Br?nsted acid ionic liquid-catalyzed direct benzylation, allylation and propargylation of 1,3-dicarbonyl compounds with alcohols as well as one-pot synthesis of 4H-chromenes

Article abstract of DOI:10.1016/j.tet.2009.07.012

Recyclable ionic Br?nsted acid was prepared in nearly quantitative yield by reacting 1-butylimidazole with an equimolar amount of 1,3-propanesultone, followed by treatment with an equimolar amount of trifluoromethanesulfonic acid. The ionic Br?nsted acid-catalyzed direct benzylation, allylation and propargylation of 1,3-dicarbonyl compounds with various alcohols in ionic liquid [N-ethyl-N-methyl imidazolium trifluoromethanesulfonate (EMIOTf)], at 100 °C for 3 h proceeded smoothly to give the corresponding products in good to excellent yields without the use of any hazardous or volatile solvents and without any by-product such as salts. Furthermore, tandem benzylation-cyclization-dehydration of 1,3-dicarbonyl compounds to give functionalized 4H-chromenes was also achieved in this catalytic reaction.

Full text of DOI:10.1016/j.tet.2009.07.012

Tetrahedron 65 (2009) 7457–7463
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
¨
Bronsted acid ionic liquid-catalyzed direct benzylation, allylation
and propargylation of 1,3-dicarbonyl compounds with alcohols
as well as one-pot synthesis of 4H-chromenes
*
Kazumasa Funabiki , Takuya Komeda, Yasuhiro Kubota, Masaki Matsui
Department of Materials Science and Technology, Faculty of Engineering, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
Recyclable ionic Bro¨nsted acid was prepared in nearly quantitative yield by reacting 1-butylimidazole with
an equimolar amount of 1,3-propanesultone, followed by treatment with an equimolar amount of tri-
fluoromethanesulfonic acid. The ionic Bro¨nsted acid-catalyzed direct benzylation, allylation and prop-
argylation of 1,3-dicarbonyl compounds with various alcohols in ionic liquid [N-ethyl-N-methyl
imidazolium trifluoromethanesulfonate (EMIOTf)], at 100 ꢀC for 3 h proceeded smoothly to give the cor-
responding products in good to excellent yields without the use of any hazardous or volatile solvents and
without any by-product such as salts. Furthermore, tandem benzylation–cyclization–dehydration of 1,3-
dicarbonyl compounds to give functionalized 4H-chromenes was also achieved in this catalytic reaction.
Ó 2009 Elsevier Ltd. All rights reserved.
Received 14 April 2009
Received in revised form 3 July 2009
Accepted 3 July 2009
Available online 8 July 2009
Keywords:
Ionic Bro¨nsted acid catalyst
Substitution
1,3-Dicarbonyl compounds
Alcohol
1. Introduction
development of a much more convenient, reusable, environmentally
friendly system for the catalytic alkylation of 1,3-dicarbonyl com-
The alkylation of 1,3-dicarbonyl compounds usually requires not
only the transformation of 1,3-dicarbonyl compounds into more re-
active species, such as enolates by reacting the 1,3-dicarbonyl com-
pounds with base, but also the use of alkyl halides, since the hydroxyl
group is not a good leaving group and 1,3-dicarbonyl compounds do
not have high nucleophilicity. However, these requirements are
limitations, as is the production of a salt as a by-product.
pounds without the use of any hazardous or volatile solvents is needed.
In this report, for the first time, we presentour recyclableBro¨nsted
acid-catalyzed direct benzylation, allylation and propargylation of
1,3-dicarbonyl compounds with various alcohols as well as the tan-
dem benzylation–cyclization–dehydration of 1,3-dicarbonyl com-
pounds to give functionalized 4H-chromene in an ionic liquid system.
From the standpoint of atom-economical and environmentally
friendly chemistry, the catalytic direct carbon–carbon bond formation
of 1,3-dicarbonyl compounds using alcohols in place of alkyl halides is
one of the most ideal and salt-free reactions in organic synthesis, since
steps are not needed for the generation of reactive enolate or for pre-
conversion to the alkyl halides, and only water is generated as a by-
product. Although some excellent catalysts, such as indium trichloride,1
proton-exchanged montmorillonite,2 trifluoromethanesulfonic acid,3
p-toluenesulfonic acid,3,4 polymer-supported p-toluenesulfonic acid,4
metal triflate,5 iron(III) chloride6 and hetropolyacid7 have recently been
examined for catalytic direct carbon–carbon bond formation in active
methylene compounds using alcohols as alkylating reagents, most of
the reported reactions require hazardous or volatile solvents, such as
nitromethane, dichloromethane, acetonitrile and toluene, and the re-
covery and reuse of the catalysts far are still limited.2,4,5b Therefore, the
2. Results and discussion
¨
2.1. Preparation of Bronsted acid ionic liquid catalyst 1
Recyclable Bronsted acid ionic liquid catalyst 1, which was used
for esterification, was prepared by modification of the method
reported by Forbes et al.8 as shown in Scheme 1. 1-Butylimidazole
¨
O
SO2
(1 equiv.)
n-Bu
n-Bu
n-Bu
N
N
N
N
N
SO3
neat
rt, 20 min
(98%)
CF3SO3H
(1 equiv.)
N
SO3H
neat
TfO
150 °C, 5 h
1 (97%)
* Corresponding author. Tel.: þ81 293 2599; fax: þ81 293 2794.
E-mail address: funabiki@gifu-u.ac.jp (K. Funabiki).
Scheme 1. Preparation of Bro¨nsted acid ionic liquid catalyst 1.
0040-4020/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2009.07.012

7458
K. Funabiki et al. / Tetrahedron 65 (2009) 7457–7463
¨
was allowed to react with an equimolar amount of 1,3-propane-
sultone at room temperature to produce zwitterionic imidazolium
salt in quantitative yield. Treatment of this zwitterionic imidazo-
lium salt with an equimolar amount of trifluoromethanesulfonic
acid at 150 ꢀC gave the Bro¨nsted acid ionic liquid catalyst 1 in
quantitative yield.
2.2. Bronsted acid ionic liquid 1-catalyzed direct benzylation,
allylation and propargylation of 1,3-dicarbonyl compounds 2
with alcohols 3
The reaction of 2,4-pentanedione (2a) with 1-phenylethanol
(3a) was conducted in the presence of 5 mol % of the prepared
Bro¨nsted acid ionic liquid catalyst 1 in a commerciallyavailable ionic
liquid, N-ethyl-N-methyl imidazolium trifluoromethanesulfonate
(EMIOTf), at 100 ꢀC for 3 h. After the mixture was allowed to cool to
room temperature, repeated extraction with a mixed solvent of
diethyl ether and hexane (v/v¼1:1) from EMIOTf, evaporation under
vacuum, and chromatography with silica gel gave 3-(1-phenyl-
ethyl)pentane-2,4-dione (4aa) in 77% yield, together with a small
amount (7%) of (E)-but-1-ene-1,3-diyldibenzene (5) (styrene dim-
mer) (Table 1, entry 1).
Other ionic liquids carrying other counter anions, such as
N-butyl-N-methylimidazolium tetrafluoroborate (BMIBF4) and
N-butyl-N-methylimidazolium hexafluorophosphite (BMIPF6),
were used (entries 2 and 3). As a result, in the case of BMIBF4, only
trace amount of the product 4aa was formed, and 1,10-oxybis-
Table 1
Bro¨nsted acid ionic liquid 1-catalyzed direct benzylation, allylation and prop-
argylation of 1,3-diketones 2a,b with various alcohols 3
O
O
O
O
OH
R4
1 (5 mol%)
+
R1
R2
R1
R2
R3
EMIOTf,
2
3
R3
R4
100 °C, 3 h
4
1
2
3a R3 = Ph, R4 = Me
3b R3 = R4 = Ph
2a
2b
R = R = Me
R
1 = R2 = Ph
3c R3 = (E)-PhCH=CH, R4 = Ph
3d R3 = (E)-MeCH=CH, R4 = Me
3e R3 = PhC C, R4 = Ph
n-Bu
Et
n-Bu
N
N
N
N
N
N
(ethane-1,1-diyl)dibenzene
(bis(1-phenylethyl)
ether)
was
PF6
TfO
BF4
obtained as a main product (33% yield, dr¼50: 50) (entry 2). The
reaction in BMIPF6 proceeded smoothly to give 4aa in 94% yield
(entry 3). Surprisingly, when the ionic liquid catalyst 1 was not
added, the reaction of diketone 2a with alcohol 3a also proceeded
to give the corresponding product 4aa in lower yield (61%), to-
gether with styrene dimmer 5 (20% yield) (entry 4).9 The use of an
equimolar amount of diketone 2a resulted in significant decrease of
the yield (39%) of 4aa (entry 5). Employing trifluoromethansulfonic
acid in place of the Bro¨nsted acid ionic liquid catalyst 1 gave the
similar yield (74%) of 4aa, together with styrene dimmer 5 (8%) as
well as 4-phenylpentan-2-one (20%) (entry 6).
The results of the Bro¨nsted acid ionic liquid 1-catalyzed reaction of
1,3-diketones 2, such as 2,4-pentanedione (2a) and 1,3-diphenyl-
propane-1,3-dione (2b), with various alcohols, such as 1-phenyl-
ethanol (3a), diphenylmethanol (3b), (E)-1,3-diphenylprop-2-en-1-ol
(3c), (E)-pent-3-en-2-ol (3d), and 1,3-diphenylprop-2-yn-1-ol (3e) in
EMIOTf, are summarized in Table 1. In the case of diphenylmethanol
(3b), the reaction also proceeded smoothly to give 3-benzhy-
drylpentane-2,4-dione (4ab) in 94% yield (entry 7). Allylation and
propargylation using (E)-1,3-diphenylprop-2-en-1-ol (3c), (E)-pent-
3-en-2-ol (3d) and 1,3-diphenylprop-2-yn-1-ol (3e) also proceeded
to give the corresponding allylated and propargylated diketones 4ac,
4ad and 4ae in 47–90% yields (entries 8–10). 1,3-Diphenylpropane-
1,3-dione (2b) participated well in the reactionwith 1-phenylethanol
(3a) and diphenylmethanol (3b) to produce the corresponding ben-
zylateddiketones4baand 4bbin81–98%yields, withoutformationof
the styrene dimer 5 (entries 11 and 12).
The results of the Bro¨nsted acid ionic liquid-catalyzed reactions
of ethyl 3-oxobutanoate (2c), ethyl 3-oxopentanoate (2d) and ethyl
3-oxo-3-phenylpropanoate (2e) with various alcohols are sum-
marized in Table 2. The use of various alcohols 3a–c,e gave the
corresponding benzylated, allylated and propargylated products
4cb, 4cc and 4ce in 76–91% yields (entries 2–4). However, the re-
action of 2c with 1-phenylethanol (3a) gave the corresponding
ketoester 4ca in 30% yield, together with a moderate amount (40%)
of styrene dimer 5, probably due to lower nucleophilicity of
ketoester 2c than those of diketones 2a,b. Other ketoesters 2d,e
also participated well in the catalytic reaction with alcohol 3b to
give the corresponding products 4db and 4eb in 89–97% yields
(entries 5 and 6). Diastereoselectivities of the products 4ca, 4cc
and 4ce are quite low.
EMIOTf
BMIBF4
BMIPF6
Entry
2
3
Product 4
Yielda (%)
1
2a
3a
3a
3a
3a
3a
3a
4aa
77 (7)
tr (tr)
94 (tr)
61 (20)
39 (22)
74 (8)
O
O
2b
3c
4d
5e
6f
2a
2a
2a
2a
2a
4aa
4aa
4aa
4aa
4aa
Me
Ph
O
Me
Me
O
7
8
9
2a
2a
2a
3b
3c
3d
4ab
4ac
4ad
94
90
47
Me
Ph
Me
Ph
O
O
Me
Ph
Me
Ph
O
O
O
Me
Me
Me
Me
O
Me
Me
Ph
10
11
2a
2b
2b
3e
3a
3b
4ae
4ba
4bb
88
81
98
Ph
O
O
Ph
Ph
Ph
O
Me
O
Ph
Ph
Ph
12
Ph
a
Yields of isolated products. Values in parentheses show the yields of styrene
dimer 5.
b
BMIBF4 was used in place of EMIOTf.1,10-Oxybis (ethane-1,1-diyl) dibenzene was
obtained in 33% yield.
c
BMIPF6 was used in place of EMIOTf.
IL catalyst 1 was not added.
An eqimolar amount of 2a was used.
Trifluoromethanesulfonic acid was used in place of IL catalyst 1. 4-Phenylpentan-
d
e
f
To confirm the reaction mechanism for the formation of styrene
dimer 5, the Bro¨nsted acid ionic liquid-catalyzed reaction of
1-phenylethanol (3a) in EMIOTf in the absence of 1,3-dicarbonyl
compound 2 was carried out, as shown in Scheme 2.
2-one was also obtained in 20% yield.
Ph
Ph
5

K. Funabiki et al. / Tetrahedron 65 (2009) 7457–7463
7459
Table 2
Table 3
Bro¨nsted acid ionic liquid 1-catalyzed direct benzylation, allylation and prop-
argylation of ester 2 with various alcohols 3
Bro¨nsted acid ionic liquid 1-catalyzed tandem direct benzylation, cyclization and
dehydration of 2 with the alcohol 3f
O
O
O
O
OH OH
O
O
OH
R4
1
(5 mol%)
1 (5 mol%)
+
+
R1
OEt
R1
R1
R2
R3
EMIOTf,
OEt
EMIOTf,
100 °C, 3 h
2
100 °C, 3 h
2
3
R3
R4
2a R1 = R2 = Me
2b
3f
2c R1 = Me
2d R11 = Et
3a R33 = Ph, R4 = Me
4
1 = R2 = Ph
4
R
3b
R = R = Ph
2c R1 = Me, R2 = OEt
2d R1 = Et, R2 = OEt
2e
2e
3c R3 = (E)-PhCH=CH, R4 = Ph
R = Ph
3e R3 = PhC C, R4 = Ph
R
1 = Ph, R2 = OEt
Entry
1
2
3
Product 4
Yielda (%) [dr]b
30 (40) [50:50]
O
O
R1
R2
O
O
O
Me
Me
OEt
R2
2c
3a
4ca
4cb
4cc
Ph
O
Me
O
O
6
R1
OH
2
3
2c
2c
3b
3c
91
OEt
Entry
1
2
Product 6
Yielda of 6 (%)
Ph
O
Ph
O
Ph
O
2a
2b
2c
2d
2e
6af
Me
77
Me
Ph
OEt
OEt
76 [51:49]
O
Ph
Me
O
Ph
O
O
2
3
4
6bf
6cf
6df
6ef
Ph
98
84
80
83
Me
4
5
2c
3e
4ce
84 [52:48]
O
Ph
Ph
O
Ph
Ph
OEt
O
O
O
Ph
Me
O
2d
2e
3b
3b
4db
4eb
89
97
Et
OEt
Ph
O
Ph
O
OEt
O
Ph
Et
O
6
Ph
OEt
Ph
Ph
5
OEt
Ph
a
Yields of isolated products. Values in parentheses show the yields of styrene
O
dimer 5.
b
a
Determined by GC.
Yields of isolated products.
OH
Me
Ph
1
(5 mol%)
This catalytic tandem reaction of 3f with diketones 2a,b and
ketoesters 2c,d,e proceeded smoothly to produce the corresponding
4H-chromenes, such as 1-(2-methyl-4-phenyl-4H-chromen-3-yl)-
ethanone (6af),(2,4-diphenyl-4H-chromen-3-yl)(phenyl)methanone
(6bf), ethyl 2-methyl-4-phenyl-4H-chromene-3-carboxylate (6cf),
ethyl 2-ethyl-4-phenyl-4H-chromene-3-carboxylate (6df) and ethyl
2,4-diphenyl-4H-chromene-3-carboxylate (6ef), in good to excellent
yields (77–98%), respectively.
Furthermore, the Bro¨nsted acid ionic liquid-catalyzed reactions
of 1,3-diphenylpropane-1,3-dione (2b) with an equimolar amount
of a highly activated tertiary alkynol, 1,1,3-triphenylprop-2-yn-1-ol
(7), also proceeded smoothly to give not a propargylated product,
but rather a dienyl product, 1,3-diphenyl-2-(1,3,3-triphenylallyli-
dene)propane-1,3-dione (8), in 66% yield, as shown in Scheme 3.
Ph
Me
Ph
EMIOTf, 120 °C, 3 h
3a
5 (50%)
Me
Ph
+
Ph
Me
Ph
Ph
H H
-H+
Scheme 2. Proposed reaction mechanism for the formation of 5.
As a result, styrene dimer 5 was formed as a sole product in 50%
yield. This result can be explained by the following mechanism: (1)
protonation of the hydroxyl group of alcohol 3a and successive
dehydration produces the benzyl cation, and subsequent deproto-
nation gives styrene. (2) The obtained styrene attacks the other
1
(5 mol%)
O
O
O
O
OH
Ph
benzyl cation, and deprotonation at the
b-carbon gives styrene
+
Ph
Ph
Ph
Ph
Ph
EMIOTf,
dimer 5.
Ph
100 °C, 24 h
2b
Ph
7
Ph
After having successfully developed an efficient benzylation of
1,3-diketones 2a,b and ketoesters 2c,d,e, we then sought to apply
this methodology to the synthesis of highly functionalized 4H-
chromene10 via catalytic tandem benzylation, cyclization and de-
hydration of the 2-(hydroxy(phenyl)methyl)phenol (3f), prepared
from salicylaldehyde and phenyllithium, as described in Table 3.
Ph
8 (66%)
Scheme 3. Bro¨nsted acid ionic liquid 1-catalyzed reaction of 1,3-diphenylpropane-1,3-
dione (2b) with tertiary alkynol 7.

7460
K. Funabiki et al. / Tetrahedron 65 (2009) 7457–7463
According to the previous report by Sanz et al.,3b this product
3. Conclusion
could be produced by the tandem Meyer–Schuster rearrangement
of tertiary alkynol 7, aldol condensation with diketone 2b and de-
hydration, as shown in Scheme 4.
In conclusion, we have developed a new recyclable Bro¨nsted acid-
catalyzed direct benzylation, allylation and propargylation of 1,3-
dicarbonyl compounds with various alcohols in an ionic liquid,
N-ethyl-N-methyl imidazolium trifluoromethanesulfonate (EMIOTf),
without the use of any hazardous or volatile solvents and without any
by-product such as salts. Furthermore, this method could also be
applied to the tandem benzylation–cyclization–dehydration of 1,3-
dicarbonyl compounds to give functionalized 4H-chromenes in good
to excellent yields.
H
OH
Ph
OH
Ph
H+
Ph
Ph
Ph
Ph
Ph
O
Ph
Ph
H
7
H
Ph
O
Ph
-H+
4. Experimental
Ph
Ph
Ph
Ph
OH
H
4.1. General
O
O
1H (400 MHz) or 13C (100 MHz) NMR spectra were measured
O
O
O
O
with a JEOL
a-400 FT-NMR spectrometer in deuteriochloroform
Ph
Ph
Ph
Ph
Ph
Ph
Ph
HO
Ph
Ph
Ph
-H2O
2b
(CDCl3) solution with tetramethylsilane (Me4Si) as an internal stan-
dard. Melting points were obtained on a Yanagimoto MP-S2 micro
melting point apparatus and are uncorrected. IR spectra were mea-
sured on a SHIMADZU FT-IR 8100A spectrometer. HRMS were
measured on a JEOL JMS-700 mass spectrometer. LRMS were mea-
sured on a JEOL JMS-K9 mass spectrometer. The pure products were
isolated by column chromatography using silica gel (Wakogel C-200,
100–200 mesh, Wako Pure Chemical Ind., Ltd.). N-Ethyl-N-methyl
imidazolium trifluoromethanesulfonate (EMIOTf) was a gift from the
Central Glass Co., Ltd. All chemicals were of reagent grade and, if
necessary, purified in the usual manner prior to use.
Ph
Ph
8
Scheme 4. Proposed reaction mechanism for the formation of 8.
¨
2.3. Reuse of the Bronsted acid ionic liquid catalyst 1
Finally, reuse of the Bro¨nsted acid ionic liquid catalyst 1 was
carried out, as shown in Scheme 5.
4.2. Preparation of 1-butyl-3-(3-sulfopropyl)-1H-imidazol-3-
O
O
OH
ium trifluoromethanesulfonate (1)
+
Me
Initial use
Me
Ph
Me
2a
3a
To propanesultone (3.908 g, 31.97 mmol) in a two-necked flask
under argonwas slowlyadded 1-butylimidazole (4.005 g, 32.25 mmol),
and the mixture was stirred for 30 min at room temperature. Repeated
washing of the obtained solid with toluene (20 mlꢁ5) and Et2O
(20 mlꢁ5), and evaporation under vacuum at room temperature gave
3-(1-butyl-1H-imidazol-3-ium-3-yl)propane-1-sulfonate in 98% yield
(7.797 g).
1
1) (5 mol%), 100 °C,
3 h / EMIOTf
2) extraction with
Et2O- hexane (1:1)
3 times
ionic liquid layer
organic layer
4.2.1. 3-(1-Butyl-1H-imidazol-3-ium-3-yl)propane-1-sulfonate
concentration
1) evaporation
Yield 98%; Mp 176.7–177.1 ꢀC; IR (KBr) 1566 (C]C), 1179 (SO),
under vacuum at rt
2) column chromatography
1038 (SO) cmꢂ1
;
1H NMR (D2O, 400 MHz)
d
0.99 (t, J¼7.37 Hz, 3H,
CH3CH2CH2CH2), 1.38 (sext, J¼7.37 Hz, 2H, CH3CH2CH2CH2), 1.88
(quint, J¼7.37 Hz, 2H, CH3CH2CH2CH2), 2.32 (quint, J¼7.37 Hz, 2H,
–CH2CH2SOꢂ3 ), 2.80 (t, J¼7.37 Hz, 2H, –CH2SOꢂ3 ), 4.23 (t, J¼7.37 Hz,
2H, –CH2N]), 4.43 (t, J¼7.37 Hz, 2H, –CH2Nþ^), 7.68 (d,
J¼15.46 Hz, 1H, imidazolium-H), 7.68 (d, J¼15.46 Hz, 1H, imidazo-
lium-H), 9.02 (s, 1H, imidazolium-H); 13C NMR (D2O, 100 MHz)
recovered
O
O
Me
Ph
1
/ EMIOTf
+
Me
Me
Me
Ph
2a, 3a
5
Ph
4aa
1st reuse
/ 100 °C, 3 h
d
24.2 (s), 30.4 (s), 36.7 (s), 42.8 (s), 58.8 (s), 59.3 (s), 61.0 (s), 133.9
a
(s), 134.2 (s), 147.0 (s); HRMS found m/z 247.1112, calcd for
C10H19N2O3S: MþH, 247.1118.
Product (%)
initial use
4aa (77), 5 (7)
4aa (77), 5 (7)
4aa (75), 5 (5)
A mixture of 3-(1-butyl-1H-imidazol-3-ium-3-yl)propane-1-sulfo-
nate (2.473 g, 10.0 mmol) and trifluoromethanesulfonic acid (1.628 g,
10.85 mmol) was heated to 150 ꢀC and stirred at the same temperature
for 5 h. After being allowed to cool to room temperature, the obtained
ionic liquid was washed repeatedly with toluene (20 mlꢁ5) and Et2O
(20 mlꢁ5) to remove non-ionic residues, and dried under vacuum at
room temperature to give 1-butyl-3-(3-sulfopropyl)-1H-imidazol-3-
ium trifluoromethanesulfonate (1) (3.924 g, 99%).
first reuse
second reuse
a
Yields of isolated products
Scheme 5. Reuse of the Bro¨nsted acid ionic liquid catalyst 1.
After the initial use of the catalyst 1 in EMIOTf, the product 4aa
and styrene dimer 5 were extracted from EMIOTf three times with
a mixed solvent of diethyl ether and hexane (1:1). Concentration of
the mixed organic layer and purification by column chromatogra-
phy gave the product 4aa with a trace amount of 5. Reuse of the
catalyst in the second and third cycles gave the product 4aa in al-
most the same yield along with a trace amount of 5.
4.2.2. 1-Butyl-3-(3-sulfopropyl)-1H-imidazol-3-ium
trifluoromethanesulfonate (1)
Yield99%;IR (neat)3415 (SO3H),1566 (C]C),1227 (SO),1170 (SO),
1030 (SO) cmꢂ1
;
1H NMR (D2O, 400 MHz)
d
0.92 (t, 3H, J¼7.34 Hz,

K. Funabiki et al. / Tetrahedron 65 (2009) 7457–7463
7461
CH3CH2CH2CH2), 1.33 (sext, 2H, J¼7.34 Hz, CH3CH2CH2CH2), 1.87
(CDCl3, 400 MHz)
d
2.00 (s, 6H, 2ꢁCOCH3), 4.81 (d, J¼12.32 Hz, 1H,
(quint, J¼7.34 Hz, CH3CH2CH2CH2), 2.34 (quint, J¼7.34 Hz, 2H,
–CH2CH2SOꢂ3 ), 2.93 (t, 2H, J¼7.34 Hz, –CH2SOꢂ3 ), 4.22 (t, 2H,
J¼7.34 Hz, –CH2N]), 4.38 (t, 2H, J¼7.34 Hz, –CH2Nþ^), 7.54 (d,
1H, J¼9.42 Hz, imidazolium-H), 7.54 (d, 1H, J¼9.42 Hz, imidazolium-
CHPh), 4.73 (d, J¼12.32 Hz, 1H, CHCOCH3), 7.15–7.20 (m, 2H, aryl H),
7.24–7.29 (m, 8H, arlyl H); 13C NMR (CDCl3, 100 MHz)
d 30.5 (s), 52.1
(s), 75.4 (s), 127.9 (s), 128.6 (s), 129.8 (s), 142.1 (s), 203.8 (s); HRMS
found m/z 266.1308, calcd for C18H18O2: M, 266.1307.
H), 8.82 (s, 1H, imidazolium-H); 13C NMR (D2O, 100 MHz)
d 23.2 (s),
29.4 (s), 35.8 (s), 41.8 (s), 57.9 (s), 58.4 (s), 60.1 (s), 50.2 (s), 130.3 (q,
J¼317.9 Hz), 133.0 (s), 133.3 (s), 146.0 (s); HRMS found m/z 247.1123,
calcd for C10H19N2O3S: MꢂCF3SO3, 247.1116.
4.3.6. (Z)-3-(1,3-Diphenylallyl)pentane-2,4-dione (4ac)1
Yield 90%; Mp 83.0–83.8 ꢀC (lit. 85 ꢀC); Rf 0.20 (hexane/
Et2O¼5:1); IR (CHCl3) 1682 (C]O), 1732 (C]O) cmꢂ1
;
1H NMR
(CDCl3, 400 MHz)
d 1.92 (s, 3H, COCH3), 2.25 (s, 3H, COCH3), 4.30–
¨
4.3. Typical procedure for the recyclable Bronsted acid 1-
4.37 (m, 2H, CHCOCH3 and CHPh), 6.16–6.22 (m, 1H, PhCH]CH),
catalyzed direct carbon–carbon bond formation of 1,3-
dicarbonyl compounds with alcohols
6.43 (d, J¼15.70 Hz, 1H, PhCH]CH), 7.20–7.33 (m, 10H, aryl H); 13C
NMR (CDCl3, 100 MHz)
d 30.4 (s), 30.7 (s), 49.8 (s), 127.0 (s), 127.9
(s), 128.4 (s), 128.6 (s), 129.2 (s), 129.7 (s), 129.9 (s), 132.3 (s), 137.2
(s), 140.7 (s), 141.9 (s), 203.4 (s), 203.5 (s); HRMS found m/z
292.1475, calcd for C20H20O2: M, 292.1464.
A mixture of 1-butyl-3-(3-sulfopropyl)-1H-imidazol-3-ium tri-
fluoromethanesulfonate (1) (0.060 g, 0.151 mmol),1-phenylethanol
(3a) (0.370 g, 3.029 mmol) and pentane-2,4-dione (2a) (1.503 g,
15.01 mmol) in 1-ethyl-3-methyl-1H-imidazol-3-ium trifluorome-
thanesulfonate (1 ml) under argon was stirred at 100 ꢀC for 3 h. The
mixture was then cooled to room temperature and extracted from
the ionic liquid with a mixed solvent of Et2O/hexane (1:1)
(30 mlꢁ3). After the solvent was removed under reduced pressure,
the product was purified by column chromatography on silica gel
with hexane/EtOAc (20:1) to give 3-(1-phenylethyl)pentane-2,4-
dione (4aa) (0.478 g, 77%) and (E)-but-1-ene-1,3-diyldibenzene (5)
(0.022 g, 7%).
4.3.7. (E)-3-(Pent-3-en-2-yl)pentane-2,4-dione (4ad)
Yield 47%; Rf 0.18 (hexane/Et2O¼5:1); IR (neat) 1698 (C]O),
1722 (C]O) cmꢂ1
;
1H NMR (CDCl3, 400 MHz)
d
0.96 (d, J¼7.19 Hz,
3H, CHCH3), 1.62 (d, J¼7.19 Hz, 3H, CH3CH:CH), 2.11 (s, 3H, COCH3),
2.19 (s, 3H, COCH3), 2.97 (sext, J¼7.19 Hz, 1H, CHCH3), 3.56 (d,
J¼7.19 Hz, 1H, CHCOCH3), 5.19–5.25 (m, 1H, CH3CH]CH), 5.46–5.55
(m, 1H, CH3CH]CH); 13C NMR (CDCl3, 100 MHz)
d 17.8 (s), 19.0 (s),
29.5 (s), 30.0 (s), 37.7 (s), 75.8 (s), 126.4 (s), 132.3 (s), 204.0 (s), 204.0
(s); HRMS found m/z 168.1158, calcd for C10H16O2: M, 168.1151.
4.3.1. 3-(1-Phenylethyl)pentane-2,4-dione (4aa)3a
4.3.8. 3-(1,3-Diphenylprop-2-ynyl)pentane-2,4-dione (4ae)3b
Yield 88%; Mp 95.4–96.0 ꢀC (lit. 90–92 ꢀC); Rf 0.50 (hexane/
Yield 77%; Mp 46.9–47.9 ꢀC (lit. 43–45 ꢀC); Rf 0.38 (hexane/
EtOAc¼5:1); IR (CHCl3) 1697 (C]O), 1722 (C]O) cmꢂ1
;
1H NMR
CH2Cl2¼1:3); IR (CHCl3) 1701 (C]O), 1733 (C]O) cmꢂ1
;
1H NMR
(CDCl3, 400 MHz)
d
1.16 (d, J¼7.00 Hz, 3H, CHCH3), 1.78 (s, 3H,
(CDCl3, 400 MHz) d 1.93 (s, 3H, COCH3), 2.39 (s, 3H, COCH3), 4.22 (d,
COCH3), 2.22 (s, 3H, COCH3), 3.51–3.59 (m, 1H, CHCH3), 3.99 (d,
J¼7.00 Hz, 1H, CHCOCH3), 7.13–7.26 (m, 5H, aryl H); 13C NMR
J¼10.87 Hz, 1H, CHPh), 4.67 (d, J¼10.87 Hz, 1H, CHCOCH3), 7.25–
7.42 (m, 10H, aryl H); 13C NMR (CDCl3, 100 MHz)
d
28.7 (s), 31.1 (s),
(CDCl3, 100 MHz)
d
21.6 (s), 30.4 (s), 30.5 (s), 41.1 (s), 77.4 (s), 127.7
38.0 (s), 75.6 (s), 84.9 (s), 88.0 (s), 122.7 (s), 127.7 (s), 128.1 (s), 128.2
(s), 128.3 (s), 128.9 (s), 131.6 (s), 138.2 (s), 201.6 (s), 201.6 (s); HRMS
found m/z 290.1310, calcd for C20H18O2: M, 290.1307.
(s), 128.0 (s), 130.0 (s), 143.8 (s), 204.1 (s), 204.2 (s); HRMS found
m/z 204.1151, calcd for C13H16O2: M, 204.1154.
4.3.2. (E)-But-1-ene-1,3-diyldibenzene (5)3a
4.3.9. 1,3-Diphenyl-2-(1-phenylethyl)propane-1,3-dione (4ba)3a
Yield 81%; Mp 126.1–126.8 ꢀC (lit. 126–127 ꢀC); Rf 0.15 (hexane/
Yield 7%; Rf 0.38 (hexane); IR (neat) 1600 (C]C) cmꢂ1; 1H NMR
(CDCl3, 400 MHz)
J¼7.00 Hz, 1H, CHCH3), 6.30–6.32 (m, 2H, 2ꢁvinyl H), 7.08–7.28 (m,
10H, aryl H); 13C NMR (CDCl3, 100 MHz)
21.4 (s), 42.7 (s), 126.3 (s),
d
1.38 (d, J¼7.00 Hz, 3H, CHCH3), 3.55 (quint,
EtOAc¼20:1); IR (KBr) 1683 (C]O), 1733 (C]O) cmꢂ1
;
1H NMR
(CDCl3, 400 MHz)
d
1.33 (d, J¼7.00 Hz, 3H, CHCH3), 4.03–4.11 (m,
d
1H, CHPh), 5.63 (d, J¼7.00 Hz, 1H, CHCOPh), 7.04 (t, J¼7.35 Hz, 1H,
aryl H), 7.14 (t, J¼7.35 Hz, 2H, aryl H), 7.22–7.26 (m, 4H, aryl H),
7.35–7.42 (m, 3H, aryl H), 7.52 (t, J¼7.35 Hz, 1H, aryl H), 7.73 (d,
J¼7.35 Hz, 2H, aryl H), 8.02 (d, J¼7.35 Hz, 2H, aryl H); 13C NMR
126.4 (s), 127.2 (s), 127.4 (s), 128.6 (s), 135.3 (s), 137.7 (s), 145.7 (s);
HRMS found m/z 208.1259, calcd for C16H16: M, 208.1253.
4.3.3. 1,10-Oxybis(ethane-1,1-diyl)dibenzene
(CDCl3, 100 MHz) d 20.5 (s), 41.5 (s), 65.0 (s), 126.9 (s), 128.0 (s),
Yield 33%; dr¼50:50; Rf 0.60 (hexane/CH2Cl2¼1:1); 1H NMR
128.7 (s), 128.8 (s), 129.1 (s), 129.1 (s), 133.3 (s), 133.9 (s), 137.1 (s),
137.4 (s), 144.1 (s), 194.9 (s), 195.3 (s); HRMS found m/z 328.1467,
calcd for C23H20O2: M, 328.1464.
(CDCl3, 400 MHz)
d
1.31 (d, 6H, J¼6.52 Hz, 2ꢁCHCH3), 1.39 (d, 6H,
J¼6.52 Hz, 2ꢁCHCH3), 4.18 (q, 2H, J¼6.52 Hz, 2ꢁCHCH3), 4.46 (q,
2H, J¼6.52 Hz, 2ꢁCHCH3), 7.13–7.31 (m, 20H, aryl H); 13C NMR
(CDCl3, 100 MHz)
d
23.9 (s), 25.6 (s), 75.3 (s), 75.5 (s), 127.1 (s), 127.2
4.3.10. 2-Benzhydryl-1,3-diphenylpropane-1,3-dione (4bb)12
Yield 98%; Mp 221.6–222.3 ꢀC (lit. 228.6–230.2 ꢀC); Rf 0.28
(s), 128.0 (s), 128.3 (s), 129.1 (s), 129.4 (s), 145.0 (s), 145.1 (s); MS (EI)
m/z 226 (M, 7.5%).
(hexane/CH2Cl2¼1:1); IR (KBr) 1661 (C]O), 1683 (C]O) cmꢂ1
;
1H
NMR (CDCl3, 400 MHz)
d
5.32 (d, J¼11.71 Hz, 1H, CHCOPh), 6.35 (d,
4.3.4. 4-Phenylpentan-2-one11
J¼11.71 Hz, 1H, CHPh), 7.05 (t, J¼7.46 Hz, 2H, aryl H), 7.15 (t,
J¼7.46 Hz, 4H, aryl H), 7.24 (s, 4H, aryl H), 7.33 (t, J¼7.46 Hz, 4H, aryl
H), 7.47 (t, J¼7.46 Hz, 2H, aryl H), 7.83 (d, J¼7.46 Hz, 4H, aryl H); 13C
Yield 20%; Rf 0.29 (hexane/CH2Cl2¼1:1); IR (neat) 1716
(C]O) cmꢂ1
;
1H NMR (CDCl3, 400 MHz)
d
1.29 (d, 3H, J¼7.00 Hz,
CH3CHPh), 2.09 (s, 3H, COCH3), 2.68 (dd, 1H, J¼7.00, 16.18 Hz,
CH2CO), 2.78 (dd, 1H, J¼7.00, 16.18 Hz, CH2CO), 2.78 (sext,
J¼7.00 Hz, 1H, CH3CHPh), 7.20–7.35 (m, 5H, aryl H); 13C NMR
NMR (CDCl3, 100 MHz) d 52.4 (s), 62.3 (s), 126.6 (s), 128.3 (s), 128.5
(s), 128.6 (s), 128.6 (s), 133.2 (s), 136.9 (s), 141.7 (s), 194.1 (s); HRMS
found m/z 390.1618, calcd for C28H22O2: M, 390.1621.
(CDCl3, 100 MHz) d 21.9 (s), 30.5 (s), 35.3 (s), 51.9 (s), 126.2 (s), 126.6
(s), 128.4 (s), 146.1 (s), 207.8 (s); MS (EI) m/z 162 (M, 34.3%).
4.3.11. Ethyl 2-acetyl-3-phenylbutanoate (4ca)2b
Yield 30%; Rf 0.63 (hexane/EtOAc¼5:1); IR (neat) 1717 (C]O),
4.3.5. 3-benzhydrylpentane-2,4-dione (4ab)3a
1747 (C]O) cmꢂ1
;
1H NMR (CDCl3, 400 MHz)
d
0.85 (t, J¼7.10 Hz,
Yield 94%; Mp 114.9–116.1 ꢀC (lit. 112–114 ꢀC); Rf 0.43 (hexane/
3H, COOCH2CH3), 1.16 (d, J¼8.88 Hz, 3H, CHCH3), 1.21 (t, J¼7.10 Hz,
3H, COOCH2CH3), 1.22 (d, J¼8.88 Hz, 3H, CHCH3), 1.85 (s, 3H,
CH2Cl2¼1:3); IR (CHCl3) 1697 (C]O), 1719 (C]O) cmꢂ1
;
1H NMR

7462
K. Funabiki et al. / Tetrahedron 65 (2009) 7457–7463
COCH3), 2.22 (s, 3H, COCH3), 3.44–3.48 (m, 2H, PhCH), 3.67 (d,
J¼8.88 Hz,1H, CHCOCH3), 3.72 (d, J¼8.88 Hz,1H, CHCOCH3), 3.80 (q,
J¼7.10 Hz, 2H, COOCH2CH3), 4.14 (q, J¼7.10 Hz, 2H, COOCH2CH3),
4.3.16. Ethyl 2-benzhydryl-3-oxo-3-phenylpropanoate (4eb)11
Yield 97%; Mp 137.0–137.5 ꢀC (lit. 141.9–143.1 ꢀC); Rf 0.54 (hex-
ane/CH2Cl2¼1:1); IR (KBr) 1682 (C]O), 1730 (C]O) cmꢂ1; 1H NMR
7.11–7.21 (m, 10H, aryl H); 13C NMR (CDCl3, 100 MHz)
d
13.7 (s), 14.2
(CDCl3, 400 MHz)
d
0.93 (t, J¼7.12 Hz, 3H, COOCH2CH3), 3.85–3.99
(s), 20.4 (s), 20.6 (s), 29.6 (s), 29.9 (s), 39.8 (s), 40.1 (s), 61.2 (s), 61.5
(s), 67.0 (s), 67.6 (s), 76.8 (s), 77.1 (s), 77.4 (s), 126.8 (s), 126.9 (s),
127.4 (s), 127.5 (s), 128.5 (s), 128.7 (s), 143.1 (s), 143.3 (s), 168.2 (s),
168.6 (s), 202.4 (s); HRMS found m/z 234.1263, calcd for C14H18O3:
M, 234.1256.
(m, 2H, COOCH2CH3), 5.08 (d, J¼11.83 Hz, 1H, CHCOPh), 5.41 (d,
J¼11.83 Hz, 1H, CHPh), 7.03–7.07 (m, 1H, arlyl H), 7.12–7.30 (m, 7H,
arlyl H), 7.34–7.45 (m, 4H, arlyl H), 7.53–7.57 (m, 1H, arlyl H), 8.00–
8.02 (m, 2H, arlyl H); 13C NMR (CDCl3, 100 MHz)
d 13.7 (s), 50.9 (s),
59.4 (s), 61.5 (s), 126.5 (s), 126.8 (s), 127.7 (s), 128.2 (s), 128.5 (s),
128.6 (s), 128.6 (s), 128.7 (s), 133.5 (s), 136.6 (s), 141.7 (s), 167.7 (s),
192.8 (s); MS (EI) m/z 340 (MꢂH2O, 46.4%).
4.3.12. Ethyl 2-benzhydryl-3-oxobutanoate (4cb)3a
Yield 91%; Mp 87.8–89.0 ꢀC (lit. 84–86 ꢀC); Rf 0.38 (hexane/
CH2Cl2¼1:1); IR (CHCl3) 1716 (C]O), 1738 (C]O) cmꢂ1
;
1H NMR
4.4. Typical procedure for the recyclable Bronsted acid
¨
(CDCl3, 400 MHz)
d
1.00 (t, J¼7.10 Hz, 3H, COOCH2CH3), 2.09 (s, 3H,
1-catalyzed tandem direct benzylation, cyclization and
dehydration of the alcohol 3f
COCH3), 3.98 (q, J¼7.10 Hz, 2H, COOCH2CH3), 4.52 (d, J¼12.20 Hz,
1H, CHPh), 4.76 (d, J¼12.20 Hz,1H, CHCOCH3), 7.14–7.18 (m, 2H, aryl
H), 7.23–7.30 (m, 8H, aryl H); 13C NMR (CDCl3, 100 MHz)
d
13.4 (s),
A mixture of 1-butyl-3-(3-sulfopropyl)-1H-imidazol-3-ium tri-
fluoromethanesulfonate (1) (0.020 g, 0.050 mmol), 2-(hydroxy-
(phenyl)methyl)phenol (3f) (0.199 g, 0.994 mmol) and pentane-2,4-
dione (2a) (0.503 g, 5.024 mmol) in 1-ethyl-3-methyl-1H-imidazol-
3-ium trifluoromethanesulfonate (1 ml) under argon was stirred at
100 ꢀC for 3 h. The mixture was then cooled to room temperature and
extracted from the ionic liquid with a mixed solvent of Et2O/hexane
(1:1) (30 mlꢁ3). After the solvent was removed under reduced
pressure, the product was purified by column chromatography on
silica gel with hexane/CH2Cl2 (1:4) to give 1-(2-methyl-4-phenyl-4H-
chromen-3-yl)ethanone (6af) (0.204 g, 77%).
29.7 (s), 50.5 (s), 61.2 (s), 64.9 (s), 126.5 (s), 126.6 (s), 127.4 (s), 127.5
(s), 128.3 (s), 128.5 (s), 140.9 (s), 141.2 (s), 167.3 (s), 201.4 (s); HRMS
found m/z 296.1419, calcd for C19H20O3: M, 296.1413. Found: C,
76.91; H, 6.87. C19H20O3 requires C, 77.00; H, 6.80.
4.3.13. (Z)-Ethyl 2-acetyl-3,5-diphenylpent-4-enoate (4cc)7
Yield 76%; Rf 0.20 (hexane/EtOAc¼20:1); IR (neat) 1714 (C]O),
1741 (C]O) cmꢂ1
;
1H NMR (CDCl3, 400 MHz)
d
0.93 (t, J¼7.10 Hz,
3H, COOCH2CH3), 1.16 (t, J¼7.10 Hz, 3H, COOCH2CH3), 1.99 (s, 3H,
COCH3), 2.26 (s, 3H, COCH3), 3.89 (q, J¼7.10 Hz, 2H, COOCH2CH3),
4.05 (d, J¼10.99 Hz, 2H, CHCOCH3), 4.08 (d, J¼10.99 Hz, 2H,
CHCOCH3), 4.12 (q, J¼7.10 Hz, 2H, COOCH2CH3), 4.26 (t, J¼10.99 Hz,
2H, CHPh), 6.18–6.30 (m, 2H, PhCH]CH), 6.39 (d, J¼10.99 Hz, 1H,
PhCH]CH), 6.43 (d, J¼10.99 Hz, 1H, PhCH]CH), 7.12–7.29 (m, 20H,
4.4.1. 1-(2-Methyl-4-phenyl-4H-chromen-3-yl)ethanone (6af)
Yield 77%; Rf 0.58 (hexane/CH2Cl2¼1:4); IR (neat) 1682
(C]O) cmꢂ1; 1H NMR (CDCl3, 400 MHz)
d 2.13 (s, 3H, COCH3), 2.43
aryl H); 13C NMR (CDCl3, 100 MHz)
d
13.3 (s), 13.7 (s), 29.4 (s), 29.5
(s, 3H, CCH3), 4.99 (s,1H, CHPh), 6.92–6.99 (m, 2H, aryl H), 7.06–7.14
(s), 48.3 (s), 48.5 (s), 60.9 (s), 61.1 (s), 64.8 (s), 65.1 (s), 125.9
(s),125.9 (s),126.6 (s), 126.7 (s),127.1 (s),127.1 (s), 127.5 (s), 127.5 (s),
128.0 (s), 128.2 (s), 128.4 (s), 128.8 (s), 129.0 (s), 131.0 (s), 131.3 (s),
136.2 (s), 136.3 (s), 139.7 (s), 139.9 (s), 167.1 (s), 167.4 (s), 200.9
(s), 201.2 (s); HRMS found m/z 322.1574, calcd for C21H22O3: M,
322.1570.
(m, 3H, aryl H), 7.19–7.30 (m, 4H, aryl H); 13C NMR (CDCl3,100 MHz)
d
20.5 (s), 30.5 (s), 42.6 (s), 114.5 (s), 116.7 (s), 124.9 (s), 125.2 (s),
127.2 (s), 127.9 (s), 128.0 (s), 129.3 (s), 129.3 (s), 146.2 (s), 149.4 (s),
159.5 (s), 199.2 (s); HRMS found m/z 264.1147, calcd for C18H16O2:
M, 264.1151.
4.4.2. (2,4-Diphenyl-4H-chromen-3-yl)(phenyl)methanone (6bf)
Yield 98%; Mp 152.5–153.0 ꢀC; Rf 0.30 (hexane/CH2Cl2¼2:1); IR
4.3.14. Ethyl 2-acetyl-3,5-diphenylpent-4-ynoate (4ce)3b
Yield 84%; Rf 0.50 (hexane/EtOAc¼15:1); IR (neat) 1719
(KBr) 1643 (C]O) cmꢂ1 1H NMR (CDCl3, 400 MHz)
; d 5.35 (s, 1H,
(C]O), 1746 (C]O) cmꢂ1
;
1H NMR (CDCl3, 400 MHz)
d
1.00 (t,
CHPh), 7.02–7.19 (m, 9H, aryl H), 7.22–7.28 (m, 4H, aryl H), 7.36–7.39
J¼7.06 Hz, 3H, COOCH2CH3), 1.24 (t, J¼7.06 Hz, 3H, COOCH2CH3),
1.97 (s, 3H, COCH3), 2.39 (s, 3H, COCH3), 3.95 (q, J¼7.06 Hz, 2H,
COOCH2CH3), 3.98 (d, J¼10.69 Hz, 1H, CHCOCH3), 4.04 (d,
J¼10.69 Hz, 1H, CHCOCH3), 4.22 (q, J¼7.06 Hz, 2H, COOCH2CH3),
4.60 (d, J¼10.69 Hz, 1H, CHPh), 4.63 (d, J¼10.69 Hz, 1H, CHPh),
(m, 2H, aryl H), 7.43–7.51 (m, 4H, aryl H); 13C NMR (CDCl3,100 MHz)
d
43.9 (s), 114.4 (s), 116.5 (s), 124.6 (s), 126.7 (s), 127.6 (s), 127.8 (s),
127.9 (s), 128.1 (s), 128.6 (s), 129.1 (s), 129.3 (s), 129.5 (s), 129.7 (s),
131.7 (s), 133.3 (s), 138.4 (s), 145.2 (s), 150.3 (s), 155.3 (s), 197.2 (s);
HRMS found m/z 388.1471, calcd for C28H20O2: M, 388.1464.
7.20–7.42 (m, 20H, aryl H); 13C NMR (CDCl3, 100 MHz)
d 13.8 (s),
14.1 (s), 29.8 (s), 30.6 (s), 37.8 (s), 37.8 (s), 61.6 (s), 61.8 (s), 66.5
(s), 66.8 (s), 84.1 (s), 84.7 (s), 88.2 (s), 88.5 (s), 122.8 (s), 123.1 (s),
127.6 (s), 127.7 (s), 128.1 (s), 128.2 (s), 128.2 (s), 128.2 (s), 128.3
(s), 128.6 (s), 128.7 (s), 131.6 (s), 138.2 (s), 138.3 (s), 166.8 (s),
167.1 (s), 200.3 (s), 200.7 (s); HRMS found m/z 320.1413, calcd for
C21H20O3: M, 320.1415.
4.4.3. Ethyl 2-methyl-4-phenyl-4H-chromene-3-carboxylate (6cf)9
Yield 84%; Rf 0.75 (hexane/CH2Cl2¼1:4); IR (neat) 1710
(C]O) cmꢂ1
;
1H NMR (CDCl3, 400 MHz)
d
1.16 (t, J¼7.12 Hz, 3H,
COOCH2CH3), 2.51 (s, 3H, CCH3), 4.02–4.15 (m, 2H, COOCH2CH3),
5.04 (s, 1H, CHPh), 6.94–6.98 (m, 1H, aryl H), 7.00–7.06 (m, 2H, aryl
H), 7.09–7.15 (m, 2H, aryl H), 7.20–7.24 (m, 4H, aryl H); 13C NMR
(CDCl3, 100 MHz) d 13.6 (s), 19.0 (s), 41.0 (s), 59.6 (s), 105.6 (s), 115.7
4.3.15. Ethyl 2-benzhydryl-3-oxopentanoate (4db)
(s), 124.0 (s), 124.3 (s), 125.9 (s), 127.0 (s), 127.3 (s), 127.9 (s), 128.7
(s), 146.2 (s), 148.8 (s), 159.5 (s), 166.6 (s), HRMS found m/z
294.1265, calcd for C19H18O3: M, 294.1256.
Yield 89%; Mp 87.8–88.1 ꢀC; Rf 0.38 (hexane/CH2Cl2¼1:1); IR
(KBr) 1714 (C]O), 1747 (C]O) cmꢂ1 1H NMR (CDCl3, 400 MHz)
;
d
0.84 (t, J¼7.25 Hz, 3H, COCH2CH3), 0.97 (t, J¼7.25 Hz, 3H,
COOCH2CH3), 2.18–2.28 (m, 1H, COCH2CH3), 2.46–2.56 (m, 1H,
COCH2CH3), 3.90–4.01 (m, 2H, COOCH2CH3), 4.56 (d, J¼12.20 Hz,
1H, CHPh), 4.82 (d, J¼12.20 Hz, 1H, CHCOCH2CH3), 7.11–7.32 (m,
4.4.4. Ethyl 2-ethyl-4-phenyl-4H-chromene-3-carboxylate (6df)
Yield 80%; Rf 0.50 (hexane/CH2Cl2¼1:1); IR (neat) 1703
(C]O) cmꢂ1
;
1H NMR (CDCl3, 400 MHz)
d
1.17 (t, J¼7.30 Hz, 3H,
10H, aryl H); 13C NMR (CDCl3, 100 MHz)
d
7.1 (s), 13.6 (s), 36.6 (s),
CCH2CH3), 1.29 (t, J¼7.30 Hz, 3H, COOCH2CH3), 2.84–3.00 (m, 2H,
CCH2CH3), 4.02–4.15 (m, 2H, COOCH2CH3), 5.03 (s, 1H, CHPh), 6.94–
6.98 (m, 1H, aryl H), 7.02–7.07 (m, 2H, aryl H), 7.10–7.16 (m, 2H, aryl
50.7 (s), 61.2 (s), 64.0 (s), 126.6 (s), 126.7 (s), 127.5 (s), 127.7 (s), 128.4
(s), 128.6 (s), 141.3 (s), 141.5 (s), 167.5 (s), 204.1 (s); MS (EI) m/z 292
(MꢂH2O, 19.3%).
H), 7.21–7.23 (m, 4H, aryl H); 13C NMR (CDCl3, 100 MHz)
d 11.9 (s),

K. Funabiki et al. / Tetrahedron 65 (2009) 7457–7463
7463
14.0 (s), 25.9 (s), 41.5 (s), 60.0 (s), 105.3 (s), 116.1 (s), 124.3 (s), 124.8
(s), 126.3 (s), 127.4 (s), 127.7 (s), 128.3 (s), 129.1 (s), 146.6 (s), 149.4
(s), 164.7 (s), 166.8 (s); MS m/z 306 (M, 9.4%).
(s), 129.9 (s), 132.5 (s), 132.7 (s), 137.0 (s), 137.6 (s), 137.7 (s), 138.7
(s), 139.4 (s), 141.9 (s), 147.8 (s), 148.9 (s), 194.3 (s), 195.7 (s); HRMS
found m/z 490.1938, calcd for C36H26O2: M, 490.1934.
4.4.5. Ethyl 2,4-diphenyl-4H-chromene-3-carboxylate (6ef)9
Yield 83%; Rf 0.43 (hexane/CH2Cl2¼1:1); IR (neat) 1700
Acknowledgements
(C]O) cmꢂ1
;
1H NMR (CDCl3, 400 MHz)
d
0.91 (t, J¼7.10 Hz, 3H,
The present work was supported in part by a grant from the New
Energy and Industrial Technology Development Organization of
Japan (NEDO) to K. F. We thank Professors T. Ishihara and T. Konno
of the Kyoto Institute of Technology for the HRMS measurements.
We are grateful to Central Glass for the gift of N-ethyl-N-methyl
imidazolium trifluoromethanesulfonate (EMIOTf).
COOCH2CH3), 3.94 (q, J¼7.10 Hz, 2H, COOCH2CH3), 5.23 (s, 1H,
CHPh), 7.07–7.11 (m, 1H, aryl H), 7.15–7.26 (m, 4H, aryl H), 7.29–7.36
(m, 2H, aryl H), 7.42–7.52 (m, 5H, aryl H), 7.58–7.67 (m, 2H, aryl H);
13C NMR (CDCl3,100 MHz)
d 14.2 (s), 43.0 (s), 60.8 (s),108.2 (s),117.2
(s), 125.3 (s), 125.4 (s), 127.4 (s), 128.4 (s), 128.5 (s), 129.3 (s), 129.4
(s), 129.9 (s), 130.2 (s), 135.9 (s), 146.7 (s), 150.6 (s), 159.1 (s), 167.7
(s); MS m/z 356 (M, 20.6%).
Supplementary data
¨
4.5. Procedure for the recyclable Bronsted acid 1-catalyzed
reaction of 1,3-diphenylpropan-1,3-dione (2b) with tertiary
alkynol 7
Supplementary data associated with this article can be found in
the online version, at doi:10.1016/j.tet.2009.07.012.
A mixture of 1-butyl-3-(3-sulfopropyl)-1H-imidazol-3-ium tri-
fluoromethanesulfonate (1) (0.020 g, 0.050 mmol), 1,1,3-triphenyl-
prop-2-yn-1-ol (7) (0.285 g, 1.002 mmol) and 1,3-diphenylpropane-
1,3-dione (2b) (0.224 g, 0.999 mmol) in 1-ethyl-3-methyl-1H-imi-
dazol-3-ium trifluoromethanesulfonate (1 ml) under argon was
stirred at 100 ꢀC for 24 h. The mixture was then cooled to room
temperature and extracted from the ionic liquid with a mixed solvent
of Et2O/hexane (1:1) (30 mlꢁ3). After the solvent was removed under
reduced pressure, the product was purified by column chromatog-
raphy on silica gel with hexane/CH2Cl2 (5:2) to give 1,3-diphenyl-2-
(1,3,3-triphenylallylidene)propane-1,3-dione (8) (0.324 g, 66%).
References and notes
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4.5.1. 1,3-Diphenyl-2-(1,3,3-triphenylallylidene)propane-1,3-
dione (8)3b
Yield 66%; Mp 152.1–153.4 ꢀC (lit. 152–153 ꢀC); Rf 0.08 (hexane/
CH2Cl2¼5:2); IR (KBr) 1648 (C]O) cmꢂ1
;
1H NMR (CDCl3,
400 MHz) d 6.58 (s, 1H, CH), 6.88–6.91 (m, 2H, aryl H), 6.98–7.03 (m,
3H, aryl H), 7.07–7.10 (m, 2H, aryl H), 7.16–7.25 (m, 11H, aryl H),
7.34–7.37 (m, 1H, aryl H), 7.43–7.47 (m, 2H, aryl H), 7.53–7.57 (m,
1H, aryl H), 7.69–7.71 (m, 2H, aryl H), 7.95–7.98 (m, 2H, aryl H); 13C
11. Nishimura, T.; Yasuhara, Y.; Hayashi, T. Angew. Chem., Int. Ed. 2006, 45, 5164–
5166.
NMR (CDCl3, 100 MHz)
d 126.9 (s), 127.6 (s), 127.6 (s), 127.7 (s), 127.8
(s), 127.9 (s), 128.0 (s), 128.4 (s), 128.4 (s), 129.3 (s), 129.3 (s), 129.4
12. Li, Z.; Cao, L.; Li, C.-H. Angew. Chem., Int. Ed. 2007, 46, 6505–6507.