Palladium-catalyzed amidation of aryl halides using 2-dialkylphosphino- 2′-alkoxyl-1,1′-binaphthyl as ligands

Article abstract of DOI:10.1021/jo3005827

Palladium-catalyzed intermolecular C-N bond-forming reactions between aryl halides and amides are described using 2-dialkylphosphino-2′-alkoxyl-1, 1′-binaphthyl, which is both bulky and electron-rich, as the ligand. A variety of amides, including aliphatic and aromatic primary amides, lactams, and carbamates, were viable substrates for the amidation, which exhibited good functional group compatibility. By tuning the substituents at the 2,2′-position of 1,1′-binaphthyl of the ligand, the palladium-catalyzed amidation of bulky aryl halides was realized and this coupling reaction was used to synthesize 2-amino-2′-methoxy-1,1′- binaphthyl in high yield.

Full text of DOI:10.1021/jo3005827

Article
pubs.acs.org/joc
Palladium-Catalyzed Amidation of Aryl Halides Using
‑Dialkylphosphino-2′-alkoxyl-1,1′-binaphthyl as Ligands
2
†
†
‡
†
§
‡
,†
Fangfang Ma, Xiaomin Xie, Lei Zhang, Zhiyong Peng, Lina Ding, Lei Fu, and Zhaoguo Zhang*
†
‡
School of Chemistry and Chemical Engineering and School of Pharmacy, Shanghai Jiao Tong University, 800 Dongchuan Road,
Shanghai 200240, China
§
School of Chemistry, Chemical Engineering and Materials, Heilongjiang University, 74 Xuefu Road, Harbin 150000, China
S Supporting Information
*
ABSTRACT: Palladium-catalyzed intermolecular C−N bond-
forming reactions between aryl halides and amides are
described using 2-dialkylphosphino-2′-alkoxyl-1,1′-binaphthyl,
which is both bulky and electron-rich, as the ligand. A variety
of amides, including aliphatic and aromatic primary amides,
lactams, and carbamates, were viable substrates for the
amidation, which exhibited good functional group compati-
bility. By tuning the substituents at the 2,2′-position of 1,1′-binaphthyl of the ligand, the palladium-catalyzed amidation of bulky
aryl halides was realized and this coupling reaction was used to synthesize 2-amino-2′-methoxy-1,1′-binaphthyl in high yield.
INTRODUCTION
N-Arylamides are key structural motifs for many natural
RESULTS AND DISCUSSION
■
■
We have reported a concise synthesis of a series of 2-
dialkylphosphino-2′-alkoxyl-1,1′-binaphthyl as the bulky and
electron-rich ligands and their high activity in Pd-catalyzed
products as well as important intermediates for primary
1
arylamines. As a more efficient and facile method, the
11
amination reactions. For example, the coupling of bromo-
transition metal-catalyzed coupling reaction of aryl halides or
pseudo halides and amides has been attractive for many years.
2
benzene with aniline employing Pd(dba) /2-di-tert-butyl
2
phosphino-2′-isopropoxy-1,1′-binaphthyl (L1) system gave
diphenylamine in good yield even at room temperature. We
initiated our investigation by examining the coupling reaction
Since Shakespeare’s first report on Pd-catalyzed amide
3
arylation, many Pd-based catalytic systems have been
4
developed for the coupling of amides with aryl sulfonates,
of bromobenzene and benzamide with Pd(dba) /2-di-tert-butyl
2
5
6
aryl bromides, and more recently, aryl chlorides, which
phosphino-2′-isopropoxy-1,1′-binaphthyl as the catalyst, t-
BuONa as the base and toluene as the solvent at room
temperature. Unfortunately, no product was detected. Increas-
ing the reaction temperature to 100 °C, only a trace amount of
product was observed. However, the coupling reaction occurred
in 78% yield when the solvent was switched to tert-BuOH
Table 1, entry 2). We then examined the effects of solvents,
bases, Pd sources and ligands in the coupling reaction at 100 °C
bath temperature). The results are summarized in Table 1. We
7
proved to be useful to synthetic chemists. However, relative to
the amination reaction, less efficient or general Pd-based
catalytic systems were developed for the amidation of aryl
halides, which was more difficult because: 1) the amides are less
nucleophilic due to their electron-withdrawing carbonyl groups;
) the amidates tend to bind with palladium in a κ -fashion, and
8
(
2
2
the resultant metal−ligand bond was expected to inhibit the
(
9
reactions. Recently, studies revealed that bidentate phosphine
found that t-BuOH was the best among the tested solvents
(Table 1, entries 1−7); K PO , t-BuONa, KOH were found to
and monodentate biarylphosphine ligands bearing a substituent
ortho to the phosphorus can promote the catalytic amidation of
aryl halides through inhibiting the formation of the κ -amidate
complex by the steric hindrance.
alkoxyl-1,1′-binaphthyl, the monodentate phosphines with a
binaphthyl skeleton and an tunable alkoxy group at the adjacent
position of phosphorus atom, incline to form hemilabile
3
4
be less effective than Cs
CO as a base (Table 1, entries 2−4
2
3
2
and 7); and Pd(dba) was superior to Pd(OAc) as the Pd
2
2
5b,6a
source (Table 1, entry 8). When using Pd(dba)2 as a
2-Dialkylphosphino-2′-
precatalyst, L1 as a ligand, Cs CO as a base, and t-BuOH as
2
3
a solvent, the amidation of bromobenzene gave a 95% yield
Table 1, entry 4). Consequently, the structure of 2-
dialkylphosphino-2′-alkoxyl-1,1′-binaphthyl can promote the
palladium-catalyzed amidations. Next, other ligands of mono-
dentate phosphines with a heteroatom at the adjacent position
of phosphorus atom were explored. When the substituent of
(
10
coordination with the palladium center, which may inhibit the
2
formation of a κ -amidate complex and thus promote the
reductive elimination of the palladium complex with an amidate
ligand. Herein, we report the efficiency of 2-dialkylphosphino-
2
′-alkoxyl-1,1′-binaphthyl as ligands in palladium-catalyzed
Received: March 20, 2012
amidation of aryl halides.
©
XXXX American Chemical Society
A
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The Journal of Organic Chemistry
Article
Table 1. Optimization of Reaction Conditions for the
a
Amidation of Bromobenzene with Benzamide
Pd(dba) , base
2
PhBr + PhCONH ⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯ ⎯→ PhCONHPh
2
1
a
ligand, solvent
3aa
2
a
b
entry
ligand
base
solvent
yield (%)
1
2
3
4
5
6
7
8
9
L1
L1
L1
L1
L1
L1
L1
L1
L2
L3
L4
t-BuONa
t-BuONa
K PO
toluene
trace
78
t-BuOH
t-BuOH
t-BuOH
1,4-dioxane
toluene
64
3
4
Figure 1. Ligands surveyed in optimization.
Cs CO
95
2
3
3
3
Cs CO
2
25
a
Table 2. Pd-catalyzed Amidation of Aryl Bromides
Cs CO
2
15
KOH
t-BuOH
t-BuOH
t-BuOH
t-BuOH
t-BuOH
75
c
Cs CO
0
2
3
3
3
3
Cs CO
2
22
46
36
1
1
0
1
Cs CO
2
Cs CO
2
a
Reaction conditions: bromobenzene (1.0 mmol), benzamide (1.2
mmol), base (1.5 mmol), Pd(dba) (2 mmol %), ligand (3 mmol %),
2
b
solvent (4.0 mL), 100 °C (bath temperature), 20 h. Isolated yields
average of two runs). Pd(OAc) (2 mmol %) as palladium source.
c
(
2
phosphorus was tert-butyl group, the ligands showed some
catalytic activity for the reaction. As a result, when di-tert-butyl-
biarylphosphine (L4) was used as a ligand, the coupling
product was obtained in 36% of yield. However, ditert-
butyl(2′,4′,6′-triisopropyl-[1,1′-biphenyl]-2-yl)phosphine, the
similar bulky biaryl monophosphine, was reported to be less
6a
active for the amidation of bromobenzene. In these P, X-type
ligands, monodentate phosphines with a heteroatom at the
adjacent position of phosphorus atom, the hemilabile
coordination of the heteroatom with the palladium center has
4g,10c
been confirmed by the X-ray crystallographic study.
Therefore, the activity of these ligands for amidation may be
attributed to the hemilabile coordination of the oxygen atom
with the palladium center to inhibit the formation of the κ -
amidate complex. Furthermore, the catalytic activity decreased
with a decrease of the steric hindrance of the ligands. When 2-
di(tert-butyl)phosphino-2′-methoxy-1,1′-binaphthyl (L2) was
used as a ligand, the yield of the amidation was reduced to
2
a
Reaction conditions: ArBr (1.0 mmol), amide (1.2 mmol), base (1.5
mmol), Pd(dba) (2 mmol %), L1 (3 mmol %), t-BuOH (4.0 mL),
1
2
00 °C (bath temperature), 20 h; isolated yields (average of two runs).
containing a free hydroxy group was converted to the desired
amidation product in high yield, and no ether product was
detected; amide containing a pyridine moiety was also a good
coupling partner in this reaction. When the substituents of
benzamide were changed from electron-donating group
(hydroxy, methoxy) to electron-withdrawing group (fluoro),
the yield of the arylation reaction did not vary remarkably.
As tert-butyloxycarbonyl (Boc) is a readily removable amine-
protecting group, Pd-catalyzed coupling of tert-butyl carba-
mates with aryl halides can directly deliver primary amines in a
conveniently protected form. Nevertheless, there are currently
only a few catalytic systems which are effective in using tert-
butyl carbamate as the ammonia equivalent in Pd-catalyzed
amidation. Xantphos is frequently encountered as a ligand to
effect this conversion of aryl bromides, especially the activated
22% (Table 1, entry 9). When the dialkylphosphino group of
the ligands was changed from di(tert-butyl)phosphino to
di(cyclohexyl)phosphine group, such as L5-L8, no amidation
products were detected. This is in accordance with the report
that the bulky steric hindrance of the ligands facilitates the
8
,11,12
reductive elimination during the C−N bond forming step.
Therefore, to actualize the Pd-catalyzed amidation reactions,
the ligand should have enough steric hindrance to promote the
reductive elimination and meanwhile, to inhibit the κ -binding
2
mode of the amides. Xantphos, a fairly general and efficient
ligand for amidation reactions of aryl iodide and bromide when
5a,b
1
,4-dioxane or THF was used as solvent, was inactive for the
intermolecular coupling of bromobenzene and the primary
amides under our reaction conditions.
The scope of the palladium-catalyzed amidation of
5,7,13
14
15
aryl bromides
Tri(tert-butyl)phosphine and X-phos are
bromobenzene was subsequently explored using Pd(dba) as
also effective ligands for the coupling reactions of aryl
bromides; however, employing sodium phenoxide or sodium
tert-butoxide as a base was crucial for the success of the
reaction, which led to a narrow functional group tolerability of
the catalytic system. Recently, Zou reported that high loading
(9%) of X-phos may actualize the coupling of aryl chlorides and
heteroaryl halides with tert-butyl carbamate in moderate
2
precatalyst, L1 as the ligand, Cs CO as the base, and t-BuOH
2
3
as the solvent at 100 °C (bath temperature). The results are
listed in Table 2. A variety of primary amides, both aliphatic
and aromatic, and lactam participated in the coupling reactions
in good to excellent yields. A number of functional groups, such
as fluoro, methoxy, and heteroaromatic, were tolerated under
such reaction conditions. Of particular interest, an amide
15b
yields. Encouraged by our results, the coupling reaction of
B
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The Journal of Organic Chemistry
Article
tert-butyl carbamate and aryl bromide was explored with our
catalytic system. To our delight, under the optimized
conditions, a quantitative yield of the product was obtained
with bromobenzene as substrate. Even when the milder base,
K PO , was employed and toluene was used as the solvent, the
yield showed only a slight decrease. We then examined the
scope of the coupling reaction of inactivated aryl halides with
tert-butyl carbamate. The results were given in Table 3. The
electron-withdrawing groups (such as trifluoromethyl, acetyl,
or ester group) gave higher yields than those with electron-
donating groups. Different from the high efficiency of the
11
catalytic system in the amination of inactivated aryl chlorides,
the lower reactivity of aryl chlorides in the amidation may be
due to the lower nucleophilicity of the amide and the poor
dissociation of chloride from Pd(II) complexes, as reported that
transmetalation is the rate-limiting step in the Pd-catalyzed
amidation when the monodentate biaryldialkyl phosphine was
3
4
6a,16
Table 3. Pd-Catalyzed the Coupling Reaction of tert-Butyl
used as ligand.
The yields of the reaction of the inactivated
a
Carbamate with Aryl Halides
aryl chlorides could be increased when more catalyst was
loaded. In the case of coupling reaction of p-methoxychlor-
obenzene, the yields increased from 41% to 78% as the
Pd(dba) , L1
2
ArX + BocNH ⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯ →⎯ BocNHAr
2
1
Cs
2
CO
3
, t‐BuOH
3
2g
Pd(bda) loading was increased from 2% to 4% and the ligand
2
londing was increased from 3% to 6%. In addition, for aryl
halides bearing a base-sensitive functional group, the conversion
was also accomplished in moderate yields.
The derivative of 2-amino-2′-hydroxy-1,1′-binaphthyl
NOBIN) is an important organocatalyst and chiral ligand of
(
the transition-metal-catalyzed reaction, which can be typically
synthesized by the oxidative coupling of the 2-naphthylamine
17
with 2-naphthol. Buchwald’s group reported a palladium-
catalyzed amination reaction of a binaphthyl triflate derivative
18
with diphenylmethanimine to give the product. However, it
was claimed that the use of benzophenone imine did not
15a
provide a convenient deprotective transformation to aniline.
The good activity of our catalyst system promoted us to
synthesize the derivative of NOBIN by the coupling reaction of
aryl bromides with tert-butyl carbamate. Because a free phenol
group on the aromatic ring (Table 2, entry 7) was compatible
under the Pd-catalyzed amidation conditions, we tried to
synthesize NOBIN by direct coupling reaction between tert-
butyl carbamate and 2-bromo-2′-hydoxy-1,1′-binaphthyl (4),
19
which can be easily obtained by our reported method.
However, under the optimized conditions, only intramolecular
coupling product (5, Scheme 1) was formed by the reductive
Scheme 1. Coupling Reaction of 2-Bromo-2′-hydroxy-1,1′-
binaphthyl and tert-Butyl Carbamate
a
Reaction conditions: ArX (1.0 mmol), tert-butyl carbamate (1.2
mmol), Cs CO (1.5 mmol), Pd(dba) (2 mmol %), L1 (3 mmol %),
2
3
2
t-BuOH (4.0 mL), 100 °C (bath temperature), 20 h; isolated yields are
b
an average of two runs. K PO as the base, toluene as the solvent.
3
4
c
Pd(dba) (4 mmol %) and L1 (6 mmol %).
2
catalyst system, Pd(dba) /L1, allowed for the use of tert-butyl
2
carbamate to form Boc-protected anilines from inactivated aryl
halides in moderate to excellent yields. The reaction was
insensitive to the electronic and steric effect of the functional
groups on the aryl bromides. Both electron-neutral and
electron-rich aryl bromides worked well, providing the
corresponding N-Boc-anilines in excellent yields. o-Methoxy-
bromobenzene was also reacted with tert-butyl carbamate in
elimination of the Pd−O bond, which is generally difficult to
20
carry out. The result may be due to the bulky steric hindrance
of aryl bromide (4) and the stability of the five-membered ring
of the product. The hydroxyl group methylated product (6)
was examined for the reaction with tert-butyl carbamate. When
L1 was used as the ligand, the coupling reaction occurred in
very low yield under previously optimized reaction conditions,
probably because the bulkier steric hindrance of 6 hindered the
coupling reaction. Several other ligands of 2-dialkylphosphino-
2′-alkoxyl-1,1′-binaphthyl were screened, and to our delight, L5
gave the best result, and the desired product (7) was obtained
in 91% yield. This result demonstrated further that the proper
steric hindrance of ligand can promote the reductive
elimination in the amidation of aryl bromide. Finally, a
derivative of NOBIN, 2′-menthoxy-1,1′-binaphthyl-2-amine
91% of yield. Furthermore, heteroaryl bromides also worked
well under the reaction conditions.
The good results with aryl bromides and hetero bromides
prompted us to extend the amidation to aryl chlorides, which
are generally the most attractive substrates for cross-coupling
reactions as they are less expensive and more readily available.
However, the yields of products were strongly affected by the
electronic effect of aryl chlorides. Aryl chlorides bearing
C
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The Journal of Organic Chemistry
8) can be prepared in 71% total yield from binaphthofuran
Article
(
Hz, 2H), 7.53 (t, J = 8.0 Hz, 1H), 7.47 (t, J = 6.4 Hz, 2H), 7.38 (t, J =
7
1
.6 Hz, 2H), 7.16 (t, J = 6.4 Hz, 1H); 13C NMR (100 MHz, CDCl ) δ
3
through a four-step transformation (Scheme 2).
66.1, 138.2, 135.3, 132.1, 129.4, 129.1, 127.3, 124.9, 120.6.
21
Acetanilide (3ab). The crude material was purified by column
chromatography on silica gel (eluting with ethyl acetate/hexanes 1:2)
to give the compound as a white solid (95.9 mg, 71%): H NMR (400
Scheme 2. Synthetic Approach of 2′-Methoxy-1,1′-
binaphthyl-2-amine (8)
1
MHz, CDCl ) δ 7.49 (d, J = 7.2 Hz, 2H), 7.32 (t, J = 8.0 Hz, 2H), 7.12
3
13
(
t, J = 7.6 Hz, 1H), 2.17 (s, 3H); C NMR (100 MHz, CDCl ) δ
3
1
69.2, 138.0, 126.7, 124.1, 120.1, 24.2.
22
N-phenylformamide (3ac). The crude material was purified by
column chromatography on silica gel (eluting with ethyl acetate/
hexanes 1:3) to give the compound as a white solid (88.4 mg, 73%):
1
H NMR (400 MHz, CDCl ) δ 8.66−8.71 (m, 1H), 8.36 (d, J = 1.6
3
Hz, 0.4H), 7.76 (br, 0.4H), 7.54 (d, J = 8.8 Hz, 1H), 7.30−7.38 (m,
2
1
1
3
H), 7.08−7.21 (m, 2H); C NMR (100 MHz, CDCl ) δ 162.8,
3
59.2, 136.7, 129.7, 129.0, 125.2, 124.8, 120.0, 118.8.
23
N-Phenylpivalamide (3ad). The crude material was purified by
column chromatography on silica gel (eluting with ethyl acetate/
hexanes 1:25) to give the title compounds as a white solid (151.2 mg,
1
8
(
(
5%): H NMR (400 MHz, CDCl ) δ 7.52 (d. J = 8.8 Hz, 2H), 7.32
3
1
3
t, J = 8.4 Hz, 2H), 7.10 (t, J = 7.6 Hz, 1H), 1.32 (s, 9H); C NMR
100 MHz, CDCl ) δ 176.6, 138.0, 128.9, 124.1, 120.0, 39.5, 27.6.
N-Phenylcyclopropanecarboxamide (3ae). The crude material
3
24
was purified by column chromatography on silica gel (eluting with
ethyl acetate/hexanes 1:2) to give the compound as a white solid
1
(
147.9 mg, 92%): H NMR (400 MHz, CDCl ) δ 7.51 (d, J = 7.6 Hz,
3
2
1
H), 7.73 (br, 1H), 7.31 (t, J = 8.0 Hz, 2H), 7.10 (t, J = 6.8 Hz, 1H),
.50 (br, 1H), 1.07−1.11 (m, 2H), 0.82−0.86 (m, 2H); C NMR
1
3
(100 MHz, CDCl ) δ 172.7, 138.2, 120.7, 123.9, 120.0, 15.3, 7.7.
3
5a
1
-Phenylpyrrolidin-2-one (3af). The crude material was purified
CONCLUSION
■
by column chromatography on silica gel (eluting with ethyl acetate/
In conclusion, we have reported a Pd-catalyzed coupling
reaction between inactivated aryl halides and amides or tert-
butyl carbamate using the bulky and electron-rich 2-
dialkylphosphino-2′-alkoxyl-1,1′-binaphthyl as ligands (L1, L5)
under optimized conditions, providing an easy method for the
synthesis of protected primary amines. The catalytic activity of
these ligands can be attributed to the hemilabile coordination of
the oxygen atom with the palladium center to inhibit the
hexanes 1:3) to give the title compounds as a white solid (136.6 mg,
1
85%): H NMR (400 MHz, CDCl
) δ 7.61 (d, J = 8.8 Hz, 2H), 7.37
3
(
t, J = 8.4 Hz, 2H), 7.14 (t, J = 8.4 Hz, 1H), 3.87 (t, J = 7.2 Hz, 2H),
.62 (t, J = 7.6 Hz, 2H), 2.14−2.18 (m, 2H); C NMR (100 MHz,
13
2
CDCl ) δ 174.0, 139.2, 128.5, 124.2, 119.7, 48.5, 32.5, 17.7.
3
25
tert-Butyl Phenylcarbamate (3ag). The crude material was
purified by column chromatography on silica gel (eluting with ethyl
acetate/hexanes 1:10) to give the compound as a white solid (191.0
1
mg, 99%): H NMR (400 MHz, CDCl ) δ 7.35 (d, J = 8.0 Hz, 2H),
3
2
formation of the κ -amidate complex and to the fact that proper
7.29 (t, J = 7.2 Hz, 2H), 7.03 (t, J = 7.2 Hz, 1H), 6.45 (br, 1H), 1.52
steric hindrance can promote the reductive elimination.
Furthermore, because the substituents on the phosphino and
oxygen group are easily to be tuned, the ligands of 2-
dialkylphosphino-2′-alkoxyl-1,1′-binaphthyl can be employed
for a wider range of the amidation reactions of various
substrates. The efficient coupling reaction of 2-bromo-2′-
methoxy- 1,1′-binaphthyl and commercially available tert-butyl
carbamate offered a facile synthetic method for the NOBIN
derivatives.
(s, 9H); 13C NMR (100 MHz, CDCl ) δ 152.7, 138.3, 128.9, 122.9,
3
118.5, 80.4, 28.3.
26
2
-Hydroxy-N-phenylbenzamide (3ah). The crude material was
purified by column chromatography on silica gel (eluting with ethyl
acetate/hexanes 1:10) to give the title compounds as a white solid
1
(
200.1 mg, 94%): H NMR (400 MHz, CDCl ) δ 12.0 (s, 1 H), 7.93
3
(
7
br, 1H), 7.58 (d, J = 8.8 Hz, 2H), 7.52 (d, J = 8.4 Hz, 1H), 7.46 (t, J =
.6 Hz, 1H), 7.41 (t, J = 6.8 Hz, 2H), 7.21 (t, J = 7.6 Hz, 1H), 7.04 (d,
13
J = 8.8 Hz, 1H), 6.93 (t, J = 6.8 Hz, 1H); C NMR (100 MHz,
CDCl ) δ 168.4, 161.6, 136.5, 134.6, 129.1, 125.6, 125.3, 121.3, 119.0,
3
1
18.8, 114.6.
4-Hydroxy-N-phenylbenzamide (3ai). The crude material was
27
EXPERIMENTAL SECTION
Experimental Procedures for the Amidation of Aryl Halides
Using 2-Dialkylphosphino-2′-alkoxy-1,1′-binaphthyl as Li-
gands. An oven-dried Schlenk tube was evacuated and backfilled
■
purified by column chromatography on silica gel (eluting with ethyl
acetate/hexanes 1:5) to give the title compounds as a white solid
(183.2 mg, 86%): H NMR (400 MHz, DMSO) δ 10.06 (s, 1H), 9.95
1
with nitrogen. The Schlenk tube was charged with Pd(dba) (11.4 mg,
(br, 1H), 7.83 (d, J = 8.8 Hz, 2H), 7.73 (dd, J = 8.8 Hz, 1.2 Hz, 2H),
7.30 (t, J = 8.0 Hz, 2H), 7.04 (t, J = 7.6 Hz, 1H), 6.84 (d, J = 8.4 Hz,
2H); 13C NMR (100 MHz, DMSO) δ 165.1, 160.5, 139.5, 129.7,
128.5, 125.5, 123.3, 120.3, 114.9.
4-methoxy-N-phenylbenzamide (3aj). The crude material was
purified by column chromatography on silica gel (eluting with ethyl
2
0
.02 mmol), L1 (13.6 mg, 0.03 mmol), amide (1.2 mmol), and base
(
1.5 mmol) and capped with a rubber septum. The Schlenk tube was
evacuated and backfilled with nitrogen three times. To the Schlenk
tube were added aryl halide (1.0 mmol) and solvent (4.0 mL). The
septum was replaced with a Teflon screw cap, and the mixture was
heated to 100 °C with stirring for 20 h. Then reaction mixture was
allowed to cool to room temperature, diluted with ethyl acetate,
filtered through Celite, and concentrated under reduced pressure. The
crude material was purified by column chromatography on silica gel.
6a
acetate/hexanes 1:5) to give the compound as a white solid (192.8 mg,
1
85%): H NMR (400 MHz, CDCl ) δ 7.85 (d, J = 8.4 Hz, 2H), 7.74
3
(br, 1H), 7.63 (dd, J = 8.8 Hz, 1.2 Hz, 2H), 7.37 (t, J = 8.8 Hz, 2H),
1
3
7.14 (t, J = 7.6 Hz, 1H), 6.98 (d, J = 8.4 Hz, 2H), 3.88 (s, 3H);
C
2
1
N-Phenylbenzamide (3aa). The crude material was purified by
NMR (100 MHz, DMSO) δ 164.9, 161.9, 139.4, 129.6, 128.5, 127.0,
column chromatography on silica gel (eluting with ethyl acetate/
123.4, 120.3, 113.6, 55.4.
4-Fluoro-N-phenylbenzamide (3ak). The crude material was
purified by column chromatography on silica gel (eluting with ethyl
28
hexanes 1:5) to give the compound as a white solid (159.6 mg, 95%):
1
H NMR (400 MHz, CDCl ) δ 7.86−7.88 (m, 3H), 7.64 (d, J = 8.8
3
D
dx.doi.org/10.1021/jo3005827 | J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry
Article
3
3
acetate/hexanes 1:10) to give the compound as a white solid (176.8
tert-Butyl 4-Acetylphenylcarbamate (3 kg). The crude material
was purified by column chromatography on silica gel (eluting with
1
mg, 82%): H NMR (400 MHz, CDCl ) δ 7.87−7.91 (m, 2H), 7.76
3
(
8
1
br, 1H), 7.62 (d, J = 8.0 Hz, 2H), 7.38 (t, J = 8.8 Hz, 2H), 7.16 (t, J =
ethyl acetate/hexanes 1:10) to give the compound as a white solid
) δ 7.91 (d, J = 8.8 Hz,
2H), 7.45 (d, J = 8.8 Hz, 2H), 6.75 (br, 1H), 2.56 (s, 3H), 1.53 (s,
.8 Hz, 3H); 13C NMR (100 MHz, DMSO) δ 165.3, 164.4, 162.8,
1
(180.0 mg, 77%): H NMR (400 MHz, CDCl
3
39.1, 131.4, 130.4, 128.6, 123.7, 120.4, 115.4, 115.2.
2
9
13
N-phenylnicotinamide (3al). The crude material was purified by
9H); C NMR (100 MHz, CDCl
3
) δ 197.1, 152.3, 143.2, 131.5,
column chromatography on silica gel (eluting with ethyl acetate/
129.7, 117.4, 81.0, 28.1, 26.2.
34
hexanes 1:2) to give the compound as a white solid (153.0 mg, 77%):
tert-Butyl 4-Trifluoromethylphenylcarbamate (3lg). The crude
material was purified by column chromatography on silica gel (eluting
with ethyl acetate/hexanes 1:10) to give the compound as a white
solid (214.4 mg, 82%): H NMR (400 MHz, CDCl ) δ 7.54 (d, J = 8.8
Hz, 2H), 7.47 (d, J = 8.4 Hz, 2H), 6.85 (br, 1H), 1.54 (s, 9H);
1
H NMR (400 MHz, CDCl ) δ 9.28 (s, 1H), 8.91 (s, 1H), 8.47 (d, J =
3
1
7
.2 Hz, 1H), 8.00 (d, J = 8.0 Hz, 1H), 7.49 (d, J = 8.0 Hz, 2H), 7.12−
1
.18 (m, 2H), 7.00 (dt, J = 8.8 Hz, 1.2 Hz, 2H); 13C NMR (100 MHz,
3
1
3
C
CDCl ) δ 164.4, 151.7, 148.0, 137.6, 135.4, 130.7, 128.8, 124.8, 123.4,
3
NMR (100 MHz, CDCl ) δ 152.4, 141.5, 126.2 (q, J = 28.0 Hz),
1
20.8.
tert-Butyl-4-tert-butylphenylcarbamate (3bg). The crude ma-
3
3
0
125.6, 124.8, 124.6, 122.9, 117.9, 81.2, 28.2.
3
5
Ethyl 4- (tert-Butoxycarbonylamino)benzoate (3mg). The
crude material was purified by column chromatography on silica gel
(eluting with ethyl acetate/hexanes 1:10) to give the compound as a
white solid (207.0 mg, 78%): H NMR (400 MHz, CDCl ) δ 7.98 (d,
J = 8.4 Hz, 2H), 7.43 (d, J = 8.8 Hz, 2H), 6.69 (br, 1H), 4.35 (q, J =
6.8 Hz, 2H), 1.53 (s, 9H), 1.38 (t, J = 7.6 Hz, 3H); C NMR (100
MHz, CDCl ) δ 166.3, 152.3, 142.6, 130.7, 124.5, 117.3, 81.0, 60.7,
terial was purified by column chromatography on silica gel (eluting
with ethyl acetate/hexanes 1:30) to give compound as a white solid
1
(
6
233.2 mg, 94%): H NMR (400 MHz, CDCl ) δ 7.26−7.32 (m, 4H),
3
1
13
.41 (br, 1H), 1.51 (s, 9H), 1.29 (s, 9H); C NMR (100 MHz,
3
CDCl ) δ 1552.9, 145.9, 135.7, 125.7, 118.4, 80.3, 34.2, 31.4, 28.3.
3
13
2
7
tert-Butyl p-Tolylcarbamate (3cg). The crude material was
purified by column chromatography on silica gel (eluting with ethyl
3
2
8.1, 14.3.
acetate/hexanes 1:30) to give the compound as a white solid (203.2
1
Synthesis of 2′-Methoxy-1,1′-binaphthyl-2-amine. 2′-Bromo-
mg, 98%): H NMR (400 MHz, CDCl ) δ 7.23 (d, J = 8.0 Hz, 2H),
19
3
13
1,1′-binaphthalen-2-ol (4). To a suspension of lithium chip (2.4 g,
7
.08 (d, J = 8.4 Hz, 2H), 6.40 (br, 1H), 2.29 (s, 3H), 1.51 (s, 9H);
C
3
40.0 mmol) in Et O (80 mL) was added dropwise a solution of
2
NMR (100 MHz, CDCl ) δ 152.9, 135.7, 132.4, 129.4, 118.7, 80.2,
3
binaphthofuran 6 (5.4 g, 20.0 mmol) in toluene (70 mL), and the
mixture was stirred at room temperature for 3 h to achieve complete
conversion of the starting material. After removal of excess lithium by
filtration, the mixture of Et O (20 mL) and 1,1,2,2-tetrabromoethane
6.9 g, 20.0 mmol) was added dropwise to the solution cooled to −30
to −40 °C, and then the mixture was stirred for 2 h at room
temperature. The reaction mixture was acidified with 1 M HCl
solution to pH < 5, and the two layers were separated; the aqueous
phase was extracted with EtOAc (2 × 30 mL), and the combined
organic fractions were washed with brine (60 mL). The organic phase
was dried over Na SO and evaporated to give a crude product, which
2
8.3, 20.6.
tert-Butyl 4-Methoxyphenylcarbamate (3eg). The crude ma-
3
0
terial was purified by column chromatography on silica gel (eluting
2
with ethyl acetate/hexanes 1:10) to give the compound as a white
(
1
solid (218.6 mg, 98%): H NMR (400 MHz, CDCl ) δ 7.25−7.27 (m,
3
2
9
1
H), 6.83 (d, J = 8.8 Hz, 2H), 6.33 (br, 1H), 3.78 (s, 3H), 1.51 (s,
H); 13C NMR (100 MHz, CDCl ) δ 155.5, 153.2, 131.4, 120.5,
3
20.3, 114.0, 80.0, 55.3, 28.3.
tert-Butyl 3-methoxyphenylcarbamate (3fg). The crude materi-
3
0
al was purified by column chromatography on silica gel (eluting with
2
4
ethyl acetate/hexanes 1:10) to give the compound as a white solid
was purified by flash chromatography eluting with hexane/EtOAc
20:1). The title compound was obtained as a white solid (5.6 g, 81%):
1
(
200.3 mg, 90%): H NMR (400 MHz, CDCl ) δ 7.17 (t, J = 8.4 Hz,
3
(
1
H), 7.10 (s, 1H), 6.83 (d, J = 7.6 Hz, 1H), 6.58 (dd, J = 8.0 Hz, 1.6
1
H NMR (400 MHz, CDCl ) δ 7.85−7.96 (m, 5H), 7.54 (td, J = 6.8
13
3
Hz, 1H), 6.48 (br, 1H), 3.80 (s, 3H), 1.52 (s, 9H); C NMR (100
Hz, 1.6 Hz, 1H), 7.31−7.36 (m, 3H), 7.24−7.28 (m, 2H), 6.96 (d, J =
MHz, CDCl ) δ 160.1, 152.7, 139.6, 129.5, 110.7, 108.8, 104.0, 80.4,
13
3
8
1
1
.0 Hz, 1H), 4.76 (s, 1H); C NMR (100 MHz, CDCl ) δ 150.6,
3
5
5.1, 28.3.
tert-Butyl 4-(Dimethylamino)phenylcarbamate (3gg). The
crude material was purified by column chromatography on silica gel
eluting with ethyl acetate/hexanes 1:15) to give the compound as a
34.1, 132.9, 132.7, 131.8, 130.5, 130.4, 130.3, 129.0, 128.3, 128.2,
27.8, 126.9, 126.7, 126.0, 124.7, 124.2, 123.6, 118.2, 117.6.
′-Bromo-2-methoxy-1,1′-binaphthalenyl (6). Methyl iodide
2.6 g, 18.0 mmol) and potassium carbonate (2.5 g, 18.0 mmol)
were added to a stirred solution of 6 (2.1 g, 6.0 mmol) in acetone
under nitrogen. The mixture was stirred overnight. The mixture was
filtered, and the filtrate was evaporated to yield the product as a white
solid (2.2 g, 99%): H NMR (400 MHz, CDCl ) δ 8.02 (d, J = 9.2 Hz,
3
0
36
2
(
(
1
white solid (185.2 mg, 79%): H NMR (400 MHz, CDCl ) δ 7.20 (d,
3
J = 8.8 Hz, 2H), 6.70 (d, J = 9.2 Hz, 2H), 6.26 (br, 1H), 2.89 (s, 6H),
1
1
.50 (s, 9H); 13C NMR (100 MHz, CDCl ) δ 153.3, 147.2, 126.5,
3
20.7, 120.6, 113.6, 79.8, 41.1, 28.3.
1
3
1
3
tert-Butyl 2-Methoxyphenylcarbamate (3hg). The crude ma-
1
2
8
H), 7.89 (dd, J = 8.0 Hz, 3.6 Hz, 2H), 7.81 (s, 2H), 7.44−7.48 (m,
terial was purified by column chromatography on silica gel (eluting
H), 7.34 (td, J = 8.0 Hz, 1.2 Hz, 1H), 7.22−7.28 (m, 2H), 7.17 (d, J =
with ethyl acetate/hexanes 1:50) to give the compounds a white solid
13
.4 Hz, 1H), 3.80 (s, 3H); C NMR (100 MHz, CDCl ) δ 154.5,
3
1
(
202.3 mg, 91%): H NMR (400 MHz, CDCl ) δ 8.07 (d, J = 6.8 Hz,
3
134.9, 134.1, 133.1, 132.4, 130.1, 130.0, 129.1, 129.0, 128.0, 126.9,
26.8, 126.3, 126.0, 124.1, 123.7, 123.3, 122.1, 113.8, 56.7.
tert-Butyl 2′-Methoxy-1,1′-binaphthyl-2-ylcarbamate (7). 2′-
Bromo-2-methoxy-1,1′-binaphthalenyl (6, 1.1 g, 3.0 mmol), tert-butyl
carbamate (421.9 mg, 3.6 mmol), Pd(dba) (34.2 mg, 60.0 μmmol),
L5 (40.8 mg, 90.0 μmol), and Cs CO (1.5 g, 4.5 mmol) in t-BuOH
1
1
1
H), 7.08 (s, 1H), 6.92−6.99 (m, 2H), 6.85 (dt, J = 6.8 Hz, 1.2 Hz,
1
H), 3.86 (s, 3H), 1.53 (s, 9H); 13C NMR (100 MHz, CDCl ) δ
3
52.7, 147.4, 128.0, 122.2, 121.0, 118.0, 109.9, 80.1, 55.5, 28.3.
3
2
tert-Butyl Thiophene-3-ylcarbamate (3ig). The crude material
2
was purified by column chromatography on silica gel (eluting with
2
3
ethyl acetate/hexanes 1:10) to give the compound as a white solid
(8.0 mL) were added to a Schlenk tube fitted with a septum. The
septum was replaced with a Teflon screw cap, and the mixture was
heated to 100 °C with stirring for 20 h. The reaction mixture was
allowed to cool to room temperature, diluted with ethyl acetate,
filtered through Celite, and concentrated under reduced pressure. The
crude material was purified by column chromatography on silica gel
(eluting with ethyl acetate/hexanes 1:15) to give the title compounds
1
(
2
168.2 mg, 85%): H NMR (400 MHz, CDCl ) δ 7.20 (dd, J = 5.6 Hz,
3
13
.4 Hz, 2H), 6.90 (d, J = 4.0 Hz, 1 H), 6.66 (br, 1H), 1.51 (s, 9H); C
NMR (100 MHz, CDCl ) δ 152.8, 136.1, 124.5, 120.7, 107.3, 80.4,
3
2
8.3.
tert-Butyl Pyridin-3-ylcarbamate (3jg). The crude material was
3
0
purified by column chromatography on silica gel (eluting with ethyl
1
acetate/hexanes 1:3) to give the title compounds as a white solid
as a white solid (1.1 g, 91%): mp 169−170 °C; H NMR (400 MHz,
1
(
166.7 mg, 86%): H NMR (400 MHz, CDCl ) δ 8.46 (d, J = 2.4 Hz,
CDCl ) δ 8.41 (d, J = 9.2 Hz, 1H), 8.03 (d, J = 8.8 Hz, 1H), 7.94 (d, J
3
3
1
H), 8.29 (d, J = 4.8 Hz, 1H), 7.99 (br, 1H), 7.24 (dd, J = 8.0 Hz, 4.4
= 9.6 Hz, 1H), 7.88 (d, J = 8.4 Hz, 1H), 7.85 (d, J = 8.0 Hz, 1H) 7.46
(d, J = 8.8 Hz, 1H), 7.33 (qd, J = 8.0 Hz, 1.2 Hz, 2H), 7.22 (td, J = 8.0
Hz, 1.2 Hz, 1H), 7.16 (td, J = 8.4 Hz, 1.2 Hz, 1H), 7.06 (d, J = 8.6 Hz,
13
Hz, 1H), 6.88 (br, 1H), 1.53 (s, 1H); C NMR (100 MHz, CDCl ) δ
1
3
52.8, 143.8, 140.1, 135.6, 125.7, 123.6, 80.9, 28.2.
E
dx.doi.org/10.1021/jo3005827 | J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry
Article
1
9
1
1
3
1
H), 6.97 (d, J = 8.0 Hz, 1H), 6.20 (br, 1H), 3.75 (s, 3H), 1.37 (s,
(6) (a) Ikawa, T.; Barder, T. E.; Biscoe, M. R.; Buchwald, S. L. J. Am.
Chem. Soc. 2007, 129, 13001. (b) Shen, Q.; Shekhar, S.; Stambuli, J. P.;
Hartwig, J. F. Angew. Chem., Int. Ed. 2005, 44, 1371. (c) Ghosh, A.;
Sieser, J. E.; Riou, M.; Cai, W.; Rivera-Ruiz, L. Org. Lett. 2003, 5, 2207.
H); 13C NMR (100 MHz, CDCl ) δ 155.2, 153.1, 134.9, 133.7,
3
33.0, 130.7, 130.3, 129.3, 128.5, 128.0, 127.1, 126.1, 125.4, 125.0,
−1
24.2, 124.0, 119.9, 117.3, 113.8, 80.3, 56.5, 28.2; IR (neat, cm )
409, 3056, 2976, 2933, 1719, 1598, 1505, 1454, 1427, 1367, 1263,
155, 1073, 956, 813; HRMS-ESI (collected on an UPLC and Q-TOF
(
d) Fors, B. P.; Dooleweerdt, K.; Zeng, Q.; Buchwald, S. L.
Tetrahedron 2009, 65, 6576. (e) Vimolratana, M.; Simard, J. L.;
Brown, S. P. Tetrahedron Lett. 2011, 52, 1020.
MS spectrometer) calcd for C H NO 399.1834, found 399.1830.
2
6
25
3
3
7
2
′-Methoxy-1,1′-binaphthyl-2-amine (8). tert-Butyl 2′-methoxy-
(7) (a) Barfoot, C.; Brooks, G.; Brown, P.; Dabbs, S.; Davies, D. T.;
1
,1′-binaphthyl-2-ylcarbamate (1.0 g) was added at room temperature
Giordano, I.; Hennessy, A.; Jones, G.; Markwell, R.; Miles, T.; Pearson,
N.; Smethurst, C. A. Tetrahedron Lett. 2010, 51, 2685. (b) Nodwell,
M.; Pereira, A.; Riffell, J. L.; Zimmerman, C.; Patrick, B. O.; Roberge,
M.; Anderson, R. J. J. Org. Chem. 2009, 74, 995. (c) Bringmann, G.;
Gulder, T.; Reichert, M.; Meyer, F. Org. Lett. 2006, 8, 1037. (d) Shi,
F.; Smith, M. R., III; Maleczka, R. E. Org. Lett. 2006, 8, 1411.
(e) Kuwahara, A.; Nakano, K.; Nozaki, K. J. Org. Chem. 2005, 70, 413.
to a solution of 2.0 N HCl in 1,4-dioxane (10.0 mL) and the mixture
stirred for 5 h. Then 1,4-dioxane was removed under reduced pressure.
The residue was added to a saturated solution of sodium bicarbonate
(
10.0 mL), the solution was extracted with diethyl ether (3 × 20 mL),
the organic layers were combined, and the mixture was dried over
Na SO . The mixture was filtered, and the filtrate was evaporated to
yield the product (0.7 g, 97%): H NMR (400 MHz, CDCl ) δ 8.00
2
4
1
3
(f) Willis, M. C.; Brace, G. N.; Holmes, I. P. Angew. Chem., Int. Ed.
(
(
6
d, J = 9.2 Hz, 1H), 7.88 (d, J = 8.4 Hz, 1H), 7.77−7.81(m, 2H), 7.48
2
005, 44, 403.
d, J = 8.4 Hz, 1H), 7.35−7.37 (m, 1H), 7.13−7.28 (m, 5H), 6.96−
.98 (m, 1H), 3.79 (s, 3H), 1.58 (br, 2H); 1 C NMR (100 MHz,
3
(8) For reviews, see: (a) Yang, B. H.; Buchwald, S, L. J. Organomet.
Chem. 1999, 576, 125. (b) Beller, M; Zapf, A; Magerlein, W. Chem.
Eng. Technol. 2001, 24, 575. (c) Muci, A. R.; Buchwald, S, L. Top. Curr.
Chem. 2002, 219, 131. (d) Hartwig, J. F. Acc. Chem. Res. 2008, 41,
CDCl ) δ 155.4, 142.0, 134.1, 133.6, 129.9, 129.5, 128.9, 128.1, 128.0,
3
1
1
27.9, 126.9, 126.2, 124.9, 124.2, 123.9, 122.1, 118.8, 118.1, 114.3,
13.7, 56.8.
1
534. (e) Surry, D. S.; Buchwald, S. L. Chem. Sci. 2011, 2, 27.
(
(
f) Schlummer, B.; Scholz, U. Adv. Synth. Catal. 2004, 346, 1599.
g) Hartwig, J. F. Nature 2008, 455, 314.
ASSOCIATED CONTENT
■
* Supporting Information
S
(9) Fujita, K.-I.; Yamashita, M.; Puuschman, F.; Alvarez-Falcon, M.
NMR data of compounds 1−8. This material is available free of
M.; Invarvito, C. D.; Hartwig, J. F. J. Am. Chem. Soc. 2006, 128, 9044.
(10) (a) Old, D. W.; Wolfe, J. P.; Buchwald, S. L. J. Am. Chem. Soc.
charge via the Internet at http://pubs.acs.org.
1
998, 120, 9722. (b) Bei, X.; Uno, T.; Norris, J.; Turner, H. W.;
Weinberg, W. H.; Guram, A. S. Organomatallics 1999, 18, 1840.
c) Lundgren, R. J.; Peters, B. D.; Alsabeh, P. G.; Stradiotto, M. Angew.
Chem., Int. Ed. 2010, 49, 4071.
AUTHOR INFORMATION
■
(
Corresponding Author
zhaoguo@sjtu.edu.cn
(
(
11) Xie, X.; Zhang, T. Y.; Zhang, Z. J. Org. Chem. 2006, 71, 6522.
12) Strieter, E. R.; Blackmond, D. G.; Buchwald, S. L. J. Am. Chem.
Notes
Soc. 2003, 125, 13978.
13) (a) Yang, B. H.; Buchwald, S. L. Org. Lett. 1999, 1, 35.
b) Trabanco, A. A.; Vega, J. A.; Fernandez, M. A. J. Org. Chem. 2007,
72, 8146.
The authors declare no competing financial interest.
(
(
́
ACKNOWLEDGMENTS
■
We thank the National Natural Science Foundation of China
for financial support.
(14) Hartwig, J. F.; Kawatsura, M.; Hauck, S. L.; Shaughnessy, K. H.;
Alcazar-Roman, L. M. J. Org. Chem. 1999, 64, 5575.
(15) (a) Bhagwanth, S.; Waterson, A. G.; Adjabeng, G. M.;
Hornberger, K. R. J. Org. Chem. 2009, 74, 4634. (b) Qin, L.; Cui,
H.; Zou, D.; Li, J.; Wu, Y.; Zhu, Z.; Wu, Y. Tetrahedron Lett. 2010, 51,
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