Commercially available simple ionic liquids-promoted dehydrative carbon-carbon bond-forming reaction of diarylmethanols and triarylmethanols with pyrroles, thiophene, furan and indoles

Article abstract of DOI:10.1016/j.tet.2014.10.004

Two commercially available simple ionic liquids, 1-ethyl-3-methylimidazolium trifluoromethanesulfonate and 1-ethyl-2,3-dimethylimidazolium trifluoromethansulfonate, effectively promote the solvent-free dehydrative carbon-carbon (C-C) bond-forming reaction

Full text of DOI:10.1016/j.tet.2014.10.004

Accepted Manuscript
Commercially available simple ionic liquids-promoted dehydrative carbon-carbon
bond-forming reaction of diarylmethanols and triarylmethanols with pyrroles,
thiophene, furan and indoles
Kazumasa Funabiki, Takuya Komeda, Kouhei Nishikawa, Kentaro Yamada, Yasuhiro
Kubota, Masaki Matsui
PII:
S0040-4020(14)01417-3
10.1016/j.tet.2014.10.004
TET 26074
DOI:
Reference:
To appear in: Tetrahedron
Received Date: 7 July 2014
Revised Date: 1 October 2014
Accepted Date: 3 October 2014
Please cite this article as: Funabiki K, Komeda T, Nishikawa K, Yamada K, Kubota Y, Matsui M,
Commercially available simple ionic liquids-promoted dehydrative carbon-carbon bond-forming reaction
of diarylmethanols and triarylmethanols with pyrroles, thiophene, furan and indoles, Tetrahedron (2014),
doi: 10.1016/j.tet.2014.10.004.
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Commercially available simple ionic liquids-
promoted dehydrative carbon-carbon bond-
forming reaction of diarylmethanols and
triarylmethanols with pyrroles, thiophene,
furan and indoles
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Kazumasa Funabiki,* Takuya Komeda, Kouhei Nishikawa, Kentaro Yamada, Yasuhiro Kubota, and Masaki
Matsui
Department of Chemistry and Bimolecular Science, Faculty of Engineering, Gifu University, 1-1 Yanagido, Gifu
501-1193, Japan

1
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Tetrahedron
journal homepage: www.elsevier.com
Commercially available simple ionic liquids-promoted dehydrative carbon-carbon
bond-forming reaction of diarylmethanols and triarylmethanols with pyrroles,
thiophene, furan and indoles
Kazumasa Funabiki, Takuya Komeda, Kouhei Nishikawa, Kentaro Yamada, Yasuhiro Kubota, and
Masaki Matsui
Department of Chemistry and Bimolecular Science, Faculty of Engineering, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan.
ARTICLE INFO
ABSTRACT
Article history:
Received
Received in revised form
Accepted
Two commercially available simple ionic liquids, 1-ethyl-3-methylimidazolium
trifluoromethanesulfonate and 1-ethyl-2,3-dimethylimidazolium trifluoromethansulfonate,
effectively promote the solvent-free dehydrative carbon-carbon (C-C) bond-forming reaction of
a variety of diarylmethanols and triarylmethanols with π–rich heteroaromatics, such as pyrroles,
indole, furan, and thiophene without ring-opening and polymerization to give the corresponding
not only 2-substituted pyrroles, furan, and thiophene but also 3-substituted indoles in good to
excellent yields with moderate to excellent regioselectivities. These dehydrative C-C bond
formation reactions of alcohols offer several advantages, such as the use of stoichiometric
amounts of π–rich heteroaromatics and ionic liquids, water is the only by-product, there is no
need for either organic solvents or expensive metal or strong Brønsted acid catalysts in the
reaction, and the diversity of diarylmethylation and triarylmethylation.
Available online
Keywords:
ionic liquid
dehydrative C-C coupling
alcohols
regioselectivity
heterocycles
2009 Elsevier Ltd. All rights reserved
.
1. Introduction
synthetic methodologies for pyrrole due to its sensitivity to acid
and air.7 Existing methods for the Brønsted or Lewis acid-
promoted C-C bond-forming reaction of pyrrole have some
disadvantages: 1) Both expensive Ru or rare earth
trifluoromethansulfonates catalysts and potent Brønsted acids,
such as trifluoromethansulfonic acid or perfluorophenylboronic
acid, are needed; 2) The substrate scope of the alcohols is limited
to a few specific benzyl alcohol derivatives,8 1-phenylallyl
alcohol9 and 1-phenyl- or 1,3-diphenylpropargyl alcohol,10 and
3) Strong acid-mediated C-C bond-forming reaction of pyrrole is
Ionic liquids have considerable received attention as
environmentally benign solvents in organic synthesis, since they
offer great advantages over common organic solvents, such as
low flammability, low volatility, low toxicity and thermal
stability.1 Notably, some commercially available simple ionic
liquids can promote various reactions, such as fluorination,
acetalization, etherification, aldol condensation, cyclization
leading to heteroaromatics, aziridination, ring-opening reaction
of styrene oxide and so on, without using a promoter or a
catalyst.2 However, to the best of our knowledge, there have
been only a few reports on the ionic liquid-promoted dehydrative
carbon-carbon (C-C) bond-forming reactions of alcohols without
the addition of a catalyst,3,4 although dehydrative C-C bond
formation reaction is one of the most ideal method in organic
synthesis due to the formation of water as a by-product.
accompanied
by
ring-opening,
polyalkylation,
and
polymerization. Therefore, the development of much more
diverse, convenient, and environmentally benign strategies for
the C-C bond-forming reaction of pyrrole without the use of any
expensive or hazardous reagents are still required.
In this paper, we disclose, for the first time, the dehydrative C-
C bond-forming reaction of a variety of diarylmethanols and
triarylmethanols promoted by commercially available simple
ionic liquids with pyrrole without the addition of a Brønsted or
Lewis acid. The present reaction offers several advantages: 1) A
couple of commercially available simple ionic liquids could be
used. 2) Water is the only by-product. 3) Stoichiometric amounts
of pyrrole and ionic liquid are sufficient to give the products in
satisfactory yields. 4) Neither organic solvents nor expensive
On the other hand, methods for the effective and
straightforward functionalization of pyrroles have attracted much
attention, since pyrrole is one of the most useful building blocks
in π–rich heteroaromatics for the synthesis of not only functional
dyes but also bioactive compounds.5 Although there have been
many reports on the C-C bond-forming reaction of indole using
benzyl alcohol derivatives,6 there are only a few successful
———
Corresponding author. Tel.: +8-58-293-2599; e-mail: funabiki@gifu-u.ac.jp

2
Tetrahedron
ACCEPTED MANUSCRIPT
metal or strong Brønsted acids are required. 5) A variety of
was also quite effective in the dehydrative C-C bond-forming
diarylmethanols and triarylmethanols as well as various π–rich
heteroaromatics, such as pyrrole, indole, furan, and thiophene,
could also participate in the reaction.
reaction of diphenylmethanol (2a) to produce 3aa in 80% yield,
together with 4aa in 11% yield similar to the results with the use
of EMIMOTf (entry 6). When thus-purified EMIMOTf by
column chromatography was used in the dehydrative C-C bond-
forming reaction of diphenylmethanol (2a) with pyrrole (1a)
under the same reaction conditions, the reaction did not proceed
at all and the starting alcohol 2a was recovered quantitatively
(entry 7), as in the reactions with BMIMBF4, BMIMPF6,
EMIMNTf2, and EMIMOMs. When dehydrative C-C bond-
forming reaction was carried out in various organic solvents,
such as hexane, tetrahydrofuran, chloroform, acetonitrile and
ethanol in place of EMIMOTf, no alkylated product 3aa was
formed and the starting alcohol 2a was recovered in quantitative
yield.
2. Results and discussion
2.1. Screening of conditions for the EMIMOTf-promoted
dehydrative C-C bond-forming reaction of diphenylmethanol
with pyrrole.
When diphenylmethanol (2a) was treated with an excess
amount (5 equiv.) of pyrrole (1a) in an excess amount (1 ml) of
1-ethyl-3-methylimidazolium
(EMIMOTf) at 100 °C for 3 h, the EMIMOTf-promoted
dehydrative C-C bond-forming reaction gave 2-diphenylmethyl-
1H-pyrrole (3aa) as a major product in 76% yield and 3-
diphenylmethyl-1H-pyrrole (4aa) as a minor product in 17%
yield (Table 1, entry 1).
trifluoromethanesulfonate
The pH values of aqueous solutions of these ionic liquids are
also summarized in Table 1. The pH values of ionic liquids
carrying PF6 , NTf2 , and MsO- groups are between 5 and 8. The
-
-
-
pH value of BMIMBF4, which carries a BF4 anion, is 3.9. The
pH values of EMIMOTf and EDMIMOTf are 3.0 and 2.5,
respectively, and thus they are more acidic than other ionic
liquids. As shown in entry 7, purification of EMIMOTf by silica
gel column chromatography increased the pH value to 6.6, which
is almost neutral and bigger than that (3.0) before purification.
Table 1
Screening of the various ionic liquids and screening of the conditions for the
EMIMOTf-promoted C-C bond-forming reaction of diphenylmethanol (2a)
with pyrrole (1a).
Other reaction conditions, such as not only different amounts
of pyrrole (1a) and EMIMOTf but also different reaction
temperatures, were also tested. Even when the amounts of both
pyrrole (1a) and EMIMOTf were decreased, the EMIMOTf-
promoted dehydrative C-C bond-forming reaction of
diphenylmethanol (2a) with pyrrole (1a) proceeded smoothly to
give the corresponding 3aa and 4aa in respective yields of 79%
and 17% (entry 8). However, a decrease in the reaction
temperature to rt resulted in no reaction, and 89% of the starting
alcohol 2a was recovered (entry 9).
Next, various EMIMOTfs, which were either received as gifts
or purchased commercially, were used in the dehydrative C-C
bond-forming reaction of diphenylmethanol (2a) with pyrrole
(1a), as shown in Table 2.
Table 2
Screening of various EMIMOTfs
The
ionic
liquids examined
included
1-butyl-3-
methylimidazolium tetrafluoroborate (BMIMBF4), 1-butyl-3-
methylimidazolium hexafluorophosphate (BMIMPF6), 1-ethyl-3-
methylimidazolium
(EMIMNTf2), 1-ethyl-3-methylimidazolium methanesulfonate
(EMIMOMs), and 1-ethyl-2,3-dimethylimidazolium
trifluoromethansulfonate (EDMIMOTf) (entries 2-6). For
bis(trifluoromethanesulfonyl)imide
BMIMBF4, BMIMPF6, EMIMNTf2, and EMIMOMs, the reaction
of the alcohol (2a) with pyrrole (1a) did not proceed at all, and
2a was recovered in quantitative yield (entries 2-5). However,
EDMIMOTf, which carries a trifluoromethanesulfonate anion,
As a result, EMIMOTfs that were received as gifts from
Central Glass Co. and purchased from TCI Fine Chemicals,

3
Wako Pure Chemicals, and Merck KGaA participated well in the
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reaction to give the 2-diphenylmethylpyrrole (3aa) in yields of
82-84% and a small amount of 3-diphenylmethylpyrrole (4aa)
(entries 1,2,3, and 4).
Table 3
Interestingly, EMIMOTf purchased from Aldrich Co. was not
effective at all in this reaction and did not give 3aa or 4aa, and
the starting alcohol 2aa was recovered in 98% yield (entry 5).
The reason for this result is not yet clear. One possible
explanation is that the method used by Aldrich for the
purification of EMIMOTf may be different than those used by
EMIMOTf-promoted dehydrative C-C bond-forming reaction of
diarylmethanols (2a-c) with pyrrole (1a).
the other companies.
The reason for the superiority of
EMIMOTf obtained from Merck and TCI compared with Central
Glass Co. and Wako Pure Chemicals Product is not clear.
Based on these results in Tables 1 and 2, the following
reaction mechanism can be considered. A lone pair of an oxygen
atom of the alcohol 2a may be protonated by a strong acid TfOH,
which may be produced by the reaction of TfO- and a small
amount of water or exists as a contamination in EMIMOTf and
EDMIMOTf, and dehydration produces dibenzyl cation, which is
attacked by pyrrole (1a). The elimination of H+ from the
intermediate then gives the corresponding 3aa and 4aa. The
regioselectivity of the pyrrole (1a) is consistent with the greater
nucleophilicity at the C2 carbon vs that at the C3 carbon.
To be confirm these hypotheses, measuring the amounts of
water and TfOH were carried out. Consequently, it was found
that the amount of water in the EMIMOTf was 1.4 wt% by direct
measuring with a Karl Fischer titrator. TfOH could not be
detected by not only 1H and 19F NMR but also HPLC. However,
based on the result that purification of EMIMOTf by silica gel
column chromatography increased the pH value to 6.6, which is
almost neutral and bigger than that (3.0) before purification
(Table 1, entry 7), trace amount of TfOH may be exist as a
contamination.
Chakraborti et al. reported that a hydrogen atom at the 2-
position of imidazolium in an ionic liquid can act as another
Brønsted acid.4a However, EDMIMOTf, which has a methyl
group rather than a hydrogen atom at the 2-position, was also
effective in the dehydrative C-C bond-forming reaction of
diphenylmethanol (2a) with pyrrole (1a).
Therefore,
Chakraborti’s explanation does not apply in the dehydrative C-C
bond-forming reaction of alcohol (2a) with pyrrole (1a).
Bis(4-trifluoromethylphenyl)methanol did not react with
pyrrole (1a) under the same reaction conditions, and the alcohol
carrying two trifluoromethyl groups was recovered in
quantitative yield, due to the difficulty of the formation of a
dibenzyl cation carrying two trifluoromethyl groups as potent
electron-withdrawing groups on the phenyl groups.
2.2. EMIMOTf-promoted solvent-free dehydrative C-C bond-
forming reaction of diarylmethanol with pyrrole.
Based on the optimized reaction conditions, the EMIMOTf-
promoted dehydrative C-C bond-forming reaction of
diarylmethanols carrying halogen atoms on the phenyl group,
such as bis(4-fluorophenyl)methanol (2b) and bis(4-
chlorophenyl)methanol (2c), was examined, as shown in Table 3.
Consequently, the corresponding 2-diarylmethyl-1H-pyrrole (3ab
and 3ac) and 3-diarylmethyl-1H-pyrrole (4ab and 4ac) were
obtained in respective yields of 81 and 63% and 15 and 8%
(entries 2 and 3). In the case of alcohol 2c, the starting alcohol
2c was recovered in 15% yield (entry 3).
As shown in Scheme 1, the use of 2-phenyl(p-tolyl)methanol
(2d) carrying a methyl group as an electron-donating group on
the phenyl group in this reaction gave 2-(phenyl(p-tolyl)methyl)-
1H-pyrrole (3ad), 3-(phenyl(p-tolyl)methyl)-1H-pyrrole (4ad),
and 2,5-bis(phenyl(p-tolyl)methyl)-1H-pyrrole (5ae) in yields of
70%, 6%, and 7% respectively.

4
Tetrahedron
trace amount of 3-(bis(4-methoxyphenyl)methyl)-1H-pyrrole
ACCEPTED MANUSCRIPT
(4ae) (entry 1). However, both the lowered temperature (27 °C)
and the use of 3 equiv. of pyrrole (1a) resulted in increasing the
yield of 2-substituted pyrrole 3ae (74%) and decreasing 2,5-
disubstituted pyrrole 5ae (13 %) (entry 2).
Under this mild conditions, 9H-xanthen-9-ol (2f), which is
commercially available as a methanol solution, also participated
in the EMIMOTf-promoted dehydrative C-C bond-forming
reaction with pyrrole (1a) to give the corresponding 2-substituted
3af in 50% yield, together with 28% yield of 2,5-disubstituted
pyrrole 5af and a trace amount of the corresponding 3-substituted
4af (entry 3).
As shown in Table 5, this EMIMOTf-promoted dehydrative C-C
bond-forming reaction of pyrrole (1a) could also be applied to
tertiary alcohols, such as triphenylmethanol (2g), 1,1-
diphenylethanol (2h), or 9-phenyl-9H-fluoren-9-ol (2i), to give
the corresponding 2-substituted pyrroles (3ag, 3ah, 3ai) in yields
of 79, 81, and 63% and 3-substituted pyrroles (4ah, 4ai) in yields
of 15 and 8%.
Scheme 1. EMIMOTf-promoted dehydrative C-C bond-forming reaction
of 2-phenyl(p-tolyl)methanol (2d) with pyrrole (1a).
The EMIMOTf-promoted dehydrative C-C bond-forming
reaction of other diarylmethanols (2e,f) such as bis(4-
methoxyphenyl)methanol (2e) and 9H-xanthen-9-ol (2f) with
pyrrole (1a) gave slightly different results, as summarized in
Table 4.
Table 5
EMIMOTf-promoted dehydrative C-C bond-forming reaction of tertiary
alcohols (2g-i) with pyrrole (1a).
Table 4
EMIMOTf-promoted dehydrative C-C bond-forming reaction of bis(4-
methoxyphenyl)methanol (2e) and 9H-xanthen-9-ol (2f) with pyrrole (1a).
That is, in the case of bis(4-methoxyphenyl)methanol (2e)
carrying a methoxy group as an electron-donating group on the
phenyl group, under the same reaction conditions (100 °C, 3 h)
Next, the reactions of mono-, di-, and tri-substituted pyrroles,
such as 2-ethylpyrrole (1b), 2,4-dimethylpyrrole (1c), and 3-
ethyl-2,4-dimethylpyrrole (1d), with diphenylmethanol (2a) in
the presence of a stoichiometric amount of EMIMOTf were
2,5-(bis(4-methoxyphenyl)methyl)-1H-pyrrole
(5ae)
were
produced as major products in yields of 62%, together with 21%
yield of 2-(bis(4-methoxyphenyl)methyl)-1H-pyrrole (3ae) and a

5
examined under the same reaction conditions. However, the
reaction did not proceed at all, and the starting alcohol 2a was
recovered in yields of 85-87%.
equiv. of EMIMOTf gave the product 3de in sufficient yield
ACCEPTED MANUSCRIPT
(74%). These results suggest that an increase in the number of
alkyl groups on the pyrrole ring resulted in a decrease in the
yields of the products, probably due to the steric hindrance of the
alkyl groups.
As shown in Table 6, bis(4-methoxyphenyl)methanol (2e)
carrying an electron-donating group on the phenyl group in place
of diphenylmethanol (2a) successfully participated in the reaction
with 2-ethylpyrrole (1b) and 2,4-dimethylpyrrole (1c) to give the
corresponding bis(4-methoxyphenyl)-substituted pyrroles 3be
and 3ce in yields of 70 and 65%, respectively.
Finally, other π–rich heterocyclic compounds in place of pyrrole
(1a), such as indole (6), 2-methylfuran (7), and 2-
methylthiophene (8), were examined in the reaction (Table 7).
Table 7
EMIMOTf-promoted dehydrative C-C bond-forming reaction of other
heterocyclic compounds (6,7,8) with diarylmethanols (2a,c,e).
Table 6
EMIMOTf-promoted dehydrative C-C bond-forming reaction of substituted
pyrroles (1b-d) with bis(4-methoxyphenyl)methanol (2e).
In the case of 3-ethyl-2,4-dimethylpyrrole (1d), the
Consequently, the EMIMOTf-promoted solvent-free dehydrative
C-C bond-forming reactions of indole (6) with diphenylmethanol
corresponding
tetra-substituted
pyrrole,
2-(bis(4-
methoxyphenyl)methyl)-4-ethyl-3,5-dimethyl-1H-pyrrole (3de)
was obtained in 52% yield, together with the starting alcohol 1d
in 44% yields under the same reaction conditions. The use of 3
(2a),
bis(4-chlorophenylmethanol
(2c),
and
bis(4-
methoxyphenyl)methanol (2e) proceeded smoothly to give the
corresponding indoles (9a,c,e) in excellent yields (93-96%). 2-

6
Tetrahedron
methylimidazolium
bis(trifluoromethanesulfonyl)imide
1-ethyl-3-methylimidazolium
Methylfuran (7) also participates in this EMIMOTf-promoted
ACCEPTED MANUSCRIPT
(EMIMNTf2),
and
dehydrative C-C bond-forming reaction of diphenylmethanols
(2a) to give 2-benzhydryl-5-methylfuran (10a) in 60% yield.
The reaction of diphenylmethanols (2a) with 2-methylthiophene
(8) proceeded smoothly to give 2-benzhydryl-5-methylthiophene
(11a) in 68% yield, together with only a trace amount of 4-
benzhydryl-2-methylthiophene.
methanesulfonate (EMIMOMs) were purchased from TCI Fine
Chemicals. 1-Ethyl-2,3-dimethylimidazolium
trifluoromethansulfonate (EDMIMOTf) was purchased from
Fluka. All chemicals were of reagent grade and, if necessary,
purified in the usual manner prior to use.
4.3. Typical procedure (Table 1, entry 7)
Finally, the reuse of EMIMOTf was examined. As results, the
first re-use of the catalyst in the second EMIMOTf-promoted
dehydrative C-C bond-forming reaction of diphenylmethanols
(2a) with pyrrole (1a) gave the product 4aa in 4% yields along
A
mixture of pyrrole (1a) (0.070 g, 1.015 mmol),
diphenylmthanol (2a) (0.184 g, 0.999 mmol), and 1-ethyl-3-
methyl-1H-imidazol-3-ium trifluoromethanesulfonate
(EMIMOTf) (0.262 g, 1.006 mmol) under argon was stirred at
100 °C for 3 h. The mixture was then cooled to room
temperature and extracted from EMIOTf with a mixed solvent of
Et2O-hexane (1 : 1) (8 ml × 3). 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 2-benzhydryl-1H-pyrrole (3aa) (0.185 g, 79%) and 3-
benzhydryl-1H-pyrrole (4aa) (0.039 g, 17%).
with an 81% recovery of 2a.
The result suggests that
contaminated TfOH is also extracted with the mixture of Et2O-
hexane (v/v =1/1) after the first reaction. Therefore, the second
EMIMOTf-promoted dehydrative C-C bond-forming reaction
does not effectively occur.
3. Conclusion
4.3.1. 2-Benzhydryl-1H-pyrrole (3aa).8 Yield 79 %; Mp 65.0-
65.5 °C; Rf 0.31 (hexane : EtOAc = 20 : 1); IR (KBr) 3456 (NH)
In conclusion, we have examined in detail various
commercially available ionic liquids as promoters for solvent-
free dehydrative C-C bond-forming reaction of a variety of
diarylmethanols with π–rich heteroaromatic pyrroles. Our main
findings were as follows: (1) Two commercially available simple
ionic liquids, EMIMOTf and EDMIMOTf, resulted in the
efficient dehydrative C-C bond-forming reaction of
diarylmethanols and triarylmethanols with pyrroles without ring-
opening and polymerization. (2) Not only various
diarylmethanols carrying 4-chloro, 4-fluoro, 4-methyl, and 4-
methoxy-phenyl groups including xanthen-9-ol but also tertiary
alcohols participated in the dehydrative C-C bond-forming
reaction with pyrroles to give the corresponding 2-substituted
pyrroles as major products. (3) The EMIMOTf-promoted
dehydrative C-C bond-forming reaction of alcohols can be
applied to other π–rich heteroaromatics, such as indole, furan,
and thiophene, and gives the corresponding products in good to
excellent yields. These reactions offer several advantages, such
as the use of stoichiometric amounts of alcohols and ionic
liquids, water is the only by-product, there is no need for organic
solvents or expensive metal or strong Brønsted acid catalysts in
the reaction, and the diversity of regioselective diarylmethylation
and triarylmethylation.
1
cm-1; H NMR (CDCl3) δ 5.30 (s, 1H), 5.67-5.68 (m, 1H), 6.01-
6.03 (m, 1H), 6.49-6.51 (m, 1H), 7.02-7.20 (m, 10H), 7.55 (br s,
1H); 13C NMR (CDCl3) δ 50.3 (s), 107.8 (s), 108.0 (s), 117.0 (s),
126.5 (s), 128.3 (s), 128.7 (s), 133.4 (s), 142.9 (s); HRMS (EI)
Found m/z 233.1206, Calcd for C17H15N: M, 233.1205.
4.3.2. 3-benzhydryl-1H-pyrrole (4aa). 8 Yield 17 %; Mp 78.0-
78.3 °C; Rf 0.18 (hexane : EtOAc = 20 : 1); IR (KBr) 3156 (NH)
1
cm-1; H NMR (CDCl3) δ 5.39 (s, 1H), 6.03-6.05 (m, 1H), 6.31-
6.32 (m, 1H), 6.74-6.76 (m, 1H), 7.17-7.30 (m, 10H), 7.99 (br s,
1H); 13C NMR (CDCl3) δ 49.9 (s), 109.2 (s), 117.0 (s), 118.0 (s),
125.9 (s), 126.9 (s), 128.1 (s), 128.9 (s), 145.3 (s); HRMS (EI)
Found m/z 233.1200, Calcd for C17H15N: M, 233.1205.
4.3.3. 2-(Bis(4-fluorophenyl)methyl)-1H-pyrrole (3ab). Yield 81
%; Rf 0.38 (hexane : CH2Cl2 = 1 : 1); IR (KBr) 3464 (NH) cm-1;
1H NMR (CDCl3) δ 5.33 (s, 1H), 5.65-5.68 (m, 1H), 6.05-6.07
(m, 1H), 6.61-6.63 (m, 1H), 6.89 (dd, J = 8.45, 8.45 Hz, 4H),
7.02 (dd, J = 5.56, 8.45 Hz, 4H), 7.69 (br s, 1H); 13C NMR
(CDCl3) δ 49.0 (s), 108.1 (s), 108.3 (s), 115.3 (d, J = 21.3 Hz),
117.4 (s), 130.2 (d, J = 8.2 Hz), 133.2 (s), 138.6 (s), 161.7 (d, J =
245.0 Hz); 19F NMR (CDCl3) δ -40.4 (tt, J = 5.56, 8.45 Hz);
HRMS Found m/z 269.1013, Calcd for C17H13NF2: M, 206.1016.
4.3.4. 3-(Bis(4-fluorophenyl)methyl)-1H-pyrrole (4ab). Yield 15
%; Mp 109.3-110.0 °C; Rf 0.37 (hexane : CH2Cl2 = 1 : 1); IR
4. Experimental section
1
(KBr) 3480 (NH) cm-1; H NMR (CDCl3) δ 5.34 (s, 1H), 5.98-
4.1. Measurements
5.99 (m, 1H), 6.27-6.29 (m, 1H), 6.75-6.77 (m, 1H), 6.92-6.98
(m, 4H), 7.12-7.17 (m, 4H), 7.24 (br s, 1H); 13C NMR (CDCl3)
δ 48.4 (s), 109.0 (s), 114.9 (d, J = 21.3 Hz), 116.9 (s), 118.3 (s),
126.8 (s), 130.2 (d, J = 8.2 Hz), 140.8 (s), 161.3 (d, J = 244.1
Hz); 19F NMR (CDCl3) δ -41.7 (tt, J = 5.34, 8.39 Hz); HRMS
(EI) Found m/z 269.1013, Calcd for C17H13NF2: M, 206.1016.
1H NMR spectra were measured at 400 MHz in
deuterochloroform (CDCl3), hexahexadeuterodimethyl sulfoxide
(DMSO-d6), or hexadeuteroacetone (CD3COCD3) solutions with
tetramethylsilane (Me4Si) as an internal standard. 13C NMR
spectra were obtained at 100 MHz in CDCl3, DMSO-d6, or
CD3COCD3 solution with Me4Si as an internal standard. 19F
NMR spectra were recorded at 372 MHz in CDCl3, DMSO-d6, or
CD3COCD3 solutions using trifluoroacetic acid as an external
standard.
4.3.5. 2-(Bis(4-chlorophenyl)methyl)-1H-pyrrole (3ac). Yield 63
%; Rf 0.60 (hexane : CH2Cl2 = 1 : 1); IR (KBr) 3457 (NH) cm-1;
1H NMR (CDCl3) δ 5.39 (s, 1H), 5.71-5.72 (m, 1H), 6.13-6.14
(m, 1H), 6.70-6.71 (m, 1H), 7.07 (AB quartet, J = 8.21 Hz, 4H),
7.26 (AB quartet, J = 8.21 Hz, 4H), 7.77 (br s, 1H); 13C NMR
(CDCl3, 100 MHz) δ 49.3 (s), 108.3 (s), 108.4 (s), 117.6 (s),
128.4 (s), 128.7 (s), 130.1 (s), 132.7 (s), 141.1 (s); HRMS (EI)
Found m/z 301.0423, Calcd for C17H13N35Cl2: M, 301.0425.
4.2. Materials
Various
1-ethyl-3-methyl-1H-imidazol-3-ium
trifluoromethanesulfonates (EMIMOTf) were a gift from Central
Glass Co. or purchased from TCI Fine Chemicals, Wako Pure
Chemicals, Merck KGaA, and Aldrich Co.
methylimidazolium tetrafluoroborate (BMIMBF4), 1-butyl-3-
methylimidazolium hexafluorophosphate (BMIMPF6), 1-ethyl-3-
1-Butyl-3-
4.3.6. 2-(Bis(4-chlorophenyl)methyl)-1H-pyrrole (4ac). Yield 8
%; Rf 0.47 (hexane : CH2Cl2 = 1 : 1); IR (KBr) 3476 (NH) cm-1;

7
8
1H NMR (CDCl3) δ 5.31 (s, 1H), 5.97-5.98 (m, 1H), 6.28-6.30
(m, 1H), 6.75-6.77 (m, 1H), 7.11 (AB quartet, J = 8.21 Hz, 4H),
7.23 (AB quartet, J = 8.21 Hz, 4H), 8.04 (br s, 1H); 13C NMR
(CDCl3) δ 48.7 (s), 109.0 (s), 117.0 (s), 118.4 (s), 126.1 (s), 128.3
(s), 130.2 (s), 132.0 (s), 143.3 (s); HRMS (EI) Found m/z
301.0427, Calcd for C17H13N35Cl2: M, 301.0425.
4.3.14. 2-Trityl-1H-pyrrole (3ag). Yield 99 %; Mp 232.5-
ACCEPTED MANUSCRIPT
233.1 °C; Rf 0.50 (hexane : EtOAc = 10 : 1); IR (KBr) 3433
(NH) cm-1; H NMR (DMSO-d6) δ 5.64-5.67 (m, 1H), 5.91-5.93
1
(m, 1H), 6.69-6.70 (m, 1H), 6.99-7.04 (m, 5H), 7.21-7.31 (m,
10H), 10.28 (br s, 1H); 13C NMR (DMSO-d6) δ 59.9 (s), 106.0 (s),
109.5 (s), 118.6 (s), 126.2 (s), 127.5 (s), 129.9 (s), 135.9 (s),
146.2 (s); HRMS (EI) Found m/z 309.1519, Calcd for C23H19N:
M, 309.1518.
4.3.7. 2-(Phenyl(p-tolyl)methyl)-1H-pyrrole (3ad). Yield 70 %;
Rf 0.40 (hexane : EtOAc = 10 : 1); IR (KBr) 3456 (NH) cm-1; 1H
NMR (CDCl3) δ 2.31 (s, 3H), 5.41 (s, 1H), 5.78-5.79 (m, 1H),
6.12-6.14 (m, 1H), 6.65-6.67 (m, 1H), 7.02-7.29 (m, 9H), 7.76
(br s, 1H); 13C NMR (CDCl3) δ 21.1 (s), 50.2 (s), 107.9 (s),
108.3 (s), 117.1 (s), 126.7 (s), 128.5 (s), 128.8 (s), 128.9 (s),
129.3 (s), 133.9 (s), 136.3 (s), 140.2 (s), 143.4 (s); HRMS (EI)
Found m/z 247.1355, Calcd for C18H17N: M, 247.1361.
4.3.15. 2-(1,1-Diphenylethyl)-1H-pyrrole (3ah). Yield 81 %; Mp
71.0-71.5 °C; Rf 0.27 (hexane : EtOAc = 20 : 1); IR (KBr) 3456
(NH) cm-1; 1H NMR (CDCl3, 400 MHz) δ 2.08 (s, 3H), 5.95-5.97
(m, 1H), 6.13-6.15 (m, 1H), 6.56-6.57 (m, 1H), 7.05-7.08 (m,
2H), 7.15-7.25 (m, 6H), 7.55 (br s, 1H); 13C NMR (CDCl3, 100
MHz) δ 30.2 (s), 49.5 (s), 107.5 (s), 108.9 (s), 117.8 (s), 127.2 (s),
128.9 (s), 129.0 (s), 138.9 (s), 149.2 (s); HRMS (EI) Found m/z
247.1363, Calcd for C18H17N: M, 247.1361.
4.3.8. 3-(Phenyl(p-tolyl)methyl)-1H-pyrrole (4ad). Yield 6 %; Rf
1
0.28 (hexane :EtOAc = 10 : 1); IR (KBr) 3476 (NH) cm-1; H
NMR (CDCl3) δ 2.31 (s, 3H), 5.34 (s, 1H), 6.02-6.03 (m, 1H),
6.31-6.32 (m, 1H), 6.73-6.75 (m, 1H), 7.06-7.28 (m, 9H), 7.99
(br s, 1H); 13C NMR (CDCl3) δ 21.0 (s), 49.5 (s), 109.2 (s), 117.0
(s), 118.0 (s), 125.9 (s), 127.1 (s), 128.1 (s), 128.76 (s), 128.82
(s), 128.9 (s), 135.4 (s), 142.3 (s), 145.5 (s); HRMS (EI) Found
m/z 247.1355, Calcd for C18H17N: M, 247.1361.
4.3.16. 3-(1,1-Diphenylethyl)-1H-pyrrole (4ah). Yield 15 %; Mp
148.1-148.8 °C; Rf 0.20 (hexane : EtOAc = 10 : 1); IR (KBr)
1
3472 (NH) cm-1; H NMR (CDCl3) δ 2.08 (s, 3H), 6.05-6.07 (m,
1H), 6.22-6.23 (m, 1H), 6.75-6.77 (m, 1H), 7.15-7.27 (m, 10H),
7.98 (br s, 1H); 13C NMR (CDCl3) δ 30.4 (s), 47.8 (s), 109.1 (s),
116.7 (s), 117.9 (s), 125.8 (s), 127.8 (s), 128.3 (s), 132.7 (s),
150.4 (s); HRMS (EI) Found m/z 247.1361, Calcd for C18H17N:
M, 247.1361.
4.3.9. 2,5-Bis(phenyl(p-tolyl)methyl)-1H-pyrrole (5ad). Yield 7
%; Mp 53.5-54.0°C; Rf 0.80 (hexane : CH2Cl2 = 1 : 1); IR (KBr)
1
3445 (NH) cm-1; H NMR (CDCl3) δ 2.30 (s, 6H), 5.32 (s, 2H),
4.3.17. 2-(9-Phenyl-9H-fluoren-9-yl)-1H-pyrrole (3ai). Yield
84 %; Mp 217.0-217.6 °C; Rf 0.33 (hexane : EtOAc = 10 : 1); IR
5.60 (d, J = 2.66 Hz, 2H), 7.03-7.08 (m, 9H), 7.14-7.20 (m, 7H),
7.22-7.27 (m, 2H), 7.45 (br s, 1H); 13C NMR (CDCl3) δ 21.0 (s),
50.2 (s), 107.9 (s), 126.5 (s), 128.3 (s), 128.7 (s), 128.8 (s), 129.1
(s), 133.5 (s), 136.1 (s), 140.1 (s), 143.3 (s); HRMS (EI) Found
m/z 427.2301, Calcd for C32H29N: M, 427.2300.
1
(KBr) 3476 (NH) cm-1; H NMR (Acetone) δ 5.72-5.74 (m, 1H),
5.93-5.95 (m, 1H), 6.75-6.76 (m, 1H), 7.05-7.07 (m, 2H), 7.15-
7.22 (m, 3H), 7.29 (dt, J = 1.21, 7.49 Hz, 2H), 7.38 (dt, J = 1.21,
7.49 Hz, 2H), 7.56-7.58 (m, 2H), 7.86-7.88 (m, 2H), 9.92 (br s,
1H); 13C NMR (acetone-d6) δ 61.5 (s), 107.5 (s), 108.4 (s), 119.2
(s), 121.0 (s), 126.7 (s), 127.5 (s), 128.2 (s), 128.3 (s), 128.4 (s),
129.0 (s), 134.0 (s), 140.8 (s), 146.1 (s), 151.7 (s); HRMS Found
m/z 307.1357, Calcd for C23H17N: M, 307.1361.
4.3.10. 2-(Bis(4-methoxyphenyl)methyl)-1H-pyrrole (3ae). Yield
74 %; Rf 0.20 (hexane : EtOAc = 10 : 1); IR (KBr) 3460 (NH)
1
cm-1; H NMR (CDCl3) δ 3.69 (s, 6H), 5.27 (s, 1H), 5.68-5.69
(m, 1H), 6.04-6.06 (m, 1H), 6.59-6.75 (m, 1H), 6.74 (AB quartet,
J = 8.69 Hz, 4H), 7.00 (AB quartet, J = 8.69 Hz, 4H), 7.71 (br,
1H); 13C NMR (CDCl3) δ 49.1 (s), 55.5 (s), 107.9 (s), 108.4 (s),
114.1 (s), 117.2 (s), 130.0 (s), 134.6 (s), 135.8 (s), 158.5 (s);
HRMS (EI) Found m/z 293.1410, Calcd for C19H19NO2: M,
293.1416.
4.3.18. 3-(9-Phenyl-9H-fluoren-9-yl)-1H-pyrrole (4ai). Yield
6 %; Mp 114.6-147.0 °C; Rf 0.18 (hexane : EtOAc = 2 : 1); IR
1
(KBr) 3476 (NH) cm-1; H NMR (CDCl3) δ 6.26-6.28 (m, 1H),
6.37-6.39 (m, 1H), 6.74-6.76 (m, 1H), 7.15-7.18 (m, 5H), 7.23-
7.27 (m, 2H), 7.33 (dt, J = 1.21, 7.49 Hz, 2H), 7.42-7.44 (m, 2H),
7.73-7.76 (m, 2H), 7.91 (br s, 1H); 13C NMR (CDCl3) δ 59.8 (s),
109.2 (s), 116.6 (s), 118.3 (s), 120.0 (s), 125.7 (s), 126.3 (s),
127.1 (s), 127.2 (s), 127.4 (s), 127.7 (s), 128.0 (s), 139.8 (s),
146.2 (s), 152.6 (s); HRMS (EI) Found m/z 307.1364, Calcd for
C23H17N: M, 307.1361.
4.3.11. 2,5-(Bis(4-methoxyphenyl)methyl)-1H-pyrrole (5ae).
Yield 13 %; Mp 149.5-150.0 °C; Rf 0.08 (hexane : EtOAc = 10 :
1
1); IR (KBr) 3441 (NH) cm-1; H NMR (CDCl3) δ 3.78 (s, 12H),
5.29 (s, 2H), 5.63 (d, J = 2.66 Hz, 2H), 6.83 (AB quartet, J = 8.69
Hz, 8H), 7.09 (AB quartet, J = 8.69 Hz, 8H), 7.56 (br s, 1H); 13
C
NMR (CDCl3) δ 48.9 (s), 55.1 (s), 107.6 (s), 113.6 (s), 129.6 (s),
134.0 (s), 135.6 (s), 158.1 (s); HRMS (EI) Found m/z 519.2403,
Calcd for C34H33NO4: M, 519.2410.
4.3.19. 2-(Bis(4-methoxyphenyl)methyl)-5-ethyl-1H-pyrrole (3be).
Yield 70 %; Rf 0.3 (chloroform : hexane = 5 : 1); IR (KBr) 3456
(NH) cm-1; 1H NMR (CDCl3) δ 1.18 (t, J = 7.50 Hz, 3H), 2.36 (q,
J = 7.50 Hz, 2H), 3.77 (s, 6H), 5.30 (s, 1H), 5.60 (s, 1H), 5.78 (s,
1H), 6.80-7.10 (m, 8H)7.47 (s, 1H); 13C NMR (CDCl3, 400 MHz)
δ 13.5 (s), 20.9 (s), 49.1 (s), 55.3 (s), 103.9 (s), 107.7 (s), 113,8
(s), 129.8 (s), 131.1 (s), 132.5 (s), 135.8 (s), 158.3 (s); HRMS
(EI) Found m/z 321.1720, Calcd for C21H23NO2: M, 321.1729.
4.3.12. 2-(9H-Xanthen-9-yl)-1H-pyrrole (3af). 8 Yield 50 %; Mp
114.2-115.8 °C; Rf 0.23 (hexane : CH2Cl2 = 3 : 1); IR (KBr) 3402
1
(NH) cm-1; H NMR (CDCl3) δ 5.35 (s, 1H), 6.10-6.12 (m, 1H),
6.15-6.16 (m, 1H), 6.59-6.61 (m, 1H), 6.99-7.24 (m, 8H) 7.66 (br
s 1H); 13C NMR (CDCl3) δ 37.2 (s), 107.2 (s), 107.9 (s), 116.6
(s), 118.0 (s), 122.8 (s), 123.3 (s), 128.1 (s), 129.3 (s), 134.1 (s),
151.2 (s); HRMS (EI) Found m/z 247.0998, Calcd for C17H13NO:
M, 247.0998.
4.3.20. 2-(Bis(4-methoxyphenyl)methyl)-3,5-dimethyl-1H-pyrrole
(3ce). Yield 65 %; Rf 0.55 (hexane : EtOAc = 5 : 1); IR (KBr)
1
3456 (NH) cm-1; H NMR (CDCl3) δ 1.85 (s, 3H), 2.13 (s, 3H),
3.78 (s, 6H), 5.41 (s, 1H), 5.71 (s, 1H), 6.84-7.09 (m, 8H); 13C
NMR (CDCl3) δ 11.2 (s), 13.1 (s), 46.9 (s), 55.3 (s), 108.5 (s),
113.9 (s), 114.9 (s), 125.4 (s), 127.6 (s), 129.8 (s), 135.7 (s),
158.2 (s); HRMS (EI) Found m/z 321.1738, Calcd for
C21H23NO2: M, 321.1729.
4.3.13. 2,5-Di(9H-xanthen-9-yl)-1H-pyrrole (5af). 8 Yield 28 %;
Mp 187.7-188.5 °C; Rf 0.35 (hexane : CH2Cl2 = 3 : 1); IR (KBr)
1
3379 (NH) cm-1; H NMR (CDCl3) δ 5.21 (s, 2H), 6.00 (d, J =
2.90 Hz, 2H), 6.91-7.02 (m, 12H), 7.12-7.22 (m, 4H), 7.35 (br s
1H); 13C NMR (CDCl3) δ 36.9 (s), 107.4 (s), 116.0 (s), 122.6 (s),
122.7 (s), 127.6 (s), 128.5 (s), 133.4 (s), 150.9 (s); HRMS (EI)
Found m/z 427.1566, Calcd for C30H21NO2: M, 427.1572.
4.3.21. 2-(Bis(4-methoxyphenyl)methyl)-4-ethyl-3,5-dimethyl-1H-
pyrrole (3de). Yield 74 %; Rf 0.4 (chloroform : hexane = 5 : 1);

8
Tetrahedron
ACCEPTED MANUSCRIPT
IR (KBr) 3456 (NH) cm-1; 1H NMR (CDCl3) δ 1.05 (t, J = 7.50
Chauhan, S. M. S. Tetrahedron 2005, 61, 1015-1060. (f) Andrade,
Carlos Kleber Z.; Alves, Luana M. Curr. Org. Chem. 2005, 9,
195-218.
Hz, 3H), 1.80 (s, 1H), 2.05 (s, 1H), 2.36 (q, J = 7.50 Hz, 2H),
3.72 (s, 6H), 5.17 (s, 1H), 5.38 (s, 1H), 6.78-7.02 (m, 8H); 13C
NMR (CDCl3) δ 10.1 (s), 12.0 (s), 17.1 (s), 19.5 (s), 48.1 (s),
56.5 (s), 115.0 (s), 115.5 (s), 122.0 (s), 122.2 (s), 127.1 (s), 131.0
(s), 137.1 (s), 159.5 (s); HRMS (EI) Found m/z 349.2048, Calcd
for C23H27NO2: M, 349.2041.
2. (a) Cui, X.; Zhang, S.; Shi, F.; Zhang, Q.; Ma, X.; Lu, L.; Deng,
Y. ChemSusChem. 2010, 3, 1043-1047. (b) Kantam, M. L.;
Chakravatri, R.; Bhargava, S. Synlett 2008, 1449-1054. (c) Sun,
W.; Xia, C.-C.; Wang, H.-W. Tetrahedron Lett. 2003, 44, 2409-
2411. (d) Yadav, J. S.; Reddy, B. V. S.; Basak, A. K.; Narsaiah, A.
V. Tetrahedron Lett. 2003, 44, 1047-1050. (e) Kim, D. W.; Song,
C. E.; Chi, D. Y. J. Am. Chem. Soc. 2002, 124, 10278-10279.
3. For a recent review for dehydrative C-C bond formation of
alcohols, see. (a) Kumar, R. E.; Van der Eycken V. Chem. Soc.
Rev. 2013, 42, 1121-1146. (b) Emer, E.; Sinisi, R.; Capdevila, M.
G.; Petruzziello, D.; Vincentiis, F. D.; Cozzi, P. G. Eur. J. Org.
Chem. 2011, 647-666. (c) Rueping, M.; Nachtsheim, B. J. Beil. J.
Org. Chem. 2010, 6, 1-24. (d) Bandini, M.; Tragni, M. Org.
Biomol. Chem. 2009, 7, 1501-1507.
6
4.3.22. 3-Benzhydryl-1H-indole (9a). Yield 93 %; Rf 0.53
(hexane : CH2Cl2 = 1 : 1); IR (KBr) 3421 (NH) cm-1; H NMR
1
(CDCl3) δ 5.63 (s, 1H), 6.427-6.429 (m, 1H), 7.08-7.29 (m, 14H),
7.67 (br s, 1H); 13C NMR (CDCl3) δ 48.7 (s), 102.4 (s), 111.0 (s),
119.3 (s), 119.7 (s), 120.6 (s), 122.0 (s), 124.0 (s), 126.2 (s),
128.2 (s), 128.9 (s), 136.6 (s), 143.9 (s); HRMS (EI) Found m/z
283.1360, Calcd for C21H17N: M, 283.1361.
4. For an ionic liquid-promoted dehydrative C-C bond formation of
aldehydes with indole without any catalyst, see. (a) Chakraborti, A.
K.; Roy, S. R.; Kumar, D.; Chopra, P. Green Chem. 2008, 10,
1111-1118. For a specific ionic liquid-promoted dehydrative C-C
bond formation reaction of 1,3-dicarbonyl compounds with
propargyl alcohols without any catalyst, see. (b) Aridoss, G.; Laali,
K. K. Tetrahedron Lett. 2011, 52, 6859-6864. For a commercially
available ionic liquid-promoted dehydrative C-C bond formation
reaction of 2,4-pentanedione with diphenylmethanol without any
catalyst (only one example), see. (c) Funabiki, K.; Komeda, T.;
Kubota, Y.; Matsui, M. Tetrahedron 2009, 65, 7457-7463.
5. For a selected book and reviews, see. (a) Jones, R. A.; Bean, G. P.
The Chemistry of Pyrroles, New York, 1968. (b) Belen’skii, I. L.
Heterocycles 1994, 37, 2029-2049.
6. (a) Cano, R.; Yus, M.; Ramon, D. J. Tetrahedron Lett. 2013, 54,
3394-3397. (b) Sato, Y.; Aoyama, T.; Takido, T.; Kodomari, M.
Tetrahedron 2012, 68, 7077-7081. (c) Liu, L.-Y.; Wang, B.; Yang,
H.-M.; Chang, W.-X.; Li, J. Tetrahedron Lett. 2011, 52, 5636-
5639. (d) Yuan, F.-Q.; Gao, L.-X.; Han, F.-S. Chem. Commun.
2011, 47, 5289-5291. (e) McCubbin, J. A.; Krokhin, O. V.
Tetrahedron Lett. 2010, 51, 2447-2449. (f) Hirashita, T.;
Kuwahara, S.; Okochi, S.; Tsuji, M.; Araki, S. Tetrahedron Lett.
2010, 51, 1847-1851. (g) De Rosa, M.; Soriente, A. Eur. J. Org.
Chem. 2010, 1029-1032, (h) Matsuo, J.; Tanaki, Y.; Ishibashi, H.
Tetrahedron 2008, 64, 5262-5267. (i) Srihari, P.; Bhunia, D. C.;
Sreedhar, P.; Yadav, J. S. Synlett 2008, 1045-1049. (j) Yadav, J.
S.; Bhunia, D. C.; Krishna, K. V.; Srihari, P. Tetrahedron Lett.
2007, 48, 8306-8310. (k) Jana, U.; Maiti, S.; Biswas, S.
4.3.23. 3-(Bis(4-fluorophenyl)methyl)-1H-indole (9c). Yield
96 %; Rf 0.23 (hexane : EtOAc = 5 : 1); IR (KBr) 3459 (NH) cm-
1
1; H NMR (CDCl3) δ 5.72 (s, 1H), 6.517-6.522 (m, 1H), 7.03-
7.16 (m, 5H), 7.23-7.40 (m, 7H), 7.85 (br s, 1H); 13C NMR
(CDCl3) δ 46.7 (s), 101.9 (s), 110.7 (s), 114.6 (d, J = 21.3 Hz),
119.0 (s), 119.2 (s), 121.7 (s), 123.5 (s), 126.1 (s), 129.7 (d, J =
8.2 Hz), 136.2 (s), 138.9 (d, J = 3.3 Hz), 160.9 (d, J = 245.0 Hz);
19F NMR (CDCl3) δ -40.8 (tt, J = 5.34, 8.39 Hz); HRMS (EI)
Found m/z 319.1172, Calcd for C21H15NF2: M, 319.1173.
6
4.3.24. 3-(Bis(4-methoxyphenyl)methyl)-1H-indole (9e). Yield
94 %; Mp 118.2-119.5 °C; Rf 0.53 (hexane : CH2Cl2 = 1 : 1); IR
(KBr) 3418 (NH) cm-1; 1H NMR (CDCl3) δ 3.74 (s, 6H), 5.55 (s,
1H), 6.476-6.481 (m, 1H), 6.79 (AB quartet, J = 8.69 Hz, 4H),
6.91-7.00 (m, 2H), 7.11 (AB quartet, J = 8.69 Hz, 4H), 7.18-7.27
(m, 2H), 7.89 (br s, 1H); 13C NMR (CDCl3) δ 47.1 (s), 55.1 (s),
111.0 (s), 113.5 (s), 119.2 (s), 119.9 (s), 120.4 (s), 121.9 (s),
123.9 (s), 126.9 (s), 129.7 (s), 136.5 (s), 136.7 (s), 157.8 (s);
HRMS (EI) Found m/z 343.1573, Calcd for C23H21NO2: M,
343.1572.
4.3.25. 2-Benzhydryl-5-methylfuran (10a).11 Yield 60 %; Rf 0.24
(hexane : CH2Cl2 = 10 : 1); 1H NMR (CDCl3) δ 2.24 (s, 3H), 5.39
(s, 1H), 5.74 (d, J = 2.30 Hz, 1H), 5.86 (d, J = 2.30 Hz, 1H), 7.10-
7.35 (m, 10H); 13C NMR (CDCl3) 13.8 (s), 51.1 (s), 106.0 (s),
109.2 (s), 126.7 (s), 128.5 (s), 128.9 (s), 142.2 (s), 151.6 (s),
154.9 (s); HRMS (EI) Found m/z 248.1207, Calcd for C18H16O:
M, 248.1202.
4.3.26. 2-Benzhydryl-5-methylthiophene (11a).11 Yield 68 %; Rf
0.19 (hexane : CH2Cl2 = 10 : 1); 1H NMR (CDCl3) δ 2.41 (s, 3H,
CH3), 5.58 (s, 1H), 6.45 (d, J = 3.68 Hz, 1H), 6.55-6.57 (m, 1H),
7.20-7.40 (m, 10H); 13C NMR (CDCl3) 15.4 (s), 52.4 (s), 124.7
(s), 126.2 (s), 126.7 (s), 128.5 (s), 128.9 (s), 129.1 (s), 139.1 (s),
144.0 (s), 145.5 (s); HRMS (EI) Found m/z 264.0974, Calcd for
C18H16S: 264.0974.
Tetrahedron Lett. 2007, 48, 7160-7163. (l) Motokura, K.; Nakagiri,
N.; Mizugaki, T.; Ebitani, K.; Kaneda, K. J. Org. Chem. 2007, 72,
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Acknowledgments
9. Zaitsev, A. B.; Gruber, S.; Plüss, P. A.; Pregosin, P. S.; Veiros, L.
F.; Wörle, M. J. Am. Chem. Soc. 2008, 130, 11604-11605.
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Yoshikawa, M.; Miltor, M. D.; Nishibayashi, Y.; Uemura, S. Eur.
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11847.
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 (EMIMOTf).
References and notes
1. For recent reviews for ionic liquid, see. (a) Shanab, K.; Neudorfer,
C.; Schirmer, E.; Spreitzer, H. Cur. Org. Chem. 2013, 17, 1179-
1187. (b) Lee, J.-W.; Shin, J.-Y.; Chun, Y.-S.; Jang, H.-B.; Song,
C.-E.; Lee, S.-G. Acc. Chem. Res. 2010, 43, 985-994. (c) Miao,
W.; Chan, T. H. Acc. Chem. Res. 2006, 39, 897-908. (d) Lee, S.-
G. Chem. Commun. 2006, 1049-1063. (d) Sheldon, R. A. Green
Chem. 2005, 7, 267-278. (e) Jain, N.; Kumar, A.; Chauhan, S.;
11. Yuan, F.; Gao, L.; Han, F. Chem. Commun. 2011, 47, 5289-5291.
Supplementary Material

ACCEPTED MANUSCRIPT
Supporting information
Commercially available simple ionic liquids-promoted
dehydrative carbon-carbon bond-forming reaction of
diarylmethanols and triarylmethanols with pyrroles, thiophene,
furan and indoles
Kazumasa Funabiki,* Takuya Komeda, Kouhei Nishikawa, Kentaro Yamada,
Yasuhiro Kubota, and Masaki Matsui
Department of Chemistry and BiomolecularScience, Faculty of Engineering,
Gifu University,
1-1 Yanagido, Gifu 501-1193, Japan
E-mail: funabiki@gifu-u.ac.jp
(Contents)
1H and 13C NMR for 3aa
1H and 13C NMR for 4aa
1H and 13C NMR for 3ab
1H and 13C NMR for 4ab
1H and 13C NMR for 3ac
1H and 13C NMR for 4ac
1H and 13C NMR for 3ad
1H and 13C NMR for 4ad
1H and 13C NMR for 5ad
1H and 13C NMR for 3ae
1H and 13C NMR for 5ae
1H and 13C NMR for 3af
1H and 13C NMR for 5af
1H and 13C NMR for 3ag
1H and 13C NMR for 3ah
1H and 13C NMR for 4ah
1H and 13C NMR for 3ai
1H and 13C NMR for 4ai
1H and 13C NMR for 3be
1H and 13C NMR for 3ce
1H and 13C NMR for 3de
1H and 13C NMR for 9a
1H and 13C NMR for 9c
1H and 13C NMR for 9e
1H and 13C NMR for 10a
1H and 13C NMR for 11a
p.2
p.3
p.4
p.5
p.6
p.7
p.8
p.9
p.10
p.11
p.12
p.13
p.14
p.15
p.16
p.17
p.18
p.19
p.20
p.21
p.22
p.23
p.24
p.25
p.26
p.27

ACCEPTED MANUSCRIPT
2-benzhydryl-1H-pyrrole (3aa)
1H NMR
N
H
13C NMR
N
H
2

ACCEPTED MANUSCRIPT
3-benzhydryl-1H-pyrrole (4aa)
1H NMR
N
H
13C NMR
N
H
3

ACCEPTED MANUSCRIPT
2-(bis(4-fluorophenyl)methyl)-1H-pyrrole (3ab)
1H NMR
F
N
H
F
13C NMR
F
N
H
F
4

ACCEPTED MANUSCRIPT
3-(bis(4-fluorophenyl)methyl)-1H-pyrrole (4ab)
1H NMR
F
F
N
H
13C NMR
F
F
N
H
5

ACCEPTED MANUSCRIPT
2-(bis(4-chlorophenyl)methyl)-1H-pyrrole (3ac)
1H NMR
Cl
N
H
Cl
13C NMR
Cl
N
H
Cl
6

ACCEPTED MANUSCRIPT
2-(bis(4-chlorophenyl)methyl)-1H-pyrrole (4ac)
1H NMR
Cl
Cl
N
H
13C NMR
Cl
Cl
N
H
7

ACCEPTED MANUSCRIPT
2-(phenyl(p-tolyl)methyl)-1H-pyrrole (3ad)
1H NMR
Me
N
H
13C NMR
Me
N
H
8

ACCEPTED MANUSCRIPT
3-(phenyl(p-tolyl)methyl)-1H-pyrrole (4ad)
1H NMR
Me
N
H
13C NMR
Me
N
H
9

ACCEPTED MANUSCRIPT
2,5-bis(phenyl(p-tolyl)methyl)-1H-pyrrole (5ad)
1H NMR
Me
Me
N
H
13C NMR
Me
Me
N
H
10

ACCEPTED MANUSCRIPT
2-(bis(4-methoxyphenyl)methyl)-1H-pyrrole (3ae)
1H NMR
OMe
N
H
OMe
13C NMR
OMe
N
H
OMe
11

ACCEPTED MANUSCRIPT
2,5-(bis(4-methoxyphenyl)methyl)-1H-pyrrole (5ae)
1H NMR
MeO
OMe
N
H
MeO
OMe
13C NMR
MeO
OMe
N
H
MeO
OMe
12

ACCEPTED MANUSCRIPT
2-(9H-xanthen-9-yl)-1H-pyrrole (3af)
1H NMR
N
O
H
13C NMR
N
O
H
13

ACCEPTED MANUSCRIPT
2,5-di(9H-xanthen-9-yl)-1H-pyrrole (5af)
1H NMR
N
H
O
O
13C NMR
N
H
O
O
14

ACCEPTED MANUSCRIPT
2-trityl-1H-pyrrole (3ag)
1H NMR
N
H
13C NMR
N
H
15

ACCEPTED MANUSCRIPT
2-(1,1-diphenylethyl)-1H-pyrrole (3ah)
1H NMR
N
H
Me
13C NMR
N
H
Me
16

ACCEPTED MANUSCRIPT
3-(1,1-diphenylethyl)-1H-pyrrole (4ah)
1H NMR
Me
N
H
13C NMR
Me
N
H
17

ACCEPTED MANUSCRIPT
2-(9-phenyl-9H-fluoren-9-yl)-1H-pyrrole (3ai)
1H NMR
N
H
13C NMR
N
H
18

ACCEPTED MANUSCRIPT
3-(9-phenyl-9H-fluoren-9-yl)-1H-pyrrole (4ai)
1H NMR
N
H
13C NMR
N
H
19

ACCEPTED MANUSCRIPT
2-(bis(4-methoxyphenyl)methyl)-5-ethyl-1H-pyrrole (3be)
1H NMR
OMe
N
H
OMe
13C NMR
OMe
N
H
OMe
20