Palladium-catalyzed C(sp2)-H arylation using formamide as a transformable directing group

Article abstract of DOI:10.1021/jo5007043

A new process for the ortho arylation of formanilides through palladium-catalyzed C-H activation is described. Formamide is reported as a transformable directing group in the transition-metal-catalyzed C-H functionalization reaction. The resulting biarylformanilide products can be readily transformed to the corresponding biarylisocyanides or N-heterocycles.

Full text of DOI:10.1021/jo5007043

Note
pubs.acs.org/joc
Palladium-Catalyzed C(sp2)−H Arylation Using Formamide as a
Transformable Directing Group
Congqing Wan,† Jiaji Zhao,‡ Mingfang Xu,*,† and Jinbo Huang*,‡
†Department of Bioengineering, College of Life Science and Technology, Jinan University, Guangzhou 510632, China
‡State Key Laboratory of Respiratory Disease, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, 190
Kaiyuan Avenue, Guangzhou 510530, China
S
* Supporting Information
ABSTRACT: A new process for the ortho arylation of
formanilides through palladium-catalyzed C−H activation is
described. Formamide is reported as a transformable directing
group in the transition-metal-catalyzed C−H functionalization
reaction. The resulting biarylformanilide products can be
readily transformed to the corresponding biarylisocyanides or
N-heterocycles.
Scheme 1. Anilides in Chelation-Assisted C−H Arylation
ransition-metal-catalyzed C−H functionalization is emerg-
Ting as a promising strategy to construct new C−C or C−
heteroatom bonds, as it employs ubiquitous C−H bonds as a
latent functional group.1 Generally, this strategy needs to have a
directing group preinstalled in the substrate that is chelating
with the transition-metal catalyst to achieve chemo- and
regioselectivity. If the chelation group is not wanted after C−
H functionalization, an extra step to remove it, which is
normally a challenging task, is required. To solve this problem,
many removable directing groups have been developed in C−H
functionalization reactions.2,3 However, simply removing the
directing groups reduces the atom economy of the whole
process, offsetting the advantages of C−H functionalization
over traditional transformations starting from C−X bonds. To
make C−H functionalization reactions more applicable in
routine organic synthesis, developing new directing groups that
are transformable to other functionalities under mild conditions
is of great interest.
Aniline is one of the most important nitrogen-containing
substances widely used in the manufacture of agrochemicals,
pharmaceuticals, dyes, pigments, and polymers. Biarylaniline is
an important building block used for the synthesis of many
biologically active molecules and functional materials.4 Ortho
arylation of aniline derivatives through transition-metal-
catalyzed C−H functionalization is undoubtedly a straightfor-
ward approach to prepare this structural motif. Therefore, a
variety of amide,5 sulfonamide,6 and urea7 derivatives of anilines
have been used for chelation-assisted C−H arylation. Among
them, various secondary anilides are the most frequently
applied, including acetanilide, propionanilide, isobutyranilide,
pivalanilide, trifluoroacetanilide, benzanilide, and others
(Scheme 1). However, most of these directing groups are not
easily removed or transformed. In this context, we report herein
a new protocol for palladium-catalyzed C−H ortho arylation
using formamide as the transformable directing group.
Formamide can serve as a precursor of isocyanide or can be
removed under relatively mild conditions (Scheme 1). It is
important to note that Shi’s group reported palladium-catalyzed
ortho arylation of formamide using a mixture of copper and
silver salts as co-oxidants and trialkoxylsilane as a coupling
partner in 2007, but the efficiency of this transformation was
low.5c
Isocyanides are versatile in organic reactions such as Ugi and
Passerini multicomponent reactions,8 transition-metal-catalyzed
imidoylation,9 and radical-based transformation.10 One of the
most common methods to prepare isocyanide is dehydration of
the corresponding formamide. The amide bond in formamide is
more flexible and labile than other amide bonds. Therefore, it is
not surprising that there are few methods reported that use
formamide as a directing group in transition-metal-catalyzed
C−H functionalization in which the reaction conditions are
usually harsh. Inspired by the palladium-catalyzed C−H ortho
arylation of anilides,5−7 we assumed that a palladium-catalyzed
C−H ortho arylation using formamide as a directing group
could be realized with iodobenzenes as a coupling partner.
Remarkably, the arylated products can be readily converted to
biaryl isocyanides, which have been extensively studied in the
synthesis of phenanthridine derivatives.11
Received: March 26, 2014
Published: April 24, 2014
© 2014 American Chemical Society
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Note
a b
,
o-Methylformanilide 1a and iodobenzene 2a were chosen as
Scheme 2. Scope of Formanilides and Aryl Iodides
substrates for an initial study, as summarized in Table 1. First,
a
Table 1. Screening of the Reaction Conditions
b
entry
catalyst
Pd(OAc)2
oxidant
solvent T (°C) yield (%)
1
Cu(OAc)2
O2
TFA
100
100
100
100
100
100
100
100
100
100
100
100
100
100
80
0
2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(TFA)2
PdCl2
TFA
0
3
AgOAc
Ag2CO3
AgSbF6
AgTFA
Ag2O
TFA
48
4
TFA
trace
44
5
TFA
6
TFA
50
7
TFA
trace
56
8
AgBF4
AgBF4
AgBF4
AgBF4
AgBF4
AgBF4
AgBF4
AgBF4
AgBF4
TFA
9
HBF4
HFIP
HFIP
HFIP
HFIP
HFIP
HFIP
HFIP
40
10
11
12
13
14
15
16
76
74
trace
40
Pd(CH3CN)2Cl2
n.d.
71
Pd(OAc)2
Pd(OAc)2
120
74
a
Reaction conditions: 1a (0.2 mmol), 2a (3.0 mmol), Pd catalyst (5
mol %), oxidants (0.3 mmol, 1.5 equiv), solvent (0.2 mL), 2 h. HFIP =
b
1,1,1,3,3,3-hexafluoro-2-propanol. Isolated yields.
the reaction was conducted by examining a suitable oxidant in
the presence of Pd(OAc)2 as a catalyst in TFA. No desired
arylation product was detected using Cu(OAc)2 or O2 as
oxidants (entries 1 and 2). To our delight, arylation product 3a
was obtained in 48% yield using AgOAc as the oxidant (entry
3). Other silver salts, such as Ag2CO3, AgSbF6, AgTFA, Ag2O,
and AgBF4, were also screened, identifying all of these silver
salts as being effective for this transformation (entries 4−8).
Then, screening the reaction solvent revealed that HFIP is the
solvent of choice and that the yield of 3a could be improved to
76% (entry 10). Further study showed that other palladium
salts, such as PdCl2 and Pd(MeCN)2Cl2, are inferior to
Pd(TFA)2 and Pd(OAc)2 in promoting this arylation process
(entries 11−13). In a control reaction where the palladium
catalyst was absent, no arylation product 3a was detected. In
addition, altering the reaction temperature (80−120 °C) gave
no significant difference in reaction yield (entries 15 and 16).
With the optimized reaction conditions established, the
substrate scope of this formamide-directed arylation reaction
was investigated (Scheme 2). A variety of electron-withdrawing
or -donating group-substituted aryl iodides, including methyl,
methoxy, halogen, trifluoromethyl, and nitro groups, were
compatible with the optimal conditions in reactions with o-
methylformanilide 1a. In general, aryl iodides bearing electron-
rich groups afforded the arylation products in higher yields (3a-
c) than those with electron-deficient ones (3d−j). It was found
that switching from AgBF4 to AgTFA as the oxidant in TFA for
the reaction employing the electron-deficient aryl iodides led to
a dramatic increase in yield at higher temperature. The reason
for this is not clear, although the results do indicate that the
new catalytic system is more effective with an electron-deficient
coupling partner. When 1-bromo-4-iodobenzene was used as
a
Formanilide 1 (0.2 mmol), aryl iodide 2 (0.6 mmol), Pd(OAc)2 (5
mol %), AgBF4 (0.3 mmol, 1.5 equiv), HFIP (0.2 mL), 100 °C, 2 h.
b
c
d
Four millimoles of 1a was used. 80 °C in N2. AgTFA (0.3 mmol,
e
1.5 equiv), TFA (1 mL), 110 °C, 5 h. Yield of biarylation of
formanilide.
the coupling partner, corresponding product 3j was obtained in
lower yield because of the formation of a significant amount of
unidentified byproducts. The reaction was sensitive to the steric
hindrance of aryl iodides. For example, meta-substituted aryl
iodides generated the corresponding products in similar yields
as their para analogues (3k−m), whereas ortho-substituted aryl
iodides failed to afford the corresponding products except for 1-
iodonaphthalenethe (3n). Other 2-substituted formanilides 1
were also applicable to this arylation process (Scheme 2).
Electron-rich groups such as ethyl (3o), tert-butyl (3p), 2,4-
dimethyl (3q), and phenyl (3r) substituted formanilides
underwent the arylation reaction effectively with iodobenzene,
affording the corresponding products in 64−80% yield.
Unfortunately, selective monoarylation of 2-unsubstituted
formanilide was not accessible, giving the diarylation product
in 51% yield (3r). It is noteworthy that under the optimized
conditions the reaction can be easily scaled up; for example,
when 4 mmol of 1a (0.54 g) was used, there was no appreciable
drop in the yield (Scheme 2, 3a).
After this formamide-directed ortho-arylation protocol was
established, further transformation of biaryl formamide product
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Note
on a 400 or 500 MHz spectrometer using TMS as an internal standard.
Infrared (IR) spectra were recorded as KBr pellets on an FTIR-8500
spectrophotometer. Melting points (mp) are uncorrected. The
following abbreviations were used to describe peak splitting patterns
when appropriate: br s, broad singlet; s, singlet; d, doublet; t, triplet; q,
quartet; and m, multiplet. Coupling constants, J, are reported in hertz
(Hz). High-resolution mass spectra (HRMS) were obtained on an
ESI−LC−MS/MS spectrometer.
3a was studied. The formamide group can be readily removed
with HCl (1.1 equiv, 36−38%), giving ortho-phenyl aniline 4 in
82% yield (1, Scheme 3).12 Dehydration of 3a with phosphorus
oxychloride provided biphenyl isocyanide 5 in 73% yield (2,
Scheme 3).11b
Scheme 3. Transformation of Biaryl Formamide
General Procedure for the Preparation of Formanilide
Derivatives.11a To an oven-dried three-necked flask equipped with
a dropping funnel were added aniline (2 mmol, 1.0 equiv) and THF (2
mL) under a N2 atmosphere, and the mixture was cooled to 0 °C.
Acetic formic anhydride (3 mmol, 1.5 equiv) was transferred to the
dropping funnel and dropped into the solution of aniline at 0 °C. After
the addition was completed, the mixture was warmed to room
temperature and stirred for 2 h. Then, the mixture was quenched by a
saturated aqueous solution of NaHCO3 and extracted with EtOAc
three times. The extract was dried over Na2SO4 and concentrated
under reduced pressure to give formamide as a pale yellow solid.
General Procedure for the Arylation of Formanilide with
Various Aryl Iodides. Procedure A. A Schlenk tube with a magnetic
stir bar was charged with formanilide (0.2 mmol, 1.0 equiv), aryl iodide
(0.6 mmol, 3.0 equiv), Pd(OAc)2 (0.01 mmol, 2.2 mg, 5 mol %),
AgBF4 (0.3 mmol, 58 mg, 1.5 equiv), and HFIP (0.2 mL). The mixture
was heated at 100 °C, stirred for 2 h, and then cooled to room
temperature. After addition of saturated NaHCO3, the reaction
mixture was extracted with ethyl acetate (3 × 10 mL), and the organic
layer was collected. The combined organic phases were washed with
brine (30 mL), dried over anhydrous sodium sulfate, filtered, and
concentrated. The residue was purified by flash column chromatog-
raphy with ethyl acetate and petroleum ether as the eluent to afford
the corresponding products.
A plausible reaction mechanism is proposed in Scheme 4.
First, formamide-directed electrophilic palladation generates a
Scheme 4. Proposed Reaction Mechanism
Procedure B. A Schlenk tube with a magnetic stir bar was charged
with formanilide (0.2 mmol, 1.0 equiv), aryl iodide (0.6 mmol, 3.0
equiv), Pd(OAc)2 (0.01 mmol, 2.2 mg, 5 mol %), AgBF4 (0.3 mmol,
58 mg, 1.5 equiv), and HFIP (0.2 mL). The mixture was heated at 80
°C, stirred for 2 h under a N2 atmosphere, and then cooled to room
temperature. After addition of saturated NaHCO3, the reaction
mixture was extracted with ethyl acetate (3 × 10 mL), and the organic
layer was collected. The combined organic phases were washed with
brine (30 mL), dried over anhydrous sodium sulfate, filtered, and
concentrated. The residue was purified by flash column chromatog-
raphy with ethyl acetate and petroleum ether as the eluent to afford
the corresponding products.
Procedure C. A Schlenk tube with a magnetic stir bar was charged
with formanilide (0.2 mmol, 1.0 equiv), aryl iodide (0.6 mmol, 3.0
equiv), Pd(OAc)2 (0.01 mmol, 2.2 mg, 5 mol %), AgTFA (0.3 mmol,
77 mg, 1.5 equiv), and TFA (1 mL). The mixture was heated at 110
°C, stirred for 5 h, and then cooled to room temperature. After
addition of saturated NaHCO3, the reaction mixture was extracted
with ethyl acetate (3 × 10 mL), and the organic layer was collected.
The combined organic phases were washed with brine (30 mL), dried
over anhydrous sodium sulfate, filtered, and concentrated. The residue
was purified by flash column chromatography with ethyl acetate and
petroleum ether as the eluent to afford the corresponding products.
Procedure for the Dehydration of N-(3-Methyl-[1,1′-biphen-
yl]-2-yl)formamide.12 To a solution of N-(3-methyl-[1,1′-biphenyl]-
2-yl)formamide (64 mg, 0.3 mmol) and triethylamine (0.25 mL, 6
equiv) in 2 mL of anhydrous THF was added POCl3 (45 uL, 1.5
equiv) dropwise with constant magnetic stirring at 0 °C under an
argon atmosphere. The mixture was stirred at 0 °C for about 2 h.
Then, 5 mL of saturated aqueous NaHCO3 was added carefully to
quench the reaction, and the mixture was stirred for about 10 min. The
mixture was then extracted with EtOAc. The organic layers were
evaporated under vacuum. The residue was purified by column
chromatography on silica gel to give 1.
palladacycle intermediate, A. Then, oxidative addition of aryl
iodide to Pd(II) in A gives a Pd(IV) intermediate, B, followed
by reductive elimination to afford the arylation product and
Pd(II). Silver salt may act as a halide scavenger to improve the
transformation under the reaction conditions.13−15 Another
reaction pathway involving a Pd(0)/Pd(II) catalytic cycle is
also possible.
In conclusion, we have developed an efficient method for Pd-
catalyzed C(sp2)−H arylation directed by a transformable
formamide group. Formanilides react with various aryl iodides
to give the corresponding ortho-arylated products in moderate
to good yields. The corresponding biaryl formanilide products
can be readily converted to biaryl isocyanides, which are useful
building blocks in the synthesis of phenanthridine derivatives.
EXPERIMENTAL SECTION
■
General Information. The materials and solvents were purchased
from common commercial sources and used without further
purification unless otherwise noted. Reactions were monitored using
thin-layer chromatography (TLC) on commercial silica gel plates
(GF254). Visualization of the developed plates was performed under
UV light (254 nm). Flash column chromatography was performed on
Procedure for the Deformylation of N-(3-Methyl-[1,1′-
biphenyl]-2-yl)formamide.11b A mixture of N-(3-methyl-[1,1′-
biphenyl]-2-yl)formamide (64 mg, 0.3 mmol) and concentrated
hydrochloric acid (275 μL, 1.1 equiv, 12 N) in ethanol (2 mL) was
1
silica gel (200−300 mesh). H and 13C NMR spectra were recorded
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The Journal of Organic Chemistry
Note
heated at 75 °C for 12 h. Upon cooling the reaction mixture to room
temperature, the mixture was neutralized with 2 N NaOH and
extracted with ethyl acetate. The combined organic layers were washed
with water and brine. The dried solution (over Na2SO4) was
concentrated, and the residue was purified by flash chromatography
to yield 2.
N-(3-Methyl-biphenyl-2-yl)-formamide (3a). Following general
procedure A (white solid). Yield (32.1 mg, 76%). mp 159−160 °C
(159−160 °C).16 1H NMR (400 MHz, CDCl3, TMS) δ 8.21 (s,
0.51H), 7.94 (d, 0.44H, J = 12.0 Hz), 7.18−7.43 (m, 8H), 6.80 (d,
0.36H, J = 10.4 Hz), 6.69 (br s, 0.41H), 2.38 (s, 1.38H), 2.34 (s,
1.62H). 13C NMR (125 MHz, CDCl3) δ 164.9, 160.0, 139.4, 139.3,
138.7, 138.5, 136.3, 134.1, 131.9, 131.1, 130.3, 130.1, 129.4, 128.9,
128.7, 128.3, 127.9, 127.6, 127.4, 127.4, 127.1, 18.8, 18.7. HRMS
(ESI): mass calcd for C14H13NO [M + H]+, 212.1075; found,
212.1071. IR (KBr pellet): 3187, 3062, 3005, 2918, 2893, 1668, 1657,
1530, 1466, 1440, 1387, 1263, 1156, 1071, 796, 757, 723, 702, 555
cm−1.
0.45H, J = 11.7 Hz), 6.69 (br s, 0.45H), 2.38 (s, 1.35H), 2.33 (s,
1.65H). 13C NMR (125 MHz, CDCl3) δ 164.9, 162.3 (d, J = 245.5
Hz), 162.2 (d, J = 245.9 Hz), 159.9, 138.7, 137.6, 136.5, 135.3 (d, J =
3.5 Hz), 134.7 (d, J = 3.4 Hz), 134.4, 132.0, 131.1, 131.1, 130.6, 130.5,
130.3, 128.9, 128.0, 127.8, 127.3, 115.7 (d, J = 21.2 Hz), 115.3 (d, J =
21.2), 18.8, 18.8. HRMS (ESI): mass calcd for C14H12FNO [M + H]+,
230.0981; found, 230.0979. IR (KBr pellet): 3234, 2916, 1650, 1604,
1511, 1466, 1377, 1221, 1160, 842, 785, 538 cm−1.
N-(3-Methyl-4′-nitro-biphenyl-2-yl)-formamide (3g). Follow-
ing general procedure C (pale yellow solid). Yield (22.5 mg, 44%). mp
221−223 °C. 1H NMR (400 MHz, DMSO-d6, TMS) δ 9.58 (s,
0.81H), 9.48 (d, 0.18H, J = 11.4 Hz), 8.28 (t, 2H, J = 9.6 Hz), 8.03 (s,
0.80H), 7.68 (d, 0.2H, J = 10.6 Hz), 7.58−7.64 (m, 2H), 7.22−7.42
(m, 3H), 2.31 (s, 0.57H), 2.23 (s, 2.43H). 13C NMR (125 MHz,
DMSO-d6) δ 164.9, 160.5, 147.1, 146.9, 146.8, 146.6, 138.1, 137.4,
136.7, 136.4, 133.3, 132.8, 131.6, 131.3, 131.1, 130.4, 128.7, 128.0,
127.8, 127.7, 123.9, 123.6, 18.7, 18.6. HRMS (ESI): mass calcd for
C14H12N2O3 [M + H]+, 257.0926; found, 257.0922. IR (KBr): 3249,
3074, 3006, 2954, 2920, 1686, 1668, 1599, 1515, 1469, 1393, 1348,
1109, 860, 846, 797, 755, 695 cm−1.
N-(3,4′-Dimethyl-biphenyl-2-yl)-formamide (3b). Following
general procedure A (white solid). Yield (31.5 mg, 70%). mp 134−
1
136 °C. H NMR (400 MHz, CDCl3, TMS) δ 8.20 (s, 0.49H), 7.93
N-(3-Methyl-4′-trifluoromethyl-biphenyl-2-yl)-formamide
(3h). Following general procedure C (pale yellow solid). Yield (29.0
(d, 0.46H, J = 11.7 Hz), 7.16−7.26 (m, 7H), 6.86 (d, 0.40H, J = 10.6
Hz), 6.71 (br s, 0.46H), 2.39 (s, 1.44H), 2.38 (s, 3H). 2.33 (s, 1.56H).
13C NMR (125 MHz, CDCl3) δ 164.9, 159.9, 139.3, 138.4, 137.2,
1
mg, 52%). mp 176−178 °C. H NMR (400 MHz, CDCl3, TMS) δ
8.21 (s, 0.58H), 7.91 (d, 0.41H, J = 11.7 Hz), 7.68 (t, 2H, J = 8.5 Hz),
7.45 (d, 2H, J = 7.8 Hz), 7.18−7.33 (m, 3H), 6.83 (d, 0.34H, J = 11.7
Hz), 6.65 (br s, 0.53H), 2.39 (s, 1.23H), 2.34 (s, 1.74). 13C NMR (125
MHz, CDCl3) δ 164.7, 159.8, 143.1, 142.5, 138.6, 137.2, 136.7, 134.7,
131.8, 131.1, 130.9, 130.8, 129.9, 129.6, 129.6, 129.3, 128.8, 128.0,
127.9, 127.5, 125.7 (q, J = 3.7 Hz), 125.3 (q, J = 3.6 Hz), 124.1 (q, J =
270.1 Hz), 124.0 (q, J = 270.3 Hz). 18.7. HRMS (ESI): mass calcd for
C15H12F3NO [M + H]+, 280.0949; found, 280.0944. IR (KBr pellet):
3229, 2922, 1654, 1519, 1402, 1382, 1329, 1168, 1107, 1080, 1065,
782 cm−1.
137.2, 136.4, 136.3, 135.7, 133.9, 132.0, 131.1, 130.1, 130.0, 129.4,
129.2, 129.0, 128.9, 128.8, 128.0, 127.5, 127.1, 21.1, 18.9, 18.8. HRMS
(ESI): mass calcd for C15H15NO [M + H]+, 226.1232; found,
226.1230. IR (KBr pellet): 3251, 2911, 2862, 1655, 1588, 1513, 1466,
1445, 1402, 1379, 1219, 1150, 1035, 826, 778, 731, 715, 577, 538, 512,
469 cm−1.
N-(4′-Methoxy-3-methyl-biphenyl-2-yl)-formamide (3c). Fol-
lowing general procedure B (pale yellow solid). Yield (30.9 mg, 64%).
mp 143−144 °C. 1H NMR (400 MHz, CDCl3, TMS) δ 8.23 (s,
0.50H), 7.96 (d, 0.46H, J = 12.0 Hz), 7.16−7.26 (m, 5H), 6.95−6.96
(m, 2H), 6.80 (br s, 0.45H), 6.69 (br s, 0.44H), 3.84 (s, 3H), 2.37 (s,
1.41H), 2.33 (s, 1.59H). 13C NMR (125 MHz, CDCl3) δ 164.8, 159.9,
159.1, 159.0, 139.1, 138.2, 136.3, 133.9, 132.0, 131.6, 131.2, 130.9,
130.5, 130.1, 130.0, 129.9, 128.9, 128.0, 127.6, 127.1, 114.3, 113.8,
55.3, 18.9, 18.9. HRMS (ESI): mass calcd for C15H15NO2 [M + H]+,
242.1181; found, 242.1173. IR (KBr pellet): 3266, 2993, 2956, 2918,
2855, 2835, 1654, 1612, 1514, 1467, 1443, 1379, 1294, 1250, 1184,
1034, 834, 820, 784, 735, 546 cm−1.
N-(4′-Acetyl-3-methyl-biphenyl-2-yl)-formamide (3d). Fol-
lowing general procedure A (pale yellow solid). Yield (25.8 mg,
51%). mp 177−179 °C. 1H NMR (400 MHz, CDCl3, TMS) δ 8.19 (s,
0.54H), 8.00 (t, 2H, J = 9.3 Hz), 7.88 (d, 0.44H, J = 11.6 Hz), 7.44 (d,
2H, J = 7.9 Hz), 7.18−7.32 (m, 3H), 7.00 (d, 0.40H, J = 11.1 Hz), 6.80
(br s, 0.51H), 2.63 (s, 3H), 2.39 (s, 1.31H), 2.34 (s, 1.69H). 13C NMR
(125 MHz, CDCl3) δ 197.8, 197.6, 164.8, 160.0, 144.5, 143.8, 138.8,
137.4, 136.6, 135.9, 134.6, 131.8, 131.0, 130.7, 129.7, 129.2, 128.8,
128.7, 128.3, 127.8, 127.8, 127.4, 26.6, 18.7, 18.7. HRMS (ESI): mass
calcd for C16H15NO2 [M + H]+, 254.1181; found, 254.1177. IR (KBr
pellet): 3256, 2968, 2910, 1682, 1655, 1606, 1501, 1402, 1376, 1359,
1269, 840, 788, 605 cm−1.
2′-Formylamino-3′-methyl-biphenyl-4-carboxylic Acid
Methyl Ester (3e). Following general procedure A (white solid).
Yield (25.8 mg, 48%). mp 188−190 °C. 1H NMR (400 MHz, CDCl3,
TMS) δ 8.20 (s, 0.54H), 8.09 (t, 2H, J = 8.4 Hz), 7.89 (d, 0.40H, J =
11.8 Hz), 7.41 (d, 2H, J = 7.4 Hz), 7.18−7.32 (m, 3H), 6.82 (d, 0.36H,
J = 9.4 Hz), 6.67 (br s, 0.48H), 3.94 (s, 3H), 2.39 (s, 1.37H), 2.34 (s,
1.73H). 13C NMR (125 MHz, CDCl3) δ 166.8, 166.7, 164.7, 159.8,
144.2, 143.5, 138.8, 137.5, 136.6, 134.5, 131.8, 131.0, 130.9, 130.7,
130.0, 129.6, 129.5, 129.2, 129.2, 129.0, 128.7, 127.8, 127.8, 127.4,
52.1, 18.8, 18.7. HRMS (ESI): mass calcd for C16H15NO3 [M + H]+,
270.1130; found, 270.1128. IR (KBr pellet): 3263, 2954, 2911, 1718,
1655, 1610, 1500, 1438, 1316, 1286, 1119, 768, 709 cm−1.
N-(4′-Chloro-3-methyl-biphenyl-2-yl)-formamide (3i). Fol-
lowing general procedure A (white solid). Yield (31.9 mg, 65%). mp
1
185−186 °C. H NMR (400 MHz, CDCl3, TMS) δ 8.21 (s, 0.55H),
7.92 (d, 0.42H, J = 11.6 Hz), 7.39 (t, 2H, J = 8.5 Hz), 7.29 (m, 2H),
7.15−7.27 (m, 3H), 6.85 (d, 0.34H, J = 11.0 Hz), 6.66 (br s, 0.46H),
2.38 (s, 1.34H), 2.33 (s, 1.66H). 13C NMR (125 MHz, CDCl3) δ
164.7, 159.9, 138.6, 137.8, 137.4, 137.2, 136.6, 134.4, 133.7, 133.6,
131.8, 131.0, 130.7, 130.7, 130.5, 130.2, 129.0, 128.8, 128.5, 127.9,
127.8, 127.4, 18.8, 18.8. HRMS (ESI): mass calcd for C14H12NOCl [M
+ H]+, 246.0686; found, 246.0681. IR (KBr pellet): 3227, 3053, 2949,
2914, 1651, 1496, 1463, 1377, 1149, 1091, 1016, 839, 781, 734, 719
cm−1.
N-(4′-Bromo-3-methyl-biphenyl-2-yl)-formamide (3j). Fol-
lowing general procedure A (white solid). Yield (17.9 mg, 31%). mp
1
194−196 °C. H NMR (400 MHz, CDCl3, TMS) δ 8.22 (s, 0.53H),
7.92 (d, 0.40H, J = 11.2 Hz), 7.55 (t, 2H, J = 8.3 Hz), 7.15−7.30 (m,
5H), 6.76 (d, 0.38H, J = 12.3 Hz), 6.63 (br s, 0.49H), 2.38 (s, 1.29H),
2.33 (s, 1.71). 13C NMR (125 MHz, CDCl3) δ 164.6, 159.8, 138.6,
138.3, 137.7, 137.4, 136.6, 134.4, 132.0, 131.7, 131.5, 131.0, 130.9,
130.8, 130.6, 130.5, 128.8, 127.9, 127.8, 127.4, 121.9, 121.8, 18.8, 18.8.
HRMS (ESI): mass calcd for C14H12BrNO [M + H]+, 290.0181;
found, 290.0176. IR (KBr pellet): 3226, 2949, 2913, 1651, 1493, 1462,
1377, 1012, 836, 780 cm−1.
N-(3,3′-Dimethyl-biphenyl-2-yl)-formamide (3k). Following
general procedure A (white solid). Yield (33.8 mg, 75%). mp 118−
1
119 °C. H NMR (400 MHz, CDCl3, TMS) δ 8.18 (s, 0.50H), 7.92
(d, 0.47H, J = 11.5 Hz), 7.13−7.32 (m, 7H), 6.98 (d, 0.50H, J = 10.3
Hz), 6.78 (br s, 0.50H), 2.37 (s, 4.35H), 2.32 (s, 1.65H). 13C NMR
(125 MHz, CDCl3) δ 164.9, 159.9, 139.5, 139.3, 138.7, 138.6, 138.4,
138.0, 136.3, 133.9, 132.0, 131.1, 130.2, 130.1, 130.0, 129.6, 128.9,
128.6, 128.3, 128.2, 128.2, 127.9, 127.5, 127.0, 126.4, 126.0, 21.4, 21.4,
18.9, 18.8. HRMS (ESI): mass calcd for C15H15NO [M + H]+,
226.1232; found, 226.1227. IR (KBr pellet): 3177, 3111, 3015, 2921,
2880, 1686, 1655, 1592, 1523, 1462, 1386, 1283, 1256, 1239, 782, 732,
707 cm−1.
N-(4′-Fluoro-3-methyl-biphenyl-2-yl)-formamide (3f). Fol-
lowing general procedure C (pale yellow solid). Yield (27.9 mg,
61%). mp 164−165 °C. 1H NMR (400 MHz, CDCl3, TMS) δ 8.21 (s,
0.52H), 7.91 (d, 0.43H, J = 11.6 Hz), 7.07−7.31 (m, 7H), 6.91 (d,
N-(3′-Chloro-3-methyl-biphenyl-2-yl)-formamide (3l). Fol-
lowing general procedure A (white solid). Yield (30.9 mg, 63%). mp
4754
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The Journal of Organic Chemistry
Note
1
172−174 °C. H NMR (400 MHz, CDCl3, TMS) δ 8.21 (s, 0.54H),
(s, 0.51H), 7.89 (d, 0.44H, J = 11.7 Hz), 7.29−7.43 (m, 5H), 7.10 (s,
1H), 7.05 (s, 0.46H), 6.99 (s, 0.54H), 6.79 (d, 0.41H, J = 11.6 Hz),
6.65 (br s, 0.47H), 2.36 (s, 1.37H), 2.34 (s, 3H), 2.29 (s, 1.63H). 13C
NMR (125 MHz, CDCl3) δ 165.0, 160.1, 139.5, 139.3, 138.9, 138.6,
137.4, 137.0, 136.1, 134.1, 131.0, 130.8, 129.5, 129.4, 129.3, 128.9,
128.7, 128.7, 128.4, 128.3, 127.4, 127.3, 20.9, 20.9, 18.7. HRMS (ESI):
mass calcd for C15H15NO [M + H]+, 226.1232; found, 226.1226. IR
(KBr pellet): 3235, 2915, 1680, 1652, 1602, 1513, 1440, 1383, 1146,
864, 773, 718, 703 cm−1.
7.92 (d, 0.41H, J = 11.6 Hz), 7.30−7.34 (m, 5H), 7.15−7.21 (m, 2H),
6.85 (d, 0.36H, J = 10.2 Hz), 6.69 (br s, 0.48H), 2.38 (s, 1.31H), 2.33
(s, 1.69H). 13C NMR (125 MHz, CDCl3) δ 164.8, 159.9, 141.2, 140.6,
138.4, 137.2, 136.6, 134.6, 134.5, 134.1, 131.9, 131.0, 130.8, 130.6,
130.0, 129.6, 129.5, 128.9, 128.8, 127.9, 127.8, 127.7, 127.6, 127.6,
127.3, 127.2, 18.8, 18.7. HRMS (ESI): mass calcd for C14H12ClNO [M
+ H]+, 246.0686; found, 246.0681. IR (KBr pellet): 3269, 3060, 2913,
1655, 1565, 1504, 1460, 1401, 1380, 1147, 1110, 779, 737, 697 cm−1.
N-(2-Methyl-6-naphthalen-2-yl-phenyl)-formamide (3m).
Following general procedure A (pale yellow solid). Yield (46.0 mg,
88%). mp 168−170 °C. 1H NMR (400 MHz, CDCl3, TMS) δ 8.19 (s,
0.52H), 7.95 (d, 0.61H, J = 11.6 Hz), 7.86−7.90 (m, 3H), 7.79 (br s,
1H), 7.52 (br s, 2H), 7.44 (t, 1H, J = 6.8 Hz), 7.28−7.33 (m, 3H),
6.89 (d, 0.38H, J = 10.3 Hz), 6.71 (br s, 0.48H), 2.40 (s, 1.34H), 2.36
(s, 1.66H). 13C NMR (125 MHz, CDCl3) δ 164.8, 159.9, 139.4, 138.4,
136.9, 136.5, 136.3, 134.1, 133.5, 133.2, 132.5, 132.5, 132.1, 131.3,
130.5, 130.3, 129.2, 128.4, 128.4, 128.2, 128.0, 128.0, 127.9, 127.7,
127.7, 127.7, 127.7, 127.2, 127.2, 126.5, 126.4, 126.3, 126.2, 18.9, 18.8.
HRMS (ESI): mass calcd for C18H15NO [M + H]+, 262.1232; found,
262.1228. IR (KBr pellet): 3188, 3055, 2983, 2923, 2886, 1669, 1658,
1528, 1506, 1481, 1461, 1439, 1386, 1266, 828, 792, 748, 724, 481
cm−1.
N-(2-Methyl-6-naphthalen-1-yl-phenyl)-formamide (3n). Fol-
lowing general procedure A (pale yellow solid). Yield (20.9 mg, 40%).
mp 193−195 °C. 1H NMR (400 MHz, CDCl3, TMS) δ 7.88−7.92 (m,
3H), 7.48−7.54 (m, 3H), 7.20−7.43 (m, 5H), 6.63 (d, 0.40H, J = 11.2
Hz), 6.52 (br s, 0.49H), 2.43 (s, 1.32H), 2.38 (s, 1.68H). 13C NMR
(125 MHz, CDCl3) δ 163.8, 159.2, 137.3, 137.1, 136.8, 136.2, 136.1,
133.8, 133.7, 133.5, 133.1, 132.4, 131.7, 131.5, 130.8, 130.5, 129.6,
128.6, 128.5, 128.3, 128.1, 127.4, 127.4, 127.0, 126.7, 126.6, 126.1,
126.1, 125.6, 125.4, 125.4, 125.0, 19.1, 18.9. HRMS (ESI): mass calcd
for C18H15NO [M + H]+, 262.1232; found, 262.1229. IR (KBr pellet):
3217, 3058, 3012, 1683, 1657, 1589, 1519, 1462, 1439, 1385, 1281,
1240, 801, 779, 727 cm−1.
N-[1,1′;3′,1″]Terphenyl-2′-yl-formamide (3s). Following gen-
eral procedure A (white solid). Yield (27.9 mg, 51%). mp 173−175
1
°C. H NMR (400 MHz, CDCl3, TMS) δ 7.85 (s, 0.29H), 7.82 (d,
0.70H, J = 11.4 Hz), 7.38−7.47 (m, 13H), 6.77 (d, 0.62H, J = 10.0
Hz), 6.64 (br s, 0.24H). 13C NMR (125 MHz, CDCl3) δ 164.5, 159.9,
140.8, 139.5, 138.5, 137.0, 130.7, 130.6, 130.0, 129.7, 129.3, 129.0,
128.8, 128.2, 127.9, 127.8, 127.4, 126.5. HRMS (ESI): mass calcd for
C19H15NO [M + H]+, 274.1232; found, 274.1225. IR (KBr pellet):
3240, 3058, 3026, 1663, 1497, 1459, 1441, 1423, 1383, 807, 756, 731,
703, 591 cm−1.
3-Methyl-biphenyl-2-ylamine (4). N-(3-Methyl-biphenyl-2-yl)-
formamide (0.2 mmol) was used. Yield (30.0 mg, 82%) (white solid).
mp 61−62 °C. 1H NMR (400 MHz, CDCl3, TMS) δ 7.44 (d, 4H, J =
4.0 Hz), 7.33−7.35 (m, 1H), 7.07 (d, 1H, J = 7.4 Hz), 7.01 (d, 1H, J =
7.5 Hz), 6.76 (r, 1H, J = 7.4 Hz), 3.70 (br s, 2H), 2.22 (s, 3H). 13C
NMR (125 MHz, CDCl3) δ 141.7, 139.9, 129.7, 129.3, 128.8, 128.3,
127.5, 127.1, 122.4, 118.1, 17.9. HRMS (ESI): mass calcd for C13H13N
[M + H]+, 184.1126; found, 184.1122. IR (KBr pellet): 3457, 3376,
3075, 3047, 3026, 2979, 2929, 2852, 1622, 1590, 1465, 1430, 1275,
1241, 1080, 1072, 1016, 784, 757, 746, 701 cm−1.
2-Isocyano-3-methyl-biphenyl (5). N-(3-Methyl-biphenyl-2-yl)-
formamide (0.2 mmol) was used. Yield (28.2 mg, 73%) (pale yellow
1
oil). H NMR (400 MHz, CDCl3, TMS) δ 7.39−7.50 (m, 5H), 7.34
(t, 1H, J = 7.6 Hz), 7.23−7.28 (m, 2H), 2.50 (s, 3H). 13C NMR (125
MHz, CDCl3) δ 168.7, 139.0, 137.5, 135.8, 129.3, 129.0, 128.9, 128.5,
128.2, 128.0, 19.4. HRMS (ESI): mass calcd for C14H11N [M + H]+,
194.0970; found, 194.0963. IR (KBr pellet): 3061, 3032, 2923, 2117,
1593, 1500, 1469, 1442, 1420, 1101, 1070, 868, 793, 760, 738, 700,
665, 593 cm−1.
N-(3-Ethyl-biphenyl-2-yl)-formamide (3o). Following general
procedure A (white solid). Yield (36.0 mg, 80%). mp 141−142 °C. 1H
NMR (400 MHz, CDCl3, TMS) δ 8.20 (s, 0.45H), 7.87 (d, 0.56H, J =
11.6 Hz), 7.19−7.42 (m, 8H), 6.87 (d, 0.43H, J = 11.8 Hz), 6.65 (br s,
0.38H), 2.71 (m, 2H), 1.28 (s, 1H), 1.26 (s, 2H). 13C NMR (125
MHz, CDCl3) δ 165.1, 160.4, 142.0, 140.4, 140.1, 139.6, 139.0, 138.9,
131.2, 130.4, 129.5, 128.9, 128.9, 128.7, 128.5, 128.3, 128.1, 128.1,
128.0, 127.6, 127.4, 127.4, 24.9, 24.8, 14.6, 14.1. HRMS (ESI): mass
calcd for C15H15NO [M + H]+, 226.1232; found, 226.1227. IR (KBr
pellet): 3195, 2965, 1671, 1658, 1530, 1456, 1435, 1390, 759, 729, 702
cm−1.
ASSOCIATED CONTENT
■
S
* Supporting Information
1H and 13C NMR spectra of all synthesized compounds. This
material is available free of charge via the Internet at http://
pubs.acs.org.
N-(3-tert-Butyl-biphenyl-2-yl)-formamide (3p). Following gen-
AUTHOR INFORMATION
Corresponding Authors
*E-mail: huang_jinbo@gibh.ac.cn (J.H.).
*E-mail: xumingfang@jnu.edu.cn (M.X.).
Notes
■
eral procedure A (white solid). Yield (35.9 mg, 71%). mp 198−200
1
°C. H NMR (400 MHz, CDCl3, TMS) δ 7.94 (s, 0.23H), 7.64 (d,
0.75H, J = 11.7 Hz), 7.50 (d, 1H, J = 7.8 Hz), 7.20−7.43 (m, 7H), 7.16
(d, 0.71H, J = 11.6 Hz), 6.87 (br s, 0.23H), 1.45 (s, 9H). 13C NMR
(125 MHz, CDCl3) δ 165.4, 160.5, 147.9, 147.2, 143.5, 141.9, 140.6,
139.4, 131.8, 130.9, 129.8, 129.4, 129.0, 128.7, 128.1, 127.9, 127.8,
127.2, 127.0, 126.5, 35.5, 35.5, 31.2. HRMS (ESI): mass calcd for
C17H19NO [M + H]+, 254.1545; found, 254.1542. IR (KBr pellet):
3237, 3059, 3006, 2965, 2864, 1690, 1667, 1516, 1447, 1421, 1381,
1303, 1267, 806, 761, 697 cm−1.
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
We are grateful for the financial support of this work from the
National Science Foundation of China (21202167 and
21272233).
N-[1,1′;3′,1″]Terphenyl-2′-yl-formamide (3q). Following gen-
eral procedure A (white solid). Yield (35.0 mg, 64%). mp 173−175
1
°C. H NMR (400 MHz, CDCl3, TMS) δ 7.84 (s, 0.28H), 7.77 (d,
0.67H, J = 11.4 Hz), 7.38−7.47 (m, 13H), 6.77 (d, 0.58H, J = 10.2
Hz), 6.64 (br s, 0.23H). 13C NMR (125 MHz, CDCl3) δ 164.5, 159.9,
140.8, 139.6, 138.5, 137.0, 130.7, 130.6, 130.0, 129.7, 129.4, 129.0,
128.9, 128.2, 127.9, 127.8, 127.4, 126.5. HRMS (ESI): mass calcd for
C19H15NO [M + H]+, 274.1232; found, 274.1225. IR (KBr pellet):
3240, 3058, 3026, 1663, 1497, 1459, 1441, 1423, 1383, 807, 756, 731,
703, 591 cm−1.
N-(3,5-Dimethyl-biphenyl-2-yl)-formamide (3r). Following
general procedure A (white solid). Yield (36.0 mg, 80%). mp 170−
172 °C (173−175 °C).17 1H NMR (400 MHz, CDCl3, TMS) δ 8.18
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