Alkylation of 1,3-dicarbonyl compounds with benzylic and propargylic alcohols using Ir-Sn bimetallic catalyst: Synthesis of fully decorated furans and pyrroles

Article abstract of DOI:10.1016/j.tet.2011.04.092

The heterobimetallic complex [Ir(COD)(SnCl₃)Cl(μ-Cl)] ₂ catalyzes the direct substitution of hydroxyl groups in benzylic and propargylic alcohols by 1,3-dicarbonyl moiety. In 4-hydroxycoumarin, benzylation and propargylation occurs at the 3-position. Selective propargylation or allenylation takes place depending on the nature of propargylic alcohol. By applying the methodology, multi-substituted furans and pyrroles have been synthesized in good yields.

Full text of DOI:10.1016/j.tet.2011.04.092

Tetrahedron 67 (2011) 4569e4577
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Alkylation of 1,3-dicarbonyl compounds with benzylic and propargylic alcohols
using IreSn bimetallic catalyst: synthesis of fully decorated furans and pyrroles
,b,
Paresh Nath Chatterjee a, Sujit Roya
*
a Organometallics and Catalysis Laboratory, Chemistry Department, Indian Institute of Technology, Kharagpur 721302, India
b School of Basic Science, Indian Institute of Technology, Bhubaneswar 751013, India
a r t i c l e i n f o
a b s t r a c t
Article history:
The heterobimetallic complex [Ir(COD)(SnCl3)Cl(m-Cl)]2 catalyzes the direct substitution of hydroxyl
Received 9 January 2011
Received in revised form 21 April 2011
Accepted 22 April 2011
groups in benzylic and propargylic alcohols by 1,3-dicarbonyl moiety. In 4-hydroxycoumarin, benzylation
and propargylation occurs at the 3-position. Selective propargylation or allenylation takes place
depending on the nature of propargylic alcohol. By applying the methodology, multi-substituted furans
and pyrroles have been synthesized in good yields.
Available online 5 May 2011
Ó 2011 Elsevier Ltd. All rights reserved.
Keywords:
Bimetallic catalysis
Benzylation
Propargylation
Allenylation
1,3-Dicarbonyl compound
Furan
Pyrrole
Iridium
Tin
1. Introduction
transformations requires the use of an organic halide and an
equimolar amount of base or Lewis acid, resulting in large amount
Our continuing interest in dual-reagent catalysis involving d8/d10
transition metal partners and tin as a main group metal partner,1
brought us to parallel investigation on organic activation across dis-
crete MeSn motif; one of the successful example being the hetero-
of salt by-products. Unquestionably, the alkylation of activated
methylene compounds with an alcohol would provide an attractive
salt-free, environment friendly and atom-economic5 procedure
with water being the sole by-product. Due to its poor leaving group
ability, the hydroxyl group of an alcohol needs in situ pre-activation
by a promoter prior to the nucleophilic substitution. In this regard,
recent demonstration of Lewis and Brønsted acid catalyzed ben-
zylation and propargylation of 1,3-dicarbonyl derivatives using al-
cohols is noteworthy.6,7 However, to the best of our knowledge,
there is only one report on the use of a bimetallic catalyst for such
transformation. We present here the first example of alkylation of
1,3-dicarbonyl compounds via cooperative heterobimetallic
catalysis.
bimetallic complex [Ir(COD)(SnCl3)Cl(
which can be easily generated from [Ir(COD)(
IrIIIeSnIV catalyst showed remarkable efficiency in the FriedeleCrafts
m
-Cl)]2 (hereafter IrIIIeSnIV),
-Cl)]2 and SnCl4.2 The
m
alkylation of arenes and heteroarenes using p
-activated 1ꢀ, 2ꢀ, and 3ꢀ
alcohols.2 In addition, the catalyst mediated the secondary benzyla-
tion and propargylation of carbon (arene, heteroarene and allyl-
trimethylsilane), oxygen (alcohol), nitrogen (amide and sulfonamide)
and sulfur (thiol) nucleophiles with respective benzylic and prop-
argylic alcohols.3 Keeping in view the efficacy of the IreSn motif to
activate
p
-activated alcohols, we aimed to explore the benzylation
The benzylation of 1,3-dicarbonyl derivatives leads to the gen-
eration of structural motifs of many bioactive compounds; Tipra-
navir (an HIV protease inhibitor), Reglitazar (a potential diabetes
drug) and Warfarine (an oral anticoagulant) being representative
examples.6e,8 Similarly propargylation of 1,3-dicarbonyl com-
pounds provides access to useful synthetic intermediates, and
heterocycles such as furans and pyrroles (Fig. 1). Substituted furans
constitute an important architecture in many natural products,
pharmaceuticals, flavours and fragrance compounds.9 Likewise the
and propargylation using 1,3-dicarbonyl derivatives as the C-nucle-
ophile (Scheme 1).
The functionalization of activated methylene moieties including
1,3-dicarbonyl compounds is one of the important methodologies
in CeC bond formation.4 The standard protocol for these
* Corresponding author. E-mail address: royiitkgp@gmail.com (S. Roy).
0040-4020/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2011.04.092

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P.N. Chatterjee, S. Roy / Tetrahedron 67 (2011) 4569e4577
Scheme 1. Activation of benzylic and propargylic alcohols by IrIIIeSnIV catalyst towards benzylation and propargylation of 1,3-dicarbonyl derivatives.
IrCl3/SnCl4 and [Ir(COD)(m-Cl)]2/SnCl4 also led to low conversion
(entries 10 and 11). These observations emphasize the importance
of high-valent IrIIIeSnIV moiety; although we are yet to fully com-
prehend the exact nature of synergism in such a motif.
Next we explored the benzylation of 1,3-dicarbonyl derivatives 2
taking 1ꢀ and 2ꢀ benzylic alcohols 1 as electrophiles (alcohol/nu-
cleophile molar ratio is 1:1.5). The reactions were carried out in the
Fig. 1. Synthetic application of propargylated 1,3-dicarbonyl moiety.
presence of 1 mol % of [Ir(COD)(SnCl3)Cl(
chloroethane (DCE) at 80 ꢀC (Table 2). Secondary benzylic alcohols
1aec and 1eeh (entries 1e3, and 7e10), having a -hydrogen atom,
m-Cl)]2 catalyst in 1,2-di-
substituted pyrrole ring is an important structural attribute in
several bioactive natural products10 and pharmaceuticals11 as well
as a useful building block in organic synthesis.12
In continuation to our exploration on heterobimetallic re-
activity, we report here an efficient and highly regioselective sub-
stitution of benzylic and secondary/tertiary propargylic alcohols
with 1,3-dicarbonyl derivatives and 4-hydroxycoumarin which is
catalyzed by [Ir(COD)(SnCl3)Cl(m-Cl)]2. Further, the propargylated
1,3-dicarbonyl products have been steered to ring-closure with the
formation of substituted furans and pyrroles.
b
reacted smoothly with dibenzoylmethane 2a to provide the desired
benzylated products, without forming any alkene side-products.
Alcohols 1b and 1c, bearing electron-donating and electron-
withdrawing substituent at the para position of the phenyl ring,
afforded the respective benzylated product 3b and 3c in good yields
(entries 2 and 3). The reaction of 1-(2-naphthyl) ethanol 1e with 2a
went smoothly affording the 3g (entry 7). Alcohol 1f was effective
yielding 3h in 80% yield (entry 8), while no 1,2-dihydronaphthalene
was detected as side-product. A mixture of diastereomers was
isolated when alcohol 1a was coupled with unsymmetrical 1,3-
dicarbonyl compound 2c (entry 6). Alcohol 1g and 1h, where the
2. Results and discussion
p
-activation is provided by heteroarenes like thiophene or furan
Initially we examined the efficiency of various catalysts towards
the formation of alkylated product 3a from benzylic alcohol 1a and
dibenzoylmethane 2a (Table 1). The efficiency of IreSn hetero-
moiety, underwent benzylation of 2a in good yield (entries 9 and
10). In spite of lower enol ratios,6d benzylation of ketoester 2d and
2e reacted with activated electrophile, like diphenylmethanol 1i
(entries 11 and 12). The structure of product 3k was established by
X-ray crystallographic analysis (Supplementary data). The benzy-
lation of 1,3-dicarbonyl derivatives was not limited to secondary
benzylic substrates. Primary benzylic alcohol 1d reacted with 2a
leading to 3e in moderate yield (entry 5).
bimetallic catalyst [Ir(COD)(SnCl3)Cl(
parison to others and the desired product 3a was obtained in 81%
yield after 45 min (entry 1). Individually [Ir(COD)( -Cl)]2 was in-
m-Cl)]2 was highest in com-
m
active, while IrCl3 and SnCl4 were poorly active (entries 5e7).
Similarly [Ir(COD)(MeCN)2]PF6 and [Ir(COD)2(SnCl3)] showed very
negligible efficiencies (entries 8 and 9). A simple 1:1 combination of
Afterwards we examined the propargylation of 1,3-dicarbonyl
derivatives 2 with a variety of propargylic alcohols 4 using 1 mol % of
IrIIIeSnIV catalyst in DCE at 80 ꢀC (Table 3). As shown in Table 3
(entries 1e5), the reaction was general with respect to sub-
stitution in the 1,3-dicarbonyl framework. Variation at the alkyne
terminus in propargyl alcohol from an alkyl to an aryl, or trimethy-
silane (4aec, 4e) was well tolerated (entries 1e6 and 8). Gratifyingly,
alcohol 4d bearing terminal alkyne group successfully underwent
the coupling reaction with 2a under the same reaction conditions
leading to 5g and no polymerization was detected (entry 7). The
structure of 5g was established by X-ray crystallographic analysis
(Supplementary data). The ketoester 2d reacted equally well with
alcohol 4b affording a mixture of diastereomers (entry 5). Also
noteworthy is the fact that attempted reaction of secondary and
Table 1
Benzylation of dibenzoylmethane 2a with benzylic alcohol 1a: catalyst screeninga
O
O
OH
1 mol% cat.
Ph
O
O
Ph
DCE, 80 oC, 45 min
+
Ph
Ph
2a
3a
1a
Entry
Catalyst
[Ir(COD)(SnCl3)Cl(
[Ir(COD)(SnBr3)Br(
[Ir(COD)(MeSnCl2)Cl(
IrCl(CO)(PPh3)2(SnCl4)
Yield (%)
TOF (hꢁ1
)
1
2
3
4
5
6
7
8
m
m
-Cl)]2
-Br)]2
-Cl)]2
81
65
57
<5
0
108
87
76
<7
0
11
14
<7
<7
20
16
m
tertiary propargylic alcohol containing b-hydrogen atom (4f and 4g)
[Ir(COD)(
IrCl3
m-Cl)]2
8
with 2a as nucleophile failed to give the desired propargylated
products. The reaction of secondary alcohol 4f with 2a ended with
unidentified complex mixture, whereas the tertiary alcohol 4g un-
derwent fast dehydration yielding 1,3-enyne and rearrangement to
SnCl4
10
<5
<5
15
12
[Ir(COD)(MeCN)2]PF6
[Ir(COD)2(SnCl3)]
IrCl3/SnCl4 (1:1)
9
10
11
a,b
-unsaturated ketone3b simultaneously. We also noted that both
[Ir(COD)(m-Cl)]2/SnCl4 (1:1)
the benzylation and propargylation reactions of 1,3-dicarbonyl de-
rivatives can tolerate moisture or air without compromising product
yield.
a
Unless otherwise mentioned, reaction conditions: alcohol (0.5 mmol), nucleo-
phile (0.75 mmol), catalyst (0.005 mmol), solvent DCE (2 mL), 80 ꢀC, 45 min. Yield
refers to isolated yield.

P.N. Chatterjee, S. Roy / Tetrahedron 67 (2011) 4569e4577
4571
Table 2
Benzylation of 1,3-dicarbonyl derivatives 2 with benzylic alcohols 1a
Entry
Alcohol 1
NueH 2
Product 3
Time (min)
Yield (%)
O
O
OH
O
O
Ph
Ph
1
45
81
Ph
Ph
2a
1a
3a
O
O
OH
O
O
O
O
Ph
Ph
2
3
30
55
85
75
Ph
Ph
Ph
Ph
2a
1b
OH
1c
3b
O
O
Ph
Ph
2a
Br
3c
Br
O
O
OH
O
O
O
O
4
80
85
2b
1b
3d
O
O
Ph
Ph
OH
1d
5
6
85
35
68
Ph
Ph
MeO
2a
3e
MeO
O
O
OH
O
O
Ph
85b
Ph
2c
1a
3f
O
O
OH
O
O
O
O
Ph
Ph
7
8
30
45
88
80
Ph
Ph
Ph
Ph
2a
1e
3g
O
O
OH
Ph
Ph
2a
1f
3h
O
O
O
O
O
O
OH
Ph
Ph
9
60
70
76
S
Ph
Ph
Ph
Ph
1g
2a
S
3i
O
O
OH
Ph
Ph
10
72
O
1h
2a
3j
O
(continued on next page)

4572
P.N. Chatterjee, S. Roy / Tetrahedron 67 (2011) 4569e4577
Table 2 (continued )
Entry
Alcohol 1
NueH 2
Product 3
Time (min)
Yield (%)
O
O
OH
O
O
O
O
11
30
92
O
2d
1i
3k
O
O
OH
O
O
Ph
12
30
90
Ph
O
2e
1i
3l
a
Unless otherwise mentioned, reaction conditions: alcohol (0.25 mmol), nucleophile (0.38 mmol), IrIIIeSnIV cat. (0.0025 mmol), solvent DCE (1 mL), 80 ꢀC.
dr¼1:1.3. Yield refers to isolated yield.
b
Table 3
Propargylation of 1,3-Dicarbonyl Derivatives 2 with Propargylic Alcohols 4a
Entry
Alcohol 4
NueH 2
Product 5
Time (min)
Yield (%)
O
O
O
O
OH
O
O
Ph
Ph
Ph
1
45
95
4-MeC6H4
Ph
Ph
4-MeC6H4
2a
Ph
Ph
Ph
4a
5a
Ph
Ph
Ph
O
OH
O
O
2
3
50
45
91b
4-MeC6H4
Ph
4-MeC6H4
O
2c
4a
5b
OH
O
O
89
4-MeC6H4
4-MeC6H4
O
2f
4a
5c
5d
5e
O
OH
O
O
4
5
55
80
84
4-ClC6H4
4-ClC6H4
O
2b
Ph
Ph
4b
Ph
O
OH
O
O
O
79c
4-ClC6H4
O
4-ClC6H4
4b
2d
Ph

P.N. Chatterjee, S. Roy / Tetrahedron 67 (2011) 4569e4577
4573
Table 3 (continued )
Entry
Alcohol 4
NueH 2
Product 5
Time (min)
Yield (%)
O
O
OH
O
O
O
O
O
O
Ph
Ph
4-ClC6H4
6
7
8
60
85
62
85
4-ClC6H4
Ph
Ph
Ph
Ph
Ph
Ph
TMS
4c
2a
2a
2a
TMS
5f
O
O
OH
4-MeC6H4
4d
Ph
Ph
65
60
4-MeC6H4
H
H
5g
O
O
OH
4-MeC6H4
4e
Ph
Ph
4-MeC6H4
n-Bu
n-Bu
5h
OH
Me
O
O
O
O
9
d
90
35
d
Ph
Ph
Ph
Ph
Ph
2a
4f
Ph
Ph
OH
Me
Me
10
62 30
Me
O
Me
Ph
2a
4g
Me
a
Unless otherwise mentioned, reaction conditions: alcohol (0.25 mmol), nucleophile (0.38 mmol), IrIIIeSnIV cat. (0.0025 mmol), solvent DCE (1 mL), 80 ꢀC.
b
c
dr¼1:1.5.
dr¼1:1.1. Yield refers to isolated yield.
We investigated the reactivity of tertiary propargylic alcohol 4h
of importance as they constitute valuable building blocks for po-
tential new pharmaceuticals, especially anticoagulants.14 We ex-
plored the reaction of 4-hydroxycoumarin 2g with different
benzylic alcohols 1b, 1eef and 1i, and in each case the products 8
were obtained in good yields (entries 1e4). Similar reaction of
propargylic alcohols 4aec, and 4i with 2g led to propargylated
products 9 in good yields (entries 5e8).
towards 1,3-dicarbonyl compound 2a (Scheme 2). However, the
conjugated diene-dione 6 was obtained as the only isolable product
in this case. We believe that the highly activated tertiary prop-
argylic alcohol 4h first undergoes isomerization into corresponding
a,b
-unsaturated ketone,13 followed by aldol-type condensation
with 2a under catalytic conditions to afford compound 6. In-
terestingly, we found that the presence of a substituent at the active
methylene carbon of the 1,3-dicarbonyl compound, as, for example,
in 2f, gave rise to substitution reaction with tertiary propargylic
alcohol 4h under IrIIIeSnIV catalysis. In this case a regioselective
allenylation took place instead of propargylation and 7 was isolated
in 63% yield (Scheme 2). The result suggests that the steric hin-
drance around hydroxyl group plays a pivotal role in promoting the
nucleophile attack at the acetylenic centre of the ambient electro-
phile. One may note that the carbonyl-functionalized allenes are
important building blocks in organic synthesis.
Having successfully developed an efficient propargylation of
1,3-dicarbonyl derivatives, we finally turned our attention to the
application of this methodology to
a one-pot synthesis of
substituted furans.7aeg,i,lem The reaction of propargylic alcohol 4i
with 1,3-dicarbonyl derivatives 2 and a catalytic amount of
[Ir(COD)(SnCl3)Cl(m-Cl)]2 in DCE followed by the addition of cesium
carbonate (Cs2CO3) allowed the synthesis of functionalized furans
10 in good yields (Scheme 3). Remarkably, for 1,3-dicarbonyl
compound 2d the cyclization went regioselectively since only the
keto group participated in the cyclization process while the ester
function remained as a spectator. On the other hand, for unsym-
metric 1,3-dicarbonyl compound 2c, a mixture of substituted furans
(10c-1 and 10c-2) was isolated. In the presence of inorganic base
the propargylated 1,3-dicarbonyl 5 tautomerises to A, which sub-
sequently isomerizes to 10 in a 5-exo-dig fashion.
We also found that when a primary aromatic amine was in-
troduced in the reaction medium, substituted pyrroles could be
selectively formed.7a,15 Thus reaction of propargylic alcohol 4i with
1,3-dicarbonyl derivatives 2 and in situ generated [IreSn] catalyst2a
in DCE was followed by the addition of primary aromatic amines 11
giving rise to tetrasubstituted pyrroles 12 in good yields (Scheme 3).
However, aliphatic amines remained unreactive under the condi-
tion. Interestingly, unsymmetric 1,3-dicarbonyl compound 2c led to
Scheme 2. Differential reactivity of tertiary propargylic alcohol 4h towards 1,3-di-
carbonyl derivatives 2a and 2f.
Encouraged by the reactivity of IrIIIeSnIV as above, we sought to
synthesize substituted coumarins through the benzylation and
propargylation of 4-hydroxycoumarin 2g with various benzylic and
propargylic alcohols (Table 4). Substituted coumarin analogues are

4574
P.N. Chatterjee, S. Roy / Tetrahedron 67 (2011) 4569e4577
Table 4
Syntheses of coumarin analogue by IrIIIeSnIV catalyzed benzylation and propargylation of 4-hydroxycoumarin 2ga
Entry
Alcohol
Product
Yield (%)
OH
OH
1
82
O
O
8a
1b
OH
O
OH
2
3
85
78
O
1e
8b
OH
OH
O
O
8c
1f
OH Ph
OH
1i
4
95
O
O
8d
HO 4-MeC6H4
OH
5
6
7
93
90
89
4-MeC6H4
Ph
Ph
Ph
Ph
Ph
4a
O
O
9a
HO 4-ClC6H4
OH
4-ClC6H4
4b
O
O
9b
OH Ph
OH
Ph
Ph
O
O
4i
9c
HO 4-ClC6H4
OH
4-ClC6H4
4c
8
84
TMS
TMS
O
O
9d
a
Unless otherwise mentioned, reaction conditions: alcohol (0.25 mmol), nucleophile 2g (0.38 mmol), IrIIIeSnIV cat. (0.0025 mmol), solvent DCE (1 mL), 80 ꢀC. Yield refers to
isolated yield.

P.N. Chatterjee, S. Roy / Tetrahedron 67 (2011) 4569e4577
4575
Scheme 3. Synthesis of substituted furans 10 and pyrroles 12 from 1,3-dicarbonyl derivatives.
the regioselective formation of substituted pyrrole 12c. The forma-
tion of pyrroles may be explained by the following steps: (i) gener-
ation of intermediate B via the condensation of amine 11 with 5,
followed by tautomerization; (ii) the cycloisomerization of B in
a 5-exo-dig manner.15d,e
silica gel. For reaction monitoring, pre-coated silica gel 60 F254 TLC
sheets were used. Petroleum ether refers to the fraction boiling
in the range 60e80 ꢀC. 1,2-Dichloroethane (DCE) was dried
and distilled prior to use. IrCl3$xH2O, 1,5-cyclooctadiene and tin
tetrachloride were commercially available. [Ir(COD)(
prepared according to the literature procedure16 and the hetero-
bimetallic catalysts [Ir(COD)(SnCl3)Cl(
-Cl)]2,2 [Ir(COD)(SnBr3)Br(
Br)]2,2b [Ir(COD)(MeSnCl2)Cl( -Cl)]2,2b [IrCl(CO)(PPh3)2(SnCl4)],17
m-Cl)]2 was
m
m-
3. Conclusions
m
[Ir(COD)2(SnCl3)]18 were prepared according to literature pro-
cedure. Benzylic alcohols (1d, 1aec and 1eei)19 and propargylic
alcohols (4aei)20 were also prepared according to literature.
In summary, we presented here a facile benzylation and
propargylation of 1,3-dicarbonyl derivatives with benzylic and
propargylic alcohols catalyzed by [Ir(COD)(SnCl3)Cl(m-Cl)]2 heter-
obimetallic complex. Selective propargylation or allenylation
products can be obtained depending on the structure of the
propargylic alcohol. In addition, the IrIIIeSnIV catalyst can promote
the benzylation and propargylation of 4-hydroxycoumarin at the
3-position. Furthermore, we have introduced one more strategy
for the synthesis of substituted furans and pyrroles by employing
IreSn catalyzed nucleophilic substitution of propargylic alcohols
with 1,3-dicarbonyl compounds as the key step. By virtue of their
generality, selectivity and efficiency, the strategies presented here
could be a meaningful addition to the existing methods of ben-
zylation, propargylation of 1,3-dicarbonyl compounds.
4.2. Representative procedure for the benzylation of
dibenzoylmethane 2a with 1-phenylethanol 1a catalyzed by
[Ir(COD)(SnCl3)Cl(m-Cl)]2
A 10 mL Schlenk flask equipped with a magnetic bar was
charged with [Ir(COD)(SnCl3)Cl( -Cl)]2 (0.0025 mmol), dibenzoyl-
m
methane 2a (0.38 mmol), 1-phenylethanol 1a (0.25 mmol) and 1,2-
dichloroethane (1 mL). The flask was degassed, flushed with argon
and placed in a constant temperature bath at 80 ꢀC. The reaction
was allowed to continue at 80 ꢀC, and monitored by TLC. After
completion, solvent was removed under reduced pressure and the
mixture was subjected to column chromatography over silica gel
(eluent: gradient mixture of EtOAc/pet ether) to afford the benzy-
lated product 3a in 81% isolated yield.
4. Experimental
4.1. General remarks
1H NMR spectra were recorded at 400 MHz and 200 MHz on
Bruker Spectrometers. Chemical shifts are reported in parts per
million from tetramethylsilane with the solvent resonance as the
4.3. Representative procedure for the propargylation of
dibenzoylmethane 2a with 3-phenyl-1-(p-tolylprop)-2-yn-1-ol
4a catalyzed by [Ir(COD)(SnCl3)Cl(m-Cl)]2
internal standard (deuterochloroform:
d
7.26 ppm). 13C NMR
spectra were recorded at 100 MHz and 54.6 MHz with complete
proton decoupling. Chemical shifts are reported in ppm from tet-
ramethylsilane with the solvent resonance as the internal standard
A 10 mL Schlenk flask equipped with a magnetic bar was
charged with [Ir(COD)(SnCl3)Cl( -Cl)]2 (0.0025 mmol), dibenzoyl-
m
(deuterochloroform:
d
77.0 ppm). ESI-MS was recorded using
methane 2a (0.38 mmol), 3-phenyl-1-(p-tolylprop)-2-yn-1-ol 4a
(0.25 mmol) and 1,2-dichloroethane (1 mL). The flask was
degassed, flushed with argon and placed in a constant temperature
bath at 80 ꢀC. The reaction was allowed to continue at 80 ꢀC, and
monitored by TLC. After completion, solvent was removed under
reduced pressure and the mixture was subjected to column chro-
matography over silica gel (eluent: gradient mixture of EtOAc/pet
ether) to afford the propargylated product 5a in 95% isolated yield.
a Waters LCT mass spectrometer. Elemental analyses were carried
out using a CHNS/O Analyzer PerkineElmer 2400 Series II in-
strument. Melting points were determined on an Electrothermal
9100 melting point apparatus and are uncorrected.
All reactions were carried out under an argon atmosphere in
flame-dried glassware using Schlenk techniques. Chromatographic
purifications were done using either 60e120 or 100e200 mesh

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P.N. Chatterjee, S. Roy / Tetrahedron 67 (2011) 4569e4577
4.4. General procedure for the synthesis of substituted furans
10
136.4, 136.9, 141.1, 156.2, 194.4, 194.8. ESI-MS: for C21H18O3,
[MþNa]þ¼341.01. Anal. (C21H18O3) calcd, C: 79.22, H: 5.70; found,
C: 79.63, H: 5.36.
A 10 mL Schlenk flask equipped with a magnetic bar was
charged with [Ir(COD)(SnCl3)Cl(
m
-Cl)]2 (0.0025 mmol), 1,3-dicar-
4.6.4. 1-Phenyl-2-(3-phenyl-1-p-tolylprop-2-ynyl)butane-1,3-dione
bonyl compound 2 (0.25 mmol), propargylic alcohol 4 (0.25 mmol)
and 1,2-dichloroethane (1 mL). The flask was degassed with argon,
placed in a constant temperature bath at 80 ꢀC, and monitored for
propargylic alcohol (vide TLC). Upon completion, Cs2CO3 (1.5 equiv)
was added, and the reaction was continued at 80 ꢀC until in-
termediate 5 was consumed (vide TLC). The mixture was cooled to
room temperature, solvent removed under reduced pressure and
the mixture was subjected to column chromatography over silica
gel (eluent: gradient mixture of ethyl acetate/petroleum ether) to
afford the corresponding furan 10.
(5b). Diastereomers 1H NMR (CDCl3, 200 MHz):
d (ppm) 1.99 (s,
3H), 2.24 (s, 3H), 2.34 (s, 3H), 2.38 (s, 3H), 4.85 (d, 1H, J¼10.6 Hz),
4.95 (d, 1H, J¼11.0 Hz), 5.03 (d, 1H, J¼11.0 Hz), 5.14 (d, 1H,
J¼10.6 Hz), 7.04 (d, 2H, J¼8.0 Hz), 7.04 (d, 2H, J¼8.0 Hz), 7.13 (d, 2H,
J¼8.0 Hz), 7.13 (d, 2H, J¼8.0 Hz), 7.27e7.42 (m, 6H), 7.27e7.42 (m,
6H), 7.48e7.63 (m, 2H), 7.48e7.63 (m, 2H), 7.86 (d, 1H, J¼7.2 Hz),
7.86 (d, 1H, J¼7.2 Hz), 8.10 (d, 1H, J¼7.2 Hz), 8.10 (d, 1H, J¼7.2 Hz).
13C NMR (CDCl3, 54.6 MHz):
d (ppm) 21.2, 21.3, 27.8, 29.8, 38.0,
38.4, 69.2, 71.2, 83.5, 85.3, 88.8, 89.3, 123.1, 128.2, 128.3, 128.4,
128.9, 129.0, 129.1, 129.5, 129.8, 131.6, 131.9, 133.9, 135.7, 136.7,
137.3, 137.6, 193.4, 194.1, 200.9, 201.8. ESI-MS: for C26H22O2,
[MþNa]þ¼389.07. Anal. (C26H22O2) calcd, C: 85.22, H: 6.05; found,
C: 85.40, H: 6.13.
4.5. General procedure for the synthesis of substituted
pyrroles 12
In a 10 mL Schlenk flask equipped with a magnetic bar were
4.6.5. 3-Methyl-3-(3-phenyl-1-p-tolylprop-2-ynyl)pentane-2,4-di-
added [Ir(COD)(m-Cl)]2 (0.0075 mmol), SnCl4 (0.03 mmol) and 1,2-
one (5c). 1H NMR (CDCl3, 200 MHz):
d (ppm) 1.47 (s, 3H), 1.94 (s,
dichloroethane (0.5 mL) under an argon atmosphere. After stirring
for 10 min at room temperature, a solution of propargylic alcohol
4 (0.25 mmol) and 1,3-dicarbonyl compound 2 (0.25 mmol) in 1,2-
dichloroethane (0.5 mL) was added to the mixture, and the reaction
was monitored for propargylic alcohol (vide TLC). Upon comple-
tion, PhNH2 (0.25 mmol) was added, and the mixture was stirred
at 80 ꢀC until intermediate 5 is consumed (vide TLC). The
mixture was cooled to room temperature, solvent removed under
reduced pressure and the mixture was subjected to column
chromatography over silica gel (eluent: gradient mixture of ethyl
acetate/petroleum ether) to afford the corresponding pyrrole 12.
3H), 2.32 (s, 3H), 2.39 (s, 3H), 5.17 (s, 1H), 7.08e7.13 (m, 2H),
7.28e7.32 (m, 5H), 7.36e7.39 (m, 2H). 13C NMR (CDCl3, 54.6 MHz):
d
(ppm) 14.9, 21.0, 26.5, 28.0, 41.7, 72.2, 85.3, 88.4, 122.9, 128.3,
128.9, 129.6, 131.6, 133.55, 137.3, 203.9, 206.1. ESI-MS: for C22H22O2,
[MþNa]þ¼341.05. Anal. (C22H22O2) calcd, C: 82.99, H: 6.96; found,
C: 83.21, H: 7.09.
4.6.6. Ethyl-2-acetyl-3-(4-chlorophenyl)-5-phenylpent-4-ynoate
(5e). Diastereomers 1H NMR (CDCl3, 400 MHz):
d (ppm) 1.08 (t, 3H,
J¼7.0 Hz), 1.26 (t, 3H, J¼7.2 Hz), 2.06 (s, 3H), 2.41 (s, 3H), 3.94e4.04
(m, 2H), 3.94e4.04 (m, 2H), 4.22e4.29 (m, 1H), 4.22e4.29 (m, 1H),
4.59 (d, 1H, J¼10.8 Hz), 4.64 (d, 1H, J¼10.0 Hz), 7.28e7.39 (m, 9H),
4.6. Spectral and analytical data of products
7.28e7.39 (m, 9H). 13C NMR (CDCl3, 100 MHz):
d (ppm) 13.8, 14.1,
29.8, 30.5, 36.9, 37.1, 61.7, 61.9, 66.4, 66.5, 84.3, 84.9, 87.5, 87.8,
122.5, 122.7, 128.1, 128.2, 128.3, 128.7, 128.8, 129.6, 129.7, 131.5,
133.4, 136.7, 136.9, 166.5, 166.8, 199.9, 200.3. Anal. (C21H19ClO3)
calcd, C: 71.08, H: 5.40; found, C: 71.33, H: 5.14.
The spectral data of compound 3a,6d 3b,6d 3d,21 3e,6d 3f,6f 3g,22
3h,23 3k,6g 3l,23 5a,7e 5d,7e 6,7d 7,7d 8a,6k 8b,6k 8c,24 8d,6k 9b,6j 9c,7e
10a,7d 10b,7d 12a,15e 12b,15e 12c,15e were in excellent agreement
with those in the literature. The spectral data for the products 3c, 3i,
3j, 5b, 5c, 5e, 5f, 5g, 5h, 9a, 9d, 10c-1 and 10c-2 are shown below.
4.6.7. 2-(1-(4-Chlorophenyl)-3-(trimethylsilyl)prop-2-ynyl)-1,3-di-
phenylpropane-1,3-dione (5f). 1H NMR (CDCl3, 200 MHz):
d (ppm)
4.6.1. 2-(1-(4-Bromophenyl)ethyl)-1, 3-diphenylpropane-1,3-dione
0.10 (s, 9H), 4.96 (d, 1H, J¼10.0 Hz), 5.75 (d, 1H, J¼10.0 Hz),
(3c). 1H NMR (CDCl3, 200 MHz):
d
(ppm) 1.29 (t, 3H, J¼6.8 Hz), 4.05
7.19e7.33 (m, 5H), 7.41e7.61 (m, 5H), 7.71 (dd, 2H, J¼1.4 and 7.2 Hz),
(dq, 1H, J¼6.8 and 10.2 Hz), 5.55 (d, 1H, J¼10.2 Hz), 7.14 (d, 2H,
J¼8.4 Hz), 7.25e7.33 (m, 4H), 7.41e7.61 (m, 4H), 7.75 (d, 2H,
J¼8.6 Hz), 8.04 (d, 2H, J¼8.6 Hz). 13C NMR (CDCl3, 54.6 MHz):
8.07 (dd, 2H, J¼1.4 and 7.2 Hz). 13C NMR (CDCl3, 54.6 MHz):
d (ppm)
0.43, 38.5, 62.9, 90.3, 105.1, 128.5, 128.7, 128.8, 129.2, 130.0, 133.3,
133.6, 136.3, 136.9, 137.7, 192.1, 193.1. Anal. (C27H25ClO2Si) calcd, C:
72.87, H: 5.66; found, C: 72.65, H: 5.51.
d
(ppm) 20.3, 40.7, 64.3,120.4, 128.5, 128.6,128.8,129.0,129.6,131.5,
133.4, 133.8, 136.7, 136.9, 142.9, 194.4, 194.8. Anal. (C23H19BrO2)
calcd, C: 67.82, H: 4.70; found, C: 68.41, H: 4.51.
4.6.8. 1,3-Diphenyl-2-(1-p-tolylprop-2-ynyl)propane-1,3-dione
(5g). 1H NMR (CDCl3, 200 MHz):
d
(ppm) 2.13 (d, 1H, J¼1.8 Hz),
4.6.2. 1,3-Diphenyl-2-(1-(thiophen-2-yl)ethyl)propane-1,3-dione
2.19 (s, 3H), 4.89 (dd, 1H, J¼1.8 and 8.2 Hz), 5.78 (d, 1H. J¼8.2 Hz),
(3i). 1H NMR (CDCl3, 200 MHz):
d
(ppm) 1.40 (d, 3H, J¼6.8 Hz),
6.99 (d, 2H, J¼8.0 Hz), 7.12e7.59 (m, 8H), 7.68 (d, 2H. J¼8.0 Hz),
4.21e4.47 (dq, 1H, J¼6.8 and 9.6 Hz), 5.56 (d, 1H, J¼9.6 Hz),
6.70e6.77 (m, 2H), 6.99 (dd, 1H, J¼1.2 and 3.6 Hz), 7.23e7.56 (m,
6H), 7.75 (dd, 2H, J¼1.6 and 7.0 Hz), 7.95 (dd, 2H, J¼1.6 and 7.0 Hz).
7.99 (d, 2H, J¼8.0 Hz). 13C NMR (CDCl3, 54.6 MHz):
d (ppm) 20.9,
37.7, 63.3, 72.6, 84.1, 128.3, 128.6, 128.8, 129.0, 129.3, 133.4, 133.6,
135.3, 136.4, 136.8, 137.2, 192.7, 193.2. ESI-MS: for C25H20O2,
[MþNa]þ¼375.04. Anal. (C25H20O2) calcd, C: 85.20, H: 5.72; found,
C: 85.53, H: 5.56.
13C NMR (CDCl3, 54.6 MHz):
d (ppm) 21.2, 36.6, 65.1, 123.3, 125.0,
126.5, 128.5, 128.7, 128.8, 133.2, 133.6, 136.8, 136.9, 147.4, 194.3,
194.4. ESI-MS: for C21H18O2S, [MþNa]þ¼357.00. Anal. (C21H18O2S)
calcd, C: 75.42, H: 5.43; found, C: 75.66, H: 5.26.
4.6.9. 1,3-Diphenyl-2-(1-p-tolylhept-2-ynyl)propane-1,3-dione
(5h). 1H NMR (CDCl3, 400 MHz):
d
(ppm) 0.74 (t, 3H, J¼7.6 Hz),
4.6.3. 2-(1-(Furan-2-yl)ethyl)-1,3-diphenylpropane-1,3-dione
1.14e1.15 (m, 4H), 1.90e1.92 (m, 2H), 2.24 (s, 3H), 4.89 (dt, 1H, J¼2.4
and 10.0 Hz), 5.76 (d, 1H, J¼10.0 Hz), 7.03 (d, 2H, J¼8.0 Hz), 7.29 (d,
2H, J¼8.0 Hz), 7.35 (d, 2H, J¼8.0 Hz), 7.41e7.50 (m, 3H), 7.58 (t, 1H,
J¼7.6 Hz), 7.73 (d, 2H, J¼8.4 Hz), 8.08 (d, 2H, J¼8.4 Hz). 13C NMR
(3j). 1H NMR (CDCl3, 200 MHz):
4.05e4.20 (dq, 1H, J¼7.0 and 9.0 Hz), 5.71 (d, 1H, J¼9.0 Hz), 5.95 (d,
1H, J¼3.2 Hz), 6.08 (dd, 1H, J¼1.8 and 3.2 Hz), 7.17 (d, 1H, J¼1.8 Hz),
7.32e7.57 (m, 6H), 7.82e7.93 (m, 4H). 13C NMR (CDCl3, 54.6 MHz):
d
(ppm) 1.36 (d, 3H, J¼7.0 Hz),
(CDCl3, 54.6 MHz):
d (ppm) 13.6, 18.3, 21.0, 21.7, 30.5, 37.9, 63.6,
d
(ppm) 17.2, 34.4, 61.1, 106.2, 110.2, 128.5, 128.6, 128.8, 133.2, 133.5,
79.9, 85.4, 128.3, 128.5, 128.6, 128.7, 129.1, 133.3, 133.4, 136.6, 136.8,

P.N. Chatterjee, S. Roy / Tetrahedron 67 (2011) 4569e4577
4577
136.9, 137.1, 192.8, 193.7. ESI-MS: for C29H28O2, [MþNa]þ¼431.09.
Inada, Y.; Hidai, M.; Uemura, S. J. Org. Chem. 2004, 69, 3408; (c) Cadierno, V.;
Gimeno, J.; Nebra, N. Adv. Synth. Catal. 2007, 349, 382; (d) Sanz, R.; Miguel, D.;
Anal. (C29H28O2) calcd, C: 85.26, H: 6.91; found, C: 85.14, H: 7.02.
ꢀ
ꢀ
Martínez, A.; Alvarez-Gutierrez, J. M.; Rodríguez, F. Org. Lett. 2007, 9, 727; (e)
Huang, W.; Wang, J.; Shena, Q.; Zhou, X. Tetrahedron 2007, 63, 11636; (f) Feng,
X.; Tan, Z.; Chen, D.; Shen, Y.; Guo, C. C.; Xiang, J.; Zhu, C. Tetrahedron Lett.
2008, 49, 4110; (g) Ji, W.; Pan, Y.; Zhao, S.; Zhan, Z. Synlett 2008, 3046; (h)
Cadierno, V.; Diez, J.; Gimeno, J.; Nebra, N. J. Org. Chem. 2008, 73, 5852; (i)
Yadav, J. S.; Subba Reddy, B. V.; Pandurangam, T.; Raghavendra Rao, K. V.;
Praneeth, K.; Narayana Kumar, G. G. K. S.; Madavi, C.; Kunwar, A. C. Tetrahedron
Lett. 2008, 49, 4296; (j) Arcadi, A.; Alfosni, M.; Chiarini, M.; Marinelli, F. J.
Organomet. Chem. 2009, 694, 576; (k) Funabiki, K.; Komeda, T.; Kubota, Y.;
Matsui, M. Tetrahedron 2009, 65, 7457; (l) Yadav, J. S.; Subba Reddy, B. V.; Rao,
K. V. R.; Narender, R. Tetrahedron Lett. 2009, 50, 3963; (m) Ji, W.; Pan, Y.; Zhao,
S.; Zhan, Z. J. Comb. Chem. 2009, 11, 103; (n) Ohta, K.; Kobayashi, T.; Tanabe, G.;
Muraoka, O.; Yoshimatsu, M. Chem. Pharm. Bull. 2010, 58, 1180; (o) Zhang, M.;
Yang, H.; Cheng, Y.; Zhu, Y.; Zhu, C. Tetrahedron Lett. 2010, 51, 1176 and ref-
erences therein.
4.6.10. 4-Hydroxy-3-(3-phenyl-1-p-tolylprop-2-ynyl)-2H-chromen-
2-one (9a). 1H NMR (CDCl3, 200 MHz):
d (ppm) 2.34 (s, 3H), 5.77 (s,
1H), 7.18 (d, 2H, J¼8.0 Hz), 7.25e7.39 (m, 5H), 7.50e7.54 (m, 5H),
7.87 (dd, 1H, J¼1.2 and 6.8 Hz), 8.38 (s, 1H). 13C NMR (CDCl3,
54.6 MHz):
d (ppm) 21.1, 33.1, 86.7, 87.7, 105.2, 116.0, 116.5, 121.5,
123.4,124.1,127.0,128.6,129.2, 129.7,131.9,132.8,135.5,137.6,152.7,
161.1, 162.6. ESI-MS: for C25H18O3, [MþH]þ¼367.02. Anal.
(C25H18O3) calcd, C: 81.95, H: 4.95; found, C: 82.24, H: 4.81.
4.6.11. 3-(1-(4-Chlorophenyl)-3-(trimethylsilyl)prop-2-ynyl)-4-hy-
droxy-2H-chromen-2-one (9d). 1H NMR (CDCl3, 200 MHz):
d (ppm)
8. RodWs, B.; Sheldon, J.; Toro, C.; JimWnez, V.; Xlvarez, M. A.; Soriano, V. J.
Antimicrob. Chemother. 2006, 57, 709.
0.31 (s, 9H), 5.49 (s, 1H), 7.30e7.36 (m, 4H), 7.48e7.62 (m, 3H), 7.92
9. Selected reviews: (a) Lipshutz, B. H. Chem. Rev. 1986, 86, 795; (b) Benassi, R. In
Comprehensive Heterocyclic Chemistry II; Katritzky, A. R., Rees, C. W., Scriven, E.
F. V., Eds.; Pergamon: Oxford, 1996; Vol. 2, p 259; (c) Heaney, H.; Ahn, J. S. In
Comprehensive Heterocyclic Chemistry II; Katritzky, A. R., Rees, C. W., Scriven, E.
F. V., Eds.; Pergamon: Oxford, 1996; Vol. 2, p 297; (d) Friedrichsen, W. In
Comprehensive Heterocyclic Chemistry II; Katritzky, A. R., Rees, C. W., Scriven, E.
F. V., Eds.; Pergamon: Oxford, 1996; Vol. 2, p 351; (e) Keay, B. A.; Dibble, P. W. In
Comprehensive Heterocyclic Chemistry II; Katritzky, A. R., Rees, C. W., Eds.;
Elsevier: Oxford, 1997; Vol. 2, p 395.
(dd, 1H, J¼1.2 and 6.8 Hz), 8.97 (s, 1H). 13C NMR (CDCl3, 54.6 MHz):
d
(ppm) 0.28, 33.6, 94.1, 103.6, 104.0, 116.0, 116.5, 123.6, 124.2, 128.6,
129.0, 132.5, 133.5, 137.1, 152.6, 161.4, 162.4. Anal. (C21H19ClO3Si)
calcd, C: 65.87, H: 5.00; found, C: 66.13, H: 4.85.
4.6.12. (5-Benzyl-2-methyl-4-phenylfuran-3-yl)(phenyl)methanone
(10c-1)þ1-(5-benzyl-2,4-di-phenylfuran-3-yl)ethanone (10c-2). 1H
€
10. See, for instance: (a) Furstner, A. Angew. Chem., Int. Ed. 2003, 42, 3582; (b)
NMR (CDCl3, 200 MHz):
d
(ppm) 2.08 (s, 3H), 2.36 (s, 3H), 4.00 (s,
Hoffmann, H.; Lindel, T. Synthesis 2003, 1753; (c) Agarwal, S.; Ctmmerer, S.;
Filali, S.; Frc¸ hner, W.; Knc¸ ll, J.; Krahl, M. P.; Reddy, K. R.; Knc¸ lker, H.-J. Curr. Org.
Chem. 2005, 9, 1601; (d) Walsh, C. T.; Garneau-Tsodikova, S.; Howard-Jones, A.
R. Nat. Prod. Rep. 2006, 23, 517; (e) Bellina, F.; Rossi, R. Tetrahedron 2006, 62,
7213.
2H), 4.02 (s, 2H), 7.06e7.47 (m, 13H), 7.06e7.47 (m, 13H), 7.69 (d,
2H, J¼7.2 Hz), 7.77 (d, 2H, J¼7.0 Hz). 13C NMR (CDCl3, 54.6 MHz):
d
(ppm) 13.8, 31.6, 32.3, 121.9, 123.1, 123.4, 124.4, 126.6, 126.8, 127.6,
11. See, for instance: (a) Cozzi, P.; Mongelli, N. Curr. Pharm. Des. 1998, 4, 181; (b)
Huffman, J. W. Curr. Med. Chem.1999, 6, 705; (c) Kidwai, M.; Venkataramanan, R.;
Mohan, R.; Sapra, P. Curr. Med. Chem. 2002, 9, 1209; (d) Huffman, J. W.; Padgett, L.
W. Curr. Med. Chem. 2005, 12, 1395.
127.7, 128.0, 128.2, 128.5, 128.6, 129.1, 129.4, 129.5, 129.6, 130.1,
132.4, 137.9, 138.3, 138.4, 148.6, 150.1, 152.7, 155.8, 192.5, 198.1. Anal.
(C25H20O2) calcd, C: 85.20, H: 5.72; found, C: 84.98, H: 6.01.
12. See, for instance: (a) Pyrroles, The Synthesis Reactivity and Physical Properties of
Substituted Pyrroles, Part II; Jones, R. A., Ed.; Wiley: New York, NY, 1992; (b)
Black, D. S. C. In Comprehensive Heterocyclic Chemistry II; Katritzky, A. R., Rees,
C. W., Scriven, E. F. V., Eds.; Elsevier: Oxford, 1996; Vol. 2, p 39; (c) Beccalli, E.
M.; Broggini, G.; Martinelli, M.; Paladino, G. Tetrahedron 2005, 61, 1077; (d)
Beccalli, E. M.; Broggini, G.; Martinelli, M.; Paladino, G.; Zoni, C. Eur. J. Org. Chem.
2005, 2091; (e) Beck, E. M.; Grimster, N. P.; Hatley, R.; Gaunt, M. J. J. Am. Chem.
Soc. 2006, 128, 2528; (f) Kuwano, R.; Kashiwabara, M.; Ohsumi, M.; Kusano, H. J.
Am. Chem. Soc. 2008, 130, 808; (g) Borsini, E.; Broggini, G.; Contini, A.; Zecchi, G.
Eur. J. Org. Chem. 2008, 2808; (h) Beck, E. M.; Hatley, R.; Gaunt, M. J. Angew.
Chem., Int. Ed. 2008, 47, 3004; (i) Gruit, M.; Michalik, D.; Tillack, A.; Beller, M.
Angew. Chem., Int. Ed. 2009, 48, 7212; (j) Lage, S.; Martinez, U.-E.; Sotomayor, N.;
Lete, E. Adv. Synth. Catal. 2009, 351, 2460; (k) Gruit, M.; Michalik, D.; Kruger, K.;
Spannenberg, A.; Tillack, A.; Pews-Davtyan, A.; Beller, M. Tetrahedron 2010, 66,
3341.
Acknowledgements
We thank DST (financial support to S.R.), and IIT Kharagpur
(fellowship to PNC). S.R. thanks Prof. Manish Bhattacharjee for
encouragement and many help.
Supplementary data
Supplementary data associated with this article can be found in
online version at doi:10.1016/j.tet.2011.04.092.
13. Selected examples of propargyl alcohols to enones conversion
(MeyereSchuster rearrangement): (a) Fukuda, Y.; Utimoto, K. Bull. Chem. Soc.
Jpn. 1991, 64, 2013; (b) Narasaka, K.; Kusama, H.; Hayashi, Y. Tetrahedron 1992,
48, 2059; (c) Yoshimatsu, M.; Naito, M.; Kawahigashi, M.; Shimizu, H.; Kataoka,
T. J. Org. Chem. 1995, 60, 4798; (d) Lorber, C. Y.; Osborn, J. A. Tetrahedron Lett.
1996, 37, 853.
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