ICl-mediated intramolecular twofold iodoarylation of diynes and diynyl diethers and amines: Synthesis of bis(2 H-hydronaphthalene and chromene) and 2H-quinoline bearing an alkenyl iodide moiety

Article abstract of DOI:10.1021/jo401922b

Electrophilic intramolecular twofold iodoarylation was developed from the reaction of diynes and diynyl diethers and amines with iodine monochloride under mild conditions, which produced bis(2H-hydronaphthalene and chromene) and 2H-quinoline bearing an al

Full text of DOI:10.1021/jo401922b

Article
pubs.acs.org/joc
ICl-Mediated Intramolecular Twofold Iodoarylation of Diynes and
Diynyl Diethers and Amines: Synthesis of Bis(2H‑hydronaphthalene
and chromene) and 2H‑Quinoline Bearing an Alkenyl Iodide Moiety
Juntae Mo,† Wonseok Choi,† Jiae Min,† Cheol-Eui Kim,† Dahan Eom,† Sung Hong Kim,‡
and Phil Ho Lee*,†
†Department of Chemistry, Kangwon National University, Chuncheon 200-701, Republic of Korea
‡Analysis Research Division Daegu Center, Korea Basic Science Institute, Daegu 702-701, Republic of Korea
S
* Supporting Information
ABSTRACT: Electrophilic intramolecular twofold iodoarylation was developed from the reaction of diynes and diynyl diethers
and amines with iodine monochloride under mild conditions, which produced bis(2H-hydronaphthalene and chromene) and
2H-quinoline bearing an alkenyl iodide moiety in good to excellent yields. These compounds underwent Pd-catalyzed cross-
coupling reactions with arylboronic acid and indium tris(arylthiolate) to produce the functionalized styrene derivatives.
iodoarylation of diynes and diynyl diethers and amines with
iodonium ion provides an efficient synthetic method of bis(2H-
hydronaphthalene and chromene) and 2H-quinoline bearing an
alkenyl iodide moiety, compounds which have potential for
further functionalization (Scheme 1).
INTRODUCTION
■
Intramolecular hydroarylation of alkynyl arenes has emerged as
an extremely useful method for the synthesis of a wide range of
carbocyclic and heterocyclic compounds, which are valuable in
the preparation of natural products and biologically active
compounds.1 In general, these methods can be accomplished
either by transition-metal or Lewis acid catalysts. Alternatively,
electrophilic addition reactions of polarized reagents to
functionalized alkynyl arenes are good approaches to prepare
carbocycles and heterocycles through hydroarylation. In
comparison to hydroarylation using transition-metal and
Lewis acid catalysts, intramolecular iodoarylation of alkynyl
arenes using the iodonium ion has advantages such as further
functionalization due to giving carbocycles and heterocycles
possessing an alkenyl or aryl iodide moiety.2 This method has
been studied in detail by Barluenga,3 Larock,4 and others5 and
has thus been used as a widely applicable strategy for the
efficient synthesis of target molecules.
Recently, we developed the intramolecular hydroarylation of
aryl enynes and aryl alkynyl sulfides, amines, selenides, and
tellurides.6 In addition, we reported Au-catalyzed intra-
molecular 2-fold hydroarylation that allows an efficient
synthesis of bis(2H-chromene and quinoline) from diyne
diethers and diamines.7 These results and the current
importance of hydroarylation stimulated us to search for an
intramolecular iodoarylation based on iodonium reagents.
Herein, we report that electrophilic intramolecular 2-fold
Scheme 1. Twofold Iodoarylation
RESULTS AND DISCUSSION
■
First, a variety of functionalized diynyl diethers and amines
were prepared by treatment of phenol and N-tosylaniline
derivatives with propargyl bromide in the presence of
potassium carbonate followed by CuCl-catalyzed oxidative
homo- or heterocoupling reactions using TMEDA and pyridine
in DMF under oxygen (Scheme 2).8
We studied the reaction of 1,6-bis(phenoxy)-2,4-hexadiyne
1a with NIS in various solvents (DCE, DCM, and AcOH) at
Received: September 2, 2013
© XXXX American Chemical Society
A
dx.doi.org/10.1021/jo401922b | J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry
Article
(entry 3). 1,6-Bis(p-chlorophenoxy)-2,4-hexadiyne (1d) under-
went the intramolecular twofold iodoarylation using ICl (4
equiv) to provide the 4,4′-bis(2H-chromene) 2d having both
iodo and chloro groups in 66% yield (entry 4). Exposure of the
o-bromo-substituted diynyl diether 1e to ICl (2 equiv) afforded
the iodoarylated compound 2e in 87% yield (entry 5). 1,6-
Bis(p-iodophenoxy)-2,4-hexadiyne (1f) turned out to be
compatible with the reaction conditions using 4 equiv of ICl
(entry 6). The tolerance of chlodide, bromide, and iodide
groups on the phenyl ring is especially valuable, affording an
opportunity for further functionalization. In addition, reaction
of 1,8-bis(phenyl)-3,5-octadiyne (1g) with ICl led to the
formation of the 4,4′-bis(2H-hydronaphthalene) 2g in 90%
yield (entry 7). In contrast, 1g was not cyclized with either
Ph3PAuCl and AgSbF6 (5 mol % each) or trifluoromethane-
sulfonic acid (5 or 30 mol %) (eq 1). These results indicate that
Scheme 2. Preparation of Diynyl Diethers and Amines
−78 °C. However, only the iodination product 3a was obtained
together with the starting material 1a (Table 1, entries 1−3).
The use of IPy2BF4 is totally ineffective for iodoarylation (entry
4). In general, the iodine molecule (I2) shows electrophilic
properties, but its reactivity in the iodoarylation reaction is low,
thus producing 2-fold iodoarylated product 2a in 17% yield
(entry 5). Low temperature and addition of NaHCO3 are not
effective for intramolecular iodoarylation (entries 6 and 7).
When iodine monochloride (ICl) was used as an electrophilic
reagent in DCM at 25 °C, 1a disappeared on TLC, but a
complex mixture was obtained (entry 8). The best result was
obtained with ICl (2 equiv) in DCM at 0 °C after 10 min,
producing 2a in 76% yield (entry 9). The iodoarylarion
reaction was not complete at −78 °C (entry 10). Use of an
increased amount (3 equiv) of ICl at 0 °C (10 min) and at −78
°C (30 min) gave 1a in 71% yield (entry 11). On the whole,
1,6-bis(phenoxy)-2,4-hexadiyne (1a) and the twofold iodoary-
lated product 2a are sensitive to the temperature and amount of
iodine monochloride.
the existence of the phenoxy and phenylamino moieties in ICl-
mediated intramolecular 2twofold iodoarylation is not critical,
while the presence of oxygen and nitrogen atoms having
nonbonding electrons in Au-catalyzed 2-fold hydroarylation is
critical (eq 1).7
With this newly developed protocol in hand, we applied the
optimum reaction conditions of intramolecular 2-fold iodoar-
ylation of 1,6-bis(phenoxy)-2,4-hexadiyne (1a) to a wide range
of diynes and diynyl diethers and amines 1 to demonstrate the
efficiency and scope of the present method (Table 2).
Treatment of 1,6-bis(p-tert-butylphenoxy)-2,4-hexadiyne (1b)
with ICl (2 equiv) in DCM at 0 °C after 10 min produced the
4,4′-bis(2H-chromene) 2b bearing an alkenyl iodide moiety in
60% yield (entry 2). The 2,4-hexadiyne 1c, having an o-
phenylphenoxy group at the 1,6-positions was reacted with ICl
to afford the desired iodoarylated product 2c in 90% yield
In the case of unsymmetrical 1-(o-phenylphenoxy)-7-phenyl-
2,4-heptadiyne (1h), intramolecular 2-fold iodoarylation
proceeded efficiently to give 2h in 81% yield in DCE at 0 °C
after 10 min (entry 8). 1-(o-Bromophenoxy)-7-phenyl-2,4-
heptadiyne (1i) worked equally well (entry 9). When the
unsymmetrical diyne 1j having phenoxy and N-phenyl-N-
tosylamino groups was treated with ICl (2 equiv) in DCM at 0
°C, the intramolecular twofold iodoarylated compound 2j was
obtained in 53% yield (entry 10). In addition, phenoxy- and N-
(3,5-dimethylphenyl)-N-tosylamino-substituted diyne 1k was
cyclized to produce 2k in 55% yield (entry 11).
a
Table 1. Optimization of Intramolecular Twofold Iodoarylation
yield (%)
entry
I+ (amt (equiv))
additive (amt (equiv))
temp (°C)
solvent
time
10 h
2a
3a
b
b
b
b
1
NIS (3)
NIS (3)
NIS (3)
IPy2BF4 (3)
I2 (4)
−78
−78
−78
−78
25
DCE
0
0
28 (31)
38 (30)
34 (12)
46 (45)
2
CH2Cl2
AcOH
12 h
3
8 h
0
4
HBF4 (6)
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
12 h
0
5
1 h
17
0
8
6
I2 (4)
−78
25
24 h
67
64
0
7
I2 (4)
NaHCO3 (2)
12 h
0
8
ICl (2)
ICl (2)
ICl (2)
ICl (3)
ICl (3)
25
10 min
10 min
2 h
0
9
0
76
47
71
71
0
b
10
11
12
−78
0
0 (46)
10 min
30 min
0
0
−78
a
b
Reaction conditions: 1a (0.2 mmol) in solvent (0.1 M). Recovery yields of 1a.
B
dx.doi.org/10.1021/jo401922b | J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry
Article
further transformation through cross-coupling reactions (Table
3). Reaction of 2a with (4-Me-C6H4)B(OH)2 in the presence
of Pd(OAc)2 catalyst and CsF in THF proceeded smoothly to
afford the coupling product 4a in 75% yield. We were pleased
to obtain 4b,c in 66% and 67% yields, respectively, from the
treatment of 2a with the corresponding boronic acids (4-MeO-
C6H4)B(OH)2 and (3-Cl-C6H4)B(OH)2.
Table 2. Twofold Iodoarylation of Diyne and Diynyl
Diethers and Diamines
a
Next, a Pd-catalyzed cross-coupling reaction using indium
tris(arylthiolate) was applied to 2a (Table 4).9 Subjecting 2a to
(4-Me-C6H4S)3In in the presence of Pd(OAc)2 (4 mol %),
Xantphos (4.2 mol %), and DIPEA (0.2 mmol) in DMF (100
°C, 2 h) gave the desired product 5a in 71% yield. Treatment of
2a with (4-MeO-C6H4S)3In resulted in the formation of C−S
coupling product 5b in 75% yield.
A possible reaction mechanism is described in Scheme 3.
Activation of the iodonium cation to triple bond in diyne 1
results in the formation of the intermediate I, which upon
nucleophilic attack of the carbon on the aromatic ring is
cyclized, leading to the intermediates II and V.3,4 Subsequent
aromatization might deliver the iodoarylated compounds IV
and VI. The repeated intramolecular iodoarylation of
intermediates IV and VI with iodonium cation would provide
the twofold iodoarylation product 2. Because the rate of the
iodoarylation reaction is fast, the first iodoarylated products IV
and VI are not detected in TLC as well as NMR studies. In the
case of unsymmetrical diynes, we cannot determine which side
nucleophilic attack of the phenyl ring occurs first.
CONCLUSION
■
In conclusion, we developed herein electrophilic intramolecular
twofold iodoarylation from the reaction of diynes and diynyl
diethers and amines with iodine monochloride under mild
conditions (DCE, 0 °C, 10−40 min), which produced bis(2H-
hydronaphthalene and chromene) and 2H-quinoline bearing an
alkenyl iodide moiety in good to excellent yields. These
compounds underwent Pd-catalyzed cross-coupling reactions
with arylboronic acid and indium tris(arylthiolate) to produce
the functionalized styrene derivatives.
EXPERIMENTAL SECTION
■
General Considerations. Reactions were carried out in oven-
dried glassware under a nitrogen atmosphere. Pd(OAc)2, Xantphos,
and ICl (1.0 M in CH2Cl2) were purchased. Commercially available
reagents were used without purification. DCE, dichloromethane, and
DMF were dried with CaH2. THF was dried with Na−benzophenone.
All reaction mixtures were stirred magnetically and were monitored by
thin-layer chromatography using silica gel precoated glass plates, which
were visualized with UV light and then developed using either iodine
or a solution of anisaldehyde. Flash column chromatography was
carried out using silica gel (230−400 mesh). 1H NMR (400 MHz) and
13C NMR (100 MHz) spectra were recorded on an NMR
spectrometer. Deuterated chloroform was used as the solvent, and
chemical shift values (δ) are reported in parts per million relative to
the residual signals of this solvent (δ 7.26 for H and δ 77.0 for 13C).
1
Infrared spectra were recorded on an FT-IR spectrometer as either a
thin film pressed between two sodium chloride plates or as a solid
suspended in a potassium bromide disk. Mass spectrometry was
performed on a GC/HRMS spectrometer by electron impact (EI)
ionization techniques (magnetic sector−electric sector double focusing
mass analyzer). Melting points were determined in open capillary
tubes.
a
Reaction conditions: 1 (0.2 mmol), ICl (0.4 mmol), 0 °C, CH2Cl2.
ICl (0.8 mmol) was used.
b
General Procedure for the Preparation of 1,6-Bis(phenoxy)-
2,4-hexadiyne Derivatives. (Prop-2-ynyloxy)benzene derivatives
were prepared from the reaction of the appropriate phenol (1 equiv)
with propargyl bromide (1.5 equiv) at room temperature in DMF in
Because 4,4′-bis(2H-chromenes) bearing an alkenyl iodide
moiety were now in hand, we investigated the feasibility of
C
dx.doi.org/10.1021/jo401922b | J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry
Article
a
Table 3. Pd-Catalyzed Suzuki−Miyaura Cross-Coupling Reaction using 2a
a
Reaction conditions: 2a (0.2 mmol), Pd(OAc)2 (10 mol %), ArB(OH)2 (1.2 mmol), and CsF (1.6 mmol), in THF (4 mL) at 70 °C for 12 h.
the presence of potassium carbonate (2 equiv). Purification of the
crude product was achieved via flash column chromatography. Then,
in a 50 mL flask were dissolved (prop-2-ynyloxy)benzene derivatives
(6 mmol) in 4 mL of DMF. To the solution were added copper(I)
chloride (30 mg, 5 mol %), 0.1 mL (10 mol %) of N,N,N′,N′-
tetramethylethylenediamine, and 0.1 mL (10 mol %) of pyridine. The
mixture was bubbled with oxygen and stirred at room temperature for
6−12 h. A 30 mL portion of DMF was added, and the mixture was
filtered through a short silica column to remove copper. The filtrate
was poured into 100 mL of water. The resultant precipitate was
filtered, washed with water, and dried under vacuum to afford a beige
powder (36−96%).
Table 4. Pd-Catalyzed Cross-Coupling Reactions using
Indium Tris(arylthiolate)
a
1,6-Bis(phenoxy)-2,4-hexadiyne (1a):10 white solid (96%, 980
1
mg); mp 61−64 °C; H NMR (400 MHz, CDCl3) δ 7.33−7.28 (m,
4H), 7.02−6.93 (m, 6H), 4.75 (s, 4H); 13C NMR (100 MHz, CDCl3)
δ 157.8, 130.0, 122.2, 115.3, 75.0, 71.4, 56.6; IR (pellet) 3062, 3041,
2912, 1598, 1494, 1361, 1211, 1034 cm−1.
1,6-Bis(4-tert-butylphenoxy)-2,4-hexadiyne (1b):7 white solid
(88%, 825 mg); mp 78−82 °C; 1H NMR (400 MHz, CDCl3) δ
7.31 (d, J = 8.9 Hz, 4H), 6.88 (d, J = 8.8 Hz, 4H), 4.73 (s, 4H), 1.30
(s, 18H); 13C NMR (100 MHz, CDCl3) δ 155.2, 144.5, 126.4, 114.3,
74.8, 71.0, 56.3, 34.1, 31.5; IR (pellet) 2962, 2904, 2868, 1512, 1363,
1297, 1221 cm−1.
a
Reaction conditions: 2a (0.2 mmol), (ArS)3In (0.28 mmol),
Pd(OAc)2 (4 mol %), Xantphos (4.2 mol %), and DIPEA
(diisopropylethylamine) (0.2 mmol) in DMF (2 mL) at 100 °C for
2 h.
1,6-Bis(biphenyl-2-yloxy)-2,4-hexadiyne (1c):7 pale yellow solid
(89%, 1.0 g); mp 102−105 °C; 1H NMR (400 MHz, CDCl3) δ 7.52−
Scheme 3. Plausible Mechanism
D
dx.doi.org/10.1021/jo401922b | J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry
Article
7.48 (m, 4H), 7.40 (t, J = 6.7 Hz, 4H), 7.35−7.31 (m, 6H), 7.10 (t, J =
8.1 Hz, 4H), 4.71 (s, 4H); 13C NMR (100 MHz, CDCl3) δ 154.8,
138.6, 132.1, 131.7, 130.1, 129.1, 128.6, 127.6, 122.7, 114.0, 75.5, 71.7,
57.2; IR (pellet) 3542, 3060, 3027, 1597, 1583, 1503, 1480, 1208
cm−1.
quenched with 10 mol % KI aqueous (2 mL). The aqueous layer was
extracted with CH2Cl2 (3 × 5 mL), and the combined organic layers
were washed with Na2S2O3·5H2O and water, dried with MgSO4,
filtered, and concentrated under reduced pressure. Silica gel column
chromatography (acetone/hexane 1/9) gave 5,5′-diiodo-2H,2′H-4,4′-
bichromene 2a (77.5 mg, 76%) as a white solid.
5,5′-Diiodo-2H,2′H-4,4′-bichromene (2a): white solid (76%, 78
mg); mp 101−104 °C; 1H NMR (400 MHz, CDCl3) δ 7.20−7.16 (m,
2H), 6.92−6.87 (m, 4H), 6.84−6.80 (m, 2H), 5.11−5.03 (m, 4H); 13C
NMR (100 MHz, CDCl3) δ 153.0, 140.2, 130.2, 125.1, 122.1, 120.9,
116.3, 93.4, 74.4; IR (pellet) 3067, 2832, 1598, 1481, 1455, 1221,
1036, 993 cm−1; HRMS (EI) calcd for C18H12I2O2 513.8927, found
513.8930.
1,6-Bis(4-chlorophenoxy)-2,4-hexadiyne (1d): white solid (89%,
730 mg); mp 140−143 °C; 1H NMR (400 MHz, CDCl3) δ 7.27−7.23
(m, 4H), 6.89−6.85 (m, 4H), 4.73 (s, 4H); 13C NMR (100 MHz,
CDCl3) δ 155.9, 129.5, 126.8, 116.3, 74.4, 71.2, 56.5; IR (pellet) 3094,
2906, 2860, 1493, 1370, 1244, 1031, 819 cm−1; HRMS (EI) calcd for
C18H12Cl2O2 330.0214, found 330.0213.
1,6-Bis(2-bromophenoxy)-2,4-hexadiyne (1e):7 white solid (90%,
1
945 mg); mp 80 °C; H NMR (400 MHz, CDCl3) δ 7.56 (d, J = 8.2
3,3′-Diiodo-8,8′-diphenyl-2H,2′H-4,4′-bichromene (2b): white
solid (60%, 75 mg); mp 111−114 °C; 1H NMR (400 MHz,
CDCl3) δ 7.20 (dd, J = 8.5, 2.4 Hz, 2H), 6.88 (d, J = 2.4, 2H), 6.83 (d,
J = 8.4, 2H), 5.04 (s, 4H), 1.14 (s, 18H); 13C NMR (100 MHz,
CDCl3) δ 150.8, 144.7, 140.8, 126.9, 122.4, 120.7, 115.5, 92.6, 74.5,
34.1, 31.3; IR (pellet) 2961, 2904, 2867, 1606, 1490, 1363, 1004, 952
cm−1; HRMS (EI) calcd for C26H28I2O2 626.0179, found 626.0176.
6,6′-Di-tert-butyl-3,3′-diiodo-2H,2′H-4,4′-bichromene (2c): white
solid (90%, 120 mg); mp 97−100 °C; 1H NMR (400 MHz, CDCl3) δ
7.57−7.54 (m, 4H), 7.46−7.42 (m, 4H), 7.38−7.36 (m, 2H), 7.28−
7.24 (m, 2H), 7.00−6.97 (m, 2H), 6.94−6.90 (m, 2H), 5.10−5.02 (m,
4H); 13C NMR (100 MHz, CDCl3) δ 149.9 140.7, 137.4, 131.6, 130.1,
129.5, 128.1, 127.3, 124.6, 122.1, 121.7, 93.7, 74.4; IR (pellet) 3057,
2835, 1456, 1428, 1264, 1210, 1072, 1003 cm−1; HRMS (EI) calcd for
C30H20I2O2 665.9553, found 665.9556.
6,6′-Dichloro-3,3′-diiodo-2H,2′H-4,4′-bichromene (2d): white
solid (66%, 76.8 mg); mp 220−223 °C; 1H NMR (400 MHz,
CDCl3) δ 7.15 (dd, J = 8.6, 2.5 Hz, 2H), 6.83 (d, J = 12.5 Hz, 2H),
6.82 (d, J = 1.2 Hz, 2H), 5.12−5.03 (m, 4H); 13C NMR (100 MHz,
CDCl3) δ 151.7, 138.8, 130.1, 127.1, 124.4, 121.7, 117.9, 95.7, 74.4; IR
(pellet) 2848, 1479, 1404, 1260, 1093, 999, 817, 732 cm−1; HRMS
(EI) calcd for C18H10Cl2I2O2 581.8147, found 581.8146.
Hz, 2H), 7.29 (t, J = 7.9 Hz, 2H), 7.01 (d, J = 8.2 Hz, 2H), 6.90 (t, J =
7.6 Hz, 2H), 4.84 (s, 4H); 13C NMR (100 MHz, CDCl3) δ 154.3,
134.1, 128.9, 123.6, 114.6, 112.9, 74.7, 71.9, 57.7; IR (pellet) 3064,
2912, 1476, 1277, 1224, 1051, 1031, 1017 cm−1.
1,6-Bis(4-iodophenoxy)-2,4-hexadiyne (1f):7 pale yellow solid
(88%, 1.1 g); mp 164−167 °C; 1H NMR (400 MHz, CDCl3) δ
7.58 (d, J = 8.9 Hz, 4H), 6.72 (d, J = 8.8 Hz, 4H), 4.72 (s, 4H); 13C
NMR (100 MHz, CDCl3) δ 157.2, 138.3, 117.2, 84.2, 74.3, 71.2, 56.2;
IR (pellet) 1571, 1484, 1284, 1236, 1026, 823, 797 cm−1.
1,8-Bis(phenyl)-3,5-octadiyne (1g): white solid (94%, 608 mg); mp
66−69 °C; 1H NMR (400 MHz, CDCl3) δ 7.32−7.28 (m, 4H), 7.24−
7.20 (m, 6H), 2.84 (t, J = 7.5 Hz, 4H), 2.54 (t, J = 7.6 Hz, 4H); 13C
NMR (100 MHz, CDCl3) δ 140.2, 128.5, 128.4, 126.4, 76.9, 65.9, 34.7,
21.5; IR (pellet) 3028, 2927, 2256, 1603, 1453, 1424, 1227, 1032, 699,
511 cm−1; HRMS (EI) calcd for C20H18 258.1409, found 258.1407.
2-((7-Phenylhepta-2,4-diyn-1-yl)oxy)-1,1′-biphenyl (1h): pale yel-
low oil (48%, 403 mg), 1H NMR (400 MHz, CDCl3) δ 7.54−7.51 (m,
2H), 7.43−7.39 (m, 2H), 7.35−7.28 (m, 5H), 7.24−7.18 (m, 3H),
7.12−7.07 (m, 2H), 4.70 (s, 2H), 2.84 (t, J = 7.5 Hz, 2H), 2.56 (t, J =
7.5 Hz, 2H); 13C NMR (100 MHz, CDCl3) δ 154.4, 139.9, 138.2,
131.5, 131.1, 129.6, 128.5, 128.3, 128.0, 127.0, 126.5, 122.0, 113.6,
80.9, 72.1, 71.0, 65.2, 56.8, 34.4, 21.5; IR (film) 3060, 3022, 2928,
2255, 1480, 1209, 1018, 751, 698 cm−1; HRMS (FAB) calcd for
C25H20O 336.1514, found 336.1511.
8,8′-Dibromo-3,3′-diiodo-2H,2′H-4,4′-bichromene (2e): white
1
solid (87%, 116.5 mg), 166−169 °C; H NMR (400 MHz, CDCl3)
δ 7.41 (dd, J = 7.96, 1.44 Hz, 2H), 6.84−6.82 (m, 2H), 6.73−6.69 (m,
2H), 5.22−5.14 (m, 4H);13C NMR (100 MHz, CDCl3) δ 149.9, 139.4,
133.9, 124.2, 123.0, 121.8, 110.4, 94.8, 74.8; IR (pellet) 3069, 2844,
1635, 1588, 1556, 1457, 1440, 1233, 997, 907, 778 cm−1; HRMS (EI)
calcd for C18H10Br2I2O2 669.7137, found 669.7141.
1-Bromo-2-((7-phenylhepta-2,4-diyn-1-yl)oxy)benzene (1i): yel-
1
low oil (43%, 365 mg), H NMR (400 MHz, CDCl3) δ 7.53 (dd, J =
7.9, 1.6 Hz, 1H), 7.30−7.27 (m, 3H), 7.25−7.23 (m, 1H), 7.21−7.17
(m, 2H), 7.02 (dd, J = 8.2, 1.2 Hz, 1H), 6.87 (td, J = 7.7, 1.3 Hz, 1H),
4.79 (s, 2H), 2.82 (t, J = 7.5, Hz, 2H), 2.55 (t, J = 7.5, Hz, 2H); 13C
NMR (100 MHz, CDCl3) δ 154.0, 139.9, 133.3, 128.5, 128.5, 128.4,
126.6, 122.9, 114.3, 112.5, 81.4, 72.8, 70.1, 65.1, 57.5, 34.4, 21.5; R
(film) 3062, 3027, 2927, 2860, 2256, 1585, 1476, 1225, 1031, 748
cm−1; HRMS (FAB) calcd for C19H15BrO 338.0306, found 338.0302.
4-Methyl-N-(6-phenoxyhexa-2,4-diyn-1-yl)-N-phenylbenzenesul-
fonamide (1j): brown solid (36%, 374 mg); mp 51−56 °C; 1H NMR
(400 MHz, CDCl3) 7.51 (d, J = 8.3 Hz, 2H), 7.34−7.29 (m, 5H),
7.22−7.17 (m, 4H), 7.02 (t, J = 7.3 Hz, 1H), 6.94 (d, J = 7.6 Hz, 2H),
4.73 (s, 2H), 4.51 (s, 2H), 2.38 (s, 3H); 13C NMR (100 MHz, CDCl3)
δ 157.8, 144.2, 139.8, 135.7, 129.9, 129.7, 129.5, 128.6, 128.4, 122.2,
115.3, 74.7, 74.0, 71.4, 69.9, 56.5, 42.2, 21.9; IR (pellet) 3063, 1597,
1493, 1351, 1212, 1163, 754, 694 cm−1; HRMS (EI) calcd for
C25H21NO3S 415.1242, found 415.1239.
3,3′,6,6′-Tetraiodo-2H,2′H-4,4′-bichromene (2f): white solid
(70%, 107.2 mg), 110−112 °C; 1H NMR (400 MHz, CDCl3) δ
7.50−7.48 (m, 2H), 7.09 (s, 2H), 6.67 (d, J = 8.5 Hz, 2H), 5.13−5.02
(m, 4H); 13C NMR (100 MHz, CDCl3) δ 153.0, 139.2, 138.5, 132.8,
122.6, 118.8, 95.6, 84.4, 74.3; IR (pellet) 2831, 1473, 1394, 1265,
1228, 1073, 997, 815, 736 cm−1; HRMS (EI) calcd for C18H10I4O2
765.6860, found 765.6856.
2,2′-Diiodo-3,3′,4,4′-tetrahydro-1,1′-binaphthalene (2g): white
solid (90%, 91.8 mg); mp 111−114 °C; 1H NMR (400 MHz,
CDCl3) δ 7.18−7.15 9 (m, 4H), 7.08−7.04 (m, 2H), 6.98−6.96 (m,
2H), 3.10−3.05 (m, 4H), 3.03−2.96 (m, 4H); 13C NMR (100 MHz,
CDCl3) δ 145.2, 134.7, 132.5, 127.8, 127.6, 127.0, 125.2, 103.2, 39.1,
29.9; IR (pellet) 3061, 2934, 2884, 2827, 1482, 1449, 1422, 907 cm−1;
HRMS (EI) calcd for C20H16I2 509.9341, found 509.9344.
N-(3,5-Dimethylphenyl)-4-methyl-N-(6-phenoxyhexa-2,4-diyn-1-
1
yl)benzenesulfonamide (1k): colorless oil (40%, 443 mg), H NMR
3-Iodo-4-(2-iodo-3,4-dihydronaphthalen-1-yl)-8-phenyl-2H-chro-
1
(400 MHz, CDCl3) 7.54 (d, J = 8.2 Hz, 2H), 7.32 (t, J = 8.0 Hz, 2H),
7.20 (d, J = 8.2 Hz, 2H), 7.02 (t, J = 7.4 Hz, 1H), 6.95 (d, J = 8.2 Hz,
3H), 6.78 (s, 2H), 4.73 (s, 2H), 4.46 (s, 2H), 2.39 (s, 3H), 2.25 (s,
6H); 13C NMR (100 MHz, CDCl3) δ 158.4, 144.6, 140.0, 139.6,
136.4, 130.9, 130.3, 130.0, 128.8, 126.7, 122.6, 115.5, 75.0, 73.9, 71.6,
69.7, 56.5, 42.2, 21.7, 21.4; IR (film) 2955, 2919, 1597, 1494, 1350,
1162, 1034, 664 cm−1; HRMS (EI) calcd for C27H25NO3S 443.1555,
found 443.1553.
General Procedure for the Preparation of Diiodo-2H,2′H-
4,4′-bichromene Derivatives. To a solution of 1,6-bis(phenoxy)-
2,4-hexadiyne (1a; 52.5 mg, 0.2 mmol) in CH2Cl2 (1.6 mL) was slowly
added ICl (1.0 M in CH2Cl2, 0.4 mL) dropwise at 0 °C. The resulting
solution was stirred at 0 °C for 10 min. The reaction mixture was
mene (2h): white solid (81%, 95.2 mg); mp 107−110 °C; H NMR
(400 MHz, CDCl3) δ 7.57−7.54 (m, 2H), 7.45−7.41 (m, 2H), 7.37−
7.32 (m, 1H), 7.26−7.24 (m, 1H), 7.20−7.16 (m, 2H), 7.12−7.08 (m,
1H), 7.04−7.02 (m, 1H), 7.00−6.95 (m, 1H), 6.90−6.88 (m, 1H),
5.08−5.00 (m, 2H), 3,14−3.09 (m, 2H), 3.04−2.98 (m, 2H); 13C
NMR (100 MHz, CDCl3) δ 150.0, 143.1, 142.7, 137.5, 134.5, 132.0,
131.3, 130.0, 129.5, 128.1, 128.0, 127.7, 127.2, 127.1, 125.0, 124.8,
122.1, 121.9, 103.4, 93.4, 74.4, 39.1, 29.8; IR (pellet) 2925, 14555,
1428, 1213, 1002, 907 cm−1; HRMS (EI) calcd for C25H18I2O
587.9447, found 587.9448.
8-Bromo-3-iodo-4-(2-iodo-3,4-dihydronaphthalen-1-yl)-2H-chro-
1
mene (2i): white solid (88%, 103.8 mg); mp 169−172 °C; H NMR
(400 MHz, CDCl3) δ 6.94 (d, J = 7.8 Hz, 1H), 7.21−7.15 (m, 2H),
E
dx.doi.org/10.1021/jo401922b | J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry
Article
7.09−7.06 (m, 1H), 6.95−6.93 (m, 1H), 6.87−6.84 (m, 1H), 6.68 (t, J
= 7.8 Hz, 1H), 5.22−5.13 (m, 2H), 3.10−3.08 (m, 2H), 3.01−2.97 (m,
2H); 13C NMR (100 MHz, CDCl3) δ 150.0, 142.2, 134.4, 133.5,
131.7, 128.5, 128.1, 127.8, 127.1, 124.8, 124.6, 122.8, 122.5, 110.2,
103.6, 94.4, 74.9, 39.1, 29.6; IR (pellet) 3060, 2946, 2886, 2829, 1479,
1456, 1441, 1232, 1088, 998 cm−1; HRMS (EI) calcd for C19H13BrI2O
589.8239, found 589.8242.
122.1, 116.2, 68.6; IR (pellet) 3027, 2920, 2828, 2248, 1600, 1485,
1218, 1038, 908, 813, 756 cm−1; HRMS (EI) calcd for C30H20Cl2O2
482.0840, found 482.0839.
Typical Experimental Procedures for Palladium-Catalyzed
C−S Bond Formation Cross-Coupling Reactions. A suspention of
Pd(OAc)2 (1.8 mg, 4 mol %) and Xantphos (4.8 mg, 4.2 mol %) in
DMF (1 mL) was stirred at 25 °C for 5 min. To this suspension was
added 3,3′-diiodo-2H,2′H-4,4′-bichromene (0.2 mmol) in DMF (1
mL) at 25 °C under a nitrogen atmosphere. After the mixture was
stirred for 10 min, (ArS)3In (0.28 mmol) and DIPEA (34.8 μL, 0.2
mmol) in DMF (1 mL) were transferred via a double-ended needle,
and this mixture was stirred at 100 °C for 2 h. The reaction mixture
was quenched with NaHCO3 (1 mL). The aqueous layer was extracted
with ether (3 × 10 mL), and the combined organic layers were washed
with water and brine, dried with MgSO4, filtered, and concentrated
under reduced pressure. The residue was purified by silica gel column
chromatography on silica gel with a gradient eluent of EtOAc/hexane
to give the corresponding 3,3′-bis(arylthio)-2H,2′H-4,4′-bichromene.
3,3′-Bis((4-methylphenyl)thio)-2H,2′H-4,4′-bichromene (5a): yel-
low solid (71%, 71.9 mg); mp 77−80 °C; 1H NMR (400 MHz,
CDCl3) δ 7.37−7.35 (m, 4H), 7.14−7.09 (m, 6H), 6.98−6.96 (m,
2H), 6.87−6.85 (m, 4H), 4.76−4.66 (m, 4H), 2.32 (s, 6H); 13C NMR
(100 MHz, CDCl3) δ 153.3, 138.0, 132.2, 130.6, 130.0, 129.2, 128.3,
128.0, 124.9, 123.0, 121.9, 116.1, 67.6, 21.1; IR (pellet) 3032, 2921,
2838, 1901, 1598, 1482, 1125, 1038, 755 cm−1; HRMS (EI) calcd for
C32H26O2S2 506.1374, found 506.1378.
3-Iodo-4-(3-iodo-2H-chromen-4-yl)-1-tosyl-1,2-dihydroquinoline
(2j): white solid (53%, 71 mg); mp 99−102 °C; 1H NMR (400 MHz,
CDCl3) δ 7.92−7.89 (m, 1H), 7.64 (d, J = 8.3 Hz, 2H), 7.36−7.31 (m,
1H), 7.26−7.24 (m, 2H), 7.12−7.06 (m, 2H), 6.90 (d, J = 7.8 Hz,
1H), 6.80 (d, J = 8.1 Hz, 1H), 6.42 (t, J = 7.6 Hz, 1H), 5.49 (d, J = 6.2
Hz, 1H), 5.27 (d, J = 17.9 Hz, 1H), 5.02−4.93 (m, 2H), 4.69 (d, J =
17.9 Hz, 1H), 2.42 (s, 3H); 13C NMR (100 MHz, CDCl3) δ 153.0,
143.9, 141.7, 140.5, 137.2, 134.0, 130.2, 129.8, 129.1, 127.6, 127.1,
126.7, 126.4, 126.0, 125.6, 121.7, 120.8, 116.2, 95.2, 74.4, 56.2, 21.8; IR
(pellet) 3058, 2923, 2845, 1597, 1482, 1452, 1353, 1220, 1161 cm−1;
HRMS (EI) calcd for C25H19I2NO3S 666.9175, found 666.9179.
3-Iodo-4-(3-iodo-2H-chromen-4-yl)-5,7-dimethyl-1-tosyl-1,2-di-
hydroquinoline (2k): white solid (55%, 76.5 mg); mp 98−101 °C; 1H
NMR (400 MHz, CDCl3) δ 7.75 (d, J = 8.3, 2H), 7.66 (s, 1H), 7.22
(d, J = 8.0 Hz, 2H), 7.12−7.07 (m, 1H), 6.79−6.77 (m, 1H), 6.74 (s,
1H), 6.44 (t, J = 7.6 Hz, 1H), 5.71 (t, J = 7.7 Hz, 1H), 5.17 (d, J = 17.2
Hz, 1H), 4.97−4.85 (m, 2H), 4.65 (d, J = 17.2 Hz, 1H), 2.36 (s, 3H),
2.31 (s, 3H), 2.12 (s, 3H); 13C NMR (100 MHz, CDCl3) δ 155.1,
144.2, 138.8, 138.3, 137.4, 137.1, 136.5, 136.1, 131.6, 130.2, 129.9,
128.6, 127.4, 125.7, 125.6, 125.1, 123.7, 121.9, 119.8, 116.7, 65.4, 45.3,
21.9, 21.6, 21.4; IR (pellet) 3063, 2922, 2840, 1481, 1452, 1357, 1164,
1089, 1035; HRMS (EI) calcd for C27H23I2NO3S 694.9488, found
694.9490.
3,3′-Bis((4-methoxyphenyl)thio)-2H,2′H-4,4′-bichromene (5b):
1
pale yellow solid (75%, 80.7 mg); mp 88−91 °C; H NMR (400
MHz, CDCl3) δ 7.43−7.41 (m, 4H), 7.13−7.09 (m, 2H), 6.96−6.94
(m, 2H), 6.86−6.83 (m, 8H), 4.74−4.63 (m, 4H), 3.80 (s, 6H); 13C
NMR (100 MHz, CDCl3) δ 160.0, 153.1, 134.7, 129.2, 129.0, 128.7,
124.8, 129.9, 121.9, 121.9, 116.0, 114.9, 67.5, 55.4; IR (pellet) 2937,
2835, 1683, 1590, 1493, 1247, 1173, 1032, 756 cm−1; HRMS (EI)
calcd for C32H26O4S2 538.1273, found 538.1270.
(((2E,4E)-2,3,4,5-Tetraiodohexa-2,4-diene-1,6-diyl)bis(oxy))-
1
dibenzene (3a): white solid (67%, 103.1 mg); mp 169−172 °C; H
NMR (400 MHz, CDCl3) δ 7.31−7.25 (m, 5H), 6.98−6.94 (m, 5H),
4.84−4.80 (m, 2H), 4.71−4.67 (m, 2H); 13C NMR (100 MHz,
CDCl3) δ 157.3, 129.6, 121.9, 115.9, 104.4, 103.6, 77.7; IR (pellet)
3038, 2919, 1596, 1492, 1210, 689 cm−1; HRMS (EI) calcd for
C18H14I4O2 769.7173, found 769.7169.
ASSOCIATED CONTENT
* Supporting Information
■
S
Typical Experimental Procedures for Palladium-Catalyzed
Suzuki−Miyaura Cross-Coupling Reactions. A suspension of
Pd(OAc)2 (4.5 mg, 10 mol %), (4-methoxyphenyl)boronic acid (182
mg, 1.2 mmol), and CsF (243 mg, 1.6 mmol) in THF (4 mL) was
stirred at 25 °C for 5 min. To this suspension was added 3,3′-diiodo-
2H,2′H-4,4′-bichromene (0.2 mmol). The resulting mixture was
stirred under a nitrogen atmosphere at 70 °C (bath temperature) for
12 h. After Celite filtration and evaporation of the solvents in vacuo,
the crude product was purified by column chromatography on silica
gel with a gradient eluent of EtOAc/hexane to give the corresponding
3,3′-diaryl-2H,2′H-4,4′-bichromene.
Text and figures giving experimental procedures, character-
ization data, and 1H and 13C NMR spectra for new compounds.
This material is available free of charge via the Internet at
http://pubs.acs.org.
AUTHOR INFORMATION
Corresponding Author
*E-mail for P.H.L.: phlee@kangwon.ac.kr.
■
Notes
The authors declare no competing financial interest.
3,3′-Di-p-tolyl-2H,2′H-4,4′-bichromene (4a): white solid (75%,
66.4 mg); mp 136−139 °C; 1H NMR (400 MHz, CDCl3) δ 7.16−7.12
(m, 2H), 7.09−7.06 (m, 2H), 6.93−6.82 (m, 8H), 6.60−6.58 (m, 4H),
4.87−7.78 (m, 4H), 2.26 (s, 6H); 13C NMR (100 MHz, CDCl3) δ
153.4, 136.9, 135.0, 132.4, 128.9, 128.4, 127.4, 126.3, 126.2, 124.5,
121.8, 115.8, 69.2, 21.2; IR (pellet) 3027, 2920, 2828, 2248, 1600,
1485, 1218, 1038, 908, 813, 756 cm−1; HRMS (EI) calcd for C32H26O2
442.1933, found 442.1935.
ACKNOWLEDGMENTS
■
This work was supported by the National Research Foundation
of Korea (NRF) grant funded by the Korea government
(MSIP) (No. 2011-0018355) and BRL (2009-0087013). This
paper is dedicated to Professor Sung Ho Kang, KAIST, on the
occasion of his retirement.
3,3′-Bis(4-methoxyphenyl)-2H,2′H-4,4′-bichromene (4b): white
1
solid (66%, 62.6 mg); mp 78−81 °C; H NMR (400 MHz, CDCl3)
REFERENCES
δ 7.16−7.12 (m, 2H), 7.07−7.05 (m, 2H), 6.93−6.91 (m, 2H), 6.85−
6.81 (m, 2H), 6.67−6.61 (m, 8H), 4.87−4.77 (m, 4H), 3.74 (s, 6H);
13C NMR (100 MHz, CDCl3) δ 158.7, 153.4, 132.0, 130.5, 128.9,
127.6, 127.1, 126.2, 124.5, 121.8, 115.8, 113.1, 69.1, 55.2; IR (pellet)
2955, 2835, 1607, 1512, 1248, 1179, 1034, 827, 757 cm−1; HRMS (EI)
calcd for C32H26O4 474.1831, found 474.1832.
■
(1) (a) Sohel, S. M. A.; Liu, R.-S. Chem. Soc. Rev. 2009, 38, 2269.
(b) Jia, C.; Kitamura, T.; Fujiwara, Y. Acc. Chem. Res. 2001, 34, 633.
(c) Nevado, C.; Echavarren, A. M. Synthesis 2005, 167. (d) Goj, L. A.;
Gunnoe, T. B. Curr. Org. Chem. 2005, 9, 671. (e) Wang, X.; Zhou, L.;
Lu, W. Curr. Org. Chem. 2010, 14, 289. (f) Ciochina, R.; Grossman, R.
B. Chem. Rev. 2006, 106, 3963. (g) Nevado, C.; Echavarren, A. M.
Chem. Eur. J. 2005, 11, 3155. (h) Bandini, M.; Emer, E.; Tommasi, S.;
Umani-Ronchi, A. Eur. J. Org. Chem. 2006, 3527. (i) Kitamura, T. Eur.
J. Org. Chem. 2009, 1111. (j) Choi, D. S.; Kim, J. H.; Shin, U. S.;
Deshmukh, R. R.; Song, C. E. Chem. Commun. 2007, 3482.
(k) Kakiuchi, F.; Chatani, N. Adv. Synth. Catal. 2003, 345, 1077.
3,3′-Bis(3-chlorophenyl)-2H,2′H-4,4′-bichromene (4c): white solid
(67%, 64.8 mg); mp 65−69 °C; 1H NMR (400 MHz, CDCl3) δ 7.22−
7.17 (m, 2H), 7.16−7.13 (m, 2H), 7.07−7.03 (m, 4H), 6.97−6.94 (m,
2H), 6.88−6.84 (m, 2H), 6.67−6.64 (m, 2H), 6.51−6.50 (m, 2H),
4.84−4.75 (m, 4H); ; 13C NMR (100 MHz, CDCl3) δ 153.5, 139.4,
133.9, 131.3, 129.8, 129.1, 128.9, 127.5, 126.4, 126.0, 124.6, 123.9,
F
dx.doi.org/10.1021/jo401922b | J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry
Article
(l) Jia, C.; Piao, D.; Oyamada, J.; Lu, W.; Kitamura, T.; Fujiwara, Y.
Science 2000, 287, 1992. (m) Mamane, V.; Hannen, P.; Furstner, A.
̈
Chem. Eur. J. 2004, 10, 4556. (n) Chatani, N.; Inoue, H.; Ikeda, T.;
Murai, S. J. Org. Chem. 2000, 65, 4913. (o) Furstner, A.; Mamane, V.
̈
Chem. Commun. 2003, 2112. (p) Menon, R. S.; Findlay, A. D.;
Bissember, A. C.; Banwell, M. G. J. Org. Chem. 2009, 74, 8901.
(q) Song, C. E.; Jung, D.-u.; Choung, S. Y.; Roh, E. J.; Lee, S.-g. Angew.
Chem., Int. Ed. 2004, 43, 6183. (r) Inoue, H.; Chatani, N.; Muari, S. J.
Org. Chem. 2002, 67, 1414. (s) Hu, T.; Liu, K.; Shen, M.; Yuan, X.;
Tang, Y.; Li, C. J. Org. Chem. 2007, 72, 8555.
(2) (a) De La Mare, P. B. D.; Bolton, R. Electrophilic Additions to
Unsaturated Systems, 2nd ed.; Elsevier: Amsterdam, 1982. (b) Block,
E.; Schwan, A. L. In Comprehensive Organic Synthesis; Trost, B. M.,
Fleming, I., Eds.; Pergamon: Oxford, U.K., 1991; Vol. 4, Chapter 1.8, p
329.
(3) (a) Barluenga, J.; Gonzal
Angew. Chem., Int. Ed. 1988, 27, 1546. (b) Barluenga, J.; Trincado, M.;
Marco-Arias, M.; Ballesteros, A.; Rubio, E.; Gonzalez, J. M. Chem.
Commun. 2005, 2008. (c) Barluenga, J.; Trincado, M.; Rubio, E.;
Gonzalez, J. M. Angew. Chem., Int. Ed. 2006, 45, 3140. (d) Barluenga,
J.; Vazquez-Villa, H.; Ballesteros, A.; Gonzalez, J. M. J. Am. Chem. Soc.
2003, 125, 9028. (e) Barluenga, J.; Vazquez-Villa, H.; Ballesteros, A.;
Gonzalez, J. M. Org. Lett. 2003, 5, 4121. (f) Barluenga, J.; Trincado,
M.; Rubio, E.; Gonzalez, J. M. Angew. Chem., Int. Ed. 2003, 42, 2406.
(g) Barluenga, J.; Palomas, D.; Rubio, E.; Gonzalez, J. M. Org. Lett.
2007, 9, 2823.
́
ez, J. M.; Campos, P. J.; Asensio, G.
́
́
́
́
́
́
(4) (a) Mehta, S.; Waldo, J. P.; Larock, R. C. J. Org. Chem. 2009, 74,
1141. (b) Yao, T.; Campo, M. A.; Larock, R. C. Org. Lett. 2004, 6,
2677. (c) Zhang, X.; Sarkar, S.; Larock, R. C. J. Org. Chem. 2006, 71,
236. (d) Zhang, X.; Campo, M. A.; Yao, T.; Larock, R. C. Org. Lett.
2005, 7, 763. (e) Yao, T.; Larock, R. C. J. Org. Chem. 2005, 70, 1432.
(f) Yao, T.; Campo, M. A.; Larock, R. C. J. Org. Chem. 2005, 70, 3511.
(g) Yue, D.; Yao, T.; Larock, R. C. J. Org. Chem. 2005, 70, 10292.
(h) Yue, D.; Yao, T.; Larock, R. C. J. Org. Chem. 2006, 71, 62.
(i) Worlikar, S. A.; Kesharwani, T.; Yao, T.; Larock, R. C. J. Org. Chem.
2007, 72, 1347. (j) Zhang, X.; Larock, R. C. J. Am. Chem. Soc. 2005,
127, 12230.
(5) (a) Goldfinger, M. B.; Crawford, K. B.; Swager, T. M. J. Am.
Chem. Soc. 1997, 119, 4578. (b) Feng, X.; Wu, J.; Ai, M.; Pisula, W.;
Zhi, L.; Rabe, J. P.; Mullen, K. Angew. Chem., Int. Ed. 2007, 46, 3033.
̈
(6) (a) Kang, D.; Kim, J.; Oh, S.; Lee, P. H. Org. Lett. 2012, 14, 5636.
(b) Mo, J.; Lee, P. H. Org. Lett. 2010, 12, 2570. (c) Eom, D.; Mo, J.;
Lee, P. H.; Gao, Z.; Kim, S. Eur. J. Org. Chem. 2013, 533. (d) Eom, D.;
Park, S.; Park, Y.; Lee, K.; Hong, G.; Lee, P. H. Eur. J. Org. Chem.
2013, 2672.
(7) Mo, J.; Eom, D.; Lee, E.; Lee, P. H. Org. Lett. 2012, 14, 3684.
(8) (a) Chernykh, A.; Agag, T.; Ishida, H. Polymer 2009, 50, 3153.
(b) Huerta, G.; Fomina, L.; Rumsh, L.; Zolotukhin, M. G. Polym. Bull.
2006, 57, 433.
(9) (a) Lee, P. H.; Park, Y.; Park, S.; Lee, E.; Kim, S. J. Org. Chem.
2011, 76, 760. (b) Mo, J.; Eom, D.; Kim, S. H.; Lee, P. H. Chem. Lett.
2011, 40, 980. (c) Lee, J.-Y.; Lee, P. H. J. Org. Chem. 2008, 73, 7413.
(10) Buckley, R. B.; Dann, S. E.; Harris, D. P.; Heaney, H.; Stubbs, E.
C. Chem. Commun. 2010, 46, 2274.
G
dx.doi.org/10.1021/jo401922b | J. Org. Chem. XXXX, XXX, XXX−XXX