Palladium(II)-catalyzed ortho-arylation via phosphate-group-directed C-H activation

Article abstract of DOI:10.1016/j.tet.2013.04.067

Aryl dialkyl phosphate, which is readily available from phenol, was a good substrate for the Pd(II) catalyzed aryl-aryl coupling reaction through ortho-C-H activation. Although a phosphate group is regarded as a poor coordinating group, highly regioselective ortho-arylation could be achieved by employing Pd(OTf)₂·2H₂O and Ar₂IOTf as a catalyst and an aryl group source, respectively. The phosphate group of the resulting coupled product can be transformed into an aryl anion via reductive cleavage and used for further C-C bond formation.

Full text of DOI:10.1016/j.tet.2013.04.067

Tetrahedron 69 (2013) 5152e5159
Contents lists available at SciVerse ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Palladium(II)-catalyzed ortho-arylation via phosphate-group-
directed CeH activation
y
*
Woo Hyung Jeon, Tae Seob Lee, Eun Jin Kim, Bongjin Moon , Jahyo Kang
Department of Chemistry, Sogang University, Seoul 121-742, Republic of Korea
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 8 March 2013
Received in revised form 12 April 2013
Accepted 15 April 2013
Available online 18 April 2013
Aryl dialkyl phosphate, which is readily available from phenol, was a good substrate for the Pd(II) cat-
alyzed arylearyl coupling reaction through ortho-CeH activation. Although a phosphate group is re-
garded as a poor coordinating group, highly regioselective ortho-arylation could be achieved by
employing Pd(OTf)2$2H2O and Ar2IOTf as a catalyst and an aryl group source, respectively. The phosphate
group of the resulting coupled product can be transformed into an aryl anion via reductive cleavage and
used for further CeC bond formation.
Keywords:
Phosphate
Ó 2013 Elsevier Ltd. All rights reserved.
Palladium catalyst
CeH activation
Diaryliodonium salt
Directing group
1. Introduction
DG
H
DG
Ar
Ar source
Transition-metal-catalyzed CeH activation is a very attractive
approach to arylearyl coupling reactions because it bypasses the
need for a pre-activated aryl group, such as an aryl halide or aryl
triflate. However, a directing group is typically required to dictate
the regioselectivity of such coupling reactions.1 Good coordinating
groups, such as aldehyde, ketone, imine, ester, amide, and triazene
are known to be efficient in assisting ortho-CeH bond activation
with high regioselectivity.2 In the case of phenol, since a phenolic
group alone does not induce high ortho-specific regioselectivity,
temporary transformation of the phenol into a good directing group
followed by removal of the temporary group after the coupling re-
action was performed. Some examples of temporary directing
groups include phenol ester, phenoxypyrimidine, phenol carba-
mate, and phenylphosphinite.3 A common feature of these directing
groups is that they are highly polarizable and exhibit strong co-
ordinating ability. While a convenient and efficient transformation
method for phenol masking is phosphorylation, the utility of the
phosphate group as an ortho-directing group in CeH activated
arylearyl coupling reactions has not yet been reported, likely due to
its poor coordinating characteristics (Scheme 1). In this paper, we
report the first successful example of a palladium-catalyzed ortho-
arylation via phosphate-group-directed CeH activation.
Pd (II) cat.,
Previously reported (good coordinating groups)
NR2
O
R
O
DG =
O
O
O
N
O
PR3
N
This work (poor coordinating group)
O
OR
OR
P
O
DG =
Scheme 1. Various directing groups developed for palladium catalyzed arylearyl
coupling reaction via ortho-CeH activation. DG¼directing group. Ar¼aryl group.
2. Results and discussion
Initially, we explored many different aryl CeH bond activation
reaction conditions4 and learned that employment of more elec-
trophilic transition metal complexes along with a pre-oxidized
coupling partner was desirable for phosphate-directed CeH bond
* Corresponding author. Fax: þ82 2 701 0967; e-mail address: bjmoon@sogang.
ac.kr (B. Moon).
y
Deceased on Nov. 9, 2012.
0040-4020/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tet.2013.04.067

W.H. Jeon et al. / Tetrahedron 69 (2013) 5152e5159
5153
ꢀ
activation. To optimize the reaction conditions, we chose o-tolyl
diethyl phosphate (1a) as a test substrate and screened various Pd
catalysts for the coupling reaction using diphenyliodonium triflate
as the coupling partner.5,6 The results of this study are summarized
in Table 1. Aryl phosphate 1a was prepared from diethyl phosphite
following the literature procedure.7 Yields of the coupling reactions
were determined by 1H NMR spectroscopy using n-decane as an
internal reference.
4 A molecular sieves in the reaction mixture did not improve the
yields.
We also investigated the effect of the base on the reaction. The
use of mild organic bases, such as pyridine (entry 14) and
2,6-lutidine (entry 15) completely inhibited the reaction. This is
probably because these stronger coordinating bases competitively
inhibit coordination of the palladium species with the neighboring
phosphate group. In contrast, when a non-coordinating, sterically
Table 1
Optimization of the ortho-CeH activated arylation reaction conditions with diethyl o-tolyl phosphate (1a)a
Entry
Pd(II) cat.(10 mol %)
Acid (mol %)
T (ꢀC)
Yieldb (%)
Entry
Pd(II) cat. (10 mol %)
Acid (mol %)
Base (1.0 equiv)
T (ꢀC)
Yieldb (%)
1c
2
3
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
TfOH (10)
TfOH (20)
TfOH (50)
40
40
40
23
30
52
14
15
16
Pd(OTf)2$2H2O
Pd(OTf)2$2H2O
Pd(OTf)2$2H2O
d
d
d
Pyridine
60
60
60
NRe
NRe
47
2,6-Lutidine
2,6-Di-tert-butyl-
4-methylpyridine
CaCO3
Cs2CO3
K3PO4
K2CO3
KHCO3
NaHCO3
Na2CO3
4
5
6
7
8
9
10
11
12
13
Pd(OAc)2
TfOH (100)
TfOH (50)
TfOH (50)
TfOH (50)
TfOH (50)
TFA (50)
TsOH (50)
PivOH (50)
d
40
40
40
60
80
60
60
60
60
60
20
11
76
60
65
40
Trace
NRe
37
17f
18f
19f
20f
21f
22f
23f
24
Pd(OTf)2$2H2O
Pd(OTf)2$2H2O
Pd(OTf)2$2H2O
Pd(OTf)2$2H2O
Pd(OTf)2$2H2O
Pd(OTf)2$2H2O
Pd(OTf)2$2H2O
d
d
60
60
60
60
60
60
60
60
60
32
41
44
55
56
44
Pd(OAc)2 (5)d
Pd(OAc)2 (20)d
Pd(OAc)2
d
d
d
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OTf)2$2H2O
Pd(OTf)2$2H2O
d
d
d
67
d
Na2CO3
NRe
NRe
25
d
TfOH
TfOH (30)
45
a
o-Tolyl diethyl phosphate (1a, 0.25 mmol), diphenyliodonium triflate (2a, 0.5 mmol), Pd(II) catalyst (0.025 mmol), and acid or base were reacted in 1,2-dichloroethane
(0.5 mL) at the designated temperature under Ar for 1 h.
b
Determined by 1H NMR spectroscopy with n-decane as an internal standard.
Liu conditions except pivaloyl anhydride. Ref. 3e.
Loading amounts of Pd catalyst were varied to 5 mol % and 20 mol % for entries 5 and 6, respectively.
No reaction. Starting material was recovered.
c
d
e
f
The amount of 1,2-dichloroethane was increased to 1.0 mL.
The first attempt employing Liu’s reaction conditions [Pd(OAc)2,
TfOH in 1,2-dichloroethane] provided the desired coupling product
3a at a 23% yield (Table 1, entry 1).3e,8 Yields were improved when
the amount of TfOH was increased up to 0.5 equiv (52%) (entries 2
and 3). However, the use of more than 0.5 equiv of TfOH was det-
rimental to the reaction. For example, the yield diminished to 20%
when 1.0 equiv of TfOH was used (entry 4).
The yield of the coupling reaction was significantly improved as
the amount of Pd(OAc)2 catalyst was increased (entries 5 and 6).
However, the amount of catalyst was fixed at 10 mol % for sub-
sequent reactions. Since the temperature effect was minimal for the
reactions (entries 7 and 8), subsequent reactions were performed at
60 ꢀC.
bulky pyridine, 2,6-di-tert-butyl-4-methylpyridine,4i was employed,
the desired coupling product was obtained in reasonable yield (47%,
entry 16). To our delight, the reaction also proceeded successfully in
the presence of various inorganic bases, such as CaCO3, Cs2CO3,
K3PO4, K2CO3, KHCO3, NaHCO3, and Na2CO3 (entries 17e23). Among
these, Na2CO3 gave the highest yield (67%) under similar reaction
conditions. As control experiments, reactions were attempted with
either Na2CO3 or TfOH as the sole reagent, but no desired product
was obtained under these conditions (entries 24 and 25). Therefore,
we concluded that the reactions were truly catalyzed by palladium
species, and not by Brønsted acids or bases. From this investigation,
we learned that the phosphate-directed CeH activationearylation
reaction could be promoted by Pd(OTf)2 in conjunction with
diphenyliodonium salt as an aryl group source and that higher yields
could be obtained either with strong acids or non-coordinating, mild
bases.
Once the reaction conditions were optimized, the scope and
limitations of the reaction were explored with various aryl diethyl
phosphates, as shown in Table 2. Aryl diethyl phosphates were
prepared from diethyl phosphite and commercially available phe-
nols following the literature procedure.7 The amounts of
Pd(OTf)2$2H2O and Ph2IOTf were fixed at 10 mol % and 2.0 equiv,
respectively. In general, phosphates with an electron-rich aryl
group provided the desired ortho-arylated products in good yields.
In particular, introduction of an electron-donating substituent at
the meta-position of the phenyl ring greatly improved the yields
(3cee, 3hem in Table 2). This result implies that the ortho-CeH
bond activation step is significantly influenced by the meta-sub-
stituent, which is analogous to the conventional electrophilic aro-
matic substitution reaction. While meta-tolyl phosphate 1c
We also screened weaker organic acids, such as trifluoroacetic
acid (TFA), p-toluenesulfonic acid (TsOH), and pivalic acid (PivOH)
instead of trifluorosulfonic acid (TfOH) (entries 9e11). However, the
use of weaker organic acids was not beneficial for the reaction.
Employment of the strong, non-nucleophilic acid, TfOH, was es-
sential for the coupling reaction. Since it was presumed that co-
addition of Pd(OAc)2 and TfOH formed Pd(OTf)2 as an in-
termediate in situ, we determined whether the reaction could be
catalyzed by pre-formed Pd(OTf)2. Pd(OTf)2$2H2O was prepared
following the literature procedure.9 When 10 mol
% of
Pd(OTf)2$2H2O was used as the catalyst, the reaction proceeded
readily as expected, and the product was obtained at a 37% yield
(entry 12), which was analogous to the reaction conditions of entry
2 (10 mol % of Pd(OAc)2, 20 mol % of TfOH, 30% yield). When TfOH
(30 mol %) was added to this system, the yield was slightly im-
proved, which is consistent with the results given in entry 7. An
attempt to trap the water molecules from Pd(OTf)2$2H2O by adding

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W.H. Jeon et al. / Tetrahedron 69 (2013) 5152e5159
Table 2
ortho-arylation products, 3l and 3m, were obtained in reasonable
yields (67% and 81%, respectively) starting from the corresponding
7-hydroxy-4-methylcoumarin and 5-indanol derived phosphates.
The scope of the reaction was also investigated by varying the
diaryliodonium triflate, and the results are summarized in Table 3.
For this study, the phosphate substrate was fixed as 2,3-
dimethoxyphenyl diethyl phosphate (1b). Various diaryliodonium
salts were prepared from the corresponding aryl iodide or arene
with iodine using m-CPBA as an oxidant.5 To our surprise, even the
sterically demanding dimesityliodonium triflate (2b) provided the
ortho-arylation product 4b in moderate yield (61%, entry 1 in Table
3). This reaction did not go to completion under the reaction con-
ditions, and a small amount of starting material was recovered,
which is probably due to the high steric bulkiness of the mesityl
group. On the other hand, use of less sterically demanding diary-
liodonium triflates, 4cef, provided the desired ortho-arylation
products in higher yields with complete conversion, even at a lower
reaction temperature (60 ꢀC) (entries 2e5, Table 3).
Pd(II)-catalyzed ortho-arylation of various phosphates (1) with diphenyliodonium
triflate (2a) via CeH activationa,b
Table 3
Pd(II)-catalyzed arylation of phosphate 1b with various diaryliodonium triflates (2)a
Entry
1
Iodonium salt
T (ꢀC)
Product
Yieldb (%)
61
80
2
3
4
60
91
provided the mono-ortho-phenylated product 3c in the highest
yield (91%), the reaction with ortho-tolyl phosphate 1a did not go to
completion under the same conditions, and the desired product 3a
was obtained in moderate yield (64%). In the case of para-tolyl
phosphate 1f, the desired mono-ortho-phenylated product 3f was
obtained in 39% yield along with the bis-ortho-phenylated product
3f0 in 30% yield. Yields of the mono-phenylated products 3a and 3f
were estimated by 1H NMR spectral analyses of the reaction mix-
tures because these products were not separable from the starting
materials 1a and 1f by conventional flash chromatography.
The reaction with pre-ortho-phenylated phenyl phosphate 1b
also afforded the coupled product 3b in 63% yield, and the product
was readily separable from the reaction mixture by conventional
column chromatography. While the reaction with 3-tert-butyl-
phenyl diethyl phosphate (1d) provided the mono-ortho-arylation
product 3d in 84% yield, the analogous reaction with 4-tert-butyl-
phenyl diethyl phosphate (1g) provided not only mono-arylation
product 3g in 44% yield but also bis-arylation product 3g0 in 27%
yield. Bis-arylation product 3g0 could be separated from the re-
action mixture, but mono-arylation product 3g was inseparable
from the starting material 1g, and its yield was estimated by 1H
NMR spectral analysis of the mixture.
Introduction of an electron-donating group, such as a methoxy
group to the meta-position of the aryl phosphate delivered high
yields of the coupled products (3e and 3i). Similarly, reactions with
dimethylphenyl diethyl phosphates provided the desired products
3h and 3j in good yields. The presence of a halide at the para-po-
sition to the phosphate group was not deleterious to the ortho-
arylation reaction, and the desired product 3k was obtained in high
yield (80%). The ortho-arylation reaction was also applicable to
more complicated bicyclic aromatic compounds. For example,
60
60
60
73
72
72
5
a
General conditions: Phosphate (1b, 0.25 mmol), diaryliodonium triflate (2bef,
0.5 mmol), Pd(OTf)2$2H2O (0.025 mmol), and Na2CO3 (0.25 mmol) in 1,2-
dichloroethane (1.0 mL, 0.25 M) at the designated temperature under Ar for 1 h.
b
Isolated yields after column chromatography.
A plausible mechanism for the phosphate-group-directed ortho-
CeH-activated arylearyl coupling reaction is shown in Scheme 2.
It appears that Pd(II)/Pd(IV) catalytic species are engaged in the re-
action, as has been proposed by other research groups.10 In a typical
CeH activation reaction, Pd(II)/Pd(IV) species are involved in various
bond-forming reductive elimination steps. Likewise, the mechanism
of our reaction is consistent with the coordination of an electron-
deficient Pd(II) species and the directing phosphate group as the
initial step. The formation of a palladacycle occurs after the elec-
trophilic aromatic substitution at the Pd(II) site. It seems that the

W.H. Jeon et al. / Tetrahedron 69 (2013) 5152e5159
5155
4. Experimental section
4.1. General
OEt
P
O
OEt
P
O
O
OEt
O
H
OEt
Ar
PdII
All reactions were carried out with dry, freshly distilled solvent
under anhydrous conditions. 1,2-Dichloroethane was freshly dis-
tilled from calcium hydride under nitrogen atmosphere prior to use.
All reagents were purchased at the highest commercial quality and
used without further purification, unless otherwise stated. All ex-
periments involving moisture- and/or air-sensitive compounds
were performed in oven- and/or flame-dried glassware with rubber
septa under positive pressure of argon using glove box. Reactions
were monitored by thin-layer chromatography (TLC) carried out on
0.25 mm Merck silica gel plate (60F254) using UV light and p-ani-
saldehyde solution, phosphomolybdic acid solution (PMA) and/or
ninhydrin solution, as a visualizing agent. NMR spectra were taken
using a Varian 400 (400 MHz for 1H) or Varian Inova-500 (500 MHz
for 1H) NMR spectrometer. Flash chromatography was performed
using Merck 230e400 mesh silica gel. Melting points were de-
termined using an Electrothermal capillary melting point apparatus
and are uncorrected. Infrared spectra were obtained on a Nicolet
avatar FT-IR spectrometer. NMR spectra were obtained either on
Varian Inova-500 (500 MHz for 1H, 125 MHz for 13C, 202 MHz for
31P, and 470 MHz for 19F) or Varian 400 (400 MHz for 1H, 100 MHz
for 13C, 162 MHz for 31P, and 376 MHz for 19F) NMR spectrometers.
C-H
activation
Reductive
elimination
TfOH
OEt
OEt
OEt
P
O
OEt
O
P
O
O
PdII
PdIV
Oxidative
addition
Ar
TfO
ArI
Ar2IOTf
Scheme 2. A proposed mechanism for phosphate-directed ortho-CeH bond activated
arylearyl coupling reactions.
ortho-CeH bond activation step is the rate determining step sincewe
have observed a significant kinetic isotope effect (KIE) (kH/kD¼8.4)
for the coupling reaction. The detailed scheme and data for the KIE
experiment are described in the Supplementary data. Oxidative
addition of diaryliodonium salts to the palladacycle would generate
the Pd(IV) complex. Subsequent release of aryl iodide and reductive
elimination of the complex should provide the desired product. At
this stage, the Pd(II) catalyst is restored and can re-enter the catalytic
cycle. Therefore, our reaction did not require any additional oxidant.
To further demonstrate the utility of our reaction, we treated 4b
with lithium metal in the presence of DTBB (4,40-di-tert-butylbi-
phenyl) in THF at ꢁ78 ꢀC,11 and the resulting aryl lithium was
successfully trapped with benzaldehyde to afford 5 at a 73% yield
(Scheme 3). This reaction demonstrates that the phosphate group
can be used not only as a phenol-masking group for directed CeH
activation, but also as the precursor of a phenyl anion in which the
ortho-CeH bond is activated. Further investigation of this reaction
is currently underway in our lab.
1H NMR spectra were referenced to tetramethylsilane (
d 0.00 ppm)
as an internal standard and are reported as follows: (s¼singlet,
d¼doublet, t¼triplet, q¼quartet, m¼multiplet). 13C NMR spectra
were referenced to the residual CDCl3 (d 77.16 ppm). Elemental
analyses were performed by the Organic Chemistry Research
Center at Sogang University using a Carlo Erba EA 1180 elemental
analyzer.
4.2. Characterization data for aryl diethyl phosphate (1aem)
4.2.1. Diethyl o-tolyl phosphate (1a). Yellow oil (83%). Bp:
(100e106 ꢀC (2 mmHg)). 1H NMR (CDCl3, 500 MHz)
d 7.28
OMe
OMe
OEt
P
O
(d, J¼8 Hz, 1H), 7.19 (d, J¼7.5 Hz, 1H), 7.15 (t, J¼7.5 Hz, 1H), 7.06
1. Lithium (5 eq.),
DTBB (10 mol%)
THF, -78 oC, 30 min
O
Me
OEt
Li
MeO
MeO
(t, J¼7.5 Hz, 1H), 4.19e4.24 (m, 4H), 2.31 (s, 3H), 1.34 (t, J¼7.5 Hz,
Me
6H); 13C NMR (CDCl3, 125 MHz)
d 149.42, 131.38, 129.32, 127.08,
124.98, 119.84, 64.64, 64.59, 16.42, 16.23, 16.17; 31P NMR (CDCl3,
Me
Me
OH
2. -40 oC, 30 min
ꢁ5.55. IR (neat, cmꢁ1): 2983, 1588, 1496, 1270, 1018,
Me
Me
202 MHz)
d
956, 759. Anal. Calcd for C11H17O4P: C, 54.10; H, 7.02. Found: C,
54.11, H, 7.10.
4b
OMe
4.2.2. [1,10-Biphenyl]-2-yl diethyl phosphate (1b). Yellow oil (52%).
MeO
3. PhCHO (3.0 eq), THF
Ph
Bp: (154e160 ꢀC (2 mmHg)). 1H NMR (CDCl3, 500 MHz)
d 7.49 (d,
Me
-40 oC, 2 h, 73%
J¼8 Hz, 2H), 7.45 (d, J¼8.5 Hz, 1H), 7.41 (t, J¼7.5 Hz, 2H), 7.30e7.37
(m, 3H), 7.23 (t, J¼7.5 Hz, 1H), 3.87e4.98 (m, 4H), 1.19 (t, J¼7 Hz,
Me
Me
6H); 13C NMR (CDCl3, 125 MHz, all 2C unless indicated)
d 147.88,
5
137.65, 133.76, 131.27, 129.64, 128.80, 128.18, 127.47, 125.25, 120.62,
64.52, 64.46, 16.10, 16.04; 31P NMR (CDCl3, 202 MHz)
d
ꢁ6.37. IR
Scheme 3. Direct transformation of phosphates.
(neat, cmꢁ1): 2983, 1582, 1479, 1274, 1024, 931, 759. Anal. Calcd for
C16H19O4P: C, 62.74; H, 6.25. Found: C, 62.77, H, 6.28.
3. Conclusion
We have developed a Pd(OTf)2$2H2O-catalyzed ortho-arylation
reaction via CeH bond functionalization using a phosphate group
as a directing group. This is the first example involving phosphate
as a directing group in this class of reaction. Various diaryliodonium
salts could be used as the aryl group coupling partner for these
reactions. The reactions were particularly favorable for electron-
rich aryl phosphates. Substitution at the meta-position of the aryl
phosphate greatly enhanced the reaction yields and reaction rates.
The mechanism of the reaction appears to involve Pd(II)/Pd(IV)
species. Additional study of the reaction mechanism is under in-
vestigation, and the results will be disclosed in due course.
4.2.3. Diethyl m-tolyl phosphate (1c). Yellow oil (77%). Bp:
(116e120 ꢀC (2 mmHg)). 1H NMR (CDCl3, 500 MHz)
d
7.19 (t, J¼8 Hz,
1H), 7.03 (s, 1H), 7.01 (d, J¼7 Hz, 1H), 6.97 (d, J¼7.5 Hz, 1H),
4.17e4.23 (m, 4H), 2.33 (s, 3H), 1.34 (t, J¼7 Hz, 6H); 13C NMR (CDCl3,
125 MHz)
d 150.85, 140.04, 129.41, 125.80, 120.62, 116.97, 64.66,
64.61, 21.44, 16.24, 16.18; 31P NMR (CDCl3, 202 MHz)
d
ꢁ5.79. IR
(neat, cmꢁ1): 2984, 1610, 1488, 1272, 1023, 959, 782. Anal. Calcd for
C11H17O4P: C, 54.10; H, 7.02. Found: C, 54.07, H, 7.17.
4.2.4. 3-(tert-Butyl)phenyl diethyl phosphate (1d). Yellow oil (86%).
Bp: (134e138 ꢀC (2 mmHg)). 1H NMR (CDCl3, 500 MHz)
d 7.24

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W.H. Jeon et al. / Tetrahedron 69 (2013) 5152e5159
(t, J¼8 Hz, 1H), 7.20 (s, 1H), 7.18 (d, J¼8 Hz, 1H), 7.04 (d, J¼8 Hz, 1H),
4.19e4.24 (m, 4H), 1.35 (t, J¼7 Hz, 6H), 1.30 (s, 9H); 13C NMR (CDCl3,
16.16; 31P NMR (CDCl3, 202 MHz)
1601, 1477, 1270, 1023, 967, 756. Anal. Calcd for C11H16ClO4P: C,
47.41; H, 5.79. Found: C, 47.38, H, 5.78.
d
ꢁ5.82. IR (neat, cmꢁ1): 2984,
125 MHz)
d 153.50, 150.80, 129.22, 122.06, 117.38, 116.98, 64.63,
64.58, 34.91, 31.35, 16.26, 16.21; 31P NMR (CDCl3, 202 MHz)
d
ꢁ5.77.
IR (neat, cmꢁ1): 2964, 1583, 1487, 1268, 1024, 963, 796. Anal. Calcd
for C14H23O4P: C, 58.73; H, 8.10. Found: C, 58.63, H, 8.16.
4.2.12. Diethyl
(4-methyl-2-oxo-2H-chromen-7-yl)
phosphate
(1l). Colorless oil (75%). Bp: (220e224 ꢀC (2 mmHg)). 1H NMR
(CDCl3, 500 MHz)
d
7.55 (d, J¼8.5 Hz, 1H), 7.18 (d, J¼8.5 Hz, 1H), 7.17
4.2.5. Diethyl (3-methoxyphenyl) phosphate (1e). Yellow oil (66%).
(s, 1H), 4.19e4.25 (m, 4H), 2.39 (s, 3H), 1.35 (t, J¼7.5 Hz, 6H); 13C
Bp: (126e130 ꢀC (2 mmHg)). 1H NMR (CDCl3, 400 MHz)
d
7.21 (t,
NMR (CDCl3, 125 MHz) d 160.52, 154.51, 153.33, 151.95, 125.88,
J¼8 Hz, 1H), 6.81 (d, J¼8 Hz, 1H), 6.77 (s, 1H), 6.71 (dd, J¼8, 2.5 Hz,
117.23, 116.53, 114.24, 108.69, 65.11, 65.06, 18.74, 16.19, 16.14; 31P
1H), 4.15e4.24 (m, 4H), 3.78 (s, 3H), 1.34 (t, J¼7 Hz, 6H); 13C NMR
NMR (CDCl3, 202 MHz)
1566,1388,1267, 1010, 985, 748. Anal. Calcd for C14H17O6P: C, 58.85;
H, 5.49. Found: C, 58.86, H, 5.50.
d
ꢁ6.34. IR (neat, cmꢁ1): 2985, 1735, 1612,
(CDCl3, 125 MHz)
d
160.83, 151.83, 130.13, 112.26, 110.95, 106.29,
64.73, 64.68, 55.56, 16.24, 16.19; 31P NMR (CDCl3, 202 MHz)
d
ꢁ5.93.
IR (neat, cmꢁ1): 2984, 1606, 1491, 1268, 1024, 966, 771. Anal. Calcd
for C11H17O5P: C, 50.77; H, 6.58. Found: C, 50.63, H, 6.62.
4.2.13. 2,3-Dihydro-1H-inden-5-yl diethyl phosphate (1m). Yellow
oil (80%). Bp: (150e154 ꢀC (2 mmHg)). 1H NMR (CDCl3, 500 MHz)
4.2.6. Diethyl p-tolyl phosphate (1f). Yellow oil (79%). Bp:
d
7.11 (d, J¼8.5 Hz, 1H), 7.05 (s, 1H), 6.93 (d, J¼9.5 Hz, 1H), 4.15e4.22
(120e122 ꢀC (2 mmHg)). 1H NMR (CDCl3, 500 MHz)
d
7.07e7.12
(m, 4H), 2.86 (t, J¼7.5 Hz, 2H), 2.83 (t, J¼7.5 Hz, 2H), 2.02e2.08 (m,
(m, 4H), 4.16e4.22 (m, 4H), 2.30 (s, 3H), 1.33 (t, J¼7 Hz, 6H); 13C
2H),1.33 (t, J¼7 Hz, 6H); 13C NMR (CDCl3, 125 MHz)
d 149.15,146.04,
NMR (CDCl3, 125 MHz, all 2C unless indicated)
d
148.72, 134.62,
140.76, 124.93, 117.69, 116.12, 64.52, 64.47, 33.07, 32.23, 25.83, 16.18,
130.21, 119.81, 64.62, 64.57, 20.80, 16.22, 16.17; 31P NMR (CDCl3,
16.13; 31P NMR (CDCl3, 202 MHz)
d
ꢁ5.49. IR (neat, cmꢁ1): 2981,
202 MHz)
d
ꢁ5.59. IR (neat, cmꢁ1): 2985, 1608, 1507, 1272, 1030,
1609,1484,1272,1024, 980, 763. Anal. Calcd for C13H19O4P: C, 57.77;
H, 7.09. Found: C, 57.66, H, 7.01.
956, 757. Anal. Calcd for C11H17O4P: C, 54.10; H, 7.02. Found: C,
54.18, H, 7.16.
4.3. Characterization data for bis(5-(tert-butyl)-2-methyl-
phenyl)iodonium triflate (2d)
4.2.7. 4-(tert-Butyl)phenyl diethyl phosphate (1g). Yellow oil (67%).
Bp: (134e136 ꢀC (2 mmHg)). 1H NMR (CDCl3, 400 MHz)
d
7.32 (d,
J¼8 Hz, 2H), 7.12 (d, J¼8 Hz, 2H), 4.18e4.22 (m, 4H), 1.35 (t, J¼7 Hz,
6H), 1.29 (s, 9H); 13C NMR (CDCl3, 125 MHz)
148.58, 147.91, 126.65,
Off-white solid (54%). Mp: 186e188 ꢀC. 1H NMR (CDCl3,
d
500 MHz)
d
7.86 (s, 2H), 7.51 (d, J¼8 Hz, 2H), 7.36 (d, J¼8 Hz, 2H),
126.60, 119.43, 64.62, 64.57, 34.48, 31.51, 16.24, 16.18; 31P NMR
2.56 (s, 6H), 1.26 (s, 18H); 13C NMR (CDCl3, 125 MHz)
d 153.90,
(CDCl3, 202 MHz)
1034, 957, 785. Anal. Calcd for C14H23O4P: C, 58.73; H, 8.10. Found:
C, 58.82, H, 8.15.
d
ꢁ5.56. IR (neat, cmꢁ1): 2963, 1604, 1510, 1269,
138.13, 133.65, 131.94, 130.45, 120.54 ðq; J ¼ 318:25 Hz; CF3SO3ꢁÞ;
117.98, 35.14, 31.10, 24.91; 19F NMR (CDCl3, 470 MHz)
d
ꢁ78.70. IR
(neat, cmꢁ1): 2963, 1249, 1156, 1027. Anal. Calcd for C23H30F3IO3S:
C, 48.43; H, 5.30; S, 5.62. Found: C, 48.47; H, 5.38; S, 5.68.
4.2.8. 2,3-Dimethylphenyl diethyl phosphate (1h). Yellow oil (73%).
Bp: (106e110 ꢀC (2 mmHg)). 1H NMR (CDCl3, 400 MHz)
d
7.13 (d,
4.4. General procedure for the synthesis of 3aem and char-
J¼8 Hz, 1H), 7.03 (t, J¼8 Hz,1H), 6.95 (d, J¼7.5 Hz,1H), 4.17e4.25 (m,
acterization data
4H), 2.27 (s, 3H), 2.20 (s, 3H), 1.34 (t, J¼7 Hz, 6H); 13C NMR (CDCl3,
125 MHz)
d
149.06, 138.58, 127.75, 126.33, 125.95, 117.29, 64.40,
Iodonium salt 2 (0.5 mmol), Pd(OTf)2$2H2O (0.025 mmol), 1,2-
dichloroethane (1 mL, 0.25 M), phosphate 1 (0.25 mmol), and
dried Na2CO3 (0.25 mmol) were added sequentially to a flame-
dried reaction flask equipped with a magnetic stir bar under an
argon atmosphere. The reaction mixture was subsequently stirred
at the designated temperature for 1 h. The reaction mixture was
cooled to room temperature, diluted with EtOAc (10 mL), and fil-
tered through a short pad of silica gel using EtOAc (10 mL) as eluent
to remove the remaining iodonium salts. The filtrate was concen-
trated under vacuum, and the resulting crude product was further
purified by column chromatography to afford product 3.
64.35, 20.03, 16.07, 16.02, 12.29; 31P NMR (CDCl3, 202 MHz)
d
ꢁ5.49.
IR (neat, cmꢁ1): 2984, 1581, 1469, 1271, 1030, 959, 779. Anal. Calcd
for C12H19O4P: C, 55.81; H, 7.42. Found: C, 55.86, H, 7.44.
4.2.9. 2,3-Dimethoxyphenyl diethyl phosphate (1i). Yellow oil (55%).
Bp: (148e152 ꢀC (2 mmHg)). 1H NMR (CDCl3, 400 MHz)
d 6.88e6.92
(m, 2H), 6.68 (d, J¼8 Hz, 1H), 4.17e4.21 (m, 4H), 3.82 (s, 3H), 3.79 (s,
3H), 1.29 (t, J¼7 Hz, 6H); 13C NMR (CDCl3, 125 MHz)
d 153.91, 144.41,
140.38, 123.48, 113.54, 108.94, 64.55, 64.50, 60.99, 56.03, 16.04,
15.99; 31P NMR (CDCl3, 202 MHz)
d
ꢁ5.75. IR (neat, cmꢁ1): 2984,
1597, 1473, 1277, 1020, 975, 736. Anal. Calcd for C12H19O6P: C, 49.66;
H, 6.60. Found: C, 49.62; H, 6.62.
4.4.1. Diethyl (3-methyl-[1,10-biphenyl]-2-yl) phosphate (3a).
(Inseparable mixture) Reaction temperature: 83 ꢀC. Eluent: 20%
CHCl3/1% TEA in Hexane. Yellow oil (64%). 1H NMR (CDCl3,
4.2.10. 3,4-Dimethylphenyl diethyl phosphate (1j). Yellow oil (77%).
Bp: (140e144 ꢀC (2 mmHg)). 1H NMR (CDCl3, 500 MHz)
d
7.05 (d,
500 MHz)
d
7.49 (d, J¼7.5 Hz, 2H), 7.40 (t, J¼7.5 Hz, 2H), 7.32 (d,
J¼8 Hz, 1H), 6.99 (s, 1H), 6.93 (d, J¼8.5 Hz, 1H), 4.16e4.23 (m, 4H),
J¼7.5 Hz, 1H), 7.28 (d, J¼8 Hz, starting material), 7.19 (d, J¼7.5 Hz,
starting material), 7.18 (t, J¼7.5 Hz, 2H), 7.15 (t, J¼7.5 Hz, starting
material), 7.14 (d, J¼7 Hz, 1H), 7.06 (t, J¼7.5 Hz, starting material),
4.19e4.24 (m, 1.75H, starting material), 3.78e3.83 (m, 2H),
3.62e3.67 (m, 2H), 2.46 (s, 3H), 2.32 (s, 1.3H, starting material), 1.35
(t, J¼7 Hz, 2.6H, starting material), 1.11 (t, J¼7 Hz, 6H).
2.23 (s, 3H), 2.20 (s, 3H), 1.34 (t, J¼7 Hz, 6H); 13C NMR (CDCl3,
125 MHz)
d 148.79, 138.25, 133.28, 130.53, 121.08, 117.09, 64.60,
64.55, 20.00, 19.16, 16.24, 16.19; 31P NMR (CDCl3, 202 MHz)
d
ꢁ5.55.
IR (neat, cmꢁ1): 2982, 1609, 1498, 1272, 1009, 965, 757. Anal. Calcd
for C12H19O4P: C, 55.81; H, 7.42. Found: C, 55.77, H, 7.45.
4.2.11. 4-Chloro-3-methylphenyl diethyl phosphate (1k). Yellow oil
4.4.2. [1,10:30,100-Terphenyl]-20-yl diethyl phosphate (3b). Reaction
(79%). Bp: (138e140 ꢀC (2 mmHg)). 1H NMR (CDCl3, 500 MHz)
d
7.28
temperature: 83 ꢀC. Eluent: 20% CHCl3/1% TEA in Hexane. Off-white
(d, J¼9 Hz, 1H), 7.11 (s, 1H), 7.00 (d, J¼8.5 Hz, 1H), 4.17e4.24 (m, 4H),
solid (63%). Mp: 65e68 ꢀC. 1H NMR (CDCl3, 500 MHz)
d 7.59 (d,
2.35 (s, 3H),1.35 (t, J¼7 Hz, 6H); 13C NMR (CDCl3,125 MHz)
d
149.23,
J¼7.5 Hz, 4H), 7.44 (t, J¼8 Hz, 4H), 7.28e7.35 (m, 5H), 3.41e3.46 (m,
137.75, 130.53, 130.01, 122.49, 118.74, 64.81, 64.76, 20.30, 16.21,
2H), 3.11e3.16 (m, 2H), 0.86 (t, J¼7 Hz, 6H); 13C NMR (CDCl3,

W.H. Jeon et al. / Tetrahedron 69 (2013) 5152e5159
5157
125 MHz)
d
145.22, 145.15, 138.61, 136.01, 135.97, 130.81, 130.79,
148.24, 142.79, 142.73, 139.08, 135.01, 134.98, 130.03, 128.16, 127.95,
127.93, 127.25, 63.33, 63.28, 34.64, 31.53, 15.91, 15.85; 31P NMR
130.05, 128.24, 127.42, 125.72, 125.70, 63.45, 63.40, 15.94, 15.88; 31P
NMR (CDCl3, 202 MHz)
1267, 1029, 908, 710. Anal. Calcd for C22H23O4P: C, 69.10; H, 6.06.
Found: C, 69.13; H, 6.07.
d
ꢁ6.30. IR (neat, cmꢁ1): 2982, 1596, 1419,
(CDCl3, 202 MHz)
d
ꢁ6.06. IR (neat, cmꢁ1): 2963, 1593, 1426, 1268,
1030, 924, 728. Anal. Calcd for C26H31O4P: C, 71.22; H, 7.13. Found:
C, 71.26; H, 7.10.
4.4.3. Diethyl (4-methyl-[1,10-biphenyl]-2-yl) phosphate (3c).
4.4.9. 5-(tert-Butyl)-[1,10-biphenyl]-2-yl diethyl phosphate (3g).
Reaction temperature: 60 ꢀC. Eluent: 20% CHCl3/1% TEA in Hexane.
(Inseparable mixture) Reaction temperature: 83 ꢀC. Eluent: 20%
Yellow oil (91%). 1H NMR (CDCl3, 400 MHz)
d
7.40 (d, J¼7.5 Hz, 2H),
CHCl3/1% TEA in Hexane. 1H NMR (CDCl3, 500 MHz)
d 7.51 (d,
7.31 (t, J¼7.5 Hz, 2H), 7.24 (t, J¼8 Hz, 1H), 7.20 (s, 1H), 7.17 (d, J¼8 Hz,
J¼7.5 Hz, 2H), 7.41 (t, J¼7.5 Hz, 2H), 7.33 (m, 4H), 7.32 (d, J¼8 Hz,
starting material), 7.12 (d, J¼8 Hz, 1.2H, starting material),
4.21e4.23 (m, 2.83H, starting material), 3.88e3.96 (m, 4H), 1.35
(t, J¼8 Hz, starting material), 1.32 (s, 9H), 1.29 (s, starting material),
1.19 (t, J¼7 Hz, 6H).
1H), 6.96 (d, J¼8 Hz, 1H), 3.78e3.91 (m, 4H), 2.31 (s, 3H), 1.11 (t,
J¼7 Hz, 6H); 13C NMR (CDCl3, 100 MHz)
d 147.60, 147.53, 139.11,
137.67, 130.91, 130.71, 129.60, 128.12, 127.22, 126.07, 121.10, 121.06,
64.45, 64.38, 21.28, 16.10, 16.03; 31P NMR (CDCl3, 202 MHz)
d
ꢁ6.28.
IR (neat, cmꢁ1): 2983, 1618, 1485, 1267, 1026, 968, 767. Anal. Calcd
for C17H21O4P: C, 63.74; H, 6.61. Found: C, 63.75; H, 6.60.
4.4.10. 3,4-Dimethyl-[1,10-biphenyl]-2-yl diethyl phosphate (3h).
Reaction temperature: 60 ꢀC. Eluent: 20% CHCl3/1% TEA in Hexane.
4.4.4. 4-(tert-Butyl)-[1,10-biphenyl]-2-yl diethyl phosphate (3d).
Yellow oil (86%). 1H NMR (CDCl3, 500 MHz)
d
7.49 (d, J¼1 Hz, 7.5H),
Reaction temperature: 60 ꢀC. Eluent: 20% CHCl3/1% TEA in Hexane.
7.39 (t, J¼8 Hz, 2H), 7.30 (t, J¼8 Hz, 1H), 7.03e7.08 (m, 2H),
3.77e3.82 (m, 2H), 3.62e3.66 (m, 2H), 2.34 (s, 3H), 2.31 (s, 3H), 1.10
Yellow oil (84%). 1H NMR (CDCl3, 500 MHz)
d
7.50 (d, J¼8 Hz, 2H),
7.46 (s, 1H), 7.39 (t, J¼8 Hz, 2H), 7.26e7.31 (m, 3H), 3.87e3.97 (m,
(t, J¼7 Hz, 6H); 13C NMR (CDCl3, 125 MHz)
d 146.40, 146.34, 139.01,
138.14, 132.55, 132.52, 129.95, 129.93, 129.79, 128.12, 127.03, 126.93,
4H), 1.35 (s, 9H), 1.18 (t, J¼7 Hz, 6H); 13C NMR (CDCl3, 125 MHz)
d
152.47, 152.45, 147.54, 137.67, 130.69, 130.64, 129.68, 128.15,
63.97, 63.92, 20.42, 16.13, 16.07, 13.86; 31P NMR (CDCl3, 202 MHz)
127.26, 122.30, 117.90, 117.88, 64.42, 64.37, 34.87, 31.37, 16.17, 16.11;
d
ꢁ5.83. IR (neat, cmꢁ1): 2982, 1612, 1477, 1270, 1026, 956, 780.
31P NMR (CDCl3, 202 MHz)
1485, 1271, 1029, 970, 720. Anal. Calcd for C20H27O4P: C, 66.28; H,
7.51. Found: C, 66.26; H, 7.50.
d
ꢁ6.24. IR (neat, cmꢁ1): 2965, 1616,
Anal. Calcd for C18H23O4P: C, 64.66; H, 6.93. Found: C, 64.66; H, 6.97.
4.4.11. 3,4-Dimethoxy-[1,10-biphenyl]-2-yl diethyl phosphate (3i).
Reaction temperature: 60 ꢀC. Eluent: 20% CHCl3/1% TEA in Hexane.
4.4.5. Diethyl (4-methoxy-[1,10-biphenyl]-2-yl) phosphate (3e).
Yellow oil (88%). 1H NMR (CDCl3, 500 MHz)
d
7.46 (d, J¼7.5 Hz, 2H),
Reaction temperature: 60 ꢀC. Eluent: 20% CHCl3/1% TEA in Hexane.
7.38 (t, J¼7.5 Hz, 2H), 7.30 (t, J¼8 Hz, 1H), 6.99 (d, J¼9 Hz, 1H), 6.80
(d, J¼8.5 Hz, 1H), 3.98 (s, 3H), 3.90 (s, 3H), 3.85e3.93 (m, 2H),
3.70e3.78 (m, 2H), 1.14 (t, J¼7 Hz, 6H); 13C NMR (CDCl3, 125 MHz)
Yellow oil (76%). 1H NMR (CDCl3, 500 MHz)
d
7.46 (d, J¼7.5 Hz, 2H),
7.40 (t, J¼7.5 Hz, 2H), 7.31 (t, J¼7.5 Hz, 1H), 7.27 (dd, J¼7.5, 1.0 Hz,
1H), 7.04 (dd, J¼2.5, 1.0 Hz, 1H), 6.79 (ddd, J¼7.5, 2.5, 1.0 Hz, 1H),
3.87e4.00 (m, 4H), 3.83 (s, 3H), 1.19 (t, J¼7.5 Hz, 6H); 13C NMR
d
153.16, 142.17, 142.11, 141.33, 137.82, 129.83, 128.29, 128.26, 128.18,
127.15, 124.95, 109.18, 64.03, 63.98, 61.14, 56.24, 16.13, 16.06; 31P
(CDCl3, 125 MHz)
d
159.91, 148.43, 148.37, 137.54, 131.62, 129.62,
NMR (CDCl3, 202 MHz)
1276, 1026, 973, 758. Anal. Calcd for C18H23O6P: C, 59.01; H, 6.33.
Found: C, 59.03; H, 6.24.
d
ꢁ5.89. IR (neat, cmꢁ1): 2952, 1607, 1485,
128.16, 127.06, 126.16, 126.10, 111.23, 106.51, 64.55, 64.50, 55.70,
16.14, 16.08; 31P NMR (CDCl3, 202 MHz)
2983, 1614, 1484, 1274, 1158, 1020, 970, 765. Anal. Calcd for
C17H21O5P: C, 60.71; H, 6.29. Found: C, 60.65; H, 6.31.
d
ꢁ6.35. IR (neat, cmꢁ1):
4.4.12. 4,5-Dimethyl-[1,10-biphenyl]-2-yl diethyl phosphate (3j).
Reaction temperature: 60 ꢀC. Eluent: 20% CHCl3/1% TEA in Hexane.
4.4.6. Diethyl (50-methyl-[1,10:30,100-terphenyl]-20-yl) phosphate (3f0).
Reaction temperature: 83 ꢀC. Eluent: 20% CHCl3/1% TEA in Hexane.
Off-white solid (27%). Mp: 76e79 ꢀC. 1H NMR (CDCl3, 500 MHz)
Yellow oil (90%). 1H NMR (CDCl3, 500 MHz)
d
7.48 (d, J¼7.5 Hz, 2H),
7.38 (t, J¼8 Hz, 2H), 7.30 (t, J¼7 Hz, 1H), 7.22 (s, 1H), 7.12 (s, 1H),
3.86e3.98 (m, 4H), 2.28 (s, 3H), 2.25 (s, 3H), 1.18 (t, J¼7 Hz, 6H); 13C
d
7.58 (d, J¼8 Hz, 4H), 7.42 (t, J¼8 Hz, 4H), 7.33 (t, J¼7 Hz, 2H), 7.14 (s,
NMR (CDCl3, 125 MHz) d 145.57, 145.52, 137.77, 137.42, 133.53,
2H), 3.40e3.46 (m, 2H), 3.10e3.16 (m, 2H), 2.38 (s, 3H), 0.86 (t,
132.12, 130.79, 129.60, 128.10, 127.16, 121.58, 121.56, 64.38, 64.33,
J¼7 Hz, 6H); 13C NMR (CDCl3, 125 MHz)
d
142.95, 142.88, 138.67,
19.78, 19.22, 16.13, 16.07; 31P NMR (CDCl3, 202 MHz)
d
ꢁ6.04. IR
135.52, 135.49, 135.20, 135.18, 131.37, 131.35, 129.96, 128.20, 127.32,
(neat, cmꢁ1): 2983, 1618, 1485, 1272, 1015, 976, 907, 727. Anal. Calcd
for C18H23O4P: C, 64.66; H, 6.93. Found: C, 64.67; H, 6.92.
63.36, 63.32, 20.91, 15.94, 15.88; 31P NMR (CDCl3, 202 MHz)
d
ꢁ5.97.
IR (neat, cmꢁ1): 2925, 1596, 1424, 1271, 1026, 928, 781. Anal. Calcd
for C23H25O4P: C, 69.69; H, 6.36. Found: C, 69.72; H, 6.25.
4.4.13. 5-Chloro-4-methyl-[1,10-biphenyl]-2-yl diethyl phosphate (3k).
Reaction temperature: 83 ꢀC. Eluent: 20% CHCl3/1% TEA in Hexane.
4.4.7. Diethyl (5-methyl-[1,10-biphenyl]-2-yl) phosphate (3f). (Insepar-
Yellow oil (80%). 1H NMR (CDCl3, 500 MHz)
d
7.46 (d, J¼8 Hz, 2H),
able mixture) Reaction temperature: 83 ꢀC. Eluent: 20% CHCl3/1%
7.40 (t, J¼8 Hz, 2H), 7.30e7.35 (m, 3H, contained singlet of two
TEA in Hexane. 1H NMR (CDCl3, 500 MHz)
d
7.48 (d, J¼7 Hz, 2H), 7.39
protons), 3.87e3.96 (m, 4H), 2.39 (s, 3H), 1.19 (t, J¼7 Hz, 6H); 13C
(t, J¼7 Hz, 2H), 7.32 (t, J¼7.5 Hz, 2H), 7.16 (s, 1H), 7.08e7.12 (m,
starting material, contained the one proton of product), 4.18e4.22
(m, 3.07H, starting material), 3.85e3.96 (m, 4H), 2.35 (s, 3H), 2.31 (s,
2.3H, starting material), 1.34 (t, J¼7 Hz, 4.56H, starting material), 1.17
(t, J¼7 Hz, 6H).
NMR (CDCl3, 125 MHz) d 146.16,146.10,136.70,136.48, 132.76,131.16,
129.52, 128.30, 127.79, 122.92, 122.90, 64.63, 64.58, 20.08, 16.12,
16.07; 31P NMR (CDCl3, 202 MHz)
1611, 1477, 1277, 1159, 1040, 981, 887, 770. Anal. Calcd for
C17H20ClO4P: C, 57.55; H, 5.68. Found: C, 57.57; H, 5.75.
d
ꢁ6.26. IR (neat, cmꢁ1): 2982,
4.4.8. 50-(tert-Butyl)-[1,10:30,100-terphenyl]-20-yl diethyl phosphate
(3g0). Reaction temperature: 83 ꢀC. Eluent: 20% CHCl3/1% TEA in
Hexane. Off-white solid (27%). Mp: 80e83 ꢀC. 1H NMR (CDCl3,
4.4.14. Diethyl (4-methyl-2-oxo-6-phenyl-2H-chromen-7-yl) phos-
phate (3l). Reaction temperature: 83 ꢀC. Eluent: 40% EtOAc/1% TEA
in Hexane. Off-white solid (67%). Mp: 100e102 ꢀC. 1H NMR (CDCl3,
500 MHz)
d
7.61 (d, J¼8.5 Hz, 4H), 7.44 (t, J¼8 Hz, 4H), 7.36 (t,
500 MHz) d 7.56 (s, 1H), 7.39e7.50 (m, 6H), 6.28 (s, 1H), 3.95e4.03
J¼4 Hz, 2H), 7.34 (s, 2H), 3.42e3.48 (m, 2H), 3.13e3.19 (m, 2H), 1.36
(m, 4H), 2.43 (s, 3H), 1.23 (t, J¼7 Hz, 6H); 13C NMR (CDCl3, 125 MHz)
(s, 9H), 0.88 (t, J¼7.5 Hz, 6H); 13C NMR (CDCl3, 125 MHz)
d
148.26,
d 160.44, 153.44, 151.91, 150.21, 150.16, 136.28, 130.68, 130.63,

5158
W.H. Jeon et al. / Tetrahedron 69 (2013) 5152e5159
129.58, 128.37, 127.96, 126.82, 117.28, 114.51, 108.98, 64.87, 64.82,
63.96, 63.92, 63.47, 63.43, 61.12, 56.26, 34.50, 31.58, 19.56, 16.14,
18.72, 16.04, 15.98; 31P NMR (CDCl3, 202 MHz)
d
ꢁ6.50. IR (neat,
16.07; 31P NMR (CDCl3, 202 MHz)
d
ꢁ6.11. IR (neat, cmꢁ1): 2962,
cmꢁ1): 3042, 2985, 1728, 1624, 1485, 1281, 1144, 1031, 870, 774.
Anal. Calcd for C20H21O6P: C, 61.85; H, 5.45. Found: C, 61.85; H, 5.49.
1607, 1491, 1290, 1032, 978, 858, 800. Anal. Calcd for C23H33O6P: C,
63.29; H, 7.62. Found: C, 63.24; H, 7.72.
4.4.15. Diethyl (6-phenyl-2,3-dihydro-1H-inden-5-yl) phosphate
4.5.4. 3,4-Dimethoxy-20,50-dimethyl-[1,10-biphenyl]-2-yl diethyl phos-
(3m). Reaction temperature: 83 ꢀC. Eluent: 20% CHCl3/1% TEA in
phate (4e). Reaction temperature: 60 ꢀC. Eluent: 20% CHCl3/1% TEA
Hexane. Yellow oil (81%). 1H NMR (CDCl3, 400 MHz)
d
7.47 (d,
in Hexane. Yellow oil (72%). 1H NMR (CDCl3, 500 MHz)
d 7.10 (d,
J¼8.5 Hz, 2H), 7.38 (t, J¼8 Hz, 2H), 7.32 (t, J¼8.5 Hz, 1H), 7.30 (s, 1H),
7.18 (s, 1H), 4.21 (m, 0.12H, starting material), 3.85e3.97 (m, 4H),
3.34 (m, 0.17H, diphenylated product), 3.11 (m, 0.17H, diphenylated
product), 2.88e2.95 (m, 4H), 2.08e2.14 (m, 2H), 1.18 (t, J¼9 Hz, 6H);
J¼7.5 Hz, 1H), 7.06 (s, 1H), 7.03 (d, J¼8 Hz, 1H), 6.85 (d, J¼8.5 Hz, 1H),
6.78 (d, J¼7.5 Hz, 1H), 3.97 (s, 3H), 3.90 (s, 3H), 3.88e3.90 (m, 1H),
3.76e3.80 (m, 1H), 3.63e3.67 (m, 1H), 3.47e3.52 (m, 1H), 2.30 (s,
3H), 2.11 (s, 3H), 1.18 (t, J¼7 Hz, 3H), 1.07 (t, J¼7 Hz, 3H); 13C NMR
13C NMR (CDCl3, 125 MHz, all 2C unless indicated)
d
145.23, 141.07,
(CDCl3, 125 MHz) d 153.00, 142.36, 141.23, 137.39, 134.79, 134.28,
138.42, 131.50, 129.74, 128.08, 127.12, 126.60, 116.53, 116.51, 64.38,
131.48, 129.64, 128.29, 128.19, 124.91, 109.00, 63.94, 63.65, 61.10,
64.33, 33.09, 32.44, 25.94, 16.13, 16.07. 31P NMR (CDCl3, 202 MHz)
56.23, 20.90, 19.62, 16.08, 16.02; 31P NMR (CDCl3, 202 MHz)
d
ꢁ6.32.
d
ꢁ5.98. IR (neat, cmꢁ1): 2983,1712,1615,1478,1268,1027, 969, 727.
IR (neat, cmꢁ1): 2929, 1606, 1456, 1275, 1031, 981, 728. Anal. Calcd
for C20H27O6P: C, 60.91; H, 6.90. Found: C, 60.88; H, 7.01.
4.5. General procedure for the synthesis of 4bef and charac-
terization data
4.5.5. 3,4-Dimethoxy-40-methyl-[1,10-biphenyl]-2-yl diethyl phos-
phate (4f). Reaction temperature: 60 ꢀC. Eluent: 20% CHCl3/1% TEA
Iodonium salt 2 (0.5 mmol), Pd(OTf)2$2H2O (0.025 mmol), 1,2-
dichloroethane (1 mL, 0.25 M), phosphate 1 (0.25 mmol), and
dried Na2CO3 (0.25 mmol) were added sequentially to a flame-
dried reaction flask equipped with a magnetic stir bar under an
argon atmosphere. The reaction mixture was subsequently stirred
at the designated temperature for 1 h. The reaction mixture was
cooled to room temperature, diluted with EtOAc (10 mL), and fil-
tered through a short pad of silica gel using EtOAc (10 mL) as eluent
to remove the remaining iodonium salts. The filtrate was concen-
trated under vacuum, and the resulting crude product was further
purified by column chromatography to afford product 4.
in Hexane. Yellow oil (72%). 1H NMR (CDCl3, 500 MHz)
d 7.35 (d,
J¼8 Hz, 2H), 7.19 (d, J¼7.5 Hz, 2H), 6.98 (d, J¼7.5 Hz, 1H), 6.79 (d,
J¼9 Hz, 1H), 3.97 (s, 3H), 3.88 (s, 3H), 3.86e3.96 (m, 2H), 3.72e3.82
(m, 2H), 2.36 (s, 3H), 1.44 (t, J¼7 Hz, 6H); 13C NMR (CDCl3, 125 MHz)
d
153.01, 142.22, 142.16, 141.38, 136.80, 134.89, 129.67, 128.83,
128.33, 128.30, 124.86, 109.26, 64.00, 63.95, 61.09, 56.26, 21.22,
16.06, 15.99; 31P NMR (CDCl3, 202 MHz)
2986, 1606, 1492, 1274, 1029, 976, 727. Anal. Calcd for C19H25O6P: C,
59.99; H, 6.62. Found: C, 59.98; H, 6.55.
d
ꢁ5.89. IR (neat, cmꢁ1):
4.6. LiDTBB-catalyzed reduction of phosphate 4b and reaction
with benzaldehyde. (3,4-dimethoxy-20,40,60-trimethyl-[1,10-bi-
phenyl]-2-yl)(phenyl)methanol (5)
4.5.1. 3,4-Dimethoxy-20,40,60-trimethyl-[1,10-biphenyl]-2-yl
diethyl
phosphate (4b). Reaction temperature: 83 ꢀC. Eluent: 20% CHCl3/1%
TEA in Hexane. Off-white solid (61%). Mp: 90e92 ꢀC. 1H NMR
To a flame-dried Schlenk flask equipped with a magnetic stir bar
were added DTBB (0.025 mmol) and lithium powder (25% disper-
sion in oil, 1.25 mmol) in dry THF (1.0 mL) at 0 ꢀC under Ar. After
stirring for 30 min, the deep blue suspension was cooled to ꢁ78 ꢀC.
A solution of phosphate (4b) (0.25 mmol) in dry THF (1.0 mL) was
slowly added to the mixture for 30 min via dropping funnel. The
reaction mixture was then stirred at ꢁ78 ꢀC for 30 min, and
warmed up to ꢁ40 ꢀC. After 30 min of stirring at the same tem-
perature, a solution of benzaldehyde (0.75 mmol) in dry THF
(0.5 mL) was added via dropping funnel for 10 min. The brown
suspension was stirred at ꢁ40 ꢀC for 2 h. The reaction was
quenched by pouring the reaction mixture into water (10 mL). The
mixture was acidified by adding 2 N HCl. The mixture was extracted
with dichloromethane (2ꢂ20 mL). The combined organic layers
were washed with brine, dried over Na2CO3, and concentrated in
vacuo. The residue was subjected to flash column chromatograph
on silica gel to yield the desired product 5: Eluent: 5% CH2Cl2/5%
ether/1% TEA in Hexane. Off-white solid (73%). Mp: 88e91 ꢀC. 1H
(CDCl3, 500 MHz)
d
6.90 (s, 2H), 6.81 (d, J¼8.5 Hz, 1H), 6.76 (d,
J¼8.5 Hz, 1H), 3.96 (s, 3H), 3.91 (s, 3H), 3.70e3.76 (m, 2H),
3.61e3.66 (m, 2H), 2.29 (s, 3H), 2.04 (s, 6H), 1.12 (t, J¼7 Hz, 6H); 13C
NMR (CDCl3, 125 MHz)
d 152.92, 142.66, 142.60, 141.57, 137.74,
137.03, 134.10, 127.95, 126.80, 126.76, 124.89, 109.30, 63.77, 63.72,
61.09, 61.08, 56.21, 21.07, 20.59, 16.07, 16.01; 31P NMR (CDCl3,
202 MHz)
d
ꢁ6.32. IR (neat, cmꢁ1): 2975, 1603, 1453, 1291, 1031,
970, 808. Anal. Calcd for C21H29O6P: C, 61.76; H, 7.16. Found: C,
61.77; H, 7.11.
4.5.2. Diethyl (3,4,40-trimethoxy-[1,10-biphenyl]-2-yl) phosphate
(4c). Reaction temperature: 60 ꢀC. Eluent: 30% EtOAc/1% TEA in
Hexane. Red oil (91%). 1H NMR (CDCl3, 500 MHz)
d
7.38 (d, J¼8.5 Hz,
2H), 6.97 (d, J¼8.5 Hz, 1H), 6.92 (d, J¼8.5 Hz, 2H), 6.78 (d, J¼8.5 Hz,
1H), 3.97 (s, 3H), 3.88 (s, 3H), 3.87e3.96 (m, 2H), 3.82 (s, 3H),
3.76e3.85 (m, 2H), 1.16 (t, J¼8 Hz, 6H); 13C NMR (CDCl3, 125 MHz)
d
159.00, 152.92, 142.26, 142.2, 141.44, 130.88, 130.31, 128.02, 127.98,
124.85, 113.66, 109.28, 64.03, 63.98, 61.10, 56.28, 55.46, 16.13, 16.07;
NMR (CDCl3, 500 MHz) d 7.21e7.24 (m, 4H), 7.15e7.17 (m, 1H), 6.97
31P NMR (CDCl3, 202 MHz)
d
ꢁ5.97. IR (neat, cmꢁ1): 2939, 1604,
(d, J¼8 Hz,1H), 6.92 (s,1H), 6.86 (s, 1H), 6.83 (d, J¼8 Hz,1H), 5.32 (d,
J¼12 Hz, 1H), 3.90 (s, 3H), 3.85 (d, J¼12 Hz, 1H), 3.66 (s, 3H), 2.28 (s,
3H), 2.08 (s, 3H), 2.02 (s, 3H); 13C NMR (CDCl3, 125 MHz, all 2C
1491, 1245, 1050, 973, 802. Anal. Calcd for C19H25O7P: C, 57.57; H,
6.36. Found: C, 57.54; H, 6.30.
unless indicated)
d 151.94, 147.55, 145.57, 137.47, 136.87, 136.51,
4.5.3. 50-(tert-Butyl)-3,4-dimethoxy-20-methyl-[1,10-biphenyl]-2-yl
diethyl phosphate (4d). Reaction temperature: 60 ꢀC. Eluent: 20%
CHCl3/1% TEA in Hexane. Off-white solid (73%). Mp: 80e83 ꢀC. 1H
136.50, 136.16, 133.22, 128.46, 128.29, 127.94, 126.66, 125.87, 125.41,
112.48, 72.85, 60.28., 55.85, 21.42, 20.89, 20.87. IR (neat, cmꢁ1):
3538, 2960,1601,1261,1032, 815. Anal. Calcd for C24H26O3: C, 79.53;
H, 7.23. Found: C, 79.50; H, 7.25.
NMR (CDCl3, 500 MHz)
d
7.27 (d, J¼8.5 Hz, 1H), 7.26 (s, 1H), 7.16 (d,
J¼8.5 Hz, 1H), 6.89 (d, J¼8.5 Hz, 1H), 6.81 (d, J¼8.5 Hz, 1H), 3.99 (s,
3H), 3.92 (s, 3H), 3.79e3.87 (m, 2H), 3.60e3.64 (m, 1H), 3.34e3.38
(m, 1H), 2.14 (s, 3H), 1.31 (s, 9H), 1.19 (t, J¼7 Hz, 3H), 1.05 (t, J¼7 Hz,
Acknowledgements
3H); 13C NMR (CDCl3, 125 MHz)
d
153.04, 148.40, 142.52, 142.46,
This work was supported by the Sogang University Research
Grant of 2010 (201010032.01).
141.22, 137.06, 134.48, 129.40, 128.54, 127.88, 124.99, 124.59, 109.02,

W.H. Jeon et al. / Tetrahedron 69 (2013) 5152e5159
5159
2011, 133, 18566; (c) Tredwell, M. J.; Gulias, M.; Bremeyer, N. G.; Johansson, C. C.
C.; Collins, B. S. L.; Gaunt, M. J. Angew. Chem., Int. Ed. 2011, 50, 1076; (d)
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Supplementary data
Supplementary data related to this article can be found at
http://dx.doi.org/10.1016/j.tet.2013.04.067.
ꢁ
Hutchby, M.; Bailey, C. D.; Gair Ford, J.; Tyler, S. N. G.; Gagne, M. R.;
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~
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~
~
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