Ionic liquids as a convenient recyclable medium for the generation of transient carbonyl ylides: Syntheses of oxa and dioxa-bridged polycyclic systems

Article abstract of DOI:10.1016/j.tet.2004.11.008

The tandem cyclization-cycloaddition reactions of α-diazo ketones in the presence of rhodium(II) acetate, rhodium(II) octanoate or copper(II) acetyl acetonate as catalyst were performed in different imidazole based ionic liquids as solvent. A successful g

Full text of DOI:10.1016/j.tet.2004.11.008

Tetrahedron 61 (2005) 1309–1315
Ionic liquids as a convenient recyclable medium for the generation
of transient carbonyl ylides: syntheses of oxa and dioxa-bridged
polycyclic systems
*
Sengodagounder Muthusamy and Boopathy Gnanaprakasam
Central Salt and Marine Chemicals Research Institute, Bhavnagar 364 002, India
Received 12 August 2004; revised 11 October 2004; accepted 5 November 2004
Available online 15 December 2004
Abstract—The tandem cyclization-cycloaddition reactions of a-diazo ketones in the presence of rhodium(II) acetate, rhodium(II) octanoate
or copper(II) acetyl acetonate as catalyst were performed in different imidazole based ionic liquids as solvent. A successful generation of the
transient five- or six-membered-ring carbonyl ylides, followed by the 1,3-dipolar cycloaddition with olefin or carbonyl functional groups in
ionic liquid is described to furnish the oxa and dioxa-bridged polycyclic systems with high stereoselectivity. Significant advantages of this
process are the recovery of rhodium catalyst, the re-use of ionic liquid, replacement of hazardous organic solvents and the resulting high
stereoselectivity.
q 2004 Elsevier Ltd. All rights reserved.
1
. Introduction
In this aspect, a recent development is the use of ionic
liquids as a novel green solvent media for various organic
and biochemical transformations. Ionic liquids, particu-
8
a-Diazo ketones are important intermediates as they
undergo very useful tandem cyclization-cycloaddition
transformations in a highly productive manner. They
continue to be a subject of considerable interest and
larly those based on 1,3-dialkylimidazolium cations, have
been shown to be good ‘solvents’ for a wide range of
inorganic and organic reactions. This is mainly due to their
9
1
intensive investigation in synthetic organic chemistry.
non-volatile nature, insolubility in common organic sol-
vents and ability to dissolve catalysts. Although many types
of reactions have been investigated in ionic liquids,
examples of tandem reactions are absent from the literature.
Furthermore, there has been no example demonstrated on
the use of ionic liquids for the possible generation of the
transient carbonyl ylide intermediates. As a part of our
Intramolecular carbenoid–carbonyl group cyclization has
been recognized as one of the most effective methods for
generating carbonyl ylides; subsequent 1,3-dipolar cyclo-
additions with p-bonds to construct hetero/carbocyclic ring
2
systems are well documented. Based on this diazo carbonyl
chemistry, the synthesis of many bioactive natural products
1
0
3
such as brevicomin, illudins, phorbol ester derivatives,
4
5
ongoing research program to study the reactivity profile
of carbonyl ylides, we wish to report the use of ionic liquids
in the tandem cyclization-cycloaddition process using
rhodium and copper metal complexes as catalyst.
6
7
zaragozic acid A and various alkaloids have been
ingeniously approached using an olefin or a carbonyl
group as a dipolarophile. As a result, there has been
growing interest in the use of rhodium(II)-generated
carbonyl ylides as 1,3-dipoles for the construction of
many important natural/unnatural derivatives.
2. Results and discussion
To demonstrate this process, we have synthesized a series
of acyclic a-diazo ketones 1, 4, tetralone derived diazo
ketone 3, a-diazo ketones tethered on a cyclopropane 5 or
cycloalkanone 2, 6 ring systems (Fig. 1), which will, in
principle, generate five- or six-membered-ring carbonyl
ylide intermediates. Initially, we planned to study genera-
tion of the transient six-membered-ring carbonyl ylides and
the reaction with olefin dipolarophiles in the ionic liquid
(IL) medium. Among various imidazole derivatives
Many of the organic solvents particularly chlorinated
hydrocarbons and benzene possess volatile, hazardous and
carcinogenic properties. Consequently, methods that suc-
cessfully minimize their use are the focus of much attention.
Keywords: Carbonyl ylides; Diazo ketones; 1,3-Dipolar cycloadditions;
Ionic liquid; Rhodium(II) acetate dimer.
*
Corresponding author. Tel.: C91 278 2567760; fax: C91 278 2567562;
e-mail: muthu@csmcri.org
0040–4020/$ - see front matter q 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2004.11.008

1310
S. Muthusamy, B. Gnanaprakasam / Tetrahedron 61 (2005) 1309–1315
Table 1. Synthesis of oxa-bridged compounds using ionic liquid
a
Entry
a-Diazo
ketone
Oxa-bridged cycloadducts
Yield (%)
IL(DCM)
b
1a
3
b
95 (93)
c
3
c
d
e
f
1b
90 (87)
b
3
Figure 1. Synthesized a-diazo ketones.
1b
84 (88)
reported as ionic liquids, we have chosen 1-n-butyl-3-
methylimidazolium tetrafluoroborate ([bmim]BF ), 1-n-
4
c
butyl-3-butylimidazolium tetrafluoroborate ([bbim]BF4),
1
4
87 (81)
92 (85)
-n-methyl-3-methylimidazolium tetrafluoroborate
[mmim]BF ) and 1-n-butyl-3-methylimidazolium hexa-
(
fluorophosphate ([bmim]PF ), as solvents for our present
4
6
study. Initially, the reaction of a-diazo ketone 1a and
N-phenylmaleimide (NPM) in [bmim]BF4 ionic liquid
solution was carried out at room temperature in the presence
of rhodium(II) acetate catalyst under an argon atmosphere.
The reaction was stirred at room temperature for 2 h and,
after washing with 50% ethyl acetate/hexane solution,
furnished the crude reaction mixture, which was purified by
passing through silica gel column chromatography to afford
the oxa-bridged compound 7a in 86% yield with complete
diastereoselectivity (Scheme 1). Alternatively, the crude
reaction mixture can also be passed through by silica
column chromatography without extraction procedure to
obtain the same yield. The presence of a singlet resonance at
b
4
c
11
g
5
95 (93)
b,d
h
3
88 (85)
1
d 4.75 in the H NMR spectrum for the bridgehead proton
implies exo-addition. The structure of the product 7a
confirms the successful generation of the transient six-
membered-ring carbonyl ylide dipole 8 followed by the
c
6
10c
91 (88)
i
1
,3-dipolar cycloaddition with NPM in the polar ionic liquid
medium. Interested by the above tandem cyclization-
cycloaddition reaction in ionic liquid, we generalized this
reaction. This tandem process of a-diazo ketone was
repeated in the presence of dimethyl acetylenedicarboxylate
b
6
10c
87 (76)
j
(
DMAD) as a dipolarophile instead of NPM to furnish the
respective oxa-bridged compound (entry b, Table 1) in 95%
yield. Similar reactions were performed with a-diazo ketone
e
4
k
72 (66)
1b in the presence of dipolarophiles (NPM or DMAD) to
furnish the corresponding oxa-bridged seven-membered-
ring compounds (entries c, d, Table 1) in high yields.
e
6
10c
68 (65)
l
a
Yields are unoptimized and refer to isolated pure compounds.
Reaction with DMAD.
Reaction with NPM.
Inseparable mixture of diastereomers in the ratio of 1:3.
Reaction with propargyl bromide.
b
c
d
e
Next, we elaborated our work to demonstrate the generation
of the transient five-membered-ring carbonyl ylides in ionic
liquid medium. To this end, we have utilized the appropriate
a-diazo ketones 3–6 to perform the rhodium(II)-catalyzed
Scheme 1. Rhodium(II)-catalyzed tandem reaction of a-diazo ketone and
NPM in [bmim]BF ionic liquid.
reactions as described above. The [bmim]BF ionic liquid
4
4

S. Muthusamy, B. Gnanaprakasam / Tetrahedron 61 (2005) 1309–1315
Table 2. Synthesis of dioxa-bridged compounds using ionic liquid
1311
a
Entry
a-Diazo
ketone
Dioxa-bridged cycloadducts
Yield (%) IL
(DCM)
b
b
4
84 (79)
91 (85)
c
4
c
Scheme 2. Rhodium(II)-catalyzed tandem reaction of a-diazo ketone and
an aldehyde in [bmim]BF ionic liquid.
4
mediated reactions in the presence of NPM, DMAD or
propargyl bromide were also afforded the oxa-bridged six-
membered-ring systems (entries e–l, Table 1). All the
reactions were performed at room temperature to obtain the
products in high yield. Notably, these reactions provided
high diasteroselectivity with NPM (entries a, c, e, g, i) and
high regioselectivity with propargyl bromide (entries k, l).
The presence of a singlet for the bridgehead proton in the
d
d
4
97 (89)
1
H NMR spectra confirms the regioselective addition of
propargyl bromide with a-diazo ketones.
e
6
10a
85 (79)
e
To develop this process further, we considered to carry out
the tandem cyclization-cycloaddition reactions of a-diazo
ketones in the presence of carbonyl group as a hetero-
dipolarophile. To this end, we have performed the
rhodium(II)-catalyzed reactions of a-diazo ketones with
various aromatic aldehydes in ionic liquids. For example,
the rhodium(II) acetate catalyzed reaction of diazo ketone 6
c
6
f
86 (84)
and pyrene-1-carboxaldehyde in [bmim]BF ionic liquid at
4
room temperature for an hour afforded the dioxa-bridged
compound 9a in 95% yield with high regio- and exo-
selectivity (Scheme 2). The exo-selectivity in 9a was
confirmed based on a characteristic singlet resonance
f
g
6
89 (81)
85 (80)
1
around d 4.5 for the bridgehead proton in the H NMR
spectrum. The product 9a confirms the successful genera-
tion of fused five-membered-ring carbonyl ylide 10 in the
ionic liquid medium. We have further generalized the above
reaction by synthesizing several dioxa-bridged compounds
f
2
h
a
(
(
9b–h) in high yield using [bmim]BF4 ionic liquid
Table 2). Generally, the above ionic liquid reactions led
Yields are unoptimized and refer to isolated pure compounds.
Reaction with p-methoxybenzaldehyde.
Reaction with 9-anthraldehyde.
Reaction with pyrene-1-carboxaldehyde.
Reaction with p-tolualdehyde.
Reaction with 3,4-dimethoxybenzaldehyde.
b
c
d
e
f
to improvement in the yields of the products (compared with
dry dichloromethane [DCM] as solvent, Tables 1 and 2)
without lowering the selectivity. Further, the crude H NMR
1
spectrum of the above reactions indicated the formation
of a single isomer. In all the above reactions, 1 mol% of
rhodium(II) acetate catalyst was used, which is completely
that the carbonyl ylide generation in [bmim]PF gave poor
6
soluble in [bmim]BF ionic liquid. The polar nature of the
4
yield. There are no considerable differences in reaction rates
and yields by changing the substitution on the imidazole
ring. The efficiency of the ionic liquid was strongly
influenced by the nature of the anion. These results indicate
that anions play an important role in this reaction. The
reaction furnished the product in very good yield in the
presence of rhodium(II) catalysts rather than copper(II)-
catalyst.
ionic liquids helps to stabilize the 1,3-dipole generated from
a-diazo ketone and subsequent addition of the dipolarophile
led to the improvement in the yield of the product.
To generalize the metal-catalyzed carbonyl ylide generation
from diazo carbonyl compounds in ionic liquid, a repre-
sentative reaction of diazo compound 4 with p-methoxy-
benzaldehyde was carried out in other ionic liquids and the
results are depicted in Table 3. The ionic liquids having
Finally, we were interested to study the recovery and
recycling of the expensive rhodium catalyst, which is
extensively used in diazo carbonyl chemistry.
BF -counter anion in the presence of Rh(II)-catalysts
4
afforded the product in high yield. But, we have found

1312
S. Muthusamy, B. Gnanaprakasam / Tetrahedron 61 (2005) 1309–1315
Table 3. Reactions with different ionic liquids and catalysts
a
Ionic liquids
Catalysts
Reaction conditions
Yield (%)
[
[
[
[
[
[
[
[
[
[
bmim]BF
bmim]BF
bmim]BF
4
4
4
Rhodium(II) acetate
1 h, rt
1 h, rt
5 h, 80 8C
2 h, rt
2 h, rt
5 h, 80 8C
2 h, rt
5 h, 80 8C
1 h, rt
1 h, rt
84
86
66
85
82
62
55
35
88
90
Rhodium(II) octanoate
Copper(II) acetylacetonate
Rhodium(II) octanoate
Rhodium(II) acetate
Copper(II) acetylacetonate
Rhodium(II) acetate
Copper(II) acetylacetonate
Rhodium(II) acetate
Rhodium(II) octanoate
bbim]BF
bbim]BF
bbim]BF
4
4
4
bmim]PF
bmim]PF
6
6
mmim]BF
mmim]BF
4
4
a
Yields are unoptimized and refer to isolated pure compound 9b.
Representatively, the reaction of a-diazo ketone 4 and
p-methoxybenzaldehyde was performed (entry b, Table 2)
in [bmim]BF4 ionic liquid. The reaction mixture was
extracted with ethyl acetate/hexane solution to provide
the product 9b leaving a pale-yellowish ionic liquid, which
was dried under reduced pressure. The above reaction was
4. Experimental
4.1. General
1
Proton nuclear magnetic resonance ( H NMR) spectra were
recorded on a Bruker DPX 200 at 200 MHz using CDCl3,
Acetone-d and DMF-d in ppm (d) related to tetramethyl-
2
repeated in the recovered ionic liquid and Rh (OAc)4
6
7
catalyst by adding the required starting materials to provide
silane (dZ0.00) as an internal standard and are reported as
follows; chemical shift (ppm), multiplicity (sZsinglet, tZ
triplet, quatZquartet, mZmultiplet), coupling constant
(Hz) and integration. Carbon-13 nuclear magnetic reso-
nance ( C NMR) spectra were recorded at 50.3 MHz in
the corresponding dioxa-bridged product 9b with the same
yield. Notably, this process was repeated five times and the
successive reuse of the recovered ionic liquid and catalyst in
the above reaction furnished the product with a yield as high
as that of the first cycle (Table 4). The insolubility of ionic
liquid in common organic solvents and the very good
solubility of rhodium(II) acetate catalyst in ionic liquid help
to productively recycle the catalyst. In our process, the
1
3
CDCl . Chemical shifts are reported in delta (d) units, parts
3
per million (ppm) relative to the centre of the triplet at
7.7 ppm for CDCl . Carbon types were determined from
C NMR and DEPT experiments. IR spectra were recorded
7
3
1
3
catalyst Rh (OAc) could be immobilized in [bmim]BF at
2
the end of this cyclization-cycloaddition reaction.
4
4
on a Perkin–Elmer Spectrum GX FT-IR spectrophotometer
using KBr pellets or CH Cl . Mass analyses were performed
on Jeol DX-303 (with an ionizing voltage of 70 eV), Jeol M
2
2
C
Table 4. Studies on the reuse of Rh
2
(OAc)
4
and [bmim]BF
4
Station 700 (FD method in absolute dichloromethane)
a
mass spectrometers and reported as m/z (relative intensity).
Elemental analyses were performed on a Perkin Elmer
Model 2400 analyzer. Melting points were determined on a
capillary melting point apparatus and are uncorrected. Thin
layer chromatography was performed on silica plates and
components were visualized by observation under iodine or
sulfuric acid charring. 1-n-Butyl-3-methylimidazolium
Cycles time
Yield of 9b (%)
Ionic liquid recovered (%)
1
2
3
4
5
84
88
85
86
85
99
98
99
98
98
a
Yields are unoptimized and refer to isolated pure compound 9b.
tetrafluoroborate ([bmim]BF ), 1-n-butyl-3-butylimidazo-
4
lium tetrafluoroborate ([bbim]BF ), 1-n-methyl-3-methyl-
4
imidazolium tetrafluoroborate ([mmim]BF ) and 1-n-butyl-
4
3. Conclusion
3
-methylimidazolium hexafluorophosphate ([bmim]PF )
6
In conclusion, we have demonstrated for the first time that
the tandem cyclization-1,3-dipolar cycloaddition reaction of
a-diazo ketones induced by rhodium(II) acetate catalyst in
12
are prepared as described in the literature, purified and
well-dried for 30 h under reduced pressure at 100 8C and
stored under an argon atmosphere. Rhodium(II) acetate
dimer, rhodium(II) octanoate dimer and copper(II) acetyl
acetonate were purchased from Aldrich.
[
bmim]BF ionic liquid as a solvent at room temperature.
4
This process was also studied in other ionic liquids with
different rhodium and copper catalysts. In view of ‘green
chemistry’, the solvent [bmim]BF4 and the expensive
catalyst Rh (OAc) can be recovered conveniently and
4.2. General experimental procedure for the synthesis of
compounds 7 and 9
2
4
reused efficiently. Further, this process involving the
generation of the transient five- as well as six-membered-
ring cyclic carbonyl ylide 1,3-dipoles in industrially and
environmentally benign polar ionic liquid medium furn-
ished the stereoselective products with improvement in the
yield. Significantly with all the advantages mentioned
above, this process bearing the characteristic of atom
economy and many bonds formation in a single synthetic
step provides the novel alternative method to synthesize oxa
and dioxa-bridged polycyclic systems.
Method A for rhodium catalyzed reactions. A mixture of
a-diazo ketone (1.0 mmol) and the appropriate olefin or
carbonyl compound (1.1 mmol) was taken in a well-dried
ionic liquid (3.0 mL) under an argon atmosphere. The
reaction mixture was stirred at room temperature for 5 min
duration to obtain a clear oily solution. To this ionic liquid
solution, 1 mol% of rhodium(II) acetate dimer catalyst was
added and stirred at room temperature for an appropriate
1
time. The reaction was followed by H NMR. After

S. Muthusamy, B. Gnanaprakasam / Tetrahedron 61 (2005) 1309–1315
1313
completion of the reaction, the crude reaction mixture was
washed with 50% ethyl acetate in hexane (5!10 mL) till
the absence of any organic compound in the solvent layer.
The combined extracts were concentrated in vacuo and the
resulting residue subjected on a 100–200 mesh silica gel
column chromatography to afford the appropriate oxa or
dioxa-bridged compound. Alternatively, the crude reaction
mixture was directly loaded into a short silica gel column
Calcd for C H NO : C, 72.61; H, 4.93; N, 4.03. Found: C,
21 17 4
72.50; H, 4.88; N, 3.98%.
4.4.2. 1,9,9-Trimethyl-4-phenyl-10-oxa-4-azatricyclo-
2
,6
[5.2.1.0 ]decane-3,5,8-trione (7e). A mixture of
N-phenylmaleimide (0.19 g, 1.1 mmol), a-diazo ketone 4
(0.15 g, 1.0 mmol) and 1 mol% of rhodium(II) acetate
dimer (4.3 mg) in 1-n-butyl-3-methylimidazolium tetra-
fluoroborate (3.0 mL) was allowed to react according to
method A followed by chromatographic purification (20:80
EtOAc–hexane) to afford product 7e (0.252 g, 87%) as a
colourless solid; mp 185–187 8C (chloroform/hexane); Rf
0.55 (20:80 EtOAc–hexane). IR (KBr) n 2971, 1763, 1714,
(
50:50 EtOAc–hexane) to afford the appropriate product.
Method B for copper catalyzed reactions. The procedure
was followed as in method A and the reaction mixture was
heated to 80 8C. The heating was continued till the absence
of starting diazo ketone and purified as described above.
K1
1
1386, 1283, 1197 cm . H NMR (200 MHz, CDCl ) d
3
7
4
7
.52–7.40 (m, 3H, Arom-H), 7.28–7.24 (m, 2H, Arom-H),
.82 (s, 1H, OCH), 3.32 (d, 1H, JZ7.0 Hz), 3.22 (d, 1H, JZ
.0 Hz), 1.58 (s, 3H, CH ), 1.17 (s, 3H, CH ), 1.09 (s, 3H,
4.3. Typical procedure for recycling the ionic liquid and
catalyst
3
3
1
3
CH3). C NMR (50.3 MHz, CDCl ) d 214.1 (C]O), 175.1
3
(
1
5
(
(
(
NC]O), 174.6 (NC]O), 132.3 (quat-C), 129.9 (]CH),
28.6 (]CH), 127.0 (]CH), 92.0 (quat-C), 82.6 (OCH),
Representatively, a mixture of a-diazo ketone 4 (0.15 g,
1
.1 mmol) and p-methoxybenzaldehyde (0.17 g, 1.2 mmol)
was taken in a well-dried [bmim]BF (3 mL) liquid and
1.3 (quat-C), 48.2 (CH), 47.6 (CH), 21.1 (CH ), 19.7
3
4
C
CH ), 13.9 (CH ). MS (EI) m/z (%) 299 (M , 100), 257
3 3
stirred for 5 min. To the above reaction mixture, 1 mol% of
rhodium(II) acetate dimer catalyst was added and stirred at
room temperature for 1 h. After completion of reaction, the
crude reaction mixture was washed with 50% ethyl acetate
in hexane (5!10 mL) till the absence of any organic
compound in the solvent layer to provide a pale-yellowish
ionic liquid. The evaporation of combined organic solvent
and column purification afforded the product 9b (0.21 g,
27), 201 (14), 174 (22), 138 (17), 126 (61), 109 (82), 95
21), 82 (30), 77 (21). Anal. Calcd for C H NO : C, 68.21;
1
7
17
4
H, 5.72; N, 4.68. Found: C, 68.36; H, 5.81; N, 4.58%.
4
.4.3. 1,6,6-Trimethyl-5-oxo-7-oxabicyclo[2.2.1]hept-2-
ene-2,3-dicarboxylic acid dimethyl ester (7f). A mixture
of dimethyl acetylenedicarboxylate (0.15 g, 1.1 mmol),
a-diazo ketone 4 (0.15 g, 1.0 mmol) and 1 mol% of
rhodium(II) acetate dimer (4.3 mg) in 1-n-butyl-3-methyl-
imidazolium tetrafluoroborate (3.0 mL) was allowed to
react according to method A followed by chromatographic
purification (10:90 EtOAc–hexane) to afford product 7f
(0.24 g, 92%) as a colourless oil, R 0.53 (20:80 EtOAc–
hexane). IR (neat) n 2981, 2957, 1766, 1728, 1642, 1438,
1
CDCl ) d 4.92 (s, 1H, OCH), 3.86 (s, 3H, OCH ), 3.81 (s,
8
4%). The recovered ionic liquid and rhodium(II) acetate
catalyst was well-dried by heating to 100 8C under reduced
pressure for 7 h to afford 99% yield. The same reaction was
repeated with an additional amount of starting materials
[
a-diazo ketone 4 (0.15 g, 1.1 mmol), p-methoxybenzalde-
f
hyde (0.17 g, 1.2 mmol)] to furnish the product 9b in 88%
yield. We repeated this cycle up to five times and the results
are delineated in Table 4.
K1
391, 1321, 1269, 1046, 738 cm . H NMR (200 MHz,
1
3
3
3
3
1
H, OCH ), 1.85 (s, 3H, CH ), 1.19 (s, 3H, CH ), 1.12 (s,
3 3 3
13
4
4
.4. Characterization data of new compounds
H, CH3). C NMR (50.3 MHz, CDCl ) d 210.8 (C]O),
64.2 (C]O), 161.8 (C]O), 153.1 (quat-C), 138.7
3
2
.4.1. 1,4-Diphenyl-11-oxa-4-azatricyclo[5.3.1.0 ]unde-
,6
(quat-C), 94.9 (quat-C), 83.8 (OCH), 53.2 (OCH
(quat-C), 22.8 (CH ), 21.4 (CH ), 13.9 (CH ). MS (EI) m/z
(%) 268 (M , 3), 199 (4), 167 (17), 70 (100), 42 (19). Anal.
), 43.8
3
cane-3,5,8-trione (7a). A mixture of N-phenylmaleimide
0.19 g, 1.1 mmol), a-diazo ketone 1a (0.20 g, 1.0 mmol)
3
3
3
C
(
and 1 mol% of rhodium(II) acetate dimer (4.3 mg) in 1-n-
butyl-3-methylimidazolium tetrafluoroborate (3.0 mL)
was allowed to react according to method A followed by
chromatographic purification (40:60 EtOAc–hexane) to
afford product 7a (0.292 g, 86%) as a colourless solid; mp
Calcd for C13
5.92%.
H O : C, 58.20; H, 6.01. Found: C, 58.03; H,
16 6
4.4.4. 6-Bromomethyl-3,3,4-trimethyl-7-oxabicyclo-
[2.2.1]hept-5-en-2-one (7k). A mixture of propargyl
bromide (0.13 g, 1.1 mmol), a-diazo ketone 4 (0.15 g,
1.0 mmol) and 1 mol% of rhodium(II) acetate dimer
(4.3 mg) in 1-n-butyl-3-methylimidazolium tetrafluoro-
borate (3.0 mL) was allowed to react according to method
A followed by chromatographic purification (10:90 EtOAc–
hexane) to afford product 7k (0.172 g, 72%) as a colourless
2
EtOAc–hexane). IR (KBr) n 3063, 2978, 1736, 1711,
18–220 8C (dec) (chloroform/hexane); R 0.35 (40:60
f
K1
496, 1383, 1185, 1055, 1031, 745, 697 cm . H NMR
1
1
(
200 MHz, Acetone-d ) d 7.59–7.51 (m, 2H, Arom-H),
6
7
4
7
.42–7.30 (m, 6H, Arom-H), 7.10–7.06 (m, 2H, Arom-H),
.75 (s, 1H, OCH), 4.11 (d, 1H, JZ7.5 Hz), 4.03 (d, 1H, JZ
.5 Hz), 3.11–2.92 (m, 2H), 2.71–2.56 (m, 1H), 2.39–2.23
liquid, R 0.62 (20:80 EtOAc–hexane). IR (neat) n 2972,
f
1
3
K1
(
m, 1H). C NMR (50.3 MHz, DMF-d ) d 203.0 (C]O),
7
2935, 1754, 1466, 1386, 1310, 1212, 1126, 1011, 857 cm
H NMR (200 MHz, CDCl ) d 6.39 (s, 1H, ]CH), 4.61 (s,
.
1
1
74.9 (NCZO), 173.2 (NC]O), 139.1 (quat-C), 132.0
3
(
(
(
(
(
quat-C), 128.4 (]CH), 128.0 (]CH), 127.5 (]CH), 127.3
]CH), 126.2 (]CH), 124.7 (]CH), 86.4 (quat-C), 83.4
OCH), 52.0 (CH), 50.7 (CH), 37.0 (CH ), 32.0 (CH ). MS
EI) m/z (%) 347 (M , 54), 242 (11), 173 (46), 158 (17), 144
35), 128 (11), 115 (26), 105 (100), 91 (13), 77 (28). Anal.
1H, OCH), 4.11 (s, 2H, CH ), 1.51 (s, 3H, CH ), 1.13 (s, 3H,
2
3
1
CH ), 0.99 (s, 3H, CH ). C NMR (50.3 MHz, CDCl3) d
3
3
3
213.4 (C]O), 142.4 (]CH), 141.8 (quat-C), 91.9 (quat-C),
85.0 (OCH), 44.1 (quat-C), 25.2 (CH ), 24.2 (CH ), 21.1
2
2
C
2
3
C
(CH ), 14.7 (CH ). MS (EI) m/z (%) 246 (M C1, 0.5), 244
3 3

1314
S. Muthusamy, B. Gnanaprakasam / Tetrahedron 61 (2005) 1309–1315
C
(
1
M K1, 0.5), 218 (2), 216 (2), 203 (4), 201 (4), 176 (10),
74 (10), 137 (10), 95 (100), 70 (86), 41 (42). Anal. Calcd
for C H BrO : C, 49.00; H, 5.35. Found: C, 49.19; H,
4.69 (s, 1H, OCH), 1.82 (s, 3H, CH ), 1.23 (s, 3H, CH ),
3 3
1
1.09 (s, 3H, CH3). C NMR (50.3 MHz, CDCl ) d 213.4
3
3
(C]O), 131.9 (quat-C), 130.0 (quat-C), 129.8 (]CH),
129.5 (]CH), 127.7 (quat-C), 126.5 (]CH), 125.2 (]CH),
1
0
13
2
5
.26%.
1
24.7 (]CH), 115.8 (quat-C), 87.1 (OCH), 77.8 (OCH),
52.8 (quat-C), 21.1 (CH ), 20.0 (CH ), 15.0 (CH ). MS (EI)
m/z (%) 332 (M , 27), 219 (25), 207 (54), 178 (14), 97
4
.4.5.
6-Methyl-9-pyren-1-yl-10,11-dioxatricyclo-
3
3
3
1
,6
C
[
6.2.1.0 ]undecan-7-one (9a). A mixture of pyrene-1-
carboxaldehyde (0.25 g, 1.1 mmol), a-diazo ketone 6
0.18 g, 1.0 mmol) and 1 mol% of rhodium(II) acetate
(100), 84 (20), 69 (23), 41 (35). Anal. Calcd for C22
C, 79.50; H, 6.06. Found: C, 79.31; H, 6.14%.
H O :
20 3
(
dimer (4.3 mg) in 1-n-butyl-3-methylimidazolium tetra-
fluoroborate (3.0 mL) was allowed to react according to
method A followed by chromatographic purification (10:90
EtOAc–hexane) to afford product 9a (0.36 g, 95%) as a
4.4.8. 1,6,6-Trimethyl-3-pyren-1-yl-2,7-dioxabicyclo-
[2.2.1]heptan-5-one (9d). A mixture of pyrene-1-carbox-
aldehyde (0.25 g, 1.1 mmol), a-diazo ketone 4 (0.15 g,
1.0 mmol) and 1 mol% of rhodium(II) acetate dimer
(4.3 mg) in 1-n-butyl-3-methylimidazolium tetrafluoro-
borate (3.0 mL) was allowed to react according to method
A followed by chromatographic purification (10:90 EtOAc–
hexane) to afford product 9d (0.34 g, 97%) as a pale yellow
white solid; mp 212–214 8C (chloroform/hexane); R 0.72
f
(
20:80 EtOAc–hexane). IR (KBr) n 2932, 2863, 1759, 1461,
K1
372, 1272, 1224, 1187, 1098, 1035, 985, 846 cm . H
1
1
NMR (200 MHz, CDCl ) d 8.18–7.99 (m, 9H, Arom-H),
3
5
.88 (s, 1H, OCH), 4.70 (s, 1H, OCH), 2.41–1.56 (m, 8H,
CH ), 1.35 (s, 3H, CH ). C NMR (50.3 MHz, CDCl3)
1
3
solid; mp 190–192 8C (EtOAc/hexane); R 0.70 (20:80
f
2
3
d 214.2 (C]O), 132.0 (quat-C), 131.8 (quat-C), 131.2
quat-C), 129.1 (]CH), 128.2 (]CH), 127.4 (quat-C),
EtOAc–hexane). IR (KBr) n 3034, 2973, 2944, 1759, 1470,
K1
1
(
1397, 1270, 1134, 1101, 995, 849 cm
.
H NMR
(200 MHz, CDCl ) d 8.14–7.95 (m, 9H, Arom-H), 5.81 (s,
1
1
7
26.7 (]CH), 126.3 (]CH), 126.1 (]CH), 125.4 (]CH),
24.7 (]CH), 121.9 (]CH), 114.4 (quat-C), 86.8 (OCH),
5.5 (OCH), 53.0 (quat-C), 31.6 (CH ), 27.5 (CH ), 23.9
3
1H, OCH), 4.64 (s, 1H, OCH), 1.84 (s, 3H, CH ), 1.30 (s,
3
1
3H, CH ), 1.16 (s, 3H, CH ). C NMR (50.3 MHz, CDCl3)
3
2
2
3
3
C
C
(CH ), 20.9 (CH ), 16.5 (CH ). MS (FD ) m/z 382 (M ).
Anal. Calcd for C H O : C, 81.65; H, 5.80. Found: C,
d 214.6 (C]O), 131.9 (quat-C), 131.7 (quat-C), 131.1
(quat-C), 129.0 (]CH), 128.1 (]CH), 127.3 (quat-C),
126.6 (]CH), 126.2 (]CH), 126.0 (]CH), 125.3 (]CH),
2
2
3
26 22 3
8
1.51; H, 5.89%.
1
24.6 (]CH), 121.8 (]CH), 115.4 (quat-C), 86.4 (OCH),
75.6 (OCH), 53.6 (quat-C), 21.3 (CH ), 19.7 (CH ), 15.5
). MS (EI) m/z (%) 356 (M , 65), 270 (8), 244 (21),
231 (100), 215 (29), 201 (18), 126 (8), 97 (92), 69 (18).
4
.4.6. 3-(4-Methoxyphenyl)-1,6,6-trimethyl-2,7-dioxabi-
3
3
C
cyclo[2.2.1]heptan-5-one (9b). A mixture of p-methoxy-
benzaldehyde (0.14 g, 1.1 mmol), a-diazo ketone 4 (0.15 g,
(CH
3
1
(
.0 mmol) and 1 mol% of rhodium(II) acetate dimer
4.3 mg) in 1-n-butyl-3-methylimidazolium tetrafluoro-
Anal. Calcd for C24
80.67; H, 5.72%.
H O : C, 80.88; H, 5.66. Found: C,
20 3
borate (3.0 mL) was allowed to react according to method
A followed by chromatographic purification (15:85 EtOAc–
hexane) to afford product 9b (0.22 g, 84%) as a white solid;
4.4.9. 9-Anthracen-9-yl-6-methyl-10,11-dioxatricyclo-
1
,6
[6.2.1.0 ]undecan-7-one (9f). A mixture of 9-anthralde-
hyde (0.22 g, 1.1 mmol), a-diazo ketone 6 (0.18 g,
1.0 mmol) and 1 mol% of rhodium(II) acetate dimer
(4.3 mg) in 1-n-butyl-3-methylimidazolium tetrafluoro-
borate (3.0 mL) was allowed to react according to method
A followed by chromatographic purification (20:80 EtOAc–
hexane) to afford product 9f (0.31 g, 86%) as a pale yellow
mp 75–77 8C (chloroform/hexane); R 0.45 (25:75 EtOAc–
f
hexane). IR (KBr) n 2998, 2979, 1767, 1751, 1611, 1514,
1
K1
392, 1297, 1256, 1030, 975 cm . H NMR (200 MHz,
1
CDCl ) d 7.28 (d, 2H, Arom-H, JZ8.0 Hz), 6.88 (d, 2H,
3
Arom-H, JZ8.0 Hz), 4.75 (s, 1H, OCH), 4.42 (s, 1H, OCH),
3
1
.79 (s, 3H, OCH ), 1.70 (s, 3H, CH ), 1.16 (s, 3H, CH ),
3 3 3
1
.11 (s, 3H, CH3). C NMR (50.3 MHz, CDCl ) d 214.2
3
viscous oil, R 0.45 (20:80 EtOAc–hexane). IR (neat) n
f
3
(
1
5
(
C]O), 160.3 (quat-C), 131.7 (quat-C), 128.2 (]CH),
14.7 (quat-C), 114.5 (]CH), 86.6 (OCH), 77.6 (OCH),
5.8 (OCH ), 53.0 (quat-C), 21.2 (CH ), 19.5 (CH ), 15.2
3055, 2943, 2867, 1765, 1450, 1377, 1267, 1039, 983,
737 cm . H NMR (200 MHz, CDCl ) d 8.61 (d, 2H,
Arom-H, JZ8.8 Hz), 8.31 (s, 1H, Arom-H), 7.90 (d, 2H,
Arom-H, JZ8.1 Hz), 7.51–7.35 (m, 4H, Arom-H), 6.17 (s,
K1
1
3
3
3
3
C
CH ). MS (EI) m/z (%) 262 (M , 10), 150 (41), 137 (54),
3
121 (19), 97 (100), 77 (10), 69 (22), 41 (29). Anal. Calcd for
C H O : C, 68.68; H, 6.92. Found: C, 68.41; H, 6.86%.
1H, OCH), 4.76 (s, 1H, OCH), 2.60–1.57 (m, 8H, CH ),
2
1
1.32 (s, 3H, CH3). C NMR (50.3 MHz, CDCl ) d 213.2
3
1
5
18
4
3
(
C]O), 132.0 (quat-C), 130.1 (quat-C), 129.8 (]CH),
4
.4.7. 3-Anthracen-9-yl-1,6,6-trimethyl-2,7-dioxabi-
129.6 (]CH), 127.8 (quat-C), 126.7 (]CH), 125.3 (]CH),
124.8 (]CH), 114.9 (quat-C), 87.6 (OCH), 77.9 (OCH),
cyclo[2.2.1]heptan-5-one (9c). A mixture of 9-anthralde-
hyde (0.22 g, 1.1 mmol), a-diazo ketone 4 (0.15 g,
52.1 (quat-C), 31.5 (CH
(CH ), 16.8 (CH ). MS (FD ) m/z 358 (M ). Anal. Calcd
for C24 : C, 80.42; H, 6.19. Found: C, 80.55; H, 6.06%.
), 27.2 (CH ), 23.8 (CH ), 20.6
2
2 2
C
C
1
(
.0 mmol) and 1 mol% of rhodium(II) acetate dimer
4.3 mg) in 1-n-butyl-3-methylimidazolium tetrafluoro-
2
3
H O
22 3
borate (3.0 mL) was allowed to react according to method
A followed by chromatographic purification (10:90 EtOAc–
hexane) to afford product 9c (0.29 g, 91%) as a pale yellow
4.4.10. 9-(3,4-Dimethoxyphenyl)-6-methyl-10,11-dioxa-
1
,6
tricyclo[6.2.1.0 ]undecan-7-one (9g). A mixture of
3,4-dimethoxybenzaldehyde (0.18 g, 1.1 mmol), a-diazo
ketone 6 (0.18 g, 1.0 mmol) and 1 mol% of rhodium(II)
acetate dimer (4.3 mg) in 1-n-butyl-3-methylimidazolium
tetrafluoroborate (3.0 mL) was allowed to react according to
method A followed by chromatographic purification (20:80
viscous oil, R 0.72 (20:80 EtOAc–hexane). IR (neat) n
f
3
1
053, 2976, 2938, 1766, 1466, 1446, 1396, 1266, 1135,
105, 1001, 888 cm . H NMR (200 MHz, CDCl ) d 8.56
K1 1
3
(d, 2H, Arom-H), 8.17 (s, 1H, Arom-H), 7.78 (d, 2H,
Arom-H), 7.42–7.30 (m, 4H, Arom-H), 6.09 (s, 1H, OCH),

S. Muthusamy, B. Gnanaprakasam / Tetrahedron 61 (2005) 1309–1315
1315
EtOAc–hexane) to afford product 9g (0.284 g, 89%) as a
white solid; mp 112–114 8C (chloroform/hexane); R 0.51
2004, 69, 619. (b) Padwa, A.; Curtis, E. A.; Sandanayaka, V. P.
J. Org. Chem. 1997, 62, 1317. (c) Kinder, F. R. Jr.; Bair, K. W.
J. Org. Chem. 1994, 59, 6965. (d) McMills, M. C.; Zhuang, L.;
Wright, D. L.; Watt, W. Tetrahedron Lett. 1994, 35, 8311.
5. Dauben, W. G.; Dinges, J.; Smith, T. C. J. Org. Chem. 1993,
58, 7635.
f
(
1
20:80 EtOAc–hexane). IR (KBr) n 2937, 2853, 1767, 1518,
K1 1
464, 1327, 1255, 1241, 1135, 1032, 1005 cm . H NMR
(
200 MHz, CDCl ) d 6.91–6.81 (m, 3H, Arom-H), 4.76 (s,
3
1
H, OCH), 4.49 (s, 1H, OCH), 3.89 (s, 3H, OCH ), 3.86 (s,
3
1
3
3 C
NMR (50.3 MHz, CDCl ) d 213.7 (C]O), 149.6 (quat-C),
H, OCH ), 2.24–1.45 (m, 8H, CH ), 1.20 (s, 3H, CH ).
6. (a) Hodgson, D. M.; Bailley, J. M.; Villalonga-Barber, C.;
Drew, M. G. B.; Harrison, T. J. Chem. Soc., Perkin Trans. 1
2000, 3432. (b) Kataoka, O.; Kitagaki, S.; Watanabe, N.;
Kobayashi, J.; Nakumura, S.; Shiro, M.; Hashimoto, S.
Tetrahedron Lett. 1998, 39, 2371.
3
2
3
3
1
(
32.0 (quat-C), 119.3 (]CH), 113.5 (quat-C), 111.6
]CH), 110.0 (]CH), 96.3 (quat-C), 86.8 (OCH), 77.5
(
OCH), 56.4 (OCH ), 56.3 (OCH ), 52.4 (quat-C), 31.4
3
3
(
(
CH ), 27.3 (CH ), 23.6 (CH ), 20.6 (CH ), 16.2 (CH ). MS
2
FD ) m/z 318 (M ). Anal. Calcd for C H O : C, 67.91;
18 22 5
7. Padwa, A.; Harring, S. R.; Semones, M. A. J. Org. Chem.
1998, 63, 44 and references cited therein.
8. (a) Olivier-Bourbigou, H.; Magna, L. J. Mol. Catal. A: Chem.
2
C
2
2
3
C
H, 6.97. Found: C, 67.72; H, 6.89%.
2
002, 182–183, 419. (b) Wasserscheid, P.; Keim, W. Angew.
Chem., Int. Ed. Engl. 2000, 39, 3772. (c) Welton, T. Chem.
Rev. 1999, 99, 2071.
. Few recent examples of organic reactions in [bmim]BF ionic
Acknowledgements
9
4
This research work was supported by the Department of
Science and Technology, New Delhi. We thank Dr. P. K.
Ghosh, Director for his encouragement shown in this work.
B. G. thanks DST, New Delhi, for a Fellowship.
liquid, see: (a) Peng, J.; Deng, Y. Tetrahedron Lett. 2001, 42,
4
03. (b) Peng, J.; Deng, Y. Tetrahedron Lett. 2001, 42, 5917.
c) Wheeler, C.; West, K. N.; Eckert, C. A.; Liotta, C. L.
(
J. Chem. Soc., Chem. Commun. 2001, 887. (d) Kabalka, G.;
Malladi, R. R. J. Chem. Soc., Chem. Commun. 2000, 2191.
(
e) Le Boulaire, V.; Gr e´ e, R. J. Chem. Soc., Chem. Commun.
000, 2195. (f) Howarth, J. Tetrahedron Lett. 2000, 41, 6627.
2
References and notes
10. (a) Muthusamy, S.; Babu, S. A.; Gunanathan, C.; Ganguly, B.;
Suresh, E.; Dastidar, P. J. Org. Chem. 2002, 67, 8019.
(b) Muthusamy, S.; Babu, S. A.; Gunanathan, C.; Suresh, E.;
Dastidar, P. Bull. Chem. Soc. Jpn 2002, 75, 801.
(c) Muthusamy, S.; Babu, S. A.; Gunanathan, C.; Suresh, E.;
Dastidar, P.; Jasra, R. V. Tetrahedron 2000, 56, 6307 and
references cited therein.
1
. Doyle, M. P.; McKervey, M. A.; Ye, T. Modern Catalytic
Methods for Organic Synthesis with Diazo Compounds. From
Cyclopropanes to Ylides; Wiley-Interscience: New York,
1
. (a) Mehta, G.; Muthusamy, S. Tetrahedron 2002, 58, 9477.
998.
2
(
b) Padwa, A.; Weingarten, M. D. Chem. Rev. 1996, 96, 223.
c) Calter, M. A. Curr. Org. Chem. 1997, 1, 37. (d) Ye, T.;
11. Padwa, A.; Chinn, R. L.; Hornbuckle, S. F.; Zhang, Z. J.
J. Org. Chem. 1991, 56, 3271.
(
McKervey, A. Chem. Rev. 1994, 94, 1091.
. Padwa, A.; Fryxell, G. E.; Zhi, L. J. Am. Chem. Soc. 1990, 112,
12. Preparation of ionic liquids: (a) Park, S.; Kazlauskas, R. J.
J. Org. Chem. 2001, 66, 8395. (b) Suarez, P. A. Z.; Dullius,
J. E. L.; Einloft, S.; De Souza, R. F.; Dupont, J. Polyhedron
1996, 15, 1217.
3
4
3100.
. (a) McMorris, T. C.; Staake, D.; Kelner, M. J. J. Org. Chem.