Palladium-catalyzed addition of potassium aryltrifluoroborates to aliphatic nitriles: Synthesis of alkyl aryl ketones, diketone compounds, and 2-arylbenzo[b]furans

Article abstract of DOI:10.1021/jo400433m

A palladium-catalyzed addition of potassium aryltrifluoroborates to aliphatic nitriles has been developed, leading to a wide range of alkyl aryl ketones with moderate to excellent yields. Moreover, several dinitriles (e.g., malononitrile, glutaronitrile, and adiponitrile) were applicable to this process for the construction of 1,3-, 1,5-, or 1,6-dicarbonyl compounds. The scope of the developed approach is successfully explored toward the one-step synthesis of 2-arylbenzo[b]furans via sequential addition and intramolecular annulation reactions. The methodology accepted a wide range of substrates and is applicable to library synthesis.

Full text of DOI:10.1021/jo400433m

Article
pubs.acs.org/joc
Palladium-Catalyzed Addition of Potassium Aryltrifluoroborates to
Aliphatic Nitriles: Synthesis of Alkyl Aryl Ketones, Diketone
Compounds, and 2‑Arylbenzo[b]furans
Xingyong Wang, Miaochang Liu, Long Xu, Qingzong Wang, Jiuxi Chen,* Jinchang Ding,
and Huayue Wu*
College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou 325035, China
S
* Supporting Information
ABSTRACT: A palladium-catalyzed addition of potassium
aryltrifluoroborates to aliphatic nitriles has been developed,
leading to a wide range of alkyl aryl ketones with moderate to
excellent yields. Moreover, several dinitriles (e.g., malononi-
trile, glutaronitrile, and adiponitrile) were applicable to this
process for the construction of 1,3-, 1,5-, or 1,6-dicarbonyl
compounds. The scope of the developed approach is
successfully explored toward the one-step synthesis of 2-
arylbenzo[b]furans via sequential addition and intramolecular
annulation reactions. The methodology accepted a wide range
of substrates and is applicable to library synthesis.
having advantages such as low toxicity and ease of handling,
boronic acids often dimerize and trimerize to form boronic acid
anhydrides and boroxines,10 which hinder the direct
purification and the determination of the exact stoichiometry
of these reactions. Recently, potassium organotrifluoroborates,
with superior features such as higher air- and moisture-
stability,11 have been investigated as alternatives to boronic acid
derivatives that easily undergo protodeboronation.12 To the
best of our knowledge, the application of potassium organo-
trifluoroborates in transition-metal-catalyzed addition of nitriles
has not been reported thus far.
As part of the continuing efforts in our laboratory toward the
development of novel transition-metal-catalyzed addition or
coupling reactions with organoboron reagents,13,14 we herein
explored the potential of palladium-catalyzed addition of
potassium organotrifluoroborates to a nitrile group, which is
usually more challenging than an aldehyde14a or acyl
chloride14b group. This chemistry has provided a new method
for the synthesis of alkyl aryl ketones (or dicarbonyl
compounds) by Pd-catalyzed addition of potassium aryltri-
fluoroborates to aliphatic nitriles (or dinitriles) and the one-
step synthesis of 2-arylbenzo[b]furan derivatives (Scheme 1).
Successful addition of aliphatic nitriles would extend the
substrate scope in palladium-catalyzed addition reactions.
INTRODUCTION
■
Transformations of nitriles play an important role in both the
laboratory and industry due to their well-recognized chemical
versatility.1 However, the nitrile group is generally inert in
organometallic reactions, and thus acetonitrile or benzonitrile
usually participate as solvents or ligands2 in many metal-
catalyzed reactions. The insertions of nitrile groups from
Grignard reagents3 and organolithium reagents4 are powerful
tools for the construction of arylketones and heterocyclic
compounds, but the rigorous conditions of these reactions have
restricted their applications and the variety of substrates.
Transition-metal-catalyzed insertion of nitriles offers an
attractive route for the creation of novel carbon−carbon and
carbon−heteroatom bonds. While rhodium,5 palladium,6 and
nickel7 complexes have been investigated to catalyze addition
reactions of arylboronic acids to the nitrile group, the substrate
scope is usually limited to aromatic nitriles6,7 and activated
nitriles (e.g., cyanoformate5a and (benzyl-/arylsulfonyl)-
acetonitriles5b). Compared to the reactions of aromatic nitriles,
nucleophilic addition reactions of aliphatic nitriles are limited
by poor electrophilic activation that is insufficient to perform
the addition. On the other hand, aliphatic nitriles tend to be
deprotonated in the presence of palladium catalysts leading to
α-arylation products,8 making the addition reaction of aliphatic
nitriles more difficult to perform than that of aromatic nitriles.
Thus, the development of a practical and general approach to
alkyl aryl ketones and heterocyclic compounds using aliphatic
nitriles as substrates remains a challenging area for exploration.
Organoboron compounds and particularly boronic acids are
useful reagents for carbon−carbon bond formation with various
electrophiles in the presence of transition metals.9 Although
RESULTS AND DISCUSSION
■
We began our study by examining the reaction between
acetonitrile (1a) and potassium phenyltrifluoroborate (2a) to
Received: February 27, 2013
© XXXX American Chemical Society
A
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a
Scheme 1. Pd-Catalyzed Addition of ArBF3K to Aliphatic
Nitriles
Table 1. Optimization of the Reaction Conditions
obtain the optimal reaction conditions (Table 1). Through the
screening process, no target product was detected using
K2PdCl4 as the palladium source with a variety of parameters.
However, we were delighted to find that the yield of
acetophenone (3aa) could be improved to 21% when the
combination of PdCl2, 2,2′-bipyridine (L1), and CF3COOH
was employed in toluene under a N2 atmosphere (Table 1,
entry 1). Encouraged by this promising result, we further
adjusted reaction parameters including palladium sources,
ligands, additives, and solvents. Among the palladium sources
used, Pd(CF3CO2)2 exhibited the highest catalytic reactivity in
41% yield (Table 1, entries 2−11). Subsequently, the effect of
solvents was examined (Table 1, entries 3 and 12−19). The
most effective solvents were 2-MeTHF, dioxane, ethanol, and
THF, surpassing toluene, DMF, DMSO, xylene, and H2O. The
use of THF as solvent greatly increased the yield of the reaction
(98%, Table 1, entry 19). The role of the THF in the reaction is
not clear.15 THF is known to be a unique ligand in many useful
Pd(II) transformations.16
The influence of the ligand on the reaction efficiency was
also noteworthy (Table 1, entries 19−26); when 2,2′-bipyridine
(L1), 3,3′-dimethyl-2,2′-bipyridine (L2), 4,4′-dimethyl-2,2′-
bipyridine (L3), 1,10-phenanthroline (L5), and 5,6-diphenyl-
1,10-phenanthroline (L6) were used as the ligand, 3aa was
obtained in 98, 91, 82, 78, and 81% yields, respectively. Other
ligands, including N1,N1,N2,N2-tetramethylethane-1,2-diamine
(L4), 2,9-dimethyl-1,10-phenanthroline (L7) and 2,2′-biquino-
line (L8), were less efficient. No desired product was observed
in the absence of Pd(CF3CO2)2 or ligand (Table 1, entries 27−
28). Replacement of TFA17 with other acids, including
CF3SO3H, p-MeC6H4SO3H, PhCO2H, and H2SO4, resulted
in lower yields (Table 1, entries 19 and 29−32).
Having the optimized reaction conditions in hand, we next
investigated the scope and generality of the addition reaction
using various aliphatic nitriles and potassium aryltrifluorobo-
rates. Initially, various aliphatic nitriles 1a−1k were examined in
the reaction with 2a (Table 2). The steric effects of substituents
affected the yields of the reaction to some extent. For example,
nitriles bearing a relatively large group (e.g., isopropyl,
cyclopropyl or tertiary butyl), such as 1b−1d, afforded slightly
lower yields of the desired products (Table 2, entries 2−4).
Long-chain aliphatic nitriles such as pentanenitrile 1e and
octanenitrile 1f were also good partners and reacted with 2a
efficiently (Table 2, entries 5, 6). Notably, treatment of 1-
adamantanecarbonitrile 1g with 2a under the optimized
conditions afforded the desired product 3ga in 91% yield
(Table 2, entry 7). However, substrate 2-iodoacetonitrile 1h
bearing an iodine group reacted with 2a to give acetophenone
in 62% yield, accompanied by a trace amount of the desired
product 2-iodo-1-phenylethanone (Table 2, entry 8). The
results demonstrated that different functional groups, including
4-butylthio, arylsulfonyl, and benzoyl, performed well under
standard conditions (Table 2, entries 9−11). For example,
yield
b
entry
Pd source
PdCl2
ligand
additive
solvent
(%)
1
L1
L1
L1
L1
L1
L1
L1
L1
L1
L1
L1
L1
CF3CO2H
CF3CO2H
CF3CO2H
CF3CO2H
CF3CO2H
CF3CO2H
CF3CO2H
CF3CO2H
CF3CO2H
CF3CO2H
CF3CO2H
CF3CO2H
toluene/H2O
toluene/H2O
toluene/H2O
toluene/H2O
toluene/H2O
toluene/H2O
toluene/H2O
toluene/H2O
toluene/H2O
toluene/H2O
toluene/H2O
21
35
41
0
2
Pd(OAc)2
3
Pd(CF3CO2)2
Pd(PPh3)4
4
5
Pd(acac)2
33
18
0
6
Pd(dba)2
7
PdCl2(dppe)
PdCl2(cod)
PdCl2(PPh3)2
PdCl2(NH3)2
PdCl2(Py)2
Pd(CF3CO2)2
8
0
9
0
10
11
12
20
29
86
dioxane/
H2O
13
Pd(CF3CO2)2
L1
CF3CO2H
2-MeTHF/
H2O
87
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
Pd(CF3CO2)2
Pd(CF3CO2)2
Pd(CF3CO2)2
Pd(CF3CO2)2
Pd(CF3CO2)2
Pd(CF3CO2)2
Pd(CF3CO2)2
Pd(CF3CO2)2
Pd(CF3CO2)2
Pd(CF3CO2)2
Pd(CF3CO2)2
Pd(CF3CO2)2
Pd(CF3CO2)2
-
L1
L1
L1
L1
L1
L1
L2
L3
L4
L5
L6
L7
L8
L1
L1
L1
L1
CF3CO2H
CF3CO2H
CF3CO2H
CF3CO2H
CF3CO2H
CF3CO2H
CF3CO2H
CF3CO2H
CF3CO2H
CF3CO2H
CF3CO2H
CF3CO2H
CF3CO2H
CF3CO2H
CF3CO2H
CF3CO2H
DMF/H2O
DMSO/H2O
xylene/H2O
ethanol/H2O
H2O
0
29
41
83
22
98
91
82
0
THF/H2O
THF/H2O
THF/H2O
THF/H2O
THF/H2O
THF/H2O
THF/H2O
THF/H2O
THF/H2O
THF/H2O
THF/H2O
THF/H2O
78
81
16
15
0
Pd(CF3CO2)2
Pd(CF3CO2)2
Pd(CF3CO2)2
0
63
79
p-
MeC6H4SO3H
31
32
Pd(CF3CO2)2
Pd(CF3CO2)2
L1
L1
PhCO2H
H2SO4
THF/H2O
THF/H2O
19
24
a
Unless otherwise noted, reaction conditions were as follows: 1a (0.4
mmol), 2a (0.8 mmol), indicated Pd source (5 mol %), ligand (10 mol
%), additive (10 equiv), solvent (2 mL), H2O (0.4 mL), 80 °C, 36 h,
b
N2. Isolated yield.
substrate 1j bearing a p-chlorobenzenesulfonyl group afforded
the corresponding product in 98% yield (Table 2, entry 10).
Next, we turned our attention to the effect of the addition
reactions of various potassium aryltrifluoroborates to acetoni-
trile (1a) or isobutyronitrile (1b) under the standard
conditions (Table 3). The electronic properties of the groups
on the phenyl ring moiety of aryltrifluoroborates had some
effects on the reaction. Generally, aryltrifluoroborates with an
electron-donating substituent on the aryl group gave a slightly
higher yield of addition products than those analogues bearing
an electron-withdrawing substituent. Steric effects of sub-
stituents had an obvious impact on the yield of the reaction. A
B
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Table 2. Synthesis of Alkyl Aryl Ketones from the Addition
of Potassium Aryltrifluoroborates to Aliphatic Nitriles
Table 3. Synthesis of Alkyl Aryl Ketones from the Addition
a
of Potassium Aryltrifluoroborates to Acetonitrile (1a) or
a
Isobutyronitrile (1b)
a
Reaction conditions: 1 (0.4 mmol), 2 (0.8 mmol), Pd(CF3CO2)2 (5
mol %), L1 (10 mol %), TFA (10 equiv), THF (2 mL), H2O (0.4
mL), 80 °C, 36 h, N2. Isolated yield.
Table 4. Synthesis of 1,3- or 1,5- or 1,6-Dicarbonyl
Compounds from the Addition of Potassium
Aryltrifluoroborates to Dinitriles
a
Unless otherwise noted, reaction conditions were as follows: 1 (0.4
a
mmol), 2a (0.8 mmol), Pd(CF3CO2)2 (5 mol %), L1 (10 mol %),
TFA (10 equiv), THF (2 mL), H2O (0.4 mL), 80 °C, 36 h, N2.
b
c
Isolated yield. Acetophenone was obtained in 62% yield.
potassium aryltrifluoroborate (2g) bearing an ortho-methyl
group, for example, was treated with 1a to afford a slightly
lower yield of addition product 3ag. Gratifyingly, substrates
2h−2j bearing two benzene rings furnished the desired
products 3ah−3aj in moderate to good yields. It is noteworthy
that the fluoro, chloro, and bromo moieties (commonly used
for cross-coupling reactions) in substrates were all tolerated and
afforded several halogen-containing products 3bl−3bo in good
yields, leading to a useful handle for further cross-coupling
reactions.
a
Reaction conditions: dinitriles (0.4 mmol), 2 (1.6 mmol), Pd-
(CF3CO2)2 (10 mol %), L1 (20 mol %), TFA (15 equiv), THF (2
mL), H2O (0.4 mL), 80 °C, 36 h, N2. Isolated yield.
The results we observed in the reactions with different
nitriles encouraged us to study a new aspect of the reaction. As
shown in Table 4, when several dinitriles (e.g., malononitrile,
glutaronitrile, and adiponitrile) were used as the substrates, the
corresponding 1,3-, 1,5-, or 1,6-dicarbonyl compounds was
obtained as the products with moderate to good yields in one
step. For example, the transformation of malononitrile (1p),
glutaronitrile (1q), or adiponitrile (1r) with potassium
phenyltrifluoroborate 2a proceeded successfully to provide
the corresponding products 4a, 4d, and 4g in 81, 91, and 90%
yields, respectively.
As an application of this chemistry, we developed a simple
and efficient approach to benzo[b]furans, involving one-step
sequential addition and intramolecular annulation reactions of
2-(2-hydroxyphenyl)acetonitriles with potassium aryltrifluoro-
borates under mild conditions. A variety of 2-arylbenzo[b]-
furans were obtained in moderate to excellent yields (Table 5).
Initially, various potassium aryltrifluoroborates were examined
in the reaction with 2-(2-hydroxyphenyl)acetonitrile. As
expected, all the reactions proceeded smoothly with a wide
range of functional groups (e.g., methoxy, tert-butyl, naphthyl,
C
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Table 5. Synthesis of 2-Arylbenzo[b]furans from the Addition of Potassium Aryltrifluoroborates to 2-
a
Hydroxyphenylacetonitriles
a
Reaction conditions: 2-hydroxyphenylacetonitriles (0.4 mmol), 2 (0.8 mmol), Pd(CF3CO2)2 (5 mol %), L1 (10 mol %), TFA (10 equiv), THF (2
mL), H2O (0.4 mL), 80 °C, 36 h, N2. Isolated yield.
fluoro, chloro, bromo, and iodo), leading to the desired
products 5a−5k in moderate to excellent yields.
To understand the mechanism more clearly, labeling studies
were conducted using 18OH2. We next carried out the Pd-
catalyzed reaction of acetonitrile (1a) and potassium phenyl-
trifluoroborate (2a) in the presence of 18OH2 in dry THF
(Scheme 2). We found that the reaction proceeded smoothly in
Moreover, several 2-(2-hydroxyphenyl)acetonitriles were also
investigated. The electronic properties of the groups on the
phenyl ring of 2-(2-hydroxyphenyl)acetonitriles had some
effect on the reaction. Generally, the 2-(2-hydroxyphenyl)-
acetonitriles possessing electron-donating groups produced the
corresponding 2-arylbenzo[b]furans with higher yields than
electron-deficient 2-(2-hydroxyphenyl)acetonitriles. For exam-
ple, moderate yields of the desired products 5l−5o were
obtained, while good yields of 5p−5x were obtained. It is worth
noting that halogen-containing benzo[b]furans were obtained
because this substrate should be subject to facile functionaliza-
tion via various metal-catalyzed reactions.18
Scheme 2. Isotope Labeling Studies
the present of 5 equiv of 18OH2 to provide [18O]-3aa and 3aa
in 94% total yield. The 18O-atom-containing product [18O]-3aa
was determined by GC−MS (EI) analysis (see Supporting
Information).
A plausible mechanism for the formation of alkyl aryl ketones
is illustrated in Scheme 3. Step (i) involves the coordination of
Pd(CF3CO2)2 with ligand to afford a Pd(II) catalyst A. Step (ii)
The present synthetic route to alkyl aryl ketones and 2-
arylbenzo[b]furans could be readily scaled up to gram quantity
without difficulty. For instance, the addition and cascade
reaction at the 20 mmol scale afforded the corresponding
products acetophenone (3aa) and 2-phenylbenzo[b]furan (5a)
in 95 and 93% yields, respectively.
D
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1H), 7.47 (t, J = 7.4 Hz, 2H), 2.61 (s, 3H); 13C NMR (CDCl3, 125
MHz) δ 198.2, 137.2, 133.1, 128.6, 128.3, 26.6.
Scheme 3. Plausible Mechanism
2-Methyl-1-phenylpropan-1-one (3ba).19 Yellow oil (55.6 mg,
1
94% yield): H NMR (CDCl3, 500 MHz) δ 7.95 (d, J = 7.7 Hz, 2H),
7.55 (t, J = 7.3 Hz, 1H), 7.46 (t, J = 7.7 Hz, 2H), 3.60−3.56 (m, 1H),
1.22 (d, J = 6.9 Hz, 6H); 13C NMR (CDCl3, 125 MHz) δ 204.5, 136.3,
132.8, 128.6, 128.3, 35.4, 19.1.
Cyclopropyl (phenyl) methanone (3ca).20 Yellow oil (53.8 mg,
1
92% yield): H NMR (CDCl3, 500 MHz) δ 8.01 (d, J = 7.5 Hz, 2H),
7.56 (t, J = 6.8 Hz, 1H), 7.47 (t, J = 6.8 Hz, 2H), 2.69 (m, 1H), 1.25
(m, 2H), 1.05 (m, 2H); 13C NMR (CDCl3, 125 MHz) δ 200.7, 138.0,
132.7, 128.5, 128.0, 17.1, 11.6.
2,2-Dimethyl-1-phenylpropan-1-one (3da).20 Yellow oil (52.6 mg,
1
81% yield): H NMR (CDCl3, 500 MHz) δ 7.68 (d, J = 7.3 Hz, 2H),
7.45 (t, J = 7.3 Hz, 1H), 7.39 (t, J = 7.4 Hz, 2H), 1.35 (s, 9H); 13C
NMR (CDCl3, 125 MHz) δ 209.3, 138.7, 130.8, 128.0, 127.8, 44.2,
28.0.
1-Phenylpentan-1-one (3ea).21 Yellow oil (64.2 mg, 99% yield):
1H NMR (CDCl3, 500 MHz) δ 7.88 (d, J = 7.9 Hz, 2H), 7.47 (t, J =
7.4 Hz, 1H), 7.37 (t, J = 7.4 Hz, 2H), 2.89 (t, J = 7.4 Hz, 2H), 1.68−
1.62 (m, 2H), 1.38−1.30 (m, 2H), 0.88 (t, J = 7.4 Hz, 3H); 13C NMR
(CDCl3, 125 MHz) δ 199.6, 136.1, 131.8, 127.5, 127.0, 37.3, 25.5,
21.5, 12.9.
of the proposed catalytic cycle involves the transmetalation
between the Pd(II) catalyst A and potassium aryltrifluoroborate
2 to generate the palladium-aryl species B, which was followed
by the coordination of aliphatic nitrile 1 giving intermediate C.
Next, intramolecular carbopalladation of the aliphatic nitrile 1
forms the corresponding imine Pd(II) complex D. Finally,
protonation of the imine Pd(II) complex D by TFA affords the
ketimine intermediate E and regenerates the Pd(II) catalyst.
Hydrolysis of the ketimine intermediate E delivers the
corresponding alkyl aryl ketones 3 as the products.
1-Phenylheptan-1-one (3fa).19 Yellow oil (80.9 mg, 99% yield):
1H NMR (CDCl3, 500 MHz) δ 7.95 (d, J = 7.8 Hz, 2H), 7.54 (t, J =
7.4 Hz, 1H), 7.45 (t, J = 7.4 Hz, 2H), 2.96 (t, J = 7.4 Hz, 2H), 1.76−
1.69 (m, 2H), 1.42−1.22 (m, 8H), 0.88 (t, J = 6.9 Hz, 3H; 13C NMR
(CDCl3, 125 MHz) δ 199.6, 136.1, 131.8, 127.5, 127.0, 37.6, 30.7,
28.3, 28.1, 23.4, 21.6, 13.0.
1-Adamantyl phenyl (3ga).22 Yellow solid (87.5 mg, 91% yield):
CONCLUSIONS
■
1
mp 52−53 °C (Lit. 50−52 °C); H NMR (CDCl3, 500 MHz) δ 7.46
In summary, we have successfully developed an efficient
strategy for the palladium-catalyzed addition reaction of
potassium aryltrifluoroborates with aliphatic nitriles to afford
a variety of alkyl aryl ketones in moderate to excellent yields.
This protocol also allows the formation of 1,3-, 1,5-, or 1,6-
dicarbonyl compounds. A practical and efficient approach to a
variety of 2-arylbenzo[b]furans in a one-pot reaction has been
developed employing this synthetic protocol. This chemistry
may find further applications for the rapid construction of other
useful ketones or heterocyclic compounds.
(d, J = 7.1 Hz, 2H), 7.35 (d, J = 7.3 Hz, 2H), 7.31 (t, J = 7.3 Hz, 2H),
2.0 (m, 3H), 1.94−1.93 (m, 6H), 1.70−1.64 (m, 6H); 13C NMR
(CDCl3, 125 MHz) δ 210.2, 139.7, 130.1, 127.9, 127.1, 46.9, 39.1,
36.6, 28.2.
Acetophenone (3ha).19 Colorless oil (29.8 mg, 62% yield): 1H
NMR (CDCl3, 500 MHz) δ 7.96 (d, J = 7.1 Hz, 2H), 7.57 (t, J = 7.4
Hz, 1H), 7.47 (t, J = 7.4 Hz, 2H), 2.61 (s, 3H); 13C NMR (CDCl3,
125 MHz) δ 198.2, 137.2, 133.1, 128.6, 128.3, 26.6.
2-(Butylthio)-1-phenylethanone (3ia).23 Yellow oil (61.7 mg, 74%
1
yield): H NMR (CDCl3, 500 MHz) δ 7.97 (d, J = 8.2 Hz, 2H), 7.56
(t, J = 7.4 Hz, 1H), 7.45 (t, J = 7.6 Hz, 2H), 3.77 (s, 2H), 3.56 (t, J =
7.4 Hz, 2H), 1.59−1.54 (m, 2H), 1.40−1.37 (m, 2H), 0.89 (t, J = 7.4
Hz, 3H); 13C NMR (CDCl3, 125 MHz) δ 194.6, 135.3, 133.3, 128.8,
128.6, 37.1, 32.1, 31.0, 21.9, 13.6.
EXPERIMENTAL SECTION
General Information. Melting points are uncorrected. H NMR
■
1
and 13C NMR spectra were measured on a 500 MHz spectrometer
(1H at 500 MHz, 13C at 125 MHz), using CDCl3 as the solvent with
tetramethylsilane (TMS) as an internal standard at room temperature.
Chemical shifts are given in δ relative to TMS, and the coupling
constants J are given in hertz. High-resolution mass spectra were
recorded on an ESI-Q-TOF mass spectrometer. Other commercially
obtained reagents were used without further purification. All reactions
under nitrogen atmosphere were conducted using standard Schlenk
techniques. Column chromatography was performed using EM silica
gel 60 (300−400 mesh).
2-(4-Chlorophenylsulfonyl)-1-phenylethanone (3ja).24 White
solid (115.5 mg, 98% yield): mp 136−137 °C (Lit. 133−134 °C);
1H NMR (CDCl3, 500 MHz) δ 7.93 (d, J = 7.3 Hz, 2H), 7.83 (d, J =
8.7 Hz, 2H), 7.64 (t, J = 7.4 Hz, 1H), 7.53−7.48 (m, 4H), 4.74 (s,
2H); 13C NMR (CDCl3, 125 MHz) δ 187.9, 141.1, 137.1, 135.6,
134.5, 130.2, 129.5, 129.2, 129.0, 63.4.
1,3-Diphenylpropane-1,3-dione (3ka).25 Yellow solid (63.7 mg,
1
71% yield): mp 77−78 °C (Lit. 76−77 °C); H NMR (CDCl3, 500
MHz) δ 7.99 (d, J = 7.1 Hz, 4H), 7.55 (t, J = 7.4 Hz, 2H), 7.48 (t, J =
7.4 Hz, 4H), 6.86 (s, 2H); 13C NMR (CDCl3, 125 MHz) δ 185.8,
135.6, 132.5, 128.7, 127.2, 93.2.
General Procedure for the Synthesis of Alkyl Aryl Ketones 3.
Under N2 atmosphere, aliphatic nitriles 1 (0.4 mmol), potassium
aryltrifluoroborates 2 (0.8 mmol), Pd(CF3CO2)2 (5 mol %), L1 (10
mol %), TFA (10 equiv), THF (2 mL), and H2O (0.4 mL) were
successively added into a Schlenk reaction tube. The reaction mixture
was stirred vigorously at 80 °C for 36 h. After the reaction equilibrium,
the mixture was poured into ethyl acetate, which was washed with
saturated NaHCO3 (2 × 10 mL) and then brine (1 × 10 mL). After
the aqueous layer was extracted with ethyl acetate, the combined
organic layers were dried over anhydrous Na2SO4 and evaporated
under a vacuum. The residue was purified by flash column
chromatography (hexane/ethyl acetate) to afford the desired products
3.
1-(4-Tolyl)ethanone (3ab).26 Yellow oil (40.3 mg, 75% yield): H
1
NMR (CDCl3, 500 MHz) δ 7.77 (d, J = 8.2 Hz, 2H), 7.16 (d, J = 8.2
Hz, 2H), 2.49 (s, 3H), 2.32 (s, 3H); 13C NMR (CDCl3, 125 MHz) δ
196.8, 142.8, 133.7, 128.2, 127.4, 25.5, 20.6.
1-(4-Methoxyphenyl)ethanone (3ac).27 White solid (39.6 mg, 66%
yield): mp 36−37 °C (Lit. 35−35.5 °C); 1H NMR (CDCl3, 500
MHz) δ 7.92 (d, J = 8.8 Hz, 2H), 6.92 (d, J = 8.8 Hz, 2H), 3.85 (s,
3H), 2.54 (s, 3H); 13C NMR (CDCl3, 125 MHz) δ 196.7, 163.5,
130.6, 130.4, 113.7, 55.4, 26.3.
1-(4-tert-Butylphenyl)ethanone (3ad).19 Yellow oil (58.5 mg, 83%
1
yield): H NMR (CDCl3, 500 MHz) δ 7.90 (d, J = 8.5 Hz, 2H), 7.47
Acetophenone (3aa).19 Colorless oil (47 mg, 98% yield): 1H NMR
(CDCl3, 500 MHz) δ 7.96 (d, J = 7.1 Hz, 2H), 7.57 (t, J = 7.4 Hz,
(d, J = 8.5 Hz, 2H), 2.58 (s, 3H), 1.34 (s, 9H); 13C NMR (CDCl3, 125
MHz) δ 196.8, 142.8, 133.7, 128.2, 127.4, 25.5, 20.6.
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1-(3-Nitrophenyl)ethanone (3af).28 White solid (20.4 mg, 31%
yield): mp 78−79 °C (Lit. 77−79 °C); 1H NMR (CDCl3, 500 MHz)
δ 8.77 (s, 1H), 8.43 (d, J = 8.2 Hz, 2H), 8.30 (d, J = 7.8 Hz, 2H), 7.70
(t, J = 8.0 Hz, 2H) 2.70 (s, 3H); 13C NMR (CDCl3, 125 MHz) δ
195.7, 148.5, 138.3, 133.8, 129.9, 127.4, 123.2, 26.7.
evaporated under a vacuum. The residue was purified by flash column
chromatography (hexane/ethyl acetate) to afford the desired products
4.
1,3-Diphenylpropane-1,3-dione (4a).25 Yellow solid (81.1 mg,
1
81% yield): mp 77−78 °C (Lit. 76−77 °C); H NMR (CDCl3, 500
1-(2,4-Dimethylphenyl)ethanone (3ag).29 Yellow oil (30.2 mg,
MHz) δ 7.99 (d, J = 7.1 Hz, 4H), 7.55 (t, J = 7.4 Hz, 2H), 7.48 (t, J =
7.4 Hz, 4H), 6.86 (s, 2H); 13C NMR (CDCl3, 125 MHz) δ 185.8,
135.6, 132.5, 128.7, 127.2, 93.2.
1
51% yield): H NMR (CDCl3, 500 MHz) δ 7.55 (d, J = 7.7 Hz, 1H),
6.99−6.97 (m, 2H), 2.47 (s, 3H), 2.44 (s, 3H), 2.27 (s, 3H); 13C NMR
(CDCl3, 125 MHz) δ 200.0, 141.1, 137.9, 133.7, 131.9, 128.9, 125.3,
28.3, 20.7, 20.3.
1,3-Di-p-tolylpropane-1,3-dione (4b).37 Yellow solid (71.7 mg,
1
71% yield): mp 125−126 °C (not reported); H NMR (CDCl3, 500
1-(Biphenyl-4-yl)ethanone (3ah).30 White solid (71.4 mg, 91%
MHz) δ 7.89 (d, J = 8.2 Hz, 4H), 7.29 (d, J = 8.2 Hz, 4H), 6.81 (s,
2H), 2.43 (s, 6H); 13C NMR (CDCl3, 125 MHz) δ 185.5, 143.1,
133.0, 129.4, 127.2, 92.5, 21.7.
1
yield): mp 116−117 °C (Lit. 116−117 °C); H NMR (CDCl3, 500
MHz) δ 8.03 (d, J = 8.5 Hz, 2H), 7.68 (d, J = 8.5 Hz, 2H), 7.63 (d, J =
7.2 Hz, 2H), 7.48−7.45 (m, 2H), 7.40 (t, J = 7.3 Hz, 1H), 2.63 (s,
3H); 13C NMR (CDCl3, 125 MHz) δ 197.8, 145.8, 139.9, 135.9,
129.0, 128.9, 128.2, 127.3, 127.2, 26.2.
1,3-Bis(4-chlorophenyl)propane-1,3-dione (4c).38 Yellow solid
(55.1 mg, 47% yield): mp 159−160 °C (Lit. 159−160 °C); 1H
NMR (CDCl3, 500 MHz) δ 7.91 (d, J = 8.6 Hz, 4H), 7.46 (d, J = 8.6
Hz, 4H), 6.67 (s, 2H); 13C NMR (CDCl3, 125 MHz) δ 184.6, 138.9,
133.8, 129.1, 128.5, 92.9.
1-(Naphthalen-1-yl)ethanone (3ai).26 Yellow oil (44.3 mg, 65%
1
yield): H NMR (CDCl3, 500 MHz) δ 8.64 (d, J = 8.7 Hz, 1H), 7.84
1,5-Diphenylpentane-1,5-dione (4d).39 White solid (91.8 mg, 91%
yield): mp 65−66 °C (Lit. 65−66 °C); 1H NMR (CDCl3, 500 MHz)
δ 7.98 (d, J = 7.3 Hz, 4H), 7.55 (t, J = 7.4 Hz, 2H), 7.45 (t, J = 7.5 Hz,
4H), 3.12 (t, J = 7.0 Hz, 4H), 2.23−2.17 (m, 2H); 13C NMR (CDCl3,
125 MHz) δ 199.9, 136.9, 133.1, 128.6, 128.1, 37.6, 18.8.
1,5-Bis(4-tert-butylphenyl)pentane-1,5-dione (4e). Yellow oil
(118.1 mg, 81% yield): IR (KBr, cm−1) 2965, 2938, 1658, 1617,
(d, J = 8.2 Hz, 2H), 7.78 (d, J = 7.2 Hz, 1H), 7.73 (d, J = 8.2 Hz, 1H),
7.47 (t, J = 7.7 Hz, 1H), 7.39 (t, J = 7.0 Hz, 1H), 7.34 (t, J = 7.7 Hz,
1H), 2.60 (s, 3H); 13C NMR (CDCl3, 125 MHz) δ 201.8, 135.5,
134.0, 133.0, 130.2, 128.7, 128.4, 128.1, 126.5, 126.1, 124.4, 30.0.
1-(Naphthalen-2-yl)ethanone (3aj).26 Yellow oil (55.1 mg, 81%
1
yield): H NMR (CDCl3, 500 MHz) δ 8.42 (s, 1H), 8.00 (d, J = 8.6
Hz, 2H), 7.93 (d, J = 8.1 Hz, 1H), 7.86−7.83 (m, 2H), 7.57 (t, J = 6.9
Hz, 1H), 7.52 (d, J = 7.5 Hz, 1H), 2.69 (s, 3H); 13C NMR (CDCl3,
125 MHz) δ 198.1, 135.6, 134.5, 132.5, 130.2, 129.6, 128.5, 128.4,
127.8, 126.8, 123.9, 26.7.
1
1453; H NMR (CDCl3, 500 MHz) δ 7.92 (d, J = 8.4 Hz, 4H), 7.47
(d, J = 8.4 Hz, 4H), 3.09 (t, J = 7.0 Hz, 4H), 2.22−2.16 (m, 2H), 1.33
(s, 18H); 13C NMR (CDCl3, 125 MHz) δ 199.6, 156.7, 134.4, 128.1,
125.5, 37.6, 35.1, 31.1, 19.1; HRMS (ESI) calcd for C25H33O2+ ([M +
H]+) 365.2475, found 365.2488.
2-Methyl-1-p-tolylpropan-1-one (3bb).31 Yellow oil (57.1 mg,
1
88% yield): H NMR (CDCl3, 500 MHz) δ 7.86 (d, J = 8.2 Hz, 2H),
7.26 (d, J = 8.0 Hz, 2H), 3.58−3.50 (m, 1H), 2.41 (s, 3H), 1.21 (d, J =
6.9 Hz, 6H); 13C NMR (CDCl3, 125 MHz) δ 204.2, 143.5, 133.7,
129.3, 128.5, 35.2, 21.6, 19.2.
1,5-Bis(4-bromophenyl)pentane-1,5-dione (4f).40 White solid
1
(142.7 mg, 87% yield): mp 142−143 °C (not reported); H NMR
(CDCl3, 500 MHz) δ 7.84 (d, J = 8.6 Hz, 4H), 7.60 (d, J = 8.6 Hz,
4H), 3.08 (t, J = 6.9 Hz, 4H), 2.20−2.15 (m, 2H); 13C NMR (CDCl3,
125 MHz) δ 198.7, 135.5, 131.9, 129.6, 128.3, 37.4, 18.5.
1-(3-Methoxyphenyl)-2-methylpropan-1-one (3bk).32 Yellow oil
(45.6 mg, 64% yield): 1H NMR (CDCl3, 500 MHz) δ 7.53 (d, J = 7.7
Hz, 1H), 7.49 (s, 1H), 7.37 (t, J = 7.9 Hz, 1H), 7.10 (d, J = 8.2 Hz,
1H), 3.85 (s, 3H), 3.57−3.49 (m, 1H), 1.21 (d, J = 6.9 Hz, 6H); 13C
NMR (CDCl3, 125 MHz) δ 204.3, 159.9, 137.7, 129.5, 120.8, 119.1,
112.8, 55.4, 35.5, 19.2.
1,6-Diphenylhexane-1,6-dione (4g).41 White solid (95.9 mg, 90%
1
yield): mp 106−107 °C (Lit. 106−107 °C); H NMR (CDCl3, 500
MHz) δ 7.96 (d, J = 8.3 Hz, 4H), 7.55 (t, J = 7.4 Hz, 2H), 7.46 (t, J =
7.7 Hz, 4H), 3.04 (t, J = 7.0 Hz, 4H), 1.87−1.83 (m, 4H); 13C NMR
(CDCl3, 125 MHz) δ 200.0, 137.0, 133.0, 128.6, 128.0, 38.4, 23.9.
1,6-Bis(4-tert-butylphenyl)hexane-1,6-dione (4h).42 White solid
1-(4-Fluorophenyl)-2-methylpropan-1-one (3bl).33 Yellow oil
1
(53.2 mg, 80% yield): H NMR (CDCl3, 500 MHz) δ 7.99 (d, J =
8.6 Hz, 2H), 7.14 (d, J = 8.6 Hz, 2H), 3.55−3.47 (m, 1H), 1.22 (d, J =
1
(110.5 mg, 73% yield): mp 105−106 °C (not reported); H NMR
6.9 Hz, 6H); 13C NMR (CDCl3, 125 MHz) δ 202.8, 165.5 (d, JC−F
=
(CDCl3, 500 MHz) δ 7.90 (d, J = 8.5 Hz, 4H), 7.47 (d, J = 8.5 Hz,
4H), 3.021 (t, J = 6.3 Hz, 4H), 1.86−1.81 (m, 4H), 1.34 (s, 18H); 13C
NMR (CDCl3, 125 MHz) δ 199.7, 156.6, 134.4, 128.0, 125.5, 38.3,
35.0, 31.1, 24.1.
252 Hz), 132.6, 130.9 (d, JC−F = 9.1 Hz), 115.6 (d, JC−F = 21.6 Hz),
35.3, 19.1.
1-(4-Chlorophenyl)-2-methylpropan-1-one (3bm).34 Yellow oil
(62.8 mg, 86% yield): 1H NMR (CDCl3, 500 MHz) δ 7.81 (d, J = 8.6
Hz, 2H), 7.35 (d, J = 8.6 Hz, 2H), 3.46−3.38 (m, 1H), 1.13 (d, J = 6.9
Hz, 6H); 13C NMR (CDCl3, 125 MHz) δ 203.2, 139.2, 134.5, 129.7,
128.9, 35.4, 19.1.
1,6-Bis(4-chlorophenyl)hexane-1,6-dione (4i).41 Yellow solid
(114.0 mg, 85% yield): mp 175−176 °C (Lit. 175−176 °C); 1H
NMR (CDCl3, 500 MHz) δ 7.89 (d, J = 8.6 Hz, 4H), 7.43 (d, J = 8.6
Hz, 4H), 3.00 (t, J = 6.1 Hz, 4H), 1.85−1.79 (m, 4H); 13C NMR
(CDCl3, 125 MHz) δ 197.6, 138.5, 134.2, 128.4, 127.9, 37.3, 22.7.
General Procedure for the Synthesis of 2-Arylbenzo[b]-
furans 5. Under N2 atmosphere, 2-hydroxyphenylacetonitriles (0.4
mmol), potassium aryltrifluoroborates 2 (0.8 mmol), Pd(CF3CO2)2 (5
mol %), L1 (10 mol %), TFA (10 equiv), THF (2 mL), and H2O (0.4
mL) were successively added into a Schlenk reaction tube. The
reaction mixture was stirred vigorously at 80 °C for 36 h. After the
reaction equilibrium, the mixture was poured into ethyl acetate, which
was washed with saturated NaHCO3 (2 × 10 mL) and then brine (1 ×
10 mL). After the aqueous layer was extracted with ethyl acetate, the
combined organic layers were dried over anhydrous Na2SO4 and
evaporated under a vacuum. The residue was purified by flash column
chromatography (hexane/ethyl acetate) to afford the desired products
5.
1-(4-Bromophenyl)-2-methylpropan-1-one (3bn).35 Yellow oil
1
(80.8 mg, 89% yield): H NMR (CDCl3, 500 MHz) δ 7.80 (d, J =
8.6 Hz, 2H), 7.58 (d, J = 8.6 Hz, 2H), 3.51−3.43 (m, 1H), 1.19 (d, J =
6.9 Hz, 6H); 13C NMR (CDCl3, 125 MHz) δ 203.3, 134.9, 131.9,
129.9, 127.9, 35.4, 19.0.
1-(4-Iodophenyl)-2-methylpropan-1-one (3bo).36 Yellow oil (92.1
1
mg, 84% yield): H NMR (CDCl3, 500 MHz) δ 7.81 (d, J = 8.5 Hz,
2H), 7.65 (d, J = 8.5 Hz, 2H), 3.51−3.43 (m, 1H), 1.19 (d, J = 6.9 Hz,
6H); 13C NMR (CDCl3, 125 MHz) δ 203.7, 137.9, 135.5, 129.8,
100.6, 35.4, 19.0.
General Procedure for the Synthesis of Dicarbonyl
Compounds 4. Under N2 atmosphere, dinitriles (0.4 mmol),
potassium aryltrifluoroborates 2 (1.6 mmol), Pd(CF3CO2)2 (10 mol
%), L1 (20 mol %), TFA (15 equiv), THF (2 mL), and H2O (0.4 mL)
were successively added into a Schlenk reaction tube. The reaction
mixture was stirred vigorously at 80 °C for 36 h. After the reaction
equilibrium, the mixture was poured into ethyl acetate, which was
washed with saturated NaHCO3 (2 × 10 mL) and then brine (1 × 10
mL). After the aqueous layer was extracted with ethyl acetate, the
combined organic layers were dried over anhydrous Na2SO4 and
2-Phenylbenzo[b]furan (5a).43 White solid (75.3 mg, 97% yield):
mp 119−120 °C (Lit. 121.6−122.2 °C); 1H NMR (CDCl3, 500 MHz)
δ 7.86 (d, J = 7.4 Hz, 2H), 7.57 (d, J = 7.6 Hz, 1H), 7.52 (d, J = 8.1
Hz, 1H), 7.43 (t, J = 7.8 Hz, 2H), 7.34 (t, J = 7.4 Hz, 1H), 7.28 (t, J =
7.6 Hz, 1H), 7.22 (t, J = 7.4 Hz, 1H), 7.10 (s, 1H); 13C NMR (CDCl3,
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125 MHz) δ 156.0, 154.9, 130.5, 129.3, 128.8, 128.6, 125.0, 124.3,
123.0, 120.9, 111.2, 101.3.
HRMS (ESI) calcd for C14H10IO+ ([M + H]+) 320.9771, found
320.9784.
2-p-Tolylbenzo[b]furan (5b).44 White solid (76.6 mg, 92% yield):
5-Chloro-2-phenylbenzo[b]furan (5l).46 White solid (66.8 mg, 73%
yield): mp 150−152 °C (Lit. 154 °C); 1H NMR (CDCl3, 500 MHz) δ
7.84 (d, J = 7.5 Hz, 2H), 7.53 (s, 1H), 7.47−7.42 (m, 3H), 7.37 (t, J =
7.4 Hz, 1H), 7.22 (d, J = 8.7 Hz, 1H), 6.95 (s, 1H); 13C NMR (CDCl3,
125 MHz) δ 157.4, 153.3, 130.6, 130.0, 129.0, 128.9, 128.5, 125.1,
124.4, 120.4, 112.1, 100.8.
1
mp 127−128 °C (Lit. 126−128 °C); H NMR (CDCl3, 500 MHz) δ
7.75 (d, J = 8.2 Hz, 2H), 7.56 (d, J = 8.8 Hz, 1H), 7.51 (d, J = 8.0 Hz,
1H), 7.28−7.19 (m, 4H), 7.10 (s, 1H), 2.39 (s, 3H); 13C NMR
(CDCl3, 125 MHz) δ 156.3, 154.8, 138.6, 129.5, 129.4, 127.8, 125.0,
124.0, 122.9, 120.8, 111.1, 106.1, 21.4.
2-(4-tert-Butylphenyl)benzo[b]furan (5c).45 White solid (95.1 mg,
2-(4-tert-Butylphenyl)-5-chlorobenzo[b]furan (5m). White solid
(82.0 mg, 72% yield): mp 167−168 °C; IR (KBr, cm−1) 3064, 2967,
2860, 1475, 1271; 1H NMR (CDCl3, 500 MHz) δ 7.77 (d, J = 8.6 Hz,
2H), 7.52 (s, 1H), 7.47 (d, J = 8.6 Hz, 2H), 7.42 (d, J = 8.7 Hz, 1H),
7.21 (d, J = 8.7 Hz, 1H), 6.90 (s, 1H), 1.53 (s, 9H); 13C NMR
(CDCl3, 125 MHz) δ 157.6, 153.2, 152.3, 130.7, 128.4, 127.2, 125.8,
124.9, 124.1, 120.3, 112.0, 100.2, 34.8, 31.2; HRMS (ESI) calcd for
C18H18ClO+ ([M + H]+) 285.1041, found 285.1048.
1
95% yield): mp 130−131 °C (Lit. 132 °C); H NMR (CDCl3, 500
MHz) δ 7.89 (d, J = 8.5 Hz, 2H), 7.56 (d, J = 7.4 Hz, 1H), 7.51 (d, J =
8.0 Hz, 1H), 7.47 (d, J = 8.5 Hz, 2H), 7.27 (t, J = 7.0 Hz, 1H), 7.22 (t,
J = 7.0 Hz, 1H), 7.10 (s, 1H), 1.35 (s, 9H); 13C NMR (CDCl3, 125
MHz) δ 156.2, 154.9, 151.8, 129.4, 127.8, 125.8, 124.8, 124.0, 122.9,
120.8, 111.1, 100.7, 34.8, 31.3.
2-(4-Methoxyphenyl)benzo[b]furan (5d).46 White solid (70.8 mg,
5-Bromo-2-phenylbenzo[b]furan (5n).49 White solid (73.2 mg,
1
79% yield): mp 152−154 °C (Lit. 148−150 °C); H NMR (CDCl3,
1
67% yield): mp 158−159 °C (Lit. 158−159 °C); H NMR (CDCl3,
500 MHz) δ 7.79 (d, J = 8.8 Hz, 2H), 7.54 (d, J = 7.1 Hz, 1H), 7.49
(d, J = 8.0 Hz, 1H), 7.26−7.19 (m, 2H), 6.96 (d, J = 8.8 Hz, 2H), 6.87
(s, 1H) 3.85 (s, 3H); 13C NMR (CDCl3, 125 MHz) δ 160.0, 156.1,
154.7, 129.5, 126.4, 123.8, 123.4, 122.9, 120.6, 114.3, 111.0, 99.7, 55.4.
2-(Biphenyl-4-yl)benzo[b]furan (5e).45 White solid (96.2 mg, 89%
yield): mp 227−228 °C (Lit. 135 °C); 1H NMR (CDCl3, 500 MHz) δ
7.94 (d, J = 8.4 Hz, 2H), 7.68 (d, J = 8.4 Hz, 2H), 7.65 (d, J = 7.2 Hz,
2H), 7.60 (d, J = 7.5 Hz, 1H), 7.54 (d, J = 8.1 Hz, 1H), 7.46 (t, J = 7.7
Hz, 2H), 7.37 (t, J = 7.4 Hz, 1H), 7.29 (t, J = 7.1 Hz, 1H), 7.24 (d, J =
7.4 Hz, 1H), 7.06 (s, 1H); 13C NMR (CDCl3, 125 MHz) δ 155.7,
155.0, 141.3, 140.5, 129.5, 129.3, 128.9, 127.6, 127.5, 127.0, 125.4,
124.4, 123.0, 120.9, 111.2, 101.5.
500 MHz) δ 7.84 (d, J = 7.3 Hz, 2H), 7.70 (s, 1H), 7.45 (t, J = 7.6 Hz,
2H), 7.40−7.35 (m, 3H), 6.95 (s, 1H); 13C NMR (CDCl3, 125 MHz)
δ 157.2, 153.6, 131.2, 129.9, 129.0, 128.9, 127.1, 125.1, 123.5, 116.0,
112.6, 100.6.
5-Bromo-2-(4-tert-butylphenyl)benzo[b]furan (5o). White solid
(84.3 mg, 64% yield): mp 155−157 °C; IR (KBr, cm−1) 3058, 2959,
2863, 1474, 1265; 1H NMR (CDCl3, 500 MHz) δ 7.77 (d, J = 8.5 Hz,
2H), 7.67 (s, 1H), 7.47 (d, J = 8.5 Hz, 2H), 7.38−7.33 (m, 3H), 6.89
(s, 1H), 1.35 (s, 9H); 13C NMR (CDCl3, 125 MHz) δ 157.5, 153.6,
152.4, 131.4, 127.2, 126.9, 125.9, 124.9, 123.4, 116.0, 112.6, 100.1,
34.9, 31.3; HRMS (ESI) calcd for C18H18BrO+ ([M + H]+) 329.0536,
found 329.0547.
2-(Naphthalen-2-yl)benzo[b]furan (5f).45 White solid (93.8 mg,
5-Methyl-2-phenylbenzo[b]furan (5p).50 White solid (75.8 mg,
1
96% yield): mp 161−162 °C (Lit. 163 °C); H NMR (CDCl3, 500
1
91% yield): mp 127−128 °C (Lit. 128−129 °C); H NMR (CDCl3,
MHz) δ 8.36 (s, 1H), 7.92−7.87 (m, 3H), 7.83 (d, J = 7.5 Hz, 1H),
7.60 (d, J = 7.5 Hz, 1H), 7.56 (d, J = 8.1 Hz, 1H), 7.51−7.48 (m, 2H),
7.30 (t, J = 7.0 Hz, 1H), 7.24 (t, J = 7.0 Hz, 1H), 7.10 (s, 1H); 13C
NMR (CDCl3, 125 MHz) δ 156.0, 155.1, 133.5, 133.3, 129.3, 128.5,
128.4, 127.8, 127.7, 126.6, 126.5, 124.4, 123.9, 123.0, 122.8, 121.0,
111.2, 101.9.
500 MHz) δ 7.85 (d, J = 7.3 Hz, 2H), 7.43 (t, J = 7.7 Hz, 2H), 7.39 (d,
J = 8.4 Hz, 1H), 7.35−7.31 (m, 2H), 7.08 (d, J = 8.3 Hz, 1H), 6.94 (s,
1H), 2.44 (s, 3H); 13C NMR (CDCl3, 125 MHz) δ 156.1, 153.4,
132.4, 130.7, 129.4, 128.8, 128.5, 125.6, 124.9, 120.8, 110.7, 101.1,
21.4.
2-(4-Fluorophenyl)benzo[b]furan (5g).47 White solid (74.7 mg,
2-(4-tert-Butylphenyl)-5-methylbenzo[b]furan (5q). White solid
(96.2 mg, 91% yield): mp 145−146 °C; IR (KBr, cm−1) 3048, 2960,
2864, 1472, 1263; 1H NMR (CDCl3, 500 MHz) δ 7.77 (d, J = 8.5 Hz,
2H), 7.45 (d, J = 8.7 Hz, 2H), 7.38 (d, J = 8.4 Hz, 1H), 7.34 (s, 1H),
7.06 (d, J = 8.5 Hz, 1H), 6.89 (s, 1H), 2.43 (s, 3H), 1.34 (s, 9H); 13C
NMR (CDCl3, 125 MHz) δ 156.3, 153.3, 151.7, 132.3, 129.5, 128.0,
125.7, 125.3, 124.7, 120.7, 110.7, 100.5, 34.8, 31.3, 21.4; HRMS (ESI)
calcd for C19H21O+ ([M + H]+) 265.1587, found 265.1583.
2-(4-Chlorophenyl)-5-methylbenzo[b]furan (5r).51 White solid
1
88% yield): mp 123−124 °C (Lit. 122−124 °C); H NMR (CDCl3,
500 MHz) δ 7.84−7.81 (m, 2H), 7.57 (d, J = 7.6 Hz, 1H), 7.50 (d, J =
8.1 Hz, 1H), 7.27 (t, J = 7.5 Hz, 1H), 7.22 (t, J = 7.8 Hz, 1H), 7.13 (t,
J = 8.7 Hz, 2H), 6.94 (s, 1H); 13C NMR (CDCl3, 125 MHz) δ 162.9
1
(d, JC−F = 247 Hz), 155.1, 154.9, 129.2, 126.8 (d, JC−F = 3.5 Hz),
126.7, 124.3, 123.0, 120.9, 115.9 (d, JC−F = 21.8 Hz), 111.2, 101.0 (d,
JC−F = 1.5 Hz).
2-(3-Chlorophenyl)benzo[b]furan (5h).45 White solid (68.6 mg,
1
1
(78.6 mg, 81% yield): mp 185−187 °C (not reported); H NMR
75% yield): mp 84−85 °C (not reported); H NMR (CDCl3, 500
(CDCl3, 500 MHz) δ 7.76 (d, J = 8.5 Hz, 2H), 7.40−7.39 (m, 3H),
7.35 (s, 1H), 7.09 (d, J = 8.1 Hz, 1H), 6.92 (s, 1H), 2.44 (s, 3H); 13C
NMR (CDCl3, 125 MHz) δ 154.9, 153.4, 134.2, 132.6, 129.2, 129.2,
129.0, 126.1, 125.9, 120.8, 110.7, 101.6, 21.4.
MHz) δ 7.85 (s, 1H), 7.72 (d, J = 7.8 Hz, 2H), 7.59 (d, J = 7.7 Hz,
1H), 7.52 (d, J = 8.2 Hz, 1H), 7.37 (t, J = 7.8 Hz, 1H), 7.32−7.29 (m,
2H), 7.25−7.22 (m, 1H), 7.03 (s, 1H); 13C NMR (CDCl3, 125 MHz)
δ 154.9, 154.2, 134.8, 132.1, 130.0, 128.8, 128.3, 124.8, 124.7, 123.0,
122.9, 121.0, 111.2, 102.3.
6-Methoxy-2-phenylbenzo[b]furan (5s).52 White solid (82.5 mg,
1
2-(4-Chlorophenyl)benzo[b]furan (5i).48 White solid (77.7 mg,
92% yield): mp 79−81 °C (not reported); H NMR (CDCl3, 500
1
MHz) δ 7.81 (d, J = 8.0 Hz, 2H), 7.44−7.41 (m, 3H), 7.31 (t, J = 7.4
Hz, 1H), 7.07 (s, 1H), 6.94 (s, 1H), 6.88−6.86 (m, 1H), 3.87 (s, 3H);
13C NMR (CDCl3, 125 MHz) δ 158.1, 156.0, 155.2, 130.8, 128.8,
128.1, 124.5, 122.6, 121.0, 112.0, 101.2, 96.0, 55.8.
85% yield): mp 148−149 °C (Lit. 148−149 °C); H NMR (CDCl3,
500 MHz) δ 7.78 (d, J = 8.6 Hz, 2H), 7.57 (d, J = 7.6 Hz, 1H), 7.51
(d, J = 8.2 Hz, 1H), 7.40 (d, J = 8.6 Hz, 2H), 7.30−7.21 (m, 2H), 6.99
(s, 1H); 13C NMR (CDCl3, 125 MHz) δ 155.0, 154.8, 134.4, 129.1,
129.1, 129.0, 126.2, 124.6, 123.1, 121.0, 111.2, 101.8.
2-(4-tert-Butylphenyl)-6-methoxybenzo[b]furan (5t). White solid
2-(4-Bromophenyl)benzo[b]furan (5j).49 White solid (83.0 mg,
(100.9 mg, 90% yield): mp 71−72 °C; IR (KBr, cm−1) 3052, 3006,
1
1
76% yield): mp 154−155 °C (Lit. 159−160 °C); H NMR (CDCl3,
2962, 2837, 1458, 1260; H NMR (CDCl3, 500 MHz) δ 7.74 (d, J =
500 MHz) δ 7.72 (d, J = 8.6 Hz, 2H), 7.58−7.55 (m, 3H), 7.51 (d, J =
8.6 Hz, 1H), 7.30 (t, J = 7.1 Hz, 1H), 7.23 (t, J = 7.4 Hz, 1H), 7.01 (s,
1H); 13C NMR (CDCl3, 125 MHz) δ 155.0, 154.9, 132.0, 129.5,
129.1, 126.4, 124.7, 123.2, 122.6, 121.1, 111.3, 101.9.
2-(4-Iodophenyl)benzo[b]furan (5k). White solid (87.1 mg, 68%
yield): mp 175−176 °C; IR (KBr, cm−1) 3058, 1450; 1H NMR
(CDCl3, 500 MHz) δ 7.77 (d, J = 8.5 Hz, 2H), 7.59−7.57 (m, 3H),
7.51 (d, J = 8.2 Hz, 1H), 7.29 (t, J = 7.2 Hz, 1H), 7.23 (t, J = 7.4 Hz,
1H), 7.03 (s, 1H); 13C NMR (CDCl3, 125 MHz) δ 155.0, 154.9,
137.9, 130.0, 129.1, 126.5, 124.7, 123.2, 121.1, 111.3, 102.0, 94.1;
8.5 Hz, 2H), 7.45 (d, J = 8.5 Hz, 2H), 7.42 (d, J = 8.5 Hz, 1H), 7.07 (s,
1H), 6.90 (s, 1H), 6.87−6.85 (m, 1H), 3.87 (s, 3H), 1.35 (s, 9H); 13C
NMR (CDCl3, 125 MHz) δ 158.0, 155.9, 155.5, 151.3, 128.0, 125.7,
124.3, 122.8, 120.9, 111.9, 100.5, 96.5, 55.8, 34.8, 31.3; HRMS (ESI)
+
calcd for C19H21O2 ([M + H]+) 281.1536, found 281.1539.
2-(4-Chlorophenyl)-6-methoxybenzo[b]furan (5u). White solid
(89.0 mg, 86% yield): mp 110−111 °C; IR (KBr, cm−1) 3054,
2962, 1454, 1256; 1H NMR (CDCl3, 500 MHz) δ 7.73 (d, J = 8.6 Hz,
2H), 7.44 (d, J = 8.5 Hz, 1H), 7.39 (d, J = 8.6 Hz, 2H), 7.06 (s, 1H),
6.93 (s, 1H), 6.89−6.87 (m, 1H), 3.87 (s, 3H); 13C NMR (CDCl3,
G
dx.doi.org/10.1021/jo400433m | J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry
Article
125 MHz) δ 158.3, 156.0, 154.0, 133.8, 129.3, 129.0, 125.7, 122.4,
(9) (a) Suzuki, A. Acc. Chem. Res. 1982, 15, 178. (b) Miyaura, N.;
Suzuki, A. Chem. Rev. 1995, 95, 2457. (c) Suzuki, A. J. Organomet.
Chem. 1998, 576, 147.
(10) Onak, T. Organoborane Chemistry; Academic Press: New York,
1975.
+
121.1, 112.2, 101.7, 95.9, 55.8; HRMS (ESI) calcd for C15H11ClO2
([M + H]+) 259.0520, found 259.0519.
7-Methoxy-2-phenylbenzo[b]furan (5v).50 White solid (83.4 mg,
1
93% yield): mp 80−81 °C (Lit. 79−80 °C); H NMR (CDCl3, 500
MHz) δ 7.89 (d, J = 8.2 Hz, 2H), 7.43 (t, J = 7.6 Hz, 2H), 7.34 (t, J =
7.4 Hz, 1H), 7.19−7.13 (m, 3H), 7.01 (s, 1H), 6.80 (d, J = 7.6 Hz,
1H), 4.04 (s, 3H); 13C NMR (CDCl3, 125 MHz) δ 156.1, 145.4,
144.2, 131.0, 130.3, 128.6, 125.1, 123.6, 113.4, 106.7, 101.7, 56.2.
2-(4-tert-Butylphenyl)-7-methoxybenzo[b]furan (5w). White solid
(103.2 mg, 92% yield): mp 87−88 °C; IR (KBr, cm−1) 3048, 3007,
2837, 1460, 1265; 1H NMR (CDCl3, 500 MHz) δ 7.82 (d, J = 8.5 Hz,
2H), 7.45(d, J = 8.5 Hz, 2H), 7.18−7.12 (m, 2H), 6.97 (s, 1H), 6.79
(d, J = 7.6 Hz, 1H), 4.05 (s, 3H), 1.35 (s, 9H); 13C NMR (CDCl3, 125
MHz) δ 156.4, 151.8, 145.3, 144.1, 131.1, 127.6, 125.7, 124.9, 123.5,
(11) Reviews: (a) Molander, G. A.; Ellis, N. Acc. Chem. Res. 2007, 40,
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Lett. 2011, 13, 1726. (b) Lu, W.; Chen, J.; Liu, M.; Ding, J.; Gao, W.;
Wu, H. Org. Lett. 2011, 13, 6114. (c) Qin, C.; Wu, H.; Chen, J.; Liu,
M.; Cheng, J.; Su, W.; Ding, J. Org. Lett. 2008, 10, 1537. (d) Zhang, J.;
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912. (e) Zheng, H.; Zhang, Q.; Chen, J.; Liu, M.; Cheng, S.; Ding, J.;
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(14) (a) Qin, C.; Wu, H.; Cheng, J.; Chen, X.; Liu, M.; Zhang, W.;
Su, W.; Ding, J. J. Org. Chem. 2007, 72, 4102. (b) Chen, J.; Peng, Y.;
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In this Pd-catalyzed addition of phenylboronic acid to 4-
formylbenzonitrile (or 4-cyanobenzoyl chloride), the cyano group
remains intact while the 4-(hydroxy(phenyl)methyl)benzonitrile (or
phenyl 4-cyanobenzoate) is obtained via addition to the aldehyde (or
acyl chloride) group in high yield.
+
113.3, 106.6, 101.1, 56.2, 34.8, 31.3; HRMS (ESI) calcd for C19H21O2
([M + H]+) 281.1536, found 281.1537.
2-(4-Chlorophenyl)-7-methoxybenzo[b]furan (5x).53 White solid
1
(82.8 mg, 80% yield): mp 71−72 °C (Lit. 66 °C); H NMR (CDCl3,
500 MHz) δ 7.81 (d, J = 8.6 Hz, 2H), 7.40 (d, J = 8.6 Hz, 2H), 7.19−
7.14 (m, 2H), 6.99 (s, 1H), 6.81 (d, J = 7.2 Hz, 1H), 4.04 (s, 3H); 13C
NMR (CDCl3, 125 MHz) δ 155.0, 145.4, 144.2, 134.4, 130.8, 129.0,
128.9, 126.3, 123.8, 113.4, 106.9, 102.1, 56.2.
ASSOCIATED CONTENT
■
S
* Supporting Information
1H and 13C NMR spectra of all products and GC−MS of [18O]-
3aa. This material is available free of charge via the Internet at
http://pubs.acs.org.
(15) Our efforts to isolate the THF-coordinated palladium
intermediates have been unsuccessful.
(16) For studies of the coordinating ability of THF and the resulting
effect on reactions, see: Lucht, B. L.; Collum, D. B. Acc. Chem. Res.
1999, 32, 1035.
(17) (a) Jia, C.; Piao, D.; Oyamada, J.; Lu, W.; Kitamura, T.;
Fujiwara, Y. Science 2000, 287, 1992. (b) Jia, C.; Lu, W.; Oyamada, J.;
Kitamura, T.; Matsuda, K.; Irie, M.; Fujiwara, Y. J. Am. Chem. Soc.
2000, 122, 7252. (c) Jia, C.; Kitamura, T.; Fujiwara, Y. Acc. Chem. Res.
2001, 34, 633.
AUTHOR INFORMATION
Corresponding Author
*Fax: 86-577-8836-8280. E-mail: jiuxichen@wzu.edu.cn;
huayuewu@wuz.edu.cn.
■
Notes
The authors declare no competing financial interest.
(18) For a review of the metal-catalyzed functionalization of aryl
halides, see: (a) Metal-Catalyzed Cross-Coupling Reactions; Diederich,
F., Stang, P. J., Eds.; Wiley-VCH: New York, 1998. (b) Tsuji, J.
Palladium Reagents and Catalysts, Innovations in Organic Synthesis;
Wiley: New York, 1995. (c) Beletskaya, I. P; Cheprakov, A. V. Chem.
Rev. 2000, 100, 3009. (d) Littke, A. F.; Fu, G. C. Angew Chem., Int. Ed.
2002, 41, 4176. (e) Martin, R.; Buchwald, S. L. Acc. Chem. Res. 2008,
ACKNOWLEDGMENTS
■
We thank the National Natural Science Foundation of China
(Nos. 21102105 and 21272176) and Natural Science
Foundation of Zhejiang Province (No. LY12B02011) for
financial support.
41, 1461. (f) Chinchilla, R.; Naj
́
era, C. Chem. Rev. 2007, 107, 874.
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