
DMSO-d6): d=8.34 (s, 2H), 7.33–7.30 (d, J=9.2 Hz, 4H),
6.84–6.82 (d, J=8.4 Hz, 4H), 3.69 (s, 6H); 13C NMR
(100 MHz, DMSO-d6): d=159.4, 158.0, 138.0, 125.0, 119.0,
60.2; HR-MS (ESI): m/z=295.1046, calcd. for C15H16N2O3
(M+Na+): 295.1053.
1
3o: mp 118–1208C; H NMR (400 MHz, CDCl3): d=10.22
(s, 1H), 9.13 (s, 1H), 8.89–8.87 (d, J=9.2 Hz, 1H), 8.49–8.46
(d, J=12.0 Hz, 1H), 3.90 (s, 3H); 13C NMR (100 MHz,
CDCl3): d=152.8, 141.0, 140.3, 134.4, 130.0, 122.2, 120.7,
494
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ꢁ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 2012, 354, 489 – 496

Palladium-Catalyzed Carbonylation of Amines: Switchable Approaches to Carbamates
4g: mp 241–2428C (lit.[20] 245–246.58C); 1H NMR
(400 MHz, DMSO-d6): d=8.96 (s, 2H), 7.69 (s, 2H), 7.31–
7.24 (m, 4H), 7.02–7.00 (d, J=6.0 Hz, 2H); 13C NMR
(100 MHz, DMSO-d6): d=157.4, 146.1, 138.3, 135.6, 126.9,
122.9, 122.0; HR-MS (ESI): m/z=303.0055, calcd. for
C13H10Cl2N2O (M+Na+): 303.0062.
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4h: mp 231–2328C (lit.[21] 2338C); 1H NMR (400 MHz,
DMSO-d6): d=9.34 (s, 2H), 8.51 (s, 2H), 7.80–7.79 (d, J=
7.2 Hz, 2H), 7.71–7.69 (d, J=8.0 Hz, 2H), 7.55–7.51 (t, J=
8.0 Hz, 2H); 13C NMR (100 MHz, DMSO-d6): d=157.5,
153.2, 145.7, 135.2, 129.7, 121.8, 117.6; HR-MS (ESI): m/z=
325.0535, calcd. for C13H10N4O5 (M+Na+): 325.0543.
1
4i: mp 262–2638C (lit.[22] 263–2648C); H NMR (400 MHz,
DMSO-d6): d=8.65 (s, 2H), 7.29 (s, 2H), 7.22–7.20(d,
J=6.0 Hz, 2H), 7.15–7.13 (m, 2H), 6.77–6.76 (d, J=7.6 Hz,
2H), 2.26 (s, 6H); 13C NMR (100 MHz, DMSO-d6): d=
157.7, 144.8, 143.1, 133.8, 127.6, 123.8, 120.4, 26.4; HR-MS
(ESI): m/z=263.1150, calcd. for C15H16N2O (M+Na+):
263.1155.
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4j: mp 226–2278C (lit.[18] 225–2268C); 1H NMR
(400 MHz, DMSO-d6): d=9.03 (s, 2H), 8.07–8.05 (d, J=
8.8 Hz, 2H), 7.45–7.43 (d, J=8.4 Hz, 2H), 7.30–7.26 (t, J=
7.6 Hz, 2H), 7.05–7.02 (t, J=7.6 Hz, 2H); 13C NMR
(100 MHz, DMSO-d6): d=157.4, 140.9, 134.5, 132.6, 129.0,
127.9, 127.6; HR-MS (ESI): m/z=303.0057, calcd. for
C13H10Cl2N2O (M+Na+): 303.0062.
1
4k: mp 235–2368C; H NMR (400 MHz, DMSO-d6): d=
8.24 (s, 2H), 7.79–7.77 (d, J=7.6 Hz, 2H), 7.16–7.10 (m,
4H), 6.94–6.90 (t, J=7.2 Hz, 2H), 2.24 (s, 6H); 13C NMR
(100 MHz, DMSO-d6): d=158.1, 142.6, 135.3, 132.8, 131.2,
127.8, 126.6, 23.2; HR-MS (ESI): m/z=263.1154, calcd. for
C15H16N2O (M+Na+): 263.1155.
4l: mp 187–1888C (lit.[18] 1858C); 1H NMR (400 MHz,
DMSO-d6): d=8.89 (s, 2H), 8.11–8.08 (t, J=6.4 Hz, 2H),
7.00–6.87 (m, 6H), 3.86 (s, 6H); 13C NMR (100 MHz,
DMSO-d6): d=157.9, 153.3, 133.9, 127.1, 125.6, 124.2, 115.9,
60.8; HR-MS (ESI): m/z=295.1043, calcd. for C15H16N2O3
(M+Na+): 295.1053.
4m: mp 167–1688C (lit.[18] 165–1668C); 1H NMR
(400 MHz, DMSO-d6): d=7.31–7.20 (m, 10H), 6.48 (s, 2H),
4.23–4.21 (d, J=5.6 Hz, 4H); 13C NMR (100 MHz, DMSO-
d6): d=163.3, 146.0, 133.4, 132.1, 131.7, 48.1; HR-MS (ESI):
m/z=263.1153, calcd. for C15H16N2O (M+Na+): 263.1155.
Acknowledgements
[9] K. Orito, M. Miyazawa, T. Nakamura, A. Horibata, H.
Ushito, H. Nagasaki, M. Yuguchi, S. Yamashita, T. Ya-
mazaki, M. Tokuda, J. Org. Chem. 2006, 71, 5951, and
references cited therein.
[10] a) H. Li, G.-X. Cai, Z.-J. Shi, Dalton Trans. 2010, 39,
10442; b) F. Zhou, X. Han, X. Lu, J. Org. Chem. 2011,
76, 1491.
This research was supported by National Natural Science
Foundation of China (NSFC-21002077), Northwest Universi-
ty (PR09037), and Education Department of Shaanxi Provin-
cial Government (2010JK869).
[11] Iodide compounds were reported to improve the effi-
ciency in Pd-catalyzed carbonylation reactions. See:
a) S. Fukuoka, M. Chono, M. Kohno, J. Org. Chem.
1984, 49, 1458; b) V. L. K. Valli, H. Alper, Organome-
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Salerno, M. C. Costa, Chem. Commun. 2003, 486;
d) N. D. Ca’, P. Bottarellia, A. Dibenedetto, M. Aresta,
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