Direct coupling reaction of diaryl methanol with ketones or aldehydes catalyzed by AlCl3

Article abstract of DOI:10.1002/cjoc.201400516

A novel coupling reaction of diaryl methanols with ketones or aldehydes has been developed under the catalysis of AlCl₃. Various ketones and aldehydes could couple with 9H-xanthen-9-ol smoothly, affording coupling products in 48%-88% yields. A plausible mechanism using AlCl₃ to activate both diaryl methanol and ketone or aldehyde is proposed.

Full text of DOI:10.1002/cjoc.201400516

NOTE
DOI: 10.1002/cjoc.201400516
Direct Coupling Reaction of Diaryl Methanol with Ketones or
Aldehydes Catalyzed by AlCl3
Zhiqiang Zhu,a Peng Bai,a Tiantian Wang,a and Zhizhen Huang*,a,b
a Department of Chemistry, Zhejiang University, Hangzhou, Zhejiang 310028, China
b State Key Laboratory of Elemento-Organic Chemistry, Nankai University, Tianjin 300071, China
A novel coupling reaction of diaryl methanols with ketones or aldehydes has been developed under the catalysis
of AlCl3. Various ketones and aldehydes could couple with 9H-xanthen-9-ol smoothly, affording coupling products
in 48%－88% yields. A plausible mechanism using AlCl3 to activate both diaryl methanol and ketone or aldehyde is
proposed.
Keywords coupling reaction, alcohol, ketone, aldehyde, AlCl3, catalysis
Introduction
with aldehyde or ketone, we thought that Lewis acid
could promote not only the cleavage of hydroxyl group
of alcohol but also the formation of enol of aldehyde or
ketone with referring to literatures.[2e-2f,4h,13] Thus, we
envision to use Lewis acid as a sole catalyst to perform
a coupling reaction of alcohols with aldehydes or ke-
tones.
Carbon-carbon bond formation by direct coupling of
alcohols with other partners is more environmentally
benign because H2O is usually a major byproduct.[1]
Recently, alcohols, which are mainly benzylic alcohols,
have been reported as useful electrophiles to couple
with a range of nucleophiles, such as aldehydes,[2] ke-
tones,[3] active methylene compounds,[4] aromatic com-
pounds,[5] active silanes,[6] amines,[7] thiols,[8] alkynes,[9]
alkenes[1b,1c,10] and alcohols.[1b,1c] Among them, the cou-
pling reactions of alcohols, which are mainly diaryl
methanols, with aldehydes or ketones are more attrac-
tive because the conventional alkylations of aldehydes
or ketones are often performed through metal enolates,
which not only suffer from use of strong bases and alkyl
halides, but also produce a metal salt as a byprod-
uct.[4b,11]
From 2009 to 2012, several research groups dis-
closed enantioselective coupling reactions of diaryl
methanols with aldehydes or ketones by cooperative
catalysis of amine with Brønsted acid.[2a-2c,3a-3c] More-
over, a cooperative catalysis of amine with Lewis acid
was used in an enantioselective coupling reaction of
diaryl methanols or benzylic alcohols with alde-
hydes.[2d-2e] In 2011, Chi et al. revealed that only ben-
zenesulfonic acid as a Brønsted acid could also catalyze
the coupling reaction of diaryl methanols with alde-
hydes expediently.[2f] Later, Guo’s group used benzoic
acid as a Brønsted acid to catalyze the coupling reaction
of diaryl methanols with aldehydes.[2g]
Experimental
General procedure for the coupling reaction of xan-
thenol with ketones or aldehydes catalyzed by AlCl3
To a solution of xanthenol 1 (39.6 mg, 0.2 mmol) in
THF (2 mL) was added ketone or aldehyde 2 (0.6 mmol)
and AlCl3 (8.0 mg, 0.06 mmol). The reaction mixture
was stirred at room temperature for the time indicated in
Table 2. After reaction, the mixture was concentrated
under vacuum, and the residue was subjected to column
chromatography (silica gel, petroleum ether/ethyl ace-
tate as eluent) to afford the corresponding products 3.
2-(9H-Xanthen-9-yl)cyclohexanone (3a):[14] White
solid; 1H NMR (400 MHz, CDCl3) δ: 7.42 (d, J＝7.6 Hz,
1H), 7.25－7.18 (m, 3H), 7.08－7.00 (m, 4H), 4.93 (d,
J＝2.4 Hz, 1H), 2.52－2.48 (m, 1H), 2.42 (d, J＝12.0
Hz, 1H), 2.28－2.20 (m, 1H), 1.94－1.91 (m, 1H),
1.78－1.68 (m, 2H), 1.52－1.37 (m, 2H), 1.15－1.05
(m, 1H); 13C NMR (100 MHz, CDCl3) δ: 211.5, 153.4,
153.7, 131.1, 129.4, 128.4, 128.3, 126.3, 124.2, 123.9,
123.5, 116.9, 116.8, 61.3, 42.8, 37.3, 28.3, 27.3, 25.4;
MS (EI) m/z: 278 (M＋), 194, 181, 165, 152.
2-(9H-Xanthen-9-yl)cyclopentanone (3b):[14] White
Lewis acid catalyses have a lot of advantages and
become one of the most important strategies in modern
organic synthesis.[12] In the coupling reaction of alcohol
1
solid; H NMR (400 MHz, CDCl3) δ: 7.26－7.20 (m,
3H), 7.12－7.07 (m, 4H), 6.99 (t, J＝7.4 Hz, 1H), 4.76
*
E-mail: huangzhizhen@zju.edu.cn; Tel.: 0086-0571-8795-1352; Fax: 0086-0571-8880-7077
Received July 28, 2014; accepted September 7, 2014; published online November 3, 2014.
Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/cjoc.201400516 or from the author.
1176
© 2014 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Chin. J. Chem. 2014, 32, 1176—1182

Direct Coupling Reaction of Diaryl Methanol with Ketones or Aldehydes Catalyzed by AlCl3
(d, J＝2.4 Hz, 1H), 2.44 (t, J＝9.0 Hz, 1H), 2.25 (dd,
J＝18.4, 7.2 Hz, 1H), 1.82－1.73 (m, 2H), 1.68－1.61
(m, 1H), 1.58－1.50 (m, 1H), 1.44－1.33 (m, 1H); 13C
NMR (100 MHz, CDCl3) δ: 219.9, 153.8, 153.1, 129.9,
128.9, 128.8, 128.4, 125.1, 124.3, 124.1, 122.5, 117.1,
117.0, 60.5, 40.0, 38.7, 24.6, 21.0; MS (EI) m/z: 264
(M＋), 196, 182, 165, 152.
(EI-TOF) m/z: calcd for C23H26O2 334.1933, found
334.1932.
4-Phenyl-2-(9H-xanthen-9-yl)cyclohexanone (3f):
White solid, dr＝3∶1. Mixture of two diastereomers:
1H NMR (400 MHz, CDCl3) δ: 7.44 (d, J＝7.6 Hz,
0.75H), 7.33 (d, J＝7.6 Hz, 0.25H), 7.26－7.11 (m, 6H),
7.09－6.98 (m, 6H), 5.00 (d, J＝2.4 Hz, 0.75H), 4.76 (d,
J＝5.2 Hz, 0.25H), 2.89－2.82 (m, 1H), 2.76－2.72 (m,
1H), 2.54－2.40 (m, 2H), 2.10－2.03 (m, 1H), 1.95－
1.89 (m, 1H), 1.74－1.63 (m, 1H), 1.43－1.34 (m, 1H);
13C NMR (100 MHz, CDCl3) δ: 211.7, 209.9, 153.4,
153.3, 153.0, 153.0, 144.6, 143.7, 130.4, 129.9, 128.8,
128.6, 128.5, 128.3, 128.3, 128.0, 127.9, 127.7, 126.7,
126.5, 126.5, 126.3, 125.3, 124.4, 123.7, 123.5, 123.3,
122.7, 122.5, 116.6, 116.6, 116.4, 116.3, 60.2, 56.9,
42.8, 41.6, 39.8, 39.6, 37.1, 36.6, 34.3, 34.1, 32.2, 31.1;
HRMS (EI-TOF) m/z: calcd for C25H22O2 354.1620,
found 354.1618.
2-(9H-Xanthen-9-yl)cycloheptanone (3c):[15] White
1
solid; H NMR (400 MHz, CDCl3) δ: 7.27－7.21 (m,
3H), 7.11－7.05 (m, 4H), 7.01 (t, J＝7.2 Hz, 1H), 4.65
(d, J＝4.4 Hz, 1H), 2.58 (dt, J＝11.6, 3.6 Hz, 1H), 2.38
－2.34 (m, 1H), 2.11 (td, J＝12.0, 2.4 Hz, 1H), 1.75－
1.72 (m, 3H), 1.63－1.55 (m, 1H), 1.38－1.13 (m, 3H),
1.05－0.96 (m, 1H); 13C NMR (100 MHz, CDCl3) δ:
217.1, 153.8, 153.6, 129.7, 129.4, 128.8, 128.5, 125.1,
124.3, 123.8, 122.6, 117.2, 117.0, 63.1, 45.4, 42.7, 30.5,
29.1, 25.6, 25.4; MS (EI) m/z: 292 (M＋), 194, 181, 165,
152.
4-Methyl-2-(9H-xanthen-9-yl)cyclohexanone (3d):
White solid, dr＝2∶1. Low polar diastereomer (Ma-
jor):[16] 1H NMR (400 MHz, CDCl3) δ: 7.42 (d, J＝7.6
Hz, 1H), 7.24－7.18 (m, 3H), 7.09－7.00 (m, 4H), 4.94
(d, J＝2.4 Hz, 1H), 2.59－2.49 (m, 1H), 2.42－2.36 (m,
1H), 2.34－2.20 (m, 1H), 1.95－1.82 (m, 1H), 1.79－
1.64 (m, 2H), 1.50－1.41 (m, 1H), 1.21－1.08 (m, 1H),
0.82 (d, J＝6.4 Hz, 3H); 13C NMR (100 MHz, CDCl3) δ:
211.5, 153.9, 153.7, 131.1, 129.4, 128.4, 128.3, 126.2,
124.2, 123.9, 123.3, 117.0, 116.8, 60.5, 42.0, 37.1, 36.0,
3-(9H-Xanthen-9-yl)dihydro-2H-pyran-4(3H)-one
(3g): White solid; H NMR (400 MHz, CDCl3) δ: 7.38
1
(d, J＝7.2 Hz, 1H), 7.26－7.22 (m, 3H), 7.11－7.03 (m,
4H), 4.92 (d, J＝3.6 Hz, 1H), 4.07 (t, J＝8.6 Hz, 1H),
3.91－3.86 (m, 1H), 3.57 (td, J＝11.6, 3.6 Hz, 1H),
3.23 (t, J＝10.8 Hz, 1H), 2.78－2.74 (m, 1H), 2.61－
2.53 (m, 1H), 2.44 (dt, J＝15.2, 3.2 Hz, 1H); 13C NMR
(100 MHz, CDCl3) δ: 207.0, 153.8, 153.5, 130.8, 129.1,
128.9, 128.7, 125.0, 124.4, 124.1, 122.6, 117.2, 117.1,
69.3, 68.6, 60.9, 43.0, 35.6; HRMS (EI-TOF) m/z: calcd
for C18H16O3 280.1099, found 280.1101.
1
35.2, 32.2, 22.1; High polar diastereomer (Minor): H
NMR (400 MHz, CDCl3) δ: 7.32 (d, J＝7.6 Hz, 1H),
7.23－7.18 (m, 3H), 7.09－7.01 (m, 4H), 4.80 (d, J＝
4.4 Hz, 1H), 2.63－2.58 (m, 1H), 2.41－2.30 (m, 2H),
1.92－1.88 (m, 1H), 1.81－1.75 (m, 1H), 1.56－1.46
(m, 2H), 1.42－1.38 (m, 1H), 0.91 (d, J＝5.8 Hz, 3H);
13C NMR (100 MHz, CDCl3) δ: 211.9, 153.4, 153.0,
130.0, 128.3, 127.9, 127.8, 125.1, 123.5, 123.2, 122.9,
116.4, 116.3, 55.9, 38.4, 38.1, 33.4, 32.4, 26.5, 18.9;
HRMS (EI-TOF) m/z: calcd for C20H20O2 292.1463,
found 292.1465.
1-(9H-Xanthen-9-yl)propan-2-one (3h):[17] White
1
solid; H NMR (400 MHz, CDCl3) δ: 7.27－7.20 (m,
4H), 7.11－7.03 (m, 4H), 4.62 (t, J＝6.4 Hz, 1H), 2.82
(d, J＝6.8 Hz, 2H), 1.98 (s, 3H); 13C NMR (100 MHz,
CDCl3) δ: 206.6, 152.2, 128.6, 127.9, 125.2, 123.5,
116.5, 54.3, 34.4, 31.1; MS (EI) m/z: 238 (M＋), 194,
182, 165, 152.
3-(9H-Xanthen-9-yl)butan-2-one (3i):[14] Colorless
oil; 1H NMR (400 MHz, CDCl3) δ: 7.26－7.21 (m, 2H),
7.18－7.11 (m, 4H), 7.05 (t, J＝7.2 Hz, 2H), 4.34 (d,
J＝6.8 Hz, 1H), 2.78－2.71 (m, 1H), 1.93 (s, 3H), 0.91
(d, J＝7.2 Hz, 3H); 13C NMR (100 MHz, CDCl3) δ:
212.4, 153.8, 153.7, 130.2, 129.4, 128.7, 128.6, 125.4,
124.2, 123.7, 123.6, 117.2, 55.4, 42.5, 31.2, 13.9; MS
(EI) m/z: 252 (M＋), 194, 182, 165, 152.
4-tert-Butyl-2-(9H-xanthen-9-yl)cyclohexanone (3e):
White solid, dr ＝ 3 ∶ 1. Low polar diastereomer
(Major):[16] 1H NMR (400 MHz, CDCl3) δ: 7.37 (dd,
J＝7.6, 1.2 Hz, 1H), 7.25－7.17 (m, 3H), 7.08－7.00
(m, 4H), 4.91 (d, J＝3.6 Hz, 1H), 2.52 (dt, J＝8.0, 4.4
Hz, 1H), 2.40 (m, 1H), 2.29－2.20 (m, 1H), 1.96－1.89
(m, 1H), 1.78－1.72 (m, 1H), 1.38－1.19 (m, 2H), 0.94
－0.85 (m, 1H), 0.71 (s, 9H); 13C NMR (100 MHz,
CDCl3) δ: 211.9, 154.0, 153.7, 130.9, 129.4, 128.5,
128.3, 126.2, 124.1, 123.8, 123.5, 116.9, 116.7, 60.4,
47.0, 42.1, 37.6, 33.1, 29.1, 28.1, 28.0; High polar di-
3-Methyl-3-(9H-xanthen-9-yl)butan-2-one
(3j):
White solid; 1H NMR (400 MHz, CDCl3) δ: 7.25 (t, J＝
6.6 Hz, 2H), 7.13 (d, J＝6.4 Hz, 4H), 7.05 (t, J＝7.2 Hz,
2H), 4.38 (s, 1H), 1.96 (s, 3H), 0.97 (s, 6H); 13C NMR
(100 MHz, CDCl3) δ: 215.7, 154.5, 130.7, 128.7, 123.6,
123.2, 117.2, 55.0, 47.2, 28.9, 22.5; HRMS (EI-TOF)
m/z: calcd for C18H18O2 266.1307, found 266.1303.
3-(9H-Xanthen-9-yl)pentan-2-one (3k): Colorless oil;
1H NMR (400 MHz, CDCl3) δ: 7.27－7.21 (m, 2H),
7.16－7.02 (m, 6H), 4.08 (d, J＝8.4 Hz, 1H), 2.70－
2.64 (m, 1H), 1.76 (s, 3H), 1.63－1.53 (m, 1H), 1.40－
1.30 (m, 1H), 0.71 (t, J＝7.4 Hz, 3H); 13C NMR (100
MHz, CDCl3) δ: 212.5, 153.2, 129.5, 128.8, 128.0,
127.9, 124.7, 124.1, 123.4, 123.0, 116.7, 116.6, 61.1,
1
astereomer (Minor): H NMR (400 MHz, CDCl3) δ:
7.25－7.01 (m, 8H), 4.66 (d, J＝6.0 Hz, 1H), 2.57－
2.52 (m, 1H), 2.46－2.41 (m, 1H), 2.34－2.25 (m, 1H),
1.88－1.85 (m, 1H), 1.65－1.62 (m, 1H), 1.43－1.28
(m, 2H), 0.89－0.84 (m, 1H), 0.73 (s, 9H); 13C NMR
(100 MHz, CDCl3) δ: 213.7, 153.3, 153.1, 129.6, 128.1,
128.1, 128.0, 124.6, 123.5, 123.0, 122.9, 116.7, 116.5,
56.7, 41.5, 40.1, 39.8, 32.9, 27.1, 25.4, 24.9; HRMS
Chin. J. Chem. 2014, 32, 1176—1182
© 2014 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.cjc.wiley-vch.de
1177

Zhu et al.
NOTE
42.7, 33.2, 22.8, 11.9; HRMS (EI-TOF) m/z: calcd for
C18H18O2 266.1307, found 266.1306.
1,2-Diphenyl-2-(9H-xanthen-9-yl)ethanone (3r):[20]
White solid; 1H NMR (400 MHz, CDCl3) δ: 7.70 (d, J＝
7.6 Hz, 2H), 7.41－7.35 (m, 2H), 7.25 (t, J＝7.6 Hz,
2H), 7.16－7.09 (m, 7H), 7.03－6.95 (m, 3H), 6.68－
6.64 (m, 1H), 6.44 (d, J＝7.2 Hz, 1H), 4.85 (d, J＝9.6
Hz, 1H), 4.67 (d, J＝9.6 Hz, 1H); 13C NMR (100 MHz,
CDCl3) δ: 199.1, 153.6, 153.5, 137.3, 136.3, 132.8,
130.0, 129.6, 129.1, 128.5, 128.4, 128.3, 127.8, 127.5,
127.4, 125.6, 124.0, 123.3, 122.5, 116.5, 116.0, 61.1,
43.7; MS (ESI) m/z: 399.1 [M＋Na]＋.
2-(9H-Xanthen-9-yl)pentan-3-one (3l):[15] Colorless
oil; 1H NMR (400 MHz, CDCl3) δ: 7.26－7.20 (m, 2H),
7.16－7.11 (m, 4H), 7.08－7.01 (m, 2H), 4.23 (d, J＝
8.4 Hz, 1H), 2.76－2.69 (m, 1H), 2.26－2.16 (m, 1H),
1.96－1.86 (m, 1H), 0.92 (d, J＝6.8 Hz, 3H), 0.86 (t,
J＝7.2 Hz, 3H); 13C NMR (100 MHz, CDCl3) δ: 215.0,
153.8, 153.6, 130.3, 129.4, 128.6, 128.5, 125.7, 124.2,
124.0, 123.7, 117.2, 54.0, 49.1, 37.5, 14.6, 8.0; MS (EI)
m/z: 266 (M＋), 194, 182, 165, 152.
2-(9H-Xanthen-9-yl)propanal (3s):[21] Colorless oil;
1H NMR (400 MHz, CDCl3) δ: 9.76 (s, 1H), 7.27－7.23
(m, 3H), 7.12－7.05 (m, 5H), 4.62 (d, J＝3.6 Hz, 1H),
2.71－2.64 (m, 1H), 0.91 (d, J＝7.6 Hz, 3H); 13C NMR
(100 MHz, CDCl3) δ: 204.4, 153.8, 153.6, 129.7, 129.2,
129.0, 128.9, 124.2, 124.1, 124.0, 122.1, 117.3, 56.5,
40.3, 10.1; MS (EI) m/z: 238 (M＋), 194, 181, 165, 152.
2-(9H-Xanthen-9-yl)butanal (3t):[21] Colorless oil;
1H NMR (400 MHz, CDCl3) δ: 9.64 (d, J＝2.4 Hz, 1H),
7.27－7.20 (m, 3H), 7.12－7.04 (m, 5H), 4.46 (d, J＝
4.8 Hz, 1H), 2.48－2.43 (m, 1H), 1.58－1.38 (m, 2H),
0.81 (t, J＝7.4 Hz, 3H); 13C NMR (100 MHz, CDCl3) δ:
204.6, 153.0, 152.9, 129.0, 128.7, 128.3, 128.3, 123.5,
123.4, 123.2, 122.2, 116.8, 116.7, 62.4, 40.0, 18.7, 12.0;
MS (EI) m/z: 252 (M＋), 196, 181, 165, 152.
1-4-Tolyl-2-(9H-xanthen-9-yl)ethanone
(3m):[18]
White solid; 1H NMR (400 MHz, CDCl3) δ: 7.70 (d, J＝
8.4 Hz, 2H), 7.31 (d, J＝8.0 Hz, 2H), 7.22－7.15 (m,
4H), 7.11 (d, J＝8.4 Hz, 2H), 7.01 (t, J＝7.4 Hz, 2H),
4.84 (t, J＝6.6 Hz, 1H), 3.31 (d, J＝6.8 Hz, 2H), 2.35 (s,
3H); 13C NMR (100 MHz, CDCl3) δ: 198.2, 153.0,
144.6, 135.2, 129.9, 129.5, 128.9, 128.5, 126.3, 124.1,
117.2, 50.3, 35.3, 22.3; MS (EI) m/z: 314 (M＋), 194,
182, 165, 152.
1-(4-Methoxyphenyl)-2-(9H-xanthen-9-yl)ethanone
1
(3n):[19] White solid; H NMR (400 MHz, CDCl3) δ:
7.78 (dd, J＝7.2, 2.0 Hz, 2H), 7.31 (dd, J＝7.6, 1.2 Hz,
2H), 7.20 (td, J＝8.0, 1.2 Hz, 2H), 7.11 (dd, J＝8.0, 0.8
Hz, 2H), 7.01 (td, J＝7.6, 1.2 Hz, 2H), 6.83 (dd, J＝9.2,
2.0 Hz, 2H), 4.83 (t, J＝6.6 Hz, 1H), 3.82 (s, 3H), 3.29
(d, J＝6.4 Hz, 2H); 13C NMR (100 MHz, CDCl3) δ:
196.4, 163.5, 152.3, 130.4, 130.2, 128.9, 127.8, 125.7,
123.4, 116.5, 113.7, 55.5, 49.4, 34.8; MS (EI) m/z: 330
(M＋), 194, 181, 165, 152.
2-(9H-Xanthen-9-yl)pentanal (3u):[21] Colorless oil;
1H NMR (400 MHz, CDCl3) δ: 9.63 (d, J＝2.8 Hz, 1H),
7.27－7.21 (m, 3H), 7.12－7.04 (m, 5H), 4.46 (d, J＝
4.0 Hz, 1H), 2.56－2.51 (m, 1H), 1.56－1.47 (m, 1H),
1.37－1.21 (m, 2H), 1.15－1.07 (m, 1H), 0.77 (t, J＝7.0
Hz, 3H); 13C NMR (100 MHz, CDCl3) δ: 205.3, 153.6,
153.6, 129.6, 129.4, 129.0, 128.9, 124.2, 124.1, 123.7,
122.8, 117.4, 117.3, 61.2, 40.7, 28.2, 21.4, 14.6; MS (EI)
m/z: 266 (M＋), 194, 181, 165, 152.
1-Phenyl-2-(9H-xanthen-9-yl)ethanone
(3o):[17]
White solid; 1H NMR (400 MHz, CDCl3) δ: 7.80 (d, J＝
8.0 Hz, 2H), 7.49 (t, J＝7.2 Hz, 1H), 7.37 (t, J＝7.6 Hz,
2H), 7.32 (d, J＝7.6 Hz, 2H), 7.21 (t, J＝7.4 Hz, 2H),
7.11 (d, J＝8.0 Hz, 2H), 7.02 (t, J＝7.6 Hz, 2H), 4.85 (t,
J＝6.6 Hz, 1H), 3.65 (d, J＝6.8 Hz, 2H); 13C NMR (100
MHz, CDCl3) δ: 198.6, 153.0, 137.6, 133.8, 129.5,
129.2, 128.7, 128.5, 126.2, 124.1, 117.2, 50.4, 35.3; MS
(EI) m/z: 300 (M＋), 194, 181, 165, 152.
2-(9H-Xanthen-9-yl)hexanal (3v):[21] Colorless oil;
1H NMR (400 MHz, CDCl3) δ: 9.63 (d, J＝2.8 Hz, 1H),
7.27－7.20 (m, 3H), 7.12－7.04 (m, 5H), 4.46 (d, J＝
4.8 Hz, 1H), 2.54－2.49 (m, 1H), 1.57－1.47 (m, 1H),
1.39－1.32 (m, 1H), 1.20－1.08 (m, 4H), 0.76 (t, J＝7.0
Hz, 3H); 13C NMR (100 MHz, CDCl3) δ: 203.7, 152.0,
151.9, 127.9, 127.7, 127.3, 127.2, 122.5, 122.4, 122.1,
121.2, 115.8, 115.7, 59.6, 39.1, 28.6, 24.1, 21.5, 12.7;
MS (EI) m/z: 280 (M＋), 196, 181, 165, 152.
1-(4-Chlorophenyl)-2-(9H-xanthen-9-yl)ethanone
1
(3p): Yellowish solid; H NMR (400 MHz, CDCl3) δ:
7.72 (d, J＝8.4 Hz, 2H), 7.33 (d, J＝8.4 Hz, 2H), 7.30
(d, J＝7.6 Hz, 2H), 7.21 (t, J＝7.6 Hz, 2H), 7.12 (d, J＝
8.0 Hz, 2H), 7.02 (d, J＝7.4 Hz, 2H), 4.82 (t, J＝6.8 Hz,
1H), 3.30 (d, J＝6.4 Hz, 2H); 13C NMR (100 MHz,
CDCl3) δ: 196.8, 152.3, 139.6, 135.3, 129.5, 128.8 (2C),
128.0, 125.3, 123.5, 116.6, 49.6, 34.9; HRMS m/z: calcd
for C21H15ClO2 334.0761, found 334.0763.
1-(4-Nitrophenyl)-2-(9H-xanthen-9-yl)ethanone
(3q):[18] Yellowish solid; 1H NMR (400 MHz, CDCl3) δ:
8.19 (dd, J＝6.8, 2.0 Hz, 2H), 7.89 (dd, J＝6.8, 2.0 Hz,
2H), 7.29 (dd, J＝7.6, 1.6 Hz, 2H), 7.22 (td, J＝8.4, 1.6
Hz, 2H), 7.12 (dd, J＝8.4, 1.2 Hz, 2H), 7.03 (td, J＝7.2,
1.2 Hz, 2H), 4.82 (t, J＝6.6 Hz, 1H), 3.37 (d, J＝6.4 Hz,
2H); 13C NMR (100 MHz, CDCl3) δ: 196.7, 152.4,
150.2, 141.3, 129.1, 128.6, 128.2, 124.9, 123.7, 123.6,
116.7, 49.9, 35.1; MS (EI) m/z: 345 (M＋), 194, 182, 165,
152.
2-(9H-Xanthen-9-yl)heptanal (3w):[21] Colorless oil;
1H NMR (400 MHz, CDCl3) δ: 9.63 (d, J＝2.4 Hz, 1H),
7.27－7.20 (m, 3H), 7.12－7.04 (m, 5H), 4.46 (d, J＝
4.0 Hz, 1H), 2.54－2.49 (m, 1H), 1.56－1.47 (m, 1H),
1.39－1.31 (m, 1H), 1.23－1.11 (m, 6H), 0.79 (t, J＝6.8
Hz, 3H); 13C NMR (100 MHz, CDCl3) δ: 205.4, 153.6,
153.6, 129.6, 129.4, 129.0, 128.9, 124.2, 124.1, 123.8,
122.8, 117.4, 117.3, 61.3, 40.7, 32.3, 27.8, 26.0, 23.0,
14.6; MS (EI) m/z: 294 (M＋), 194, 181, 165, 152.
2-(9H-Xanthen-9-yl)octanal (3x):[21] Colorless oil;
1H NMR (400 MHz, CDCl3) δ: 9.63 (d, J＝2.8 Hz, 1H),
7.27－7.20 (m, 3H), 7.12－7.04 (m, 5H), 4.46 (d, J＝
4.8 Hz, 1H), 2.54－2.49 (m, 1H), 1.54－1.11 (m, 10H),
0.81 (t, J＝7.0 Hz, 3H); 13C NMR (100 MHz, CDCl3) δ:
204.7, 153.0, 152.9, 128.9, 128.7, 128.3, 128.3, 123.5,
1178
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© 2014 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Chin. J. Chem. 2014, 32, 1176—1182

Direct Coupling Reaction of Diaryl Methanol with Ketones or Aldehydes Catalyzed by AlCl3
123.4, 123.1, 122.2, 116.8, 116.7, 60.6, 40.1, 31.5, 29.1,
27.4, 25.4, 22.5, 14.0; MS (EI) m/z: 308 (M＋), 194, 182,
165, 152.
Table 1 Optimizing of coupling reaction of xanthenol 1 with
cychohexanone 2aa
3-Phenyl-2-(9H-xanthen-9-yl)propanal
(3y):[21]
OH
O
White solid; 1H NMR (400 MHz, CDCl3) δ: 9.65 (s, 1H),
7.28－7.26 (m, 3H), 7.21－7.06 (m, 8H), 6.97 (d, J＝
7.2 Hz, 2H), 4.60 (d, J＝3.6 Hz, 1H), 3.00－2.95 (m,
1H), 2.83－2.77 (m, 1H), 2.72－2.68 (m, 1H); 13C
NMR (100 MHz, CDCl3) δ: 204.3, 153.6, 153.5, 139.4,
129.7, 129.5, 129.3, 129.2, 129.1, 128.9, 127.0, 124.4,
124.2, 123.3, 122.4, 117.5, 117.5, 63.1, 40.2, 31.9; MS
(EI) m/z: 314 (M＋), 196, 181, 168, 152.
O
Lewis acid
solvent, r.t.
+
O
O
3a
2a
1
Entry
1
2c
Cat.
FeCl3
Lewis acids
BiCl3
AlCl3
－
Solvent
Time/h
12
12
12
12
12
12
12
12
12
12
12
12
8
Yieldb/%
18
Et2O
Et2O
Et2O
Et2O
Et2O
DCE
THF
trace
20
2-(9H-Thioxanthen-9-yl)cyclohexanone
(5a):[22]
3
White solid; 1H NMR (400 MHz, CDCl3) δ: 7.62 (d, J＝
7.2 Hz 1H), 7.43－7.37 (m, 2H), 7.25－7.11 (m, 5H),
4.68 (d, J＝9.2 Hz, 1H), 3.15－3.08 (m, 1H), 2.35－
2.32 (m, 1H), 2.23－2.15 (m, 1H), 2.00－1.97 (m, 1H),
1.75－1.72 (m, 1H), 1.67－1.45 (m, 2H), 1.38－1.35
(m, 1H), 1.26－1.16 (m, 1H); 13C NMR (100 MHz,
CDCl3) δ: 212.0, 138.5, 136.6, 133.7, 132.7, 130.9,
130.2, 127.2, 127.1, 126.6, 126.3, 126.3, 126.2, 50.4,
47.3, 43.2, 33.9, 28.9, 25.2; MS (EI) m/z: 294 (M＋), 221,
198, 165, 152.
4
39
5
－
6
AlCl3
AlCl3
AlCl3
AlCl3
AlCl3
AlCl3
AlCl3
AlCl3
AlCl3
AlCl3
AlCl3
－
7
68
8
Dioxane
DMF
MeOH
MeCN
EA
62
9
66
10
11
12
13d
14e
15f
16g
15
13
2-(9H-Thioxanthen-9-yl)propanal (5s):[2a] Colorless
36
1
oil; H NMR (400 MHz, CDCl3) δ: 9.54 (d, J＝2.0 Hz,
THF
76
1H), 7.46－7.42 (m, 2H), 7.31－7.20 (m, 6H), 4.26 (d,
J＝10.0 Hz, 1H), 3.22－3.14 (m, 1H), 0.88 (d, J＝7.2
Hz, 3H); 13C NMR (100 MHz, CDCl3) δ: 203.8, 135.9,
135.3, 133.1, 133.0, 130.0, 129.7, 127.5, 127.3, 127.0,
126.6, 126.4, 50.5, 45.7, 12.9; MS (EI) m/z: 254 (M＋),
197, 184, 165, 152.
THF
2
88
THF
2
82
THF
2
88
a A mixture of xanthydrol 1 (0.2 mmol), 2a (0.6 mmol), catalyst
(0.02 mmol) in solvent (2 mL) was stirred for the time indicated
b
c
at room temperature. Isolated yields. CuCl2, ZnCl2, InCl3,
Cu(OTf)2, Yb(OTf)3, Zn(OAc)2 were used as catalysts. d 20 mol%
Results and discussion
e
f
AlCl3. 30 mol% AlCl3. 2 equiv. 2a. g Reaction temperature was
Initially, 9H-xanthen-9-ol 1 as a diaryl methanol,
and cyclohexanone 2a were chosen as model substrates
to explore and optimize their coupling reaction. When
FeCl3 (10 mol%) was used as a Lewis acid catalyst, the
coupling reaction of xanthenol 1 with cyclohexanone 2a
occurred in Et2O at room temperature, affording the
desired product 3a in 18% yield (Table 1, Entry 1). En-
couraged by this result, other Lewis acids were exam-
ined, but most of them did not work well, and gave a
trace amount of desired product 3a (Table 1, Entry 2;
also see SI). BiCl3 gave a slightly higher yield (Table 1,
Entry 3). We were pleased to find AlCl3 had the best
catalytic activity to give 3a in 39% yield (Table 1, Entry
4). No reaction took place without the Lewis catalyst
(Table 1, Entry 5). Using AlCl3 as a catalyst, the reac-
tion was further optimized by screening different sol-
vents.
When 1,2-dichloroethane was employed as a solvent,
no 3a was observed (Table 1, Entry 6). The yield of 3a
could be dramatically improved when THF was used
(Table 1, Entry 7). Using DMF or dioxane as a solvent
led to a slight decrease in yield (Table 1, Entries 8－9),
and other solvents led to remarkable decrease in yields
(Table 1, Entries 10－12). When the loading of AlCl3
40 ℃.
was increased to 30 mol%, the yield of 3a was im-
proved to 88% (Table 1, Entries 13－14). To elevate the
reaction temperature to 40 ℃ had no effect on the yield
of 3a (Table 1, Entry 16). Thus, the optimized reaction
should be performed by the catalysis of 30 mol% AlCl3
in THF at room temperature.
Under the optimized conditions, we examined the
scope of the coupling reaction of xanthenol 1. It was
found that various aliphatic cyclic ketones 2a－2g com-
pleted the coupling reaction with xanthenol 1 in only 2 h,
affording the desired products 3a－3g in good yields
(Table 2, Entries 1－7). Using acetone 2h also resulted
in the expected product 3h in a good yield (Table 2,
Entry 8). Interestingly, the reaction was highly regiose-
lective for the nonsymmetric ketones 2i, 2j and 2k, and
the C－C bonds formed only at more substituted
α-carbon of ketones 2i, 2j and 2k to give the correspon-
ding products 3i, 2j and 3k (Table 2, Entries 9－11).
This result is consistent with the formation of a stable
enol under Lewis acid catalysis. Various aromatic ke-
tones 2m－2r were also suitable to the transformation
(Table 2, Entries 13－18). Even 1,2-di-phenylethanone
Chin. J. Chem. 2014, 32, 1176—1182
© 2014 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.cjc.wiley-vch.de
1179

Zhu et al.
NOTE
Table 2 Coupling reaction of xanthenol 1 with ketones 2a－2r or aldehydes 2s－2ya
Entry
Time/h
Product
3a
Yieldb/%
Entry
14
Time/h
5
Product
3n
Yieldb/%
O
O
OMe
1
2
3
4
5
6
7
2
2
2
2
2
2
2
88
74
70
68
61
61
85
62
2a
2b
2n
O
O
86
15
6
3b
3o
2o
O
Cl
O
82
16
20
3c
3p
2p
2c
O
Me
t-Bu
Ph
O
NO2
84c,d
85c,e
80c,e
87
17
20
3d
3q
2d
2q
O
O
Ph
18
20
3e
3r
Ph
2r
2e
O
O
19
12
3f
3s
2s
2f
O
O
O
20
12
3g
3t
2t
2g
O
O
O
O
O
O
2
8
12
12
12
12
12
80
74
60
69
48
21
22
23
24
25
12
12
12
12
12
78
71
65
75
74
3h
3i
3u
3v
3w
3x
3y
2h
2i
2u
3
9
2v
O
4
10
11
12
3j
3k
3l
2j
2w
O
5
2k
2l
2x
O
Ph
O
2y
O
Me
13
5
73
3m
2m
a A mixture of xanthydrol 1 (0.2 mmol), aldehydes or ketones 2 (0.6 mmol), catalyst (0.02 mmol) in THF (2 mL) was stirred at room
temperature. b Isolated yields. c Diastereoselectivity was determined by 1H NMR spectroscopic analysis. d dr＝2∶1. e dr＝3∶1.
1180
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© 2014 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Chin. J. Chem. 2014, 32, 1176—1182

Direct Coupling Reaction of Diaryl Methanol with Ketones or Aldehydes Catalyzed by AlCl3
2r, which has a bulky phenyl group at α-position, also
led to coupling product 3r in a 61% yield (Table 2, En-
try 18). The aromatic methyl ketones bearing electron-
rich groups on benzene rings 2m－2n led to better
yields than those bearing electron-deficient groups 2p－
2q (Table 2, Entries 13－14 vs. 16－17). Furthemore,
we also found that various aldehydes 2s－2y could per-
form the coupling reaction expediently with xanthenol 1
to give the desired products 3s－3y in satisfactory
yields (Table 2, Entries 19－25).
Further investigation indicated that diphenyl metha-
nol did not undergo the coupling reaction with ketone or
aldehyde 2. The reason may be that the less stablility of
diphenyl methyl carbocation made carbon-oxygen bond
in diaryl methanol more difficult to be broken as com-
pared to that of xanthenol 1. However, 9H-thioxanthen-
9-ol 4 was suitable to this transformation as expected.
Our experiment demonstrated that under the above op-
timized conditions, both ketone 2a and aldehyde 2s
performed the coupling reaction expediently with
9H-thioxanthen-9-ol 4 to give the desired products 5a
and 5s in 68% and 56% yields, respectively.
Scheme 2 Plausible mechanism
R1
OH
R2
O
O
1
+
H2O
AlCl3
O
3
AlCl3
H
R1
-
O
O
HOAlCl3
R2
+
OH
-
HOAlCl3
O
+
8
O
O
OH
R1
R1
6
AlCl3
O
R2
2
R2
AlCl3
R1
7
H
R2
Scheme 1 Coupling reaction of 9H-thioxanthen-9-ol 4 with
ketone 2a or aldehyde 2s
as a Lewis acid to activate both diaryl methanol and
ketone or aldehyde is proposed. Further studies on di-
rect coupling reactions of other alcohols with ketones or
aldehydes by the catalysis of Lewis acids, the mecha-
nisms and asymmetric versions are currently under way.
OH
O
30 mol% AlCl3
THF, r.t.
O
+
S
Acknowledgement
Yield = 68%
2a
4
S
5a
Financial supports from MOST of China (973 pro-
gram 2011 CB808600) and National Natural Science
Foundation of China (Nos. 21072091 and 21372195)
are gratefully acknowledged.
OH
O
30 mol% AlCl3
+
O
THF, r.t.
S
S
Yield = 56%
2s
4
5s
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© 2014 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.cjc.wiley-vch.de
1181

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(Pan, B.; Fan, Y.)
1182
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Chin. J. Chem. 2014, 32, 1176—1182