Room-temperature bismuth-catalyzed bis-arylation of carbonyl compounds with aryl ethers and phenols

Article abstract of DOI:10.1002/cjoc.201300522

Using Bi₂(SO₄)₃ as the catalyst and TMSCl as the additive, a wide variety of aldehydes, ketones, and acetals were smoothly condensed with aryl ethers at room temperature to provide the corresponding diarylmethanes and triarylmethanes selectively in good to excellent yields. Using Bi₂(SO₄)₃ as the catalyst and TMSCl as the additive, a wide variety of aldehydes, ketones, and acetals were smoothly condensed with aryl ethers at room temperature to selectively provide the corresponding diarylmethanes and triarylmethanes in good to excellent yields. Copyright

Full text of DOI:10.1002/cjoc.201300522

FULL PAPER
DOI: 10.1002/cjoc.201300522
Room-Temperature Bismuth-Catalyzed Bis-arylation of
Carbonyl Compounds with Aryl Ethers and Phenols
Congrong Liu*,a,b and Manbo Lib
a School of Environment Engineering, Nanjing Institute of Technology, Nanjing, Jiangsu 211167, China
b Joint Laboratory of Green Synthetic Chemistry, Department of Chemistry, University of Science and
Technology of China, Hefei, Anhui 230026, China
Using Bi2(SO4)3 as the catalyst and TMSCl as the additive, a wide variety of aldehydes, ketones, and acetals
were smoothly condensed with aryl ethers at room temperature to provide the corresponding diarylmethanes and
triarylmethanes selectively in good to excellent yields.
Keywords carbonyl compounds, aryl ethers, condensation, bismuth, chlorotrimethylsilane
Introduction
(2a) was selected as a model reaction to explore the
catalytic activity of Lewis acids in combination with
TMSCl. On the basis of our previous experience,[5] we
started our investigation with the examination of iron
salts.[7] Although individually neither 10 mol% of
FeSO4•7H2O nor equimolar TMSCl was effective in
catalyzing this condensation without solvent at room
temperature, their combination led to the selective for-
mation of triarylmethane 3a in 77% yield (Table 1, En-
tries 1－3). A few other iron salts, as well as ZnCl2,
were also examined, but the yield was not improved
significantly (Table 1, Entries 4－8). Surprisingly, no
reaction was observed with AlCl3,[8] a popular Lewis
acid to promote Friedel-Crafts reaction (Table 1, Entry
9). Further survey revealed that the reaction with BiCl3
and Bi2(SO4)3, inexpensive and non-toxic Lewis acids,[9]
gave triarylmethane 3a in excellent yields, respectively,
and the latter needed much shorter reaction time (Table
1, Entries 10 and 11).[10] While the decrease of the cata-
lyst loading of Bi2(SO4)3 to 5 mol% did not affect the
yield, the use of substoichiometric TMSCl led to a dra-
matic drop in yield, and no reaction was observed in the
absence of TMSCl (Table 1, Entries 12－14). To our
delight, in the presence of 5 mol% of Bi2(SO4)3 and two
equiv. of TMSCl, the room-temperature, solvent-free
condensation of benzaldehyde (1a) with anisole (2a)
proceeded smoothly with 93∶7 regioselectivity[11] and
gave triarylmethane 3a in 91% yield (Table 1, Entry
15).
The condensation of carbonyl compounds with are-
nes in the presence of acids is an important carbon-
carbon bond-forming reaction with water as the sole
by-product, and provides a direct synthetic route to di-
arylmethanes and triarylmethanes that have found
widespread applications in synthetic, medicinal, and
industrial chemistry.[1] Although this type of condensa-
tion via double Friedel-Crafts reaction[2] to form two
carbon-carbon bonds was known one hundred years ago,
efficient methods are often limited to the condensation
of aromatic aldehydes with electron-rich heteroarenes,
amino- or hydroxy-substituted arenes,[3] and restricted
by the formation of a multitude of products, high cata-
lyst loading, and at times drastic reaction conditions.[1-4]
The recent report by Roy and coworkers[4a] disclosed a
useful bimetallic catalyst system for the condensation of
aldehydes with less electron-rich aryl ethers,[4] albeit
precious and toxic metals, inert gas, and high tempera-
ture were employed.
Inspired by our recent discovery that a number of
Lewis acids in combination with chlorotrimethylsilane
(TMSCl) are powerful for the activation of imines and
amines in their reactions with nucleophiles at room
temperature,[5] we utilized these catalyst systems to
promote the condensation of carbonyl compounds with
aryl ethers.[6] Herein we report a facile, selective syn-
thesis of diarylmethanes and triarylmethanes via a bis-
muth-catalyzed condensation of various aldehydes, ke-
tones, and acetals with aryl ethers at room temperature.
Encouraged by our preliminary findings, we inves-
tigated the substrate scope for the condensation of car-
bonyl compounds with anisole (2a). Using Bi2(SO4)3 as
the catalyst and TMSCl as the additive, a number of
Results and Discussion
The condensation of benzaldehyde (1a) with anisole
*
E-mail: congrong@njit.edu.cn; Tel.: 0086-025-86118974
Received July 5, 2013; accepted August 14, 2013; published online September 16, 2013.
Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/cjoc.201300522 or from the author.
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Chin. J. Chem. 2013, 31, 1274—1278

Room-Temperature Bismuth-Catalyzed Bis-arylation of Carbonyl Compounds
Table 1 Survey of Lewis acidsa
Table 2 Bismuth-catalyzed condensation of aldehydes, ketones,
and acetals with anisole (2a)a
OMe
CHO
OMe
catalyst, TMSCl
OMe
Bi2(SO4)3 (5 mol%),
TMSCl (2.0 equiv.)
+
r.t.
+
R
R'
R'
r.t.
1
1a
2a
MeO
OMe
3a
R
R"O OR"
2a
3
OMe
Entry
Catalyst (mol%)
FeSO4•7H2O (10)
none
TMSCl/equiv. Time/h Yieldb/%
R
R'
4
1
2
3
4
5
6
7
8
9
none
48
48
48
48
22
16
16
20
48
48
8
NRc,d
traced
77
Entry 1 or 4
R
R'
R" Product Time/h Yieldb/%
1
1
1
2
1a Ph
H
3a
9
91
86
84
86
79
45
56
90
50
81
70
67
95
54
75
78
80
71
72
87
82
73
89
90
78
FeSO4•7H2O (10)
FeCl2•4H2O (10)
Fe2(SO4)3•5H2O (10)
FeCl3 (10)
1b 4-MeC6H4
1c 4-ClC6H4
H
3b
32
20
5
1
82
3
H
3c
1
81
4
1d 4-O2NC6H4
1e 4-HOOCC6H4
1f 3-HOC6H4
1g 3-MeOC6H4
1h 3-O2NC6H4
1i 2-MeOC6H4
1j 2-ClC6H4
H
3d
1
80
5
H
3e
6
FeCl3•6H2O (10)
ZnCl2 (10)
1
82
6c
7c
8
H
3f
10
12
4
1
83
NRc,d
H
3g
AlCl3 (10)
1
H
3h
10 BiCl3 (10)
1
91
9c
H
3i
18
4
11 Bi2(SO4)3 (10)
12 Bi2(SO4)3 (5)
13 Bi2(SO4)3 (5)
14 Bi2(SO4)3 (5)
15 Bi2(SO4)3 (5)
1
87
10
H
3j
1
10
48
48
9
87
11c 1k 2-O2NC6H4
12d 1l 2-HOOCC6H4
13 1m 2,4-Cl2C6H4
14 1n Et
H
3k
18
18
22
10
12
10
7
0.5
none
2
50
NRc,d
H
3l
H
3m
91
a Conditions: 1a (1.0 mmol), 2a (3.0 mmol), catalyst, TMSCl, r.t.
b Isolated yield. c No reaction. d Detected by TLC.
H
3n
15
1o PhCH2
H
3o
16 1p Me2CH
H
3p
aromatic aldehydes bearing either electron-withdrawing
groups (Cl, NO2, and COOH) or electron-donating (Me,
OH, and OMe) groups on the ortho-, meta-, or
para-positions of the aromatic rings, and aliphatic al-
dehydes, including the sterically hindered ones, were
transformed into their corresponding triarylmethanes
and diarylmethanes selectively at room temperature in
good to excellent yields (Table 2, Entries 1－18).[12]
Activated carbonyl compounds such as α-keto esters
and α-keto acids were also found to be able to serve as
suitable substrates for this condensation, and impor-
tantly, both ester and carboxylic acid groups were com-
patible with the reaction conditions (Table 2, Entries 19
－22). This condensation reaction was further extended
to masked aldehydes (Table 2, Entries 23－25) that,
stable in the air and inert to many nucleophiles, offer
significant advantages over the corresponding aldehydes
in many synthetic manipulations. It is notable that good
to excellent yields can be obtained using this condensa-
tion reaction to synthesize the same triarylmethane (or
diarylmethane) from several different acetal derivatives
of the same aldehyde.
17 1q Cyclohexyl
H
3q
18
19
1r Me3C
1s Me
H
3r
10
10
15
16
5
CO2Et
CO2Et
CO2Et
COOH
3s
20d 1t PhCH2CH2
21d 1u Ph
3t
3u
22
23
1v Me
4a Ph
3v
H
H
H
Et
3a
15
48
24
24 4b Ph
25 4c Ph
CH2 3a
Ac
3a
a Conditions: 1 (or 4, 1.0 mmol), 2a (3.0 mmol), Bi2(SO4)3 (5
mol%), TMSCl (2.0 mmol), r.t. b Isolated yield. c 10 mol% of
Bi2(SO4)3 was used. d 15 mol% of Bi2(SO4)3 was used.
(Table 3, Entries 1－3, 6, 8 and 9). This protocol was
also suitable for (substituted) phenols, and as expected,
short reaction times were needed for the successful
condensation of benzaldehyde (1a) with these more
electron-rich arenes (Table 3, Entries 4, 5, and 7). Nev-
ertheless, no reaction took place with less reactive are-
nes such as benzene (2k) (Table 3, Entry 10).
As illustrated in Tables 1－3, the combined use of
Lewis acid and TMSCl is the key for the successful
condensation of carbonyl compounds with aryl ethers.
To gain insight into the reaction mechanism, the reac-
tion mixture for the condensation of benzaldehyde (1a)
Next, we examined the reactivity of various aryl
ethers and phenols toward benzaldehyde (1a) (Table 3).
Diphenyl ether, substituted anisoles, and 1-methoxy-
naphthalene were all found to condense well with ben-
zaldehyde (1a) to provide the corresponding triaryl-
methanes 5 selectively in good to excellent yields
Chin. J. Chem. 2013, 31, 1274—1278
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FULL PAPER
Table 3 Bismuth-catalyzed condensation of benzaldehyde (1a)
with aryl ethers and (substituted) phenolsa
Table 4 The condensation of benzaldehyde (1a) with anisole
(2a)a
CHO
Ar
Bi2(SO4)3 (5 mol%),
TMSCl (2.0 equiv.)
CHO
OMe
Ar
+
Ar
H
Cb
r.t.
+
+
OH
1a
2
5
1a
MeO
2a
Entry
1c
Ar
Product Time/h Yieldb/%
6a
2
R＝OPh
R'＝H
48
5
75
94
86
75
63
2b
2c
2d
2e
2f
5a
5b
5c
5d
5e
O
+
+
R＝OMe
R'＝Me
R＝OMe
R'＝OMe
R＝OH
R'＝H
2
3
4
5
R
MeO
OMe
3a
MeO
OMe
7a
R'
12
1
OMe
R＝OH
R'＝Me
MeO
3
3a'
time = 2 h, 1a : 6a : 7a : 3a : 3a' = 5.7 : 3.3 : 3.3 : 82.0 : 5.7c
time = 9 h, 1a : 6a : 7a : 3a : 3a' = 0.0 : 0.0 : 0.0 : 92.6 : 7.4c
R＝OMe
R'＝Me
R＝OH
R'＝Me
R
6
7
40
2
73
83
2g
2h
5f
2aa
2aa
6a ⎯⎯→7a
Time/h Yieldd/% Time/h Yieldd/% Time/h Yieldd/%
6a ⎯⎯⎯→3a 7a ⎯⎯⎯→3a
Conditionb
5g
R'
OMe
A
B
C
24
24
0
0
24
24
0
0
20
16
93
95
94
8
8
97
2i
5h
0.5
96
1.0
93
8.5
a
b
2a (3.0 equiv.). Conditions for A: Bi2(SO4)3 (5 mol%), r.t.; B:
TMSCl (2.0 equiv.), r.t.; C: Bi2(SO4)3 (5 mol%), TMSCl (2.0
equiv.), r.t. c Determined by 1H NMR analysis. d Isolated yield.
OMe
9d
1
＞99
2j
5i
5j
MeO
OMe
compounds with aryl ethers (Scheme 1). The Friedel-
Crafts reaction of carbonyl compound 1 with aryl ether
2 generates intermediate 6, which can further react with
aryl ether 2 to provide product 3 (or 5). Alternatively,
intermediate 6 is converted to ether 7 followed by a
second Friedel-Crafts reaction to provide the desired
product. The combined use of Bi2(SO4)3 and TMSCl is
essential for each step of the condensation of carbonyl
compound 1 with aryl ether 2. The ability of TMSCl to
enhance the Lewis acid catalysis can drive the reaction
to take place and proceed quickly.
10
24
0
2k
a
Conditions: 1a (1.0 mmol), 2 (3.0 mmol), Bi2(SO4)3 (5 mol%),
b
c
TMSCl (2.0 mmol), r.t. Isolated yield. 15 mol% of Bi2(SO4)3
was used. d 0.20 mL of dichloromethane was added.
with anisole (2a) was analyzed with H NMR.[13,14] we
1
observed the formation of alcohol 6a and ether 7a,[15]
both of which would disappear by the end of the reac-
tion (Table 4). When treated with Bi2(SO4)3/TMSCl,
both alcohol 6a and ether 7a were quickly converted to
triarylmethane 3a in excellent yields, though neither
Bi2(SO4)3 nor TMSCl was able to promote these reac-
tions. In contrast, much longer reaction time was needed
for the generation of ether 7a from alcohol 6a in the
presence of Bi2(SO4)3 and/or TMSCl (Table 4).
Conclusions
In summary, we have developed a facile, selective
synthesis of diarylmethanes and triarylmethanes via a
bismuth-catalyzed condensation of carbonyl compounds
with aryl ethers and phenols. Using Bi2(SO4)3 as the
catalyst and TMSCl as the additive, a wide variety of
aldehydes, ketones, and acetals were condensed with
aryl ethers and phenols at room temperature to give the
corresponding diarylmethanes and triarylmethanes
These observations, along with previous studies on
the condensation of aldehydes with arenes,[16] prompt us
to propose the following plausible reaction pathways for
the bismuth-catalyzed condensation of carbonyl
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Chin. J. Chem. 2013, 31, 1274—1278

Room-Temperature Bismuth-Catalyzed Bis-arylation of Carbonyl Compounds
K. G. Tetrahedron 2006, 62, 6731; (b) Shchepinov, M. S.; Korshun,
V. A. Chem. Soc. Rev. 2003, 32, 170; (c) Duxbury, D. F. Chem. Rev.
1993, 93, 381; (d) Risberg, K.; Guldvik, I. J.; Palchaudhuri, R.; Xi,
Y. G.; Ju, J. F.; Fodstad, O.; Hergenrother, P. J.; Andersson, Y. J.
Immunother. 2011, 34, 438; (e) Parai, M. K.; Panda, G.; Chaturvedi,
V.; Manju, Y. K.; Sinha, S. Bioorg. Med. Chem. Lett. 2008, 18, 289.
[2] For reviews, see: (a) Olah, G. A. Friedel Crafts and Related Reac-
tions, Wiley-Interscience, New York, 1963; (b) Roberts, R. M.;
Khalaf, A. A. Khalaf, Friedel-Crafts Alkylation Chemistry. A Cen-
tury of Discovery, Marcel Dekker, New York, 1984.
[3] For recent examples, see: (a) Zolfigol, M. A.; Salehi, P.; Shiri, M.;
Tanbakouchian, Z. Catal. Commun. 2007, 8, 173; (b) Deb, M. L.;
Bhuyan, P. J. Tetrahedron Lett. 2006, 47, 1441; (c) Nair, V.; Ab-
hilash, K. G.; Vidya, N. Org. Lett. 2005, 7, 5857; (d) Ji, S.-J.; Zhou,
M.-F.; Gu, D.-G.; Jiang, Z.-Q.; Loh, T.-P. Eur. J. Org. Chem. 2004,
1584; (e) Guzmán-Lucero, D.; Guzmán, J.; Likhatchev, D.;
Martínez-Paloua, R. Tetrahedron Lett. 2005, 46, 1119; (f)
Udayakumar, S.; Ajaikumar, S.; Pandurangan, A. Catal. Commun.
2007, 8, 366; (g) Mibu, N.; Yokomizo, K.; Uyeda, M.; Sumoto, K.
Bioorg. Med. Chem. Lett. 2007, 17, 621; (h) Mibu, N.; Yokomizo,
K.; Uyeda, M.; Sumoto, K. Chem. Pharm. Bull. 2005, 53, 1171; (i)
Prakash, G. K. S.; Panja, C.; Shakhmin, A.; Shah, E.; Mathew, T.;
Olah, G. A. J. Org. Chem. 2009, 74, 8659.
[4] (a) Podder, S.; Choudhury, J.; Roy, U. K.; Roy, S. J. Org. Chem.
2007, 72, 3100; (b) Shao, X.-B.; Jiang, X.-K.; Zhao, X.; Zhao, C.-X.;
Chen, Y.; Li, Z.-T. J. Org. Chem. 2004, 69, 899; (c) Leikauf, E.;
Rarnekow, F.; Köster, H. Tetrahedron 1996, 52, 6913; (d) Goerlitzer,
K.; Michels, K. Pharmazie 1994, 49, 14; (e) Hellwinkel, D.; Fritsch,
H. Chem. Ber. 1990, 123, 2207; (f) Baarschers, W. H.; Vukmanich,
J. P. Can. J. Chem. 1986, 64, 932; (g) Su, J.; Liu, Y.; Zheng, Z. B.;
Xiao, J. H.; Lu, H.; Zhong, W.; Wang, L. L.; Jiang, S. B.; Li, S.
Chin. Chem. Lett. 2007, 18, 1166; (h) Xu, J. Z.; Jiang, N. Z.; Zhang,
J.; Jiang, R. S. Chem. Res. Chin. Univ. 2005, 21, 65; (i) Sun, H. B.;
Li, B.; Chen, S. J.; Li, J.; Hua, R. M. Tetrahedron 2007, 63, 10185;
(j) Hua, R. M. Curr. Org. Synth. 2008, 5, 1; (k) Hua, R. M.; He, J.
Y.; Sun, H. B. Chin. J. Chem. 2007, 25, 132; (l) Sun, H.-B.; Hua,
R.-M.; Yin, Y. Tetrahedron Lett. 2006, 47, 2291.
Scheme 1 Plausible reaction pathways
O
Ar
+
R
R'
H
1
2
Bi (III)
TMSCl
(TMS)2O
2, TMSCl
Ar OTMS
R'
Ar Ar
3 or 5
R
R
R'
Bi(III)
6
Bi(III)
Bi(III)
Ar Ar
TMSCl
(TMS)2O
R'
R'
R
R
O
2, TMSCl
(TMS)2O
7
selectively in good to excellent yields. The attractive
features of this protocol to synthesize diarylmethanes
and triarylmethanes include high selectivity and yield,
broad substrate scope, the use of inexpensive and envi-
ronmentally sound catalyst, mild reaction conditions,
and experimental simplicity.
Experimental
General information
1H and 13C NMR spectra (300 MHz and 75 MHz,
respectively) were recorded using tetramethylsilane as
internal reference. The melting points were uncorrected.
Compounds 1g, 4a－4c, 2c, 2d, 2g, 2i, 6a, 7a, and
(2-methoxyphenyl)(phenyl)methanol were prepared
according to known procedures.[17] The rest of chemi-
cals were purchased from the Sinopharm Chemical Re-
agent Co., Meryer, Acros, and Alfa Aesar, and used as
received. Products were all known compounds, which
were identified by comparing their physical and spectra
data with those reported in the literature.
[5] (a) Liu, C.-R.; Li, M.-B.; Yang, C.-F.; Tian, S.-K. Chem. Commun.
2008, 1249; (b) Liu, C.-R.; Li, M.-B.; Yang, C.-F.; Tian, S.-K.
Chem.-Eur. J. 2009, 15, 793.
[6] For the study on the activation of carbonyl groups with InCl3/
Me3SiCl system, see: (a) Onishi, Y.; Ito, T.; Yasuda, M.; Baba, A.
Tetrahedron 2002, 58, 8227; (b) Onishi, Y.; Ito, T.; Yasuda, M.;
Baba, A. Eur. J. Org. Chem. 2002, 1578.
General procedure for the condensation of carbonyl
compounds with arenas
[7] For a review on the catalysis with iron salts, see: Bolm, C.; Legros,
J.; Le Paih, J.; Zani, L. Chem. Rev. 2004, 104, 6217.
[8] 40 mol% of AlCl3 was reported to catalyze the condensation of ben-
zaldehyde (1a) with anisole (2a) to give triarylmethane 3a in 49%
yield, see reference 4b.
[9] For a review on the catalysis with bismuth(III) salts, see: Leonard, N.
M.; Wieland, L. C.; Mohan, R. S. Tetrahedron 2002, 58, 8373.
[10] Brønsted acids in combination with TMSCl could also catalyze this
condensation, but gave product 3a in lower yield. For example, 70%
and 66% yields were obtained when using conc. H2SO4 and
CF3SO3H as the catalysts, respectively.
A mixture of carbonyl compound 1 (or acetal 4, 1.0
mmol), arene 2 (3.0 mmol), TMSCl (217 mg, 0.251 mL,
2.0 mmol), and Bi2(SO4)3 (35.4 mg, 5 mol%) was
stirred at room temperature. When the reaction did not
proceed further as indicated by TLC, the reaction mix-
ture was directly purified by flash column chromatog-
raphy on silica gel, eluting with petroleum ether/EtOAc
(100∶1 to 20∶1, V∶V), to give product 3 or 5 (Tables
2 and 3).
[11] Based on the 1H NMR analysis of the reaction mixture (see refer-
ences and notes 14), only one minor isomer of 3a was detected and
identified as (2-methoxyphenyl)(4-methoxyphenyl)-phenylmethane
(3a') by comparing the 1H NMR spectra with that of authentic sam-
ple prepared from (2-methoxy-phenyl)(phenyl) methanol and anisole
(2a) in the presence of Bi2(SO4)3 at r.t. The regioselectivity was de-
termined to be 93∶7 by integration of the signals at δ 5.44 (CH of
3a) and δ 5.86 (CH of 3a').
Acknowledgement
We are grateful for the financial support from the
National Natural Science Foundation of China (No.
21202154), Nanjing Institute of Technology and the
University of Science and Technology of China.
[12] Under the same reaction conditions the reaction with in-
dole-2-carboxaldehyde and furaldehyde afforded unsatisfactory
yields.
References and Notes
[1] (a) Nair, V.; Thomas, S.; Mathew, S. C.; Abhilash, K. G.; Abhilash,
Chin. J. Chem. 2013, 31, 1274—1278
© 2013 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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Liu & Li
FULL PAPER
[13] A small portion (about 5 μL) of the reaction mixture was directly
Chem. Soc. 1993, 115, 4571; 4b: (c) Mosca, R.; Fagnoni, M.; Mella,
M.; Albini, A. Tetrahedron 2001, 57, 10319; 4c: (d) Jin, T.-S.; Du,
J.-Y.; Li, T.-S. Indian J. Chem. Sect. B 1998, 37, 939; 2c and 2g: (e)
David, G. K.; Nobuyoshi, H. Bull. Chem. Soc. Jpn. 1993, 66, 1583;
2d: (f) Vanden, E. J.; Isabelle, M. Synth. Commun. 2001, 31, 1; 2i:
(g) Andre, L.; Jean, S.; Vaziri, Z. F. Bull. Soc. Chim. Fr. 1987, 6,
1027; 6a: (h) Huang, W.-S.; Hu, Q.-S.; Pu, L. J. Org. Chem. 1999,
64, 7940; 7a: (i) Balfe, M. P.; Downer, E. A. W.; Evans, A. A.;
Kenyon, J.; Poplett, R.; Searle, C. E.; Tárnoky, A. L. J. Chem. Soc.
1946, 797; (2-methoxyphenyl)(phenyl)methanol: (j) Kelly, D. P.;
Spear, R. J. Aust. J. Chem. 1977, 30, 1993.
dissolved in CD3Cl and subjected to 1H NMR analysis.
1
[14] Compounds 6a and 7a were identified by comparing their H NMR
spectra with that of authentic samples prepared according to known
procedures (see the Supporting Information), respectively.
[15] Olah, G. A.; Rasul, G.; York, C.; Prakash, G. K. S. J. Am. Chem.
Soc. 1995, 117, 11211, and references therein.
[16] The formation of (TMS)2O was observed by direct 1H NMR analysis
of the reaction mixture (see references and notes 13).
[17] 1g: (a) Hoshang, E. M.; Shabana, I. K.; Krishna, A. P. Bioorg. Med.
Chem. 2005, 13, 4891; 4a: (b) Silverman, R. B.; Ding, C. Z. J. Am.
(Zhao, X.)
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