Electrophilic chemistry of propargylic alcohols in imidazolium ionic liquids: Propargylation of arenes and synthesis of propargylic ethers catalyzed by metallic triflates [Bi(OTf)3, Sc(OTf)3, Yb(OTf) 3], TfOH, or B(C6F5)3

Article abstract of DOI:10.1039/c0ob00872a

Metallic triflates M(OTf)₃ (M = Bi, Sc, Yb), immobilized in imidazolium ionic liquids [BMIM][BF₄], [BMIM][PF₆] and [BMIM][OTf] are efficient systems for one-pot reactions of propargylic alcohols 1,3-diphenyl-2-propyn-1-ol Ia, 1-methyl-3-phenyl-2-propyn-1-ol Ib, and 2-pentyn-1-ol Ic, with a wide range of arenes bearing activating substituents, under mild conditions. The [BMIM][PF₆]/B(C₆F ₅)₃ and [BMIM][PF₆]/TfOH systems were superior in propargylation with Ib and Ic, while reaction of 3-phenyl-2-propyn-1-ol Id with activated aromatics resulted in the formation of diaryl-propanones instead. Propargylation of anisole with Ib under M(OTf)₃ catalysis is highly para selective, but with TfOH or B(C₆F₅)₃ as catalyst the ortho isomer was also formed. Steric influence of the propargylic moiety on substrate selectivity is reflected in the lack of ortho propargylation for phenol and ethylbenzene by using propargylic alcohol Ia, and notable formation of the ortho isomer employing alcohol Ib. In the later case para selectivity could be increased by running the reaction at r. t. for 10 h. The Bi(OTf)₃-catalyzed reaction of 1,3-dimethoxybenzene with Ia led to minor formation of dipropargylated derivative, along with the monopropargyl product. Propargylation of the less reactive arenes (mesitylene, ethylbenzene, toluene), using Sc(OTf)₃ as catalyst, led increasingly to the formation of dipropargylic ethers and propargyl ketones, with no ring propargylation product with toluene. Concomitant formation of dipropargylic ether was also observed in Yb(OTf)₃-catalyzed propargylation of β-naphthol, whereas propargylation of 2-nitro and 4-nitro-aniline led to N-propargylation. The recycling/reuse of the IL was demonstrated in representative cases with no appreciable decrease in the conversions over 3 cycles. It was also shown that recycled IL could be used to propargylate a different aromatic compound. The efficacy of IL/M(OTf)₃ and IL/TfOH systems for cross-breeding two propargylic alcohols or a propargylic alcohol with a non-propargylic alcohol and/or self-coupling, to form a wide variety of functionalized ethers is also demonstrated.

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PAPER
Electrophilic chemistry of propargylic alcohols in imidazolium ionic liquids:
Propargylation of arenes and synthesis of propargylic ethers catalyzed by
metallic triflates [Bi(OTf)3, Sc(OTf)3, Yb(OTf)3], TfOH, or B(C6F5)3†
Gopalakrishnan Aridoss,a Viorel D. Sarca,b James F. Ponder Jr,‡a Jessica Crowe‡a and Kenneth K. Laali*a
Received 12th October 2010, Accepted 11th January 2011
DOI: 10.1039/c0ob00872a
Metallic triflates M(OTf)3 (M = Bi, Sc, Yb), immobilized in imidazolium ionic liquids [BMIM][BF4],
[BMIM][PF6] and [BMIM][OTf] are efficient systems for one-pot reactions of propargylic alcohols
1,3-diphenyl-2-propyn-1-ol Ia, 1-methyl-3-phenyl-2-propyn-1-ol Ib, and 2-pentyn-1-ol Ic, with a wide
range of arenes bearing activating substituents, under mild conditions. The [BMIM][PF6]/B(C6F5)3 and
[BMIM][PF6]/TfOH systems were superior in propargylation with Ib and Ic, while reaction of
3-phenyl-2-propyn-1-ol Id with activated aromatics resulted in the formation of diaryl-propanones
instead. Propargylation of anisole with Ib under M(OTf)3 catalysis is highly para selective, but with
TfOH or B(C6F5)3 as catalyst the ortho isomer was also formed. Steric influence of the propargylic
moiety on substrate selectivity is reflected in the lack of ortho propargylation for phenol and
ethylbenzene by using propargylic alcohol Ia, and notable formation of the ortho isomer employing
alcohol Ib. In the later case para selectivity could be increased by running the reaction at r. t. for 10 h.
The Bi(OTf)3-catalyzed reaction of 1,3-dimethoxybenzene with Ia led to minor formation of
dipropargylated derivative, along with the monopropargyl product. Propargylation of the less reactive
arenes (mesitylene, ethylbenzene, toluene), using Sc(OTf)3 as catalyst, led increasingly to the formation
of dipropargylic ethers and propargyl ketones, with no ring propargylation product with toluene.
Concomitant formation of dipropargylic ether was also observed in Yb(OTf)3-catalyzed propargylation
of b-naphthol, whereas propargylation of 2-nitro and 4-nitro-aniline led to N-propargylation. The
recycling/reuse of the IL was demonstrated in representative cases with no appreciable decrease in the
conversions over 3 cycles. It was also shown that recycled IL could be used to propargylate a different
aromatic compound. The efficacy of IL/M(OTf)3 and IL/TfOH systems for cross-breeding two
propargylic alcohols or a propargylic alcohol with a non-propargylic alcohol and/or self-coupling, to
form a wide variety of functionalized ethers is also demonstrated.
solvent. Nishibayashi et al. used phosphido- and thiolato-bridged
Introduction
diruthenium complexes for propargylation2 and also developed an
enantioselective propargylation method for indoles.3 Bustelo and
Dixneuf4 used in situ generated mononuclear arene ruthenium
complexes for propargylation of furan and 2-methylfuran and
for the synthesis of propargylic ethers by cross coupling in
relatively modest yields. A rhenium oxo-complex was employed
by Toste et al.5 to introduce the propargyl group into reactive
arenes/heterocycles. Zhan et al.6 reported a FeCl3-catalyzed reac-
tion using MeCN as solvent. Dyker and associates7 studied that
AuCl3/MeCN system for propargylation of representative elec-
tron rich arenes with Ia. Other propargylation reagents such as O-
propargyl trichloroacetimidates, with BF3. Et2O as catalyst,8 and
N-tosylpropargyl amine, using AuCl3 as catalyst,9 have also been
employed. Zhu and associates10 utilized MoO2(acac)2/NH4PF6
as catalyst to achieve direct substitution of propargylic alcohols
with oxygen, nitrogen and carbon nucleophiles in modest to good
yields.
Direct introduction of the propargyl group into aromatic and
heteroaromatic compounds under mild conditions with high
efficiency and regioselectivity represents a highly desirable ap-
proach for the synthesis of functional alkynes. Previous ap-
proaches in pursuit of this goal emphasized organometallic
catalysts and focused mainly on 1,3-diphenyl-2-propyn-1-ol Ia.
For example, Uemura, Nishibayashi and co-workers1 used a
cationic diruthenium complex for propargylation of representative
aromatic and heteroaromatic compounds in dichloroethane as
aDepartment of Chemistry, University of North Florida, 1, UNF Drive,
Jacksonville, Florida, 32224, USA. E-mail: kenneth.laali@unf.edu; Fax: +1-
904-620-3535; Tel: +1-904-620-1503
bCentral Washington University, Ellensburg, WA, 98926, USA
† Electronic supplementary information (ESI) available. See DOI:
10.1039/c0ob00872a
‡ UNF undergraduate student participant
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Scheme 1 Model study of propargylation of anisole in ionic liquids.
A number of recent studies have dealt with propargylation
of 1,3-dicarbonyl compounds with propargylic alcohols, em-
ploying a variety of acidic catalysts such as p-toluenesulfonic
acid monohydrate in MeCN solvent,11 heteropoly acids,12
Yb(OTf)3,13 and InCl3.14 A propargylation method utilizing
[EMIM][OTf] ionic liquid (IL) in combination with the Brønsted
acidic imidazolium IL [BIM-(CH2)3–SO3H][OTf] as catalyst at
model nucleophile under mild conditions (Scheme 1). Metal-
lic triflates M(OTf)3 (M = Bi, Sc, Yb) immobilized in im-
idazolium ILs [BMIM][BF4], [BMIM][PF6] or [BMIM][OTf]
were employed as catalysts. The results are summarized in
Table 1.
For alcohol Ia, the catalytic activity order Sc(OTf)3 > Yb(OTf)3
> Bi(OTf)3 was established in [BMIM][PF6] based on isolated
product yields, and by using ROH : ArH : M(OTf)3 ratio of
1: 2 : 0.15. The reactions were highly para selective (no ortho
isomer was detected by GC–MS). As a representative case,
the Sc(OTf)3-catalyzed reaction in [BMIM][BF4] was selected
for a recycling–reuse study at 50 ◦C (see Table 1), whereby
only a slight decrease in the isolated yields were observed over
3 consecutive cycles. Metalli◦c triflates proved less effective in
propargylation with Ib at 45 C. Whereas [BMIM] [PF6]/TfOH
system exhibited comparable results, B(C6F5)3 proved superior.
Interestingly, with TfOH or B(C6F5)3 as promoter, both ortho and
para products were formed. Moreover, with B(C6F5)3 traces of
the corresponding dipropargylic ether (reaction of propargylic
cation with the alcohol) was also detected. Relatively modest
isolated yields were obtained in propargylation with Ic, employing
Sc(OTf)3 or Bi(OTf)3 in [BMIM][OTf] ionic liquid, whereas
[BMIM][PF6]/TfOH system proved more effective (see Table 1).
Having identified the most effective catalytic systems for arene
propargylation in ILs, the study focused on the synthetic scope
of propargylation of reactive and moderately reactive arenes
and representative heterocycles with propargyl alcohols Ia–Ic
(Schemes 2–3 and Tables 2–3). Isolated yields obtained in the
present study are comparable, and some cases exceed, those from
previously reported studies using cationic diruthenium complex,1
AuCl3 and BF3.Et2O.7
Steric influence on regioselectivity is manifested in propargyla-
tion of anisole and phenol with Ia, showing no detectable ortho
isomer, and with Ib, where formation of the ortho isomer was
competitive. Propargylation of anisole with Ic was only successful
in TfOH (-5 ◦C to r.t.). Under these mild conditions, regiose-
lectivity was high (only para) but conversion was modest. With
reactive arenes, formation of dipropargylic ethers was minimal, but
it became competitive in the case of ethylbenzene. With toluene,
ring substitution was no longer competing and ether formation
was the dominant process. For propargylation of phenol, the
B(C6F5)3/IL systems proved highly suitable. For mesitylene,
[BMIM][BF4]/Sc(OTf)3 and [BMIM][BF4]/TfOH systems proved
effective with propargylic alcohols Ia and Ib respectively. The
use of TfOH as promoter resulted in competing formation of
◦
100 C has also been reported.15 Several other studies deal-
ing with propargylic substitution reactions of aryl propargyl
methanols with thiols, using methanethiolate-bridged diruthe-
nium complex,16 with C- and O-nucleophiles using iodine,17 and
18
with C, O, S, and N-nucleophiles employing FeCl3 have also
appeared. A number of examples have also been reported for
propargylic group transfer using propargylic esters/TiCl4,19 3-
sulfanyl- and 3-selanylpropargyl alcohols/Sc(OTf)3,20a and with
allenyltributylstannanes/Yb(OTf)3.20b
Interest in the synthesis of target propargyl derivatives stems
from their biological and pharmacological importance. Their bio-
potency is mainly due to their ability to penetrate biological
membranes because of their lipophilic, rigid and linear structures.
The O, N and aryl-propargylated systems have found applica-
tion in crop protection field21a and as GnRHR antagonists,21b
inhibitors of HIV-1 reverse-transcriptase21c and in the treatment
of Alzheimer’s disease.21d Apart from their biological significance,
O-propargylated systems have found application in the synthesis
of functional polymers21e and propargyl ethers have been used for
the synthesis of planar chiral cobalt metallocenes21f as potential
catalyst for a range of synthetic applications.
In continuation of our work on electrophilic chemistry in room
temperature ionic liquids (RT-IL),22–32 and in connection to a
recent ion-molecule study of gaseous propargylic carbocations,33
we report here a synthetic study in imidazolium ILs, focusing on
propargyl group introduction into aromatics and heteroaromatics,
and cross coupling of propargylic alcohols to prepare a host
of functionalized ethers, under mild conditions, in simple one-
pot procedures by using metallic triflates, TfOH, or B(C6F5)3 as
catalysts, with recycling and reuse of the ILs.
Results and discussion
Propargylation of arenes and heteroarenes
At the onset a survey of propargylation study was performed with
propargylic alcohols 1,3-diphenyl-2-propyn-1-ol Ia, 1-methyl-3-
phenyl-2-propyn-1-ol Ib, and 2-pentyn-1-ol Ic using anisole as
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Table 1 A model study of propargylation of anisole with different catalysts in three different imidazolium ILs
Selectivity (%)a
Molar ratio
I : II : Catalyst
Conversion based
on alcohol (%)a
I
Catalyst
Ionic Liquid
Temp. ◦
C
Time (h)
ortho
para
Isolated yield
Ia
Bi(OTf)3
Bi(OTf)3
Yb(OTf)3
Sc(OTf)3
Sc(OTf)3
Sc(OTf)3
Sc(OTf)3
Sc(OTf)3
Yb(OTf)3
TfOH
B(C6F5)3
Bi(OTf)3
Sc(OTf)3
TfOH
B
Bb
B
B
A
A
A
A
B
B
B
C
C
B
1 : 2 : 0.20
1 : 2 : 0.20
1 : 2 : 0.20
1 : 2 : 0.20
1 : 2 : 0.15
1 : 2 : 0.15
1 : 2 : 0.15
1 : 3 : 0.20
1 : 3 : 0.20
1 : 4 : 0.20
1 : 2 : 0.15
1 : 3 : 0.20
1 : 3 : 0.20
1 : 2.5 : 0.15
r.t.
60
60
45
50
50
50
45
45
-5 to r.t.
40
r.t. to 40
r.t. to 40
-5 to r.t.
12
8
8
6
5
5
5
14
20
10
4
18
14
4
48
89
100
100
100
98
—
—
—
—
—
—
—
—
—
28
26
—
—
—
47
85
94
97
100
99
95
50
41
50
74
50
60
100
41
80
86
91
94 (1st run)
92 (2nd run)c
93
60
45
80
88 (3rd run)c
Ib
Ic
45
25
59 (ortho & para together)
94 + 6d
65
21% -orthoe & 66% -para
25
36
42
70
100
a Based on GC assay. b Recycled ionic liquid. c No catalyst was added. d Homo ether (6%). e When the reaction was carried out at r.t. (10 h), the ortho
isomer decreased significantly.
Scheme 2 Propargylation of arenes in ionic liquids catalyzed by Lewis acids.
Scheme 3 Propargylation of heteroarenes in ionic liquids catalyzed by Sc(OTf)3.
the dipropargylic ether. Whereas propargyl introduction into b-
naphthol with Ia in [BMIM][BF4]/Sc(OTf)3 proceeded in high
yield and high chemoselectivity, lower conversion and concomi-
tant formation of dipropargylic ether were observed with Ib in
[BMIM][PF6]/Yb(OTf)3 system. Products 1–16 synthesized in this
study are shown in Fig. 1.
In propargylation of representative heterocycles (Table 3),
Sc(OTf)3 immobilized in [BMIM][BF4] or [BMIM][PF6] proved
effective with Ia, but under the mild conditions employed no
reaction occurred with alcohol Ib. Reaction of alcohol Ia with iso-
meric nitroanilines (Scheme 4, Table 4) in [BMIM][BF4]/Sc(OTf)3
resulted in N-propargylation (compounds 20 and 21).
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Table 2 Propargylation of arenes with different catalysts in imidazolium ILs
Selectivity (%)a
Time (h) III [ortho/para] IV
Isolated yield (%)
I
II
IL Catalyst Temp. ◦
C
V
III [ortho/para] IV
V
Product No.
Ia
Anisole
A
B
B
A
B
A
A
A
A
B
A
B
A
B
Sc(OTf)3 50
B(C6F5)3 40
5
4
4
5
7.5
5
3.5
6.5
8
3.5
6
7.5
6
98 [-/100]
94 [26/74]
100 [-/100]
94
93
100
—
6
—
—
7
—
71 29
51 14
—
33
—
12
—
33
trace 94
—
—
—
—
—
—
—
—
—
—
—
—
1
Ib Anisole
Ic
Ia
—
—
21b/66c
42
2/3
4
Anisole
1,3-Dimethoxybenzene
TfOH
-5 to r.t.
Sc(OTf)3 60
Yb(OTf)3 50
Yb(OTf)3 50
Sc(OTf)3 50
Sc(OTf)3 50
Sc(OTf)3 50
trace 91d
5
Ib 1,3-Dimethoxybenzene
—
—
81
92
—
28
80
62
7
Ia
Ia
Ia
Ia
1,3,5-Trimethoxybenzene
Toluene
Ethylbenzene
Mesitylene
8
—
67 21
47 11
9
35 [-/100]
87
67
98 [-/100]
88 [52/48]
100
10
11
12
13
14
15
16
13
—
10
29
—
—
—
27
—
—
—
—
—
—
Ib Mesitylene
Ia Phenol
Ib Phenol
TfOH
-5 to 50
B(C6F5)3 60
B(C6F5)3 50
Sc(OTf)3 60
Yb(OTf)3 40
trace 92
—
—
—
61e
85
61
Ia
2-Naphthol
Ib 2-Naphthol
8
67
In all cases, quantitative conversion of the limiting reagent was noted by GC.a Based on GC assay. b When the reaction was carried out at r.t. for about
10 h, the ortho isomer decreased significantly. c Product is a mixture of 3 and homo ether of 31 (i.e., Ib + Ib) by NMR. d When Bi(OTf)3 was used (at
60 ◦C for about 8 h), 21% of disubstitution product (6) along with monosubstitution (67%) and the ketone 9 (8%) were obtained. e Product obtained as
an inseparable mixture of ortho and para isomers.
Table 3 Propargylation of heteroarenes with Sc(OTf)3 in imidazolium ILs
Selectivity (%)a
III
Isolated yield (%)
III
I
II
IL
Temp. ◦
C
Time (h)
Product No.
Ia
Ia
Ia
Pyrrole
Furan
2-Methylfuran
A or B
A or B
A or B
r.t.
45
30
1.5
1.5
1
100
100
100
74
89
86
17
18
19
In all the cases, quantitative conversion of the limiting reagent was noticed by GC.a Based on GC assay.
Scheme 4 Propargylation of aniline derivatives in [BMIM][BF4] catalyzed by Sc(OTf)3.
Whereas 3-phenyl-2-propyn-1-ol (Id) did not react well under
M(OTf)3 catalysis with anisole, 1,3-dimethoxybenzene, or with
phenol, it could be activated in TfOH/IL. However, under these
conditions, the propargylic derivative was not isolated; instead, the
corresponding propanone derivatives (compounds 22–24) were
obtained in satisfactory yields (Scheme 5 and Table 5). These
products arise from nucleophilic attack by ArH on the in situ
formed ab-unsaturated ketone formed via a Meyer–Schuster type
rearrangement.34
The recycling and reuse of the IL in arene propargylation was
demonstrated in [BMIM][BF4]/Sc(OTf)3 system using propargylic
alcohol Ia (Fig. 2) in which mesitylene, b-naphthol and pyrrole
were sequentially propargylated to obtain products 11, 15, and
17 in the same IL and without adding fresh catalyst, with no
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Table 4 Propargylation of anilines with Sc(OTf)3
Aniline
IL
Temp. ◦
C
Time (h)
Selectivitya
Isolated yield (%)
Product No.
2-Nitroaniline
4-Nitroaniilne
[BMIM][BF4]
[BMIM][BF4]
50
50
1.5
4
100
100
90b
91
20
21
In both cases, quantitative conversion of the limiting reagent was noted by GC.a Based on GC assay. b Product obtained as an inseparable mixture of 20/9
(1 : 0.88).
Fig. 1 Structure of aryl propargylated products.
Scheme 5 TfOH-catalyzed propargylation of Id in ionic liquids.
noticeable decrease in the conversions. Similarly each ionic liquid
was re-used for more than six times with different substrates by
systematic handling and drying of the ionic liquid after use.
context, bearing in mind that minor amounts of bis-propargylic
ethers these by-products were observed in some cases in reactions
with arenes (compound type IV in Scheme 2 and Table 2), the
focus of the study was shifted to condensation of propargylic
alcohol Ia–Id with aliphatic and benzylic alcohols, as well as self-
condensation of propargyl alcohols and cross coupling of two
propargylic alcohols (Scheme 6). The results are summarized in
Table 6.
Synthesis of propargylic ethers
Development of simple one-pot protocols for high yield synthesis
of the mono- and bis-propargylic ethers is a desirable goal,
because it allows direct access to functional alkynes. In this
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Table 5 Synthesis of aryl bearing propanone derivatives with TfOH in imidazolium ILs
Isolated
Time (h) Conversion based on alcohol (%)b Selectivityb yield (%)
Arene
IL
Catalysta Temp. ◦
C
Product No.
Anisole
1,3-Dimethoxy benzene
Phenol
A or B
A or B
A or B
TfOH
TfOH
TfOH
-5 to r.t.
-5 to r.t.
-5 to r.t.
6
7
6
100
100
100
88
87
92
74
71
86
22
23
24
a The same product was obtained by using M(OTf)3 or B(C6F5)3 but in lower yields. However, the expected direct substitution product was not obtained
in any of the Lewis acid catalysts employed. Furan and 2-methylfuran did not react even by changing the catalyst. b Based on GC assay.
prep-TLC was performed. Melting points were recorded with a
MEL-TEMP apparatus and are uncorrected. NMR spectra were
recorded in CDCl3 (1H at 500 MHz; 13C at 125 MHz) on a Varian
500 NMR instrument with chemical shift (d values in ppm; *
indicates interchangeable assignments); IR spectra (solution, cm-1)
were obtained on SHIMADZU FT-IR spectrophotometer. Only
selected/diagnostic IR and mass data are reported.
GC and GC–MS analysis. A 2 mL sample of each compound
was analyzed in duplicate runs on a Hewlett–Packard (HP) gas
chromatograph model 5890 series II equipped with a split/splitless
injector and a capillary RTX-5 column. The injection port and
detector were kept at 250 and 300 ◦C, respectively. The oven
temperature was initially held at 50 ◦C for 2 min and programmed
◦
◦
at 7 C min-1 to 220 C and held for 10 min isothermally which
was then finally ramped to 290 ◦C (held for 5 min) at 10 ◦C
min-1. The same program was used for GC–MS with 2 mL sample
injection. GC–MS analyses were performed on an HP model 5890
series II GC attached to an HP model 5972 series mass selective
detector instrument. The split ratio was 10 : 1 with 2 mL of sample
injected. Mass spectra in the electron ionization mode (MS-EI)
were obtained at 70 eV with ion source temperature at 230 ◦C.
After a 2 min solvent delay, mass spectra were obtained over the
m/z range 50–600. The total ion chromatogram (TIC) acquired
by GC–MS was used for peak area integration.
Fig. 2 Recycling–reuse of IL and promoter.
Whereas in crossed condensation reaction of 1,3-diphenyl-2-
propyn-1-ol with benzylic and aliphatic alcohols the IL/Sc(OTf)3
system proved quite effective, for other propargylic alcohols
the IL/TfOH (at lower temperatures) became the system of
choice. The cross-coupling of two different propargylic alco-
hols to prepare bis-propargylic ethers could be performed in
IL/Sc(OTf)3 or in IL/TfOH systems in good to moderate
isolated yields. Structure of the ethers 25–36 are shown in
Fig. 3.
In summary the utility of IL/M(OTf)3 and IL/TfOH systems
for propargyl group introduction into a wide variety of arenes and
heteroarenes under mild conditions with recycling and re-use of
the IL and the catalysts has been demonstrated in simple one-pot
reactions. The same catalytic systems can promote self- or crossed-
condensation of propargylic alcohols to synthesize a variety
of bis-propargylic ethers. Condensation of propargylic ethers
with a variety of benzylic and aliphatic alcohols has also been
shown.
General procedure for propargyl introduction into aromatics.
The respective catalyst (15–20 mol%) was added to Schlenk
tube containing the desired ionic liquid (4.5 mmol) under N2
atmosphere and was immobilized by sonication for about 15–
20 min. The arene was introduced into the Schlenk tube (kept
in an ice bath) under a nitrogen atmosphere followed by the
desired propargylic alcohol. The contents were magnetically
stirred initially at r. t. for about 15 min followed by stirring in
a pre-heated oil bath either at 50 or 60 ◦C (as applicable; refer
to Tables 1–5) until completion (monitored by TLC). Once the
reaction was over, the contents were cooled to r. t. and extracted
with dry diethyl ether (until the final extraction did not indicate any
spot corresponding to the arene or the product). The combined
organic layer was washed with bicarbonate solution, dried with
MgSO4 and concentrated to give the crude direct substitution
product. Purification through column chromatography furnished
the desired products.
Experimental
General. The reagents and the ionic liquids employed in this
study were high purity commercial samples, which were used
without further purification. Triflic acid (ACROS) was stored in
Nalgene bottles flushed with nitrogen in a freezer. The reactions
were carried out in small Schlenk tubes under nitrogen. Dry
diethyl ether was used for extraction. Column chromatography
was performed on silica gel (200–400 mesh) and in some cases,
General procedure for the synthesis of propargylic ethers.
Sc(OTf)3 (15–20 mol%) was added to Schlenk tube containing
the desired ionic liquid (4.5 mmol) under N2 atmosphere and
was immobilized by sonication for about 15–20 min. The desired
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Table 6 Synthesis of propargyl ethers catalyzed by Sc(OTf)3 or TfOH in imidazolium ILs
Composition of reaction mixture
Selectivity
Isolated
I
II
IL Catalyst Temp. ◦
C
Time (h) (III,%)a
Homo ether (IV,%)a Product ratio (III + IV)b yield (%) Product No.
Ia Benzyl alcohol
Ib Benzyl alcohol
Id Benzyl alcohol
Ia 2-Propanol
Ia 2-Butanol
Ia Ia
Ib Ib
Id Id
Ib Id
Ib Ic
A
B
B
Sc(OTf)3 50
3
7
4
4
100
—
89
100
100
100
100
100
—
—
—
—
—
—
—
70/30
—
—
—
90
25
26
27
28
29
30
31g
32
33
34
35
36
TfOH
TfOH
Sc(OTf)3 50
Sc(OTf)3 50
Sc(OTf)3 50
-5 to 30
1 : 0.16c
—
79d
62
-5 to 30
A
A
A
A
A
A
A
A
A
—
—
—
—
82
3
91e
92f
63/25
61
2.5
4.5
6
3.5
7.5
7.5
3.5
TfOH
TfOH
TfOH
Sc(OTf)3 60
Sc(OTf)3 50
-5 to 30
-5 to 30
-5 to 30
—
1 : 0.04c
1 : 0.31c
1 : 0.97
1 : 0.44
78d
54d
52d
81d
—
—
—
—
—
—
Id Ic
Ib Cyclohexanol
TfOH
-5 to r.t.
In all cases, quantitative conversion of the limiting reagent was noted by GC; Isomer ratio of the isolated products were calculated by NMR.a Based on
GC assay. b Product ratio was determined by NMR. c Homo ether (Ib + Ib i.e., 31) itself exists as isomers. d Isolated product was a mixture of desired ether
and the homo ether of alcohol Ib (31) due to their very close rf values in TLC. e Exists as inseparable isomers (1 : 0.81). f Exists as inseparable isomers
(1 : 0.67). g Obtained as two separable isomers (31a & 31b).
Scheme 6 Synthesis of propargylic ethers in ionic liquids.
alcohol was introduced into the Schlenk tube (kept in an ice
bath) under a nitrogen atmosphere followed by the propargylic
alcohol. The contents were magnetically stirred initially at r. t. for
about 15 mi◦n followed by stirring in a pre-heated oil bath either
at 50 or 60 C (as applicable; refer to Table 6) until completion
(monitored by TLC). In TfOH-catalyzed reactions the ionic liquid
was charged into a Schlenk tube, and following the addition of the
desired alcohol and the propargylic alcohol, TfOH was added
under N2 atmosphere at -5◦C. Once the reaction was over, the
contents were cooled to r. t. and extracted with dry diethyl ether
(until the final extraction did not show any spots corresponding
to either alcohol). The combined organic layer was washed with
bicarbonate solution, dried with MgSO4 and concentrated to give
the crude product. Purification through column chromatography
furnished the desired products.
2-Methoxy-1-(4-phenylbut-3-yn-2-yl)benzene (2). Alcohol Ib
(1 mmol), anisole (2 mmol) and catalyst (15 mol%); Yield 21%
(colorless oil). This was obtained as a separable minor isomer
along with its para counterpart (3). 1H NMR: 1.53 (d, 3H, J = 7.0
Hz); 3.87 (s, 3H), 4.41 (q, 1H, J = 7.0 Hz), 6.88 (d, 1H, J = 10.0 Hz),
6.99 (t, 1H, J = 7.2 Hz), 7.23–7.48 (m, 6H), 7.67 (dd, 1H, J = 7.5 Hz,
J = 1.5 Hz); 13C NMR: 22.95, 26.15, 55.40, 81.71, 93.19, 110.41,
120.75, 123.99, 127.60, 127.75, 127.90, 128.17, 131.65, 156.06; IR:
2972, 2930, 1678, 1609, 1597, 1512, 1248, 1177; MS (m/z): 236
(M+), 221 (100%), 202, 178, 115.
4-Methoxy-1-(4-phenylbut-3-yn-2-yl)-benzene (3). Alcohol Ib
(1 mmol), anisole (2 mmol) and catalyst (15 mol%); Yield 66%
[colorless oil; obtained as a 1 : 0.1 mixture (by NMR) of 3 and
isomeric 31 (consisting of 31a and 31b in 1 : 0.13 ratio-by NMR)
see below]. NMR data for 3 is out of mixture. 1H NMR: 1.57 (d,
3H, J = 7.5 Hz), 3.81 (s, 3H), 3.95 (q, 1H, J = 7.0 Hz), 6.89 (d,
2H, J = 8.5 Hz), 7.29–7.33 (m, 3H), 7.38 (d, 2H, J = 9.0 Hz), 7.44–
7.47 (m, 2H); 13C NMR: 24.59, 31.64, 55.30, 82.23, 92.96, 113.92,
123.79, 127.70, 127.89, 128.19, 131.61, 135.49, 158.34; IR: 2926,
2853, 1599, 1587, 1489, 1456, 1240, 1115, 1076, 1051, 1029; Mass
(m/z): 236 (M+); 221 (100%), 178, 128, 77.
Re-use and recycling of IL. After ether extraction, the ionic
liquid was dried under high vacuum at 60–70 ◦C overnight.
4-Methoxy-1-(1,3-diphenylprop-2-ynyl)-benzene (1):35. Alco-
hol Ia (1 mmol), anisole (2 mmol) and catalyst (15 mol%): Yield
1
94% (colorless oil). H NMR: 3.79 (s, 3H), 5.19 (s, 1H), 6.88 (d,
2H, J = 9.0 Hz), 7.23–7.51 (m, 12H); 13C NMR: 42.93, 55.28,
84.72, 90.49, 113.99, 123.55, 126.83, 127.83, 128.0, 128.23, 128.61,
128.92, 131.69, 133.96, 142.08, 158.51; IR: 3059, 2924, 1597, 1508,
1491, 1252, 1173, 1029; Mass (m/z): 298 (M+, 100%); 283, 265,
205, 189, 179, 165, 126, 115.
4-Methoxy-1-(pent-2-ynyl)benzene (4). Alcohol Ic (1 mmol),
anisole (2.5 mmol) and catalyst (20 mol%); Yield 42% (pale red
semi-solid). 1H NMR: 1.16 (t, 3H, J = 7.7 Hz); 2.23 (qt, 2H, J =
7.5 Hz, J = 2.4 Hz), 3.51 (t, 2H, J = 2.3 Hz), 3.79 (s, 3H), 6.85
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Fig. 3 Propargylic ethers synthesized.
(d, 2H, J = 8.5 Hz), 7.25–7.26 (m, 2H); 13C NMR: 12.51, 14.25,
24.22, 55.29, 77.33, 83.72, 113.82, 128.78, 134.14, 158.19; IR: 2930,
1601, 1512, 1464, 1412, 1246; MS (m/z): 174 (M+,100%), 159, 145,
128, 115, 102, 91, 77, 63, 51, 39.
(s, 2H), 6.42 (s, 1H), 7.10–7.13 (m, 2H), 7.17–7.25 (m, 10H), 7.36–
7.37 (m, 4H), 7.41–7.43 (m, 4H), 8.05 (s, 1H); 13C NMR-meso:
36.41, 55.81, 83.62, 91.15, 95.28, 122.10, 123.66, 126.37, 127.65,
127.82, 128.05, 128.31, 129.21, 131.69, 142.22, 156.09. IR (isomeric
mixture): 2928, 1611, 1589, 1489, 1302, 1204, 1032; MS (m/z): 518
(M+ not detected), 504, 460, 415, 284, 179, 135.
2,4-Dimethoxy-1-(1,3-diphenylprop-2-ynyl)benzene (5):35. Al-
cohol Ia (1 mmol), 1,3-dimethoxybenzene (2 mmol) and catalyst
(15 mol%); Yield 91% (white solid; m.p.: 105–106 ◦C). 1H NMR:
3.82 (s, 3H), 3.84 (s, 3H), 5.65 (s, 1H), 6.49 (d, 1H, J = 2.5 Hz),
6.54 (dd, 1H, J = 8.8 Hz, J = 2.3 Hz), 7.21–7.34 (m, 6H), 7.49–7.52
(m, 4H), 7.54 (d, 1H, J = 8.5 Hz); 13C NMR: 36.14, 55.38, 55.57,
83.48, 91.22, 98.65, 104.60, 122.90, 123.83, 126.49, 127.79, 127.83,
128.23, 128.35, 129.53, 131.73, 142.18, 157.11, 159.94; IR: 2835,
1609, 1589, 1505, 1489, 1289, 1207, 1113, 1032; MS (m/z): 328
(M+,100%), 313, 252, 189, 115, 77.
2,4-Dimethoxy-1-(4-phenylbut-3-yn-2-yl)benzene (7):36. Alco-
hol Ib (1 mmol), 1,3-dimethoxybenzene (2.5 mmol) and catalyst
(15 mol%); Yield 81% (pale-red oil). 1H NMR: 1.51 (d, 3H, J = 7.0
Hz), 3.81 (s, 6H), 4.33 (q, 1H, J = 7.0 Hz), 6.49 (d, 1H, J = 2.5 Hz),
6.54 (dd, 1H, J = 8.0 Hz, J = 2.5 Hz), 7.28–7.32 (m, 3H), 7.46–7.48
(m, 2H), 7.56 (d, 1H, J = 8.5 Hz); 13C NMR: 23.14, 25.67, 55.37,
55.41, 81.55, 93.49, 98.53, 104.20, 124.05, 124.17, 127.57, 128.18,
128.26, 131.63, 157.00, 159.64; IR: 2962, 2835, 1593, 1493, 1458,
1410, 1265, 1207, 1149; Mass (m/z): 266 (M+); 251 (100%), 165,
152, 77.
1,5-Dimethoxy-2,4-bis-(1,3-diphenylprop-2-ynyl)benzene (6):7.
Alcohol Ia (1 mmol), 1,3-dimethoxybenzene (2 mmol) and
Bi(OTf)3 (20 mol%); Obtained as an off white solid (m.p. 154–
2,4,6-Trimethoxy-1-(1,3-diphenylprop-2-ynyl)benzene
(8):7,37
.
◦
156 C). Yield: 21% (mixture of racemic and meso compounds).
Alcohol Ia (1 mmol), 1,3,5-trimethoxybenzene (2 mmol) and
catalyst (15 mol%); Yield: 92% (off white solid m.p. 125 ◦C).
1H NMR 3.84 (s, 6H), 3.89 (s, 3H), 5.82 (s, 1H), 6.17 (s, 2H),
7.14–7.33 (m, 6H), 7.45–7.54 (m, 4H); 13C NMR 31.50, 55.38,
56.06, 81.27, 90.96, 91.61, 111.48, 124.60, 125.60, 127.31, 127.44,
127.83, 128.15, 131.78, 141.73, 158.70, 160.44; MS (m/z): 358
(M+,100%), 343, 327, 239, 115.
Specific NMR assignments for each isomer (out of the isomeric
mixture):7 1H NMR-rac: 3.82* (s, 6H), 5.58 (s, 2H), 6.42 (s, 1H),
7.10–7.13 (m, 2H), 7.25–7.30 (m, 10H), 7.36–7.37 (m, 4H), 7.48–
7.50 (m, 4H), 7.95 (s, 1H); 13C NMR-rac: 36.31, 55.78, 83.41, 91.04,
95.28, 122.47, 123.70, 126.39, 127.65, 127.76, 128.05, 128.26,
129.50, 131.72, 142.11, 155.98; 1H NMR-meso: 3.83* (s, 6H), 5.62
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1,3-Diphenylprop-2-yn-1-one (9):38. Alcohol Ia (1 mmol), ei-
ther toluene or ethyl benzene (3 mmol) and catalyst (15 mol%);
Yield: 21% (using toluene) and 11% (using ethyl benzene);
1-(1,3-Diphenylprop-2-ynyl)naphthalen-2-ol (15):35. Alcohol
Ia (1 mmol), 2-naphthol (1.7 mmol) and catalyst (15 mol%);
Yield: 85% (pale-red oil). H NMR: 6.32 (s, 1H), 6.48 (bs, 1H),
7.19 (d, 1H, J = 8.5 Hz), 7.25–7.27 (m, 1H), 7.30–7.38 (m, 6H),
7.45–7.52 (m, 5H), 7.78 (d, 1H, J = 9.0 Hz), 7.82 (d, 1H, J =
8.0 Hz), 8.06 (d, 1H, J = 8.5 Hz); 13C NMR: 33.61, 86.02, 88.37,
117.64, 118.54, 122.61, 122.74, 123.39, 126.48, 126.74, 127.38,
127.70, 127.77, 128.0, 128.13, 128.97, 129.32, 131.29, 132.39,
139.56, 152.34; IR: 3224, 2924, 2853, 1628, 1597, 1516, 1491,
1437; MS (m/z): 334 (M+, 100%), 257, 228, 77.
1
1
Obtained as colorless viscous oil. H NMR: 7.42–7.45 (m, 2H),
7.48–7.55 (m, 3H), 7.62–7.71 (m, 3H), 8.24 (dd, 2H, J = 8.3 Hz,
J = 1.3 Hz); 13C NMR: 86.89, 93.13, 120.14, 128.64, 128.70, 129.59,
130.81, 133.09, 134.14. 136.88, 178.06; IR: 3055, 2199, 1640, 1265.
MS (m/z): 206 (M+), 178 (100%), 129, 75, 51.
4-Ethyl-1-(1,3-diphenylprop-2-ynyl)benzene (10). Alcohol Ia (1
mmol), ethylbenzene (3 mmol) and catalyst (15 mol%); Yield: 28%
(pale-red semi solid). 1H NMR: 1.22 (t, 3H, J = 7.8 Hz), 2.63 (q,
2H, J = 7.5 Hz), 5.19 (s, 1H), 7.16 (d, 2H, J = 8.5 Hz), 7.29–7.34
(m, 6H), 7.35 (d, 2H, J = 8.0 Hz), 7.44–7.49 (m, 4H); 13C NMR:
15.54, 28.46, 43.43, 82.85, 86.62, 123.00, 127.35, 127.83, 127.90,
128.14, 128.24, 128.28, 128.61, 128.77, 131.84, 138.00, 141.98; IR:
3059, 2928, 1694, 1597, 1489, 1451, 1265; MS (m/z): 296 (M+),
281, 267 (100%), 202, 189, 165, 77.
1-(4-Phenylbut-3-yn-2-yl)naphthalen-2-ol (16). Alcohol Ib (1
mmol), 2-naphthol (1.7 mmol) and catalyst (15 mol%); Yield: 61%
(dark-brown viscous oil). 1H NMR: 1.68 (d, 3H, J = 7.0 Hz), 4.94
(q, 1H, J = 7.2 Hz), 7.17 (d, 1H, J = 9.0 Hz), 7.31–7.38 (m, 4H),
7.46–7.54 (m, 3H), 7.71 (d, 1H, J = 9.0 Hz), 7.80 (un resolved dd,
1H, J = 7.5 Hz), 8.00 (d, 1H, J = 8.5 Hz), OH (not observed); 13
C
NMR: 23.93, 29.71, 84.72, 90.52, 118.49, 119.64, 121.75, 122.21,
123.16, 126.75, 128.40, 128.58, 128.97, 129.07, 129.52, 131.40,
131.73, 152.38; IR: 3433, 3055, 2932, 1620, 1600, 1265; MS (m/z):
272 (M+), 257 (100%), 195, 128, 77.
2,4,6-Trimethyl-1-(1,3-diphenylprop-2-ynyl)benzene (11). Al-
cohol Ia (1 mmol), mesitylene (2 mmol) and catalyst (15 mol%);
Yield: 80% (colorless oil). 1H NMR: 2.32 (s, 3H), 2.33 (s, 3H), 2.34
(s, 3H), 5.76 (s, 1H), 6.92 (s, 2H), 7.31–7.35 (m, 5H), 7.41–7.42 (m,
3H), 7.50–7.52; (m, 2H); 13C NMR: 20.81, 20.89, 36.92, 84.15,
89.17, 123.82, 126.30, 126.96, 127.18, 127.83, 128.24, 128.32,
128.72, 131.66, 134.78, 136.60, 140.24; IR: 3024, 2916, 2198, 1605,
1489, 1451, 1026; MS (m/z): 310 (M+, 100%), 295, 219, 202, 189,
77.
2-(1,3-Diphenylprop-2-ynyl)-1H-pyrrole (17):18. Alcohol Ia (1
mmol), pyrrole (3 mmol)◦ and catalyst (15 mol%); Yield: 74%
1
(brown solid; m.p. 70–72 C). H NMR: 5.34 (s, 1H), 6.10–6.12
(m, 1H), 6.22 (dd, 1H, J = 6.2 Hz, J = 2.75 Hz), 6.74–6.76 (m,
1H), 7.31–7.42 (m, 6H), 7.49–7.54 (m, 4H), 8.21 (brs, 1H); 13C
NMR: 37.23, 84.12, 88.56, 106.50, 108.66, 117.43, 123.12, 127.28,
127.77, 128.22, 128.30, 128.74, 130.64, 131.76, 140.17; IR: 3433,
2924, 2853, 1597, 1489, 1452, 1090, 1026; MS (m/z): 257 (M+,
100%), 180, 152, 127, 77.
2,4,6-Trimethyl-1-(4-phenylbut-3-yn-2-yl)benzene (12). Alco-
hol Ib (1 mmol), mesitylene (2.5 mmol) and catalyst (20 mol%);
Yield: 62% (colorless oil). 1H NMR: 1.55 (d, 3H, J = 7.3 Hz), 2.26
(s, 3H), 2.50 (s, 6H), 4.43 (q, 1H, J = 7.3 Hz), 6.86 (s, 2H), 7.26–7.27
(m, 3H), 7.38–7.40 (m, 2H); 3C NMR: 20.41, 20.68, 20.70, 22.70,
26.77, 81.25, 93.05, 124.06, 127.49, 128.15, 130.00, 131.41, 135.80,
135.90 (two coinciding carbon resonances); IR: 2957, 2924, 2855,
1491, 1456, 1377, 1262; MS (m/z): 248 (M+), 233 (100%), 218,
202.
2-(1,3-Diphenylprop-2-ynyl)furan (18):35. Alcohol Ia (1 mmol),
furan (1.5 mmol) and catalyst (15 mol%); Yield: 89% (pale-yellow
oil). 1H NMR: 5.30 (s, 1H), 6.31–6.32 (m, 1H), 6.35–6.36 (m, 1H),
7.33–7.41 (m, 7H), 7.50–7.53 (m, 4H); 13C NMR: 37.89, 83.95,
87.43, 106.64, 110.35, 123.17, 127.41, 127.88, 128.19, 128.27,
128.68, 131.79, 138.89, 142.29, 153.80; IR: 2924, 2853, 1597, 1489,
1452, 1443, 1070; MS (m/z): 258 (M+, 100%), 229, 215, 181, 152,
126, 77.
4-Hydroxy-1-(1,3-diphenylprop-2-ynyl)benzene (13):35. Alco-
hol Ia (1 mmol), phenol (2 mmol)◦and catalyst (15 mol%); Yield:
92% (pale yellow solid; m.p. 85–87 C). 1H NMR: 5.21 (s, 1H), 5.69
(bs, 1H), 6.83 (d, 2H, J = 8.5 Hz), 7.28–7.31 (m, 1H), 7.34–7.39
(m, 7H), 7.48–7.55 (m, 4H); 13C NMR: 42.91, 84.73, 90.47, 115.46,
123.50, 126.84, 127.83, 127.98, 128.24, 128.61, 129.12, 131.68,
134.03, 142.05, 154.50; IR: 3312, 2974, 2924, 2853, 1597, 1512,
1489, 1443, 1233, 1171; MS (m/z): 284 (M+, 100%), 207, 189, 152,
77.
5-Methyl-2-(1,3-diphenylprop-2-ynyl)furan (19):1. Alcohol Ia
(1 mmol), 2-methylfuran (1.5 mmol) and catalyst (15 mol%); Yield:
86% (pale-yellow oil). 1H NMR: 2.28 (s, 3H), 5.24 (s, 1H), 5.92 (dd,
1H, J = 3.0 Hz, J = 1.0 Hz), 6.17 (d, 1H, J = 5.0 Hz) 7.29–7.40 (m,
6H), 7.50–7.53 (m, 4H); 13C NMR: 13.67, 37.91, 83.73, 87.81,
106.22, 107.33, 123.32, 127.04, 127.47, 127.72, 128.03, 128.44,
131.78, 139.19, 151.87, 151.93; IR: 2922, 2853, 1597, 1559, 1489,
1452, 1443; MS (m/z): 272 (M+), 257, 229 (100%), 195, 165, 77.
2-Hydroxy-1-(4-phenylbut-3-yn-2-yl)benzene (14):39. Alcohol
Ib (1 mmol), phenol (2 mmol) and catalyst (15 mol%); Yield:
61% (dark-brown viscous oil; mixture of ortho (major) and para
isomers by NMR). NMR data for the ortho isomer: 1H NMR (1.62
(d, 3H, J = 7.5 Hz), 4.21 (q, 1H, J = 7.2 Hz), 5.85 (s, 1H), 6.87
(dd, 1H, J = 8.0 Hz, J = 1.0 Hz), 6.95 (td, 1H, J = 7.5 Hz, J = 1.5
Hz), 7.18 (td, 1H, J = 7.8 Hz, J = 1.6 Hz); 7.31 (m, 3H), 7.39 (dd,
1H, J = 7.5 Hz, J = 1.5 Hz), 7.47–7.48 (m, 2H); 13C NMR: 22.35,
28.0, 83.43, 91.37, 116.53, 121.12, 122.98, 128.18, 128.19, 128.32,
128.36, 131.65, 131.71, 153.35; IR (isomeric mixture): 3454, 2974,
2928, 1597, 1489, 1454; MS (m/z): 222 (M+), 207 (100%), 178, 77.
N-(2-Nitrophenyl)-1,3-diphenyl-2-propynylamine (20):10. Al-
cohol Ia (1 mmol), 2-nitroaniline (1.5 mmol) and catalyst (15
mol%); Yield: 90% (orange color semi solid). Compound 20 could
not be separated from 1,3-diphenylprop-2-yn-1-one 9 obtained as
1
byproduct (in 1 : 0.88 ratio respectively). H NMR: 5.70 [d, 1H
(CH), J = 6.50 Hz], 6.74–6.77 (m, 1H), 7.13 (d, 1H, J = 8.8 Hz),
7.31–7.34 (m, 3H), 7.43–7.49 (m, 6H), 7.65–7.68 (m, 2H), 8.04–
8.06 (m, 1H), 8.45 [d, 1H (NH), J = 6.0 Hz; assignment confirmed
by D2O exchange which also confirmed coupling between NH and
CH at 5.70 ppm]. 13C NMR: 49.73, 85.90, 86.69, 114.99, 116.53,
122.25, 126.82, 127.18, 128.35, 128.48, 128.54, 129.17, 131.83,
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132.82, 136.07, 143.52, 144.86; IR: 3379, 3061, 2926, 1574, 1501,
1451; MS (m/z): 328 (M+,100%), 313, 252, 189, 115, 77.
Benzyl-(3-phenyl-prop-2-ynyl)-ether (27):43. Alcohol Id (1
mmol), benzyl alcohol (2.5 mmol) and catalyst (20 mol%); Yield:
1
62% (colorless oil). H NMR: 4.42 (s, 1H), 4.58 (s, 2H), 4.70 (s,
N-(4-Nitrophenyl)-1,3-diphenyl-2-propynylamine (21):10. Al-
cohol Ia (1 mmol), 4-nitroaniline (1.5 mmol) and catalyst (15
1H), 7.28–7.34 (m, 4H), 7.36–7.42 (m, 5H), 7.47–7.49 (m, 1H); 13
C
NMR: 57.92, 72.12, 85.06, 86.49, 122.66, 127.65, 127.81, 128.32,
128.42, 128.48, 131.80, 138.28; IR: 2974, 2857, 1954, 1659, 1599,
1491, 1454, 1381; MS (m/z): 223 [(M+1)+, 100%], 221, 105.
1
mol%); Yield: 91% (yellow semi solid). H NMR: 4.95 (bs, 1H),
5.60 (s, 1H), 6.75 (d, 2H, J = 9.0 Hz), 7.29–7.46 (m, 8H), 7.63–7.65
(m, 2H), 8.13 (d, 2H, J = 9.0 Hz); 13C NMR: 50.07, 85.96, 86.40,
112.42, 122.08, 126.17, 127.27, 128.38, 128.75, 128.78, 129.13,
131.78, 138.03, 139.08, 151.42; IR: 3375, 2924, 1597, 1505, 1304;
MS (m/z): 326 (M-2)+ , 280 (100%), 203, 189, 176, 76.
iPropyl-(1,3-diphenyl-prop-2-ynyl)-ether (28):19. Alcohol Ia (1
mmol), 2-propanol (2 mmol) and catalyst (15 mol%); Yield: 82%
1
(colorless oil): H NMR: 1.26 (d, 3H, J = 6.0 Hz), 1.29 (d, 3H,
J = 6.0 Hz), 4.06 (q, 1H), 5.44 (s, 1H), 7.30–7.41 (m, 6H), 7.46–
7.48 (m, 2H), 7.57–7.59 (m, 2H); 13C NMR: 21.75, 22.90, 69.39,
69.79, 88.60, 88.02, 122.77, 127.39, 128.18, 128.23, 128.37, 128.50,
131.76, 139.55; IR: 2976, 2866, 1962, 1491, 1383, 1121; MS (m/z):
250 (M+), 207, 191 (100%), 179, 129, 105, 77.
3-(4-Methoxyphenyl)-1-phenylpropan-1-one (22):40,41
. Alcohol
Id (1 mmol), anisole (2 mmol) and catalyst (20 mol%); Yield: 74%
(colorless semi-solid). 1H NMR: 3.01 (t, 2H, J = 7.8 Hz), 3.27 (t,
2H, J = 7.8 Hz), 3.79 (s, 3H), 6.84 (d, 2H, J = 8.5 Hz), 7.17 (d,
2H, J = 8.5 Hz), 7.45 (t, 2H, J = 7.8 Hz), 7.56 (t, 1H, J = 7.2 Hz),
7.95–7.97 (m, 2H); 13C NMR: 29.28, 40.71 55.27, 113.93, 128.04,
128.05, 128.59, 129.34, 133.02, 136.90, 157.99, 199.40; IR: 3053,
2253, 2835, 1512, 1265; Mass (m/z): 240 (M+), 135, 121 (100%),
105, 77.
secButyl-(1,3-diphenyl-prop-2-ynyl)-ether (29). Alcohol Ia (1
mmol), 2-butanol (2 mmol) and catalyst (15 mol%); Yield: 91%;
(pale yellow shiny solid; m.p.: 79–80 ◦C): Mixture of geometrical
isomers (1 : 0.81 ratio). 1H NMR: Isomer I (aliphatic signals): 0.94
(t, 3H, J = 7.3 Hz), 1.25 (d, 3H, J = 6.0 Hz), 1.51–1.61 (m, 2H),
3.81 (q, 1H, J = 6.2 Hz), 5.45 (s, 1H); Isomer II (aliphatic signals):
1.02 (t, 3H, J = 7.5 Hz), 1.29 (d, 3H, J = 6.5 Hz), 1.63–1.71 (m,
2H), 3.90 (q, 1H, J = 6.3 Hz), 5.44 (s, 1H); aromatics resonances
for both isomers: 7.31–7.35 (m, 8H), 7.38–7.41 (m, 4H), 7.46–7.49
(m, 4H), 7.59–7.61 (m, 4H); 13C NMR: Isomer I (aliphatic signals):
9.73, 19.14, 28.87, 69.56, 74.93, 86.55, 88.18: Isomer II (aliphatic
signals): 10.18, 20.07, 29.87, 70.10, 75.35, 86.56, 88.35: aromatic
resonances for both isomers: 122.83, 122.85, 127.40, 127.48, 128.17,
128.20, 128.24, 128.26, 128.34, 128.36, 128.47, 128.48, 131.71,
131,75, 139.59, 139.69; IR (mixture) 2969, 2932, 2876, 2245, 2201,
1599, 1489; MS (m/z): 264 (M+), 207, 191 (100%), 179, 129, 105,
77.
3-(2,4-Dimethoxyphenyl)-1-phenylpropan-1-one (23). Alcohol
Id (1 mmol), 1,3-dimethoxybenzene (2 mmol) and catalyst (20
mol%); Yield: 71% (pale red semi-solid). 1H NMR: 2.99 (t, 2H, J =
7.7 Hz), 3.24 (t, 2H, J = 7.8 Hz), 3.80 (s, 3H), 3.81 (s, 3H), 6.43
(dd, 1H, J = 8.0 Hz, J = 2.5 Hz), 6.47 (unresolved t, 1H, J = 2.5
Hz), 7.11 (d, 1H, J = 8.5 Hz), 7.45 (t, 2H, J = 7.8 Hz), 7.53–7.56
(m, 1H, J = 7.3 Hz), 7.97–7.99 (m, 2H); 13C NMR: 25.14, 39.21,
55.22, 55.37, 98.56, 103.86, 121.88, 128.11, 128.51, 130.34, 132.85,
137.02, 158.38, 159.49, 200.15; IR: 3053, 2959, 2936, 1684, 1614,
1587, 1505; Mass (m/z): 270 (M+), 165, 151 (100%), 121, 105, 77.
3-(4-Hydroxyphenyl)-1-phenylpropan-1-one (24):42. Alcohol Id
(1 mmol), phenol (2 mmol) and catalyst (20 mol%); Yield: 86%
(pale red solid; m.p. 105–106). 1H NMR: 3.0 (t, 2H, J = 7.50 Hz),
3.27 (t, 2H, J = 7.8 Hz), 5.05 (bs, 1H), 6.77 (d, 2H, J = 8.5 Hz), 7.11
(d, 2H, J = 9.0 Hz), 7.44 (m, 2H), 7.56 (t, 1H, J = 7.5 Hz), 7.95–7.97
(m, 2H); 13C NMR: 29.31, 40.71, 115.34, 128.07, 128.62, 129.54,
133.12, 133.29, 136.81, 153.94, 199.72; IR: 3381, 1674, 1597, 1516,
1449; MS (m/z): 226 (M+), 105 (100%), 77, 51.
Bis-(1,3-diphenyl-prop-2-ynyl)-ether (30). Alcohol Ia (2 mmol)
and catalyst (15 mol%); Yield: 92% (colorless oil): NMR shows
the presence of two geometrical isomers in 1 : 0.67 ratio with no
◦
1
appreciable change up to 60 C (VT-NMR). H NMR: 5.58 (s,
2H), 5.97 (s, 2H), 7.31–7.32 (m, 2H), 7.34–7.36 (m, 5H), 7.38–
7.42 (m, 5H), 7.47–7.49 (m, 2H), 7.53–7.55 (m, 2H), 7.63–7.64
(m, 2H), 7.67–7.69 (m, 2H); 13C NMR: 69.72, 70.18, 86.66, 87.04,
87.82, 80.09, 122.52, 122.56, 127.78, 128.0, 128.24, 128.34, 128.42,
128.48, 128.54, 128.64, 128.65, 128.69, 131.88, 131.92, 138.29,
138.50; IR: 3055, 2929, 2359, 2332, 1599, 1489, 1456, 1443;
MS (m/z): (M+ is not noticed), 206 (1,3-diphenyl-prop-2-yn-O.
radical), 178 (100%), 129, 51.
Benzyl-(1,3-diphenyl-prop-2-ynyl)-ether (25):19. Alcohol Ia (1
mmol), benzyl alcohol (2 mmol) and catalyst (15 mol%); Yield:
1
90% (pale red oil). H NMR: 4.79 (d, H, J = 11.5 Hz), 4.85 (d,
1H, J = 11.5 Hz), 5.51 (s, 1H), 7.37–7.49 (m, 11H), 7.55–7.56 (m,
2H), 7.66–7.68 (m, 2H); 13C NMR: 70.11, 71.01, 86.94, 87.91,
122.62, 127.66, 127.86, 128.24, 128.37, 128.50, 128.54, 128.59,
128.63, 131.89, 137.82, 138.70; IR: 3034, 2199, 1689, 1603; MS
(m/z): (M+ not detected), 207 (M-PhCH2), 191 (100%), 105, 77.
Bis-(4-phenyl-but-3-yn-2-yl)-ether (31). Alcohol Ib (2 mmol)
and catalyst (20 mol%); Two isomers were obtained that could
be separated by prep-TLC. Isomer I: 1H NMR (31a): Yield: 63%
(colorless oil): 1.58 (d, 6H, J = 7.0 Hz), 4.84 (q, 2H, J = 6.5 Hz),
7.30–7.33 (m, 6H), 7.45–7.47 (m, 4H); 13C NMR: 22.35, 63.56,
85.02, 88.90, 122.72, 128.26, 128.33, 131.80; IR: 2986, 2934, 2866,
1597, 1489, 1443, 1329; MS (m/z): 274 (M+), 259 (100%), 231,
215. Isomer II (31b): Yield: 25% (colorless oil): 1H NMR: 1.58 (d,
6H, J = 6.5 Hz), 4.72 (q, 2H, J = 6.5 Hz), 7.24–7.29 (m, 6H), 7.41–
7.43 (m, 4H); 13C NMR: 22.03, 63.91, 84.99, 89.30, 122.79, 128.15,
128.23, 131.78; IR: 3055, 2988, 2928, 1489, 1265; MS (m/z): 274
(M+), 259 (100%), 231, 215.
Benzyl-(4-phenyl-but-3-yn-2-yl)-ether (26). Alcohol Ib (1
mmol), benzyl alcohol (2 mmol) and catalyst (15 mol%); Yield:
79% [colorless oil; obtained as a 1 : 0.16 mixture (by NMR) of
26 and isomeric 31 (consisting of 31a and 31b in 1 : 0.83 ratio by
NMR) see below]. NMR data for 26 is out of mixture. 1H NMR:
1.57 (d, 3H, J = 6.5 Hz), 4.46 (q, 1H, J = 6.5 Hz), 4.59 (d, 1H,
J = 11.6 Hz), 4.87 (d, 1H, J = 11.5 Hz), 7.32–7.38 (m, 7H), 7.41–
7.44 (m, 3H); 13C NMR: 22.21, 64.93, 70.59, 85.24, 89.05, 122.77,
127.70, 128.07, 128.29, 128.33, 128.41, 131.75, 138.03; IR: 3053,
1489, 1421, 1265; MS (m/z): 236 (M+), 193, 129 (100%), 115, 91.
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Bis-(3-phenyl-prop-2-ynyl)-ether (32):44. Alcohol Id (2 mmol)
and catalyst (20 mol%); Yield. 61% (colorless oil). 1H NMR: 4.55
(s, 4H), 7.30–7.34 (m, 6H), 7.45–7.48 (m, 4H); 13C NMR: 57.44,
84.34, 86.80, 122.48, 128.30, 128.55, 131.82; IR: 3053, 1655, 1491,
1265; MS (m/z): 246 (M+, 100%), 217, 202, 139.
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J = 2.1 Hz), 4.59 (q, 1H, J = 6.7 Hz), 7.30–7.32 (m, 3H), 7.43–7.45
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52% (colorless oil) obtained as 1 : 0.97 mixture (by NMR) of 35
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and 32. NMR data for 35 out of the mixture: H NMR: 1.16 (t,
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3H, J = 7.5 Hz), 2.25 (qt, 2H, J = 7.7 Hz, J = 2.1 Hz), 4.29 (t, 2H,
J = 2.0 Hz), 4.47 (s, 2H), 7.31–7.34 (m, 3H), 7.43–7.45 (m, 2H);
13C NMR: 12.48, 13.77, 57.15, 57.28, 74.50, 84.52, 86.80, 89.04,
122.55, 128.28, 128.48, 131.78,; IR (mixture): 2974, 2928, 2853,
2239, 1657, 1491; MS (m/z): 198 (M+, 100%), 141, 115.
Cyclohexyl-(4-phenyl-but-3-yn-2-yl)-ether (36). Alcohol Ib (1
mmol), cyclohexanol (1.5 mmol) and catalyst (20 mol%); Yield.
81% (colorless oil) obtained as a 1 : 0.44 (by NMR) mixture of
1
36 and 31a. NMR data for 36 is out of the mixture: H NMR:
1.17–1.43 (m, 5H), 1.51 (d, 3H, J = 6.6 Hz), 1.53–1.56 (m, 1H),
1.70–1.79 (m, 2H), 1.95–2.0 (m, 2H), 3.65 (septet, 1H, J = 4.7 Hz),
4.53 (q, 1H, J = 6.6 Hz), 7.29–7.30 (m, 3H), 7.42–7.44 (m, 2H);
13C NMR: 22.79, 24.21, 24.42, 25.80, 31.59, 33.43, 62.45, 75.61,
83.94, 90.25, 123.01, 128.13, 128.23, 131.69; IR (mixture): 2986,
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(M-CH3), 129 (100%), 109.
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We thank the University of North Florida for research support and
Dr Rick Troendle of this department for technical assistance to our
group with NMR and other instrumentation. V.S. is thankful to Dr
Levente Fabry–Asztalos for technical assistance during feasibility
studies at CWU.
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2528 | Org. Biomol. Chem., 2011, 9, 2518–2529
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©