Ionic liquid soluble photosensitizers

Article abstract of DOI:10.1016/j.tet.2005.05.072

The preparation and investigation of triplet photosensitizers designed to be preferentially soluble in room-temperature ionic liquids are reported. Photosensitizers prepared by covalent attachment of 1-methylimidazole to aryl ketones are soluble in ionic liquids and remain in the ionic liquid layer when the solution is extracted with an organic solvent. The photosensitized isomerization of trans-β-ionol to cis-β-ionol was efficiently carried out in ionic liquid solution with the product ionol being extracted and the sensitizer/ionic liquid mixture being re-used in additional photosensitization reactions. The scope and utility of the sensitizers in sensitizing other reactions are discussed.

Full text of DOI:10.1016/j.tet.2005.05.072

Tetrahedron 61 (2005) 7425–7430
Ionic liquid soluble photosensitizers
Sarah C. Hubbard and Paul B. Jones
*
Department of Chemistry, Wake Forest University, Winston-Salem, NC 27109, USA
Received 15 April 2005; revised 19 May 2005; accepted 20 May 2005
Available online 15 June 2005
Abstract—The preparation and investigation of triplet photosensitizers designed to be preferentially soluble in room-temperature ionic
liquids are reported. Photosensitizers prepared by covalent attachment of 1-methylimidazole to aryl ketones are soluble in ionic liquids and
remain in the ionic liquid layer when the solution is extracted with an organic solvent. The photosensitized isomerization of trans-b-ionol to
cis-b-ionol was efficiently carried out in ionic liquid solution with the product ionol being extracted and the sensitizer/ionic liquid mixture
being re-used in additional photosensitization reactions. The scope and utility of the sensitizers in sensitizing other reactions are discussed.
q 2005 Elsevier Ltd. All rights reserved.
1. Introduction
catalyst or reagent is used to carry out a transformation on a
‘
6
normal’ organic substrate. After the reaction, the catalyst
Ionic liquids have found increasing use in organic chemistry
as chemists have improved their ability to tailor these
can easily be separated from the substrate/product by
extraction.
1
solvents to a particular need. Among the specialized ionic
liquids developed are those that carry catalysts and
While studying photochemical reactions in ionic liquids, we
noted that ionic liquids are excellent media in which to
2
reagents. Ionic liquids have been designed for specific
3
chemical function, such as fixing carbon dioxide. Although
7
perform anaerobic reactions. The negligible vapor pressure
ionic liquids are often discussed as a uniform class of
material in the literature, the physical properties and
chemical behavior of ionic liquids cannot be narrowly
defined and may vary significantly from one ionic liquid to
of the ionic liquids allows solutions to be degassed readily
without numerous cycles of freeze–pump–thaw. If none of
the reagents or reactants are volatile, the reaction mixture
can simply be placed on a vacuum line prior to irradiation. A
number of reports discussing photochemistry in ionic
4
another. Ionic liquids may be soluble in water, organics, or
1
both. Furthermore, ionic liquids may dissolve a wide range
8
liquids have appeared in the past several years. These
1
of solutes. When partitioned against an organic solvent,
observations led to the idea of an ionic liquid containing a
photosensitizing chromophore so that the ionic liquid itself
might be a photosensitizer. Photochemical energy transfer
ether for instance, many ionic species are retained in the
ionic liquid layer. This property is useful in that it allows the
rapid separation of neutral organics from charged mol-
ecules. This technique is often used to separate a metal
catalyst or other reagent following a reaction in an ionic
9
in ionic liquids has been reported previously. Unfortunately,
all attempts at preparing such a liquid have failed, as
the chromophore invariably rendered the salt a solid.
However, the ability of ionic liquids to retain other ionic
compounds suggested the idea of doping an ionic liquid
with a sensitizer bearing a charge, thereby making it
preferentially soluble in the ionic liquid. The result would
be a homogenously supported photosensitizer. We sought to
attach a dialkylimidazolium cation to a photosensitizer and
then use a solution of this new sensitizing salt dissolved in
an ionic liquid to carry out a photosensitized reaction. If
successful, the photoproduct could be separated from the
sensitizer by extraction, leaving the ionic liquid/sensitizer
mixture to be reused.
2
liquid. Several examples using homogenous supports in
5
ionic liquids have appeared in the last few years.
A
substrate is loaded onto a support that is preferentially
soluble in an ionic liquid, which then becomes a fluid solid
support. The substrate then undergoes a series of trans-
formations, until the final product is cleaved from the
support and extracted with an organic solvent. Though
fewer examples are known, homogenously supported
2
reagents have also been reported. The idea is analogous
to work done in fluorous media where a perfluorinated
Keywords: Ionic liquid; Photosensitization; Recyclable reagent.
*
A suitable photosensitizer would need three properties: (1) a
partition coefficient of zero between an ionic liquid and an
Corresponding author. Tel.: C1 3367583708; fax: C1 3367584656;
e-mail: jonespb@wfu.edu
0040–4020/$ - see front matter q 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2005.05.072

7426
S. C. Hubbard, P. B. Jones / Tetrahedron 61 (2005) 7425–7430
Scheme 1.
of 1-methylimidazole with 2-bromoacetonaphthone
(Scheme 1). Sensitizer 3 was prepared as shown in Scheme 2.
Alkylation of 4,4 -dihydroxybenzophenone with excess
Chart 1.
0
1
,2-dibromoethane gave 4 in 66% yield. Dibromide 4 was
organic solvent, (2) photochemical inertness, other than
triplet energy transfer, and (3) ease of preparation. We chose
the common ionic liquid 1-butyl-3-methylimidazolium
tetrafluoroborate ([bmim][BF ]) and diethyl ether as
4
representative example of an ionic liquid/organic solvent
pair. The sensitizers prepared are shown in Chart 1.
then used to alkylate 1-methylimidazole to give 3 in 68%
yield. The chromophore in both 2 and 3 was modified such
that the lowest triplet state should be the p,p* configur-
ation. Also, imidazole expulsion was not possible in 3. As
was the case with 1, neither 2 nor 3 was soluble in diethyl
ether.
Both 2 and 3 sensitized the isomerization of trans-b-ionol
(
2
. Results and discussion
Scheme 3) when irradiated with a medium pressure Hg
lamp with a UO2 doped glass filter (lO350 nm). In
degassed methanol, the photostationary state achieved in
sensitization with 3 was 65% cis-b-ionol (see below). This
photostationary state was reached in 48 h when 5 mol% of 3
(relative to ionol) was used. Under the same conditions,
sensitizer 2 gave a photostationary state of 100% cis-b-
ionol, which was reached in 24 h.
Our first target was acetophenone 1, which was readily
prepared by treating 1-methylimidazole with phenacyl
bromide in ethanol (Scheme 1). Acetophenones have been
widely used as triplet sensitizers and absorb well at lO
3
00 nm, which is critical in protecting the ionic liquid itself
from excitation. Compound 1 was soluble in [bmim][BF4]
and insoluble in diethyl ether. When 1 was dissolved in
[
bmim][BF ] (1 mg/mL) and extracted three times with an
4
Irradiation of trans-b-ionol in the [bmim][BF ]/2 or
4
equivalent volume of diethyl ether, no 1 was present in the
combined ether layers. Thus, 1 fulfilled two of the three
criteria listed above.
[bmim][BF ]/3 (5 mol% of 2 or 3 in each case) mixture
4
led to formation of cis-b-ionol much more effectively than
in reactions with 1. Interestingly, the reaction was much
slower in the ionic liquid than in methanol when sensitized
with 3, though no similar reduction in the rate of reaction
with 2 was observed in going from methanol to ionic liquid.
In all cases, the b-ionol product could be easily extracted
from the ionic liquid, with recovered yields between 85 and
Unfortunately, 1 did not meet criterion 2, photochemical
inertness. In the photosensitized isomerization of trans-b-
1
0
ionol, 1 invariably led to complex mixtures and low mass
recoveries. Isomerization of the ionol was observed, but it
was clear that a number of other undesired processes were
occurring. In retrospect, these side reactions might have
been anticipated. Acetophenone triplets are highly reactive
as hydrogen abstractors and electron acceptors. In addition,
the expulsion of leaving groups from the a position
following photoinduced electron transfer has also been
observed in related systems. Consistent with the latter
reaction, acetophenone was observed in small amounts in
the organic extracts from these attempted photoisomeriza-
tions. Decomposition of 1 could also be surmised because
1
00%. No sensitizer was observed in any ether extracts.
The sensitizer/ionic liquid mixture could be recycled several
times with no noticeable effect on rate, photostationary state
composition or yield. Three successive 24 h runs were
conducted using 2 (5 mol%) in 10 mL [bmim][BF ]. In each
4
case, the composition of b-ionol after 24 h of irradiation
1
1
(lO350 nm) was 100% cis. By simple extraction, pure
b-ionol could be obtained from the ionic liquid. Yields for
isomerization in recycled [bmim][BF ]/1 mixtures was
4
markedly less efficient.
the three runs were 92, 89 and 83%. Between each run, the
recovered ionic liquid was concentrated in vacuo. A H
1
NMR spectrum of the ionic liquid portion after each run
indicated pure [bmim][BF ] (the sensitizer was present in
4
too low concentration to be seen by NMR). For the fourth
attempt, the ionic liquid layer from the third reaction was
allowed to sit unused for ten days at ambient temperature
and in room light prior to the sensitization reaction. Again,
Both hydrogen abstraction and expulsion of leaving
groups, such as the alkylimidazole in 1, from a-positions
are efficient processes in n,p* triplets. Considering
this reactivity, we next prepared two additional photo-
sensitizers, 2 and 3. Sensitizer 2 was prepared by alkylation
Scheme 2.

S. C. Hubbard, P. B. Jones / Tetrahedron 61 (2005) 7425–7430
7427
Scheme 3.
the isomerization was complete in less than 24 h and the
yield of cis-b-ionol was 97%. The variation in actual
recovered yields was slight and was consistently between 80
and 100%.
In all cases described thus far, diethyl ether was used as the
organic solvent in extracting ionol from the ionic liquid.
Attempts to extract the ionic liquid ([bmim][BF ]) with
Figure 1. Amount of cis-ionol present in reactions sensitized by 2 in
] (B). The two samples were irradiated
filter (lO350 nm).
methanol (A) and in [bmim][BF
using a medium pressure Hg lamp and UO
4
4
benzene or ethyl acetate were problematic, as the ionic
liquid itself was partially soluble in the organic solvent. This
led to significant quantities of ionic liquid, and some
sensitizer, crossing into the organic layer. Significant
accumulation of the organic solvent in the ionic liquid
layer also occurred, requiring removal of the solvent under
reduced pressure. Though the suitability of an organic
solvent will vary according to the ionic liquid used, in most
cases, ether or hexane will be the most effective extraction
solvent.
2
isomerization using 2 was tested in both solvents. This
reaction gave a very complex mixture when carried out in
[BuPic][BF ]: GC analysis registered 13 volatile products in
4
greater abundance than the total amount of ionol. However,
after 24 h (lO350 nm), the ionol was 87% cis, indicating
that the sensitized isomerization did occur. NMR confirmed
that a complex mixture had resulted. We have observed
numerous undesired photoreactions in pyridinium based
7
a
ionic liquids. Given our past results and the recent data, we
suggest avoiding pyridinium based ionic liquids as solvents
for photoreactions, unless a specific interaction with the
solvent is desired.
Recoveries of b-ionol from reactions sensitized by 3 in
[
bmim][BF ] were also high (O80%). However, these
4
reactions were very slow when irradiated at lO350 nm. The
photostationary state (88% cis) was only reached after
Photoisomerization reactions (5 mol% 2) run in
[BMPyr][Tf N] proceeded smoothly. In our first attempt,
isomerization was complete after 24 h and cis-b-ionol was
4
10 h. The reduced rate is best explained by the relative
2
absorptivities of 2 and 3. Benzophenone 3 absorbs strongly
between 260 and 320 nm (3313Z5000) but poorly at 350 nm
recovered in 87% yield. The recovered [BMPyr][Tf N] was
2
(
(
3Z28). At the principal emission line of the filtered lamp
366 nm), 3 has practically no absorbance. In contrast, 2
used in a second reaction, and again, isomerization went to
completion in 24 h with 91% recovery of cis-b-ionol. This
ionic liquid was not as attractive for use in the sensitized
ionol isomerization because of its higher hydrophobicity
absorbs very well between 300 and 350 nm (3350Z1410 and
3366Z41). The rate of sensitization using 3 did appear to be
slower in [bmim][BF ] than in organic solvent, as the
4
0
relative to [bmim][BF ]. Extraction with ether was
4
photostationary state using 4,4 -dimethoxybenzophenone
an analog of 3) in benzene was reached in only 72 h (lO
50 nm). In methanol, a photosensitization reaction using 3
impossible, as the ether dissolved significant quantities of
the ionic liquid, contaminating the recovered ionol with
both [BMPyr][Tf N] and sensitizer 2. Instead, hexane was
(
3
did not proceed to the usual photostationary state. Instead,
this reaction stopped after approximately a 3:1 ratio of cis to
trans-b-ionol had been obtained. When this reaction was
concentrated, NMR analysis indicated an absence of 3,
which had apparently undergone photoreduction by the
solvent, as determined by the aromatic signals moving
upfield by 0.1–0.4 ppm.
2
used to extract the ionol from the ionic liquid.
Other sensitized photoreactions were examined to deter-
mine the scope of the ionic liquid soluble photosensitizers.
1
2
The sensitized di-p-methane rearrangement of 5 was
successfully carried out by irradiation (lO350 nm) of a
solution of 2 in [bmim][BF ] for 18 h (Scheme 4). The
4
solution was prepared and irradiated exactly as were the
ionol photoisomerization reactions. The starting dibenzo-
barrelene was remarkably soluble in the ionic liquid, 75 mg
Figure 1 shows a comparison of rates of ionol isomerizaton
in [bmim][BF ] and methanol, using 2 as the sensitizer. No
4
significant difference in the rate of sensitization in the two
solvents was observed. The rate appeared to slow as the
reaction progressed when the reaction was conducted in
methanol. However, consumption of 2 was not detected
when the residue was analyzed following removal of the
methanol.
of 5 dissolving readily in 10 mL of [bmim][BF ]. The
4
1
3
product, 6, was extracted from the ionic liquid with ether
and recovered in 87% yield. No starting material remained
and no other products were extracted with the product.
The usefulness of 2 and 3 in ionic liquids other than
[bmim][BF ] was also examined. Two additional ionic
4
liquids were chosen: 1-butyl-4-methylpyridinium tetrafluor-
oborate ([BuPic][BF ]) and N-butyl-N-methylpyrrolidinium
4
triflimide ([BMPyr][Tf N]). The sensitization of ionol
2
Scheme 4.

7428
S. C. Hubbard, P. B. Jones / Tetrahedron 61 (2005) 7425–7430
further purification: all compounds were purchased from
Sigma-Aldrich or Fisher Scientific. CH Cl was distilled
2
2
over calcium hydride. Thin-layer chromatography was
performed on silica gel (250 mm thickness doped with
fluorescein) unless otherwise indicated. The chromatograms
were visualized with UV light (254 nm) unless otherwise
indicated. GC analyses were conducted on an Agilent 6890
GC and analytes detected by FID following elution from a
30 m b-cyclodextrin column (Supelco 24304). Elemental
analyses were performed by Atlantic Microlabs, Inc. in
Norcross, GA. High-resolution mass spectrometry was
performed at Ohio State University by the laboratory of
Christopher Hadad in Columbus, OH. Photochemical
reactions were conducted using a 450 W medium pressure
Scheme 5.
In contrast, the sensitized photolysis of myrcene (7) did not
proceed when irradiated similarly in [bmim][BF ]
4
1
4
Scheme 5). Extraction of the ionic liquid with ether
(
following photolysis gave a complex mixture of products
that could not be separated, though signals of the desired
product (8) were identified in a H NMR spectrum of the
1
crude product. An explanation for this result could be found
in the behavior of the hydrocarbon upon addition to the
ionic liquid; when myrcene is added to [bmim][BF ] (or
Hg vapor lamp (Hanovia) in conjunction with a UO doped
2
glass filter.
4
other ionic liquids), visible globules form. The insolubility
of myrcene in the ionic liquid most likely produces a higher
effective concentration than indicated by the relative
amounts of substrate and solvent. Liu and Hammond
reported that at higher concentrations photosensitization of
myrcene led to dimerization, rather than photocyclization.
We believe that in this case, the phase separation that occurs
between myrcene and [bmim][BF ] results in dimerization
4
and oligomerization in addition to the desired reaction.
Thus, ionic liquids are suitable solvents for photosensitiza-
tion reactions only when they dissolve the substrates at
reasonable concentrations. Unfortunately, use of the more
hydrophobic ionic liquid, [BMPyr][Tf N], did not provide
2
improvement in the sensitized photoisomerization of
myrcene.
4.1.1. 3-Phenacyl-1-methylimidazolium bromide (1).
Phenacyl bromide (15.0 g, 76 mmol) was dissolved in
ethanol (300 mL) and the solution cooled to 0 8C by an
external ice/water bath. 1-Methylimidazole (6.2 mL,
84 mmol) was added dropwise to the stirring reaction
mixture via addition funnel. The resulting solution was
allowed to warm to ambient temperature with the bath.
After 36 h, solvent was removed in vacuo to give a
yellowish sludge. The sludge was poured into rapidly
stirring diethyl ether and a white precipitate formed. The
precipitate was collected and triturated extensively with
ether and dried in vacuo to give the desired salt as a yellow
1
4
1
powder (19.2 g, 68 mmol, 90%). H NMR (300 MHz,
CD OD) d 4.01 (s, 3H), 6.00 (s, 2H (exchanges with
3
CD OD)), 7.63 (m, 5H), 8.08 (s, 1H), 8.11 (s, 1H), 8.99 (s,
3
1
3
1
CD OD) d 192.1, 139.4, 135.7, 135.2, 130.2, 129.4, 125.4,
H (exchanges with CD OD)); C NMR (75 MHz,
3
3
C
124.5, 56.3, 36.8. HRMS calcd for C H N O :
3. Conclusion
1
2
13
2
2
01.102239. Found: 201.10241.
Imidazole-tagged aryl ketones have been developed that can
efficiently sensitize photochemical reactions in ionic
liquids. The product can be isolated simply by extraction
of the ionic liquid solution with an appropriate organic
solvent, with the sensitizer remaining in the ionic liquid
layer. The ionic liquid/sensitizer mixture can be recycled a
number of times with little loss of energy transfer efficiency
or recovered yield of the product. Due to apparent
4.1.2. 3-Acenapthyl-1-methylimidazolium bromide (2).
2 -Bromo-2-acetonaphthone (2.49 g, 10 mmol) was dissolved
0
in ethanol (50 mL). To this stirring solution was added
1-methylimidazole (0.836 mL, 10.5 mmol). The reaction
mixture warmed during addition of 1-methylimidazole; an
ice/water bath was used to keep the reaction cool. After
addition was complete, the bath was removed and the
mixture allowed to warm to ambient temperature overnight.
Solvent was removed in vacuo to give a yellow-orange
powder. The residue was recrystallized from boiling CHCl3
participation of the solvent, [BuPic][BF ] was not an
4
effective ionic liquid for these reactions. The most effective
combination was acetonapthone 2 in [bmim][BF ], using
4
ether as the solvent for extraction, though this will likely
vary according to reaction and substrate. This method is
effective for rapid isolation of product and as a means of
avoiding chromatography of sensitive photoproducts in
cases where photosensitization via energy transfer is
required.
to give the desired salt as small yellow crystals (2.41 g,
7.3 mmol, 73%). H NMR (300 MHz, CD OD) d 4.02 (s,
3H), 6.15 (s, 2H (exchanges with CD OD)), 7.68 (m, 4H),
3
1
3
7.99 (m, 4H), 8.74 (s, 1H), 9.01 (s, 1H, exchanges with
CD OD)); C NMR (75 MHz, CD OD) d 191.3, 139.5,
1
3
3
3
137.7, 134.0, 132.5, 130.9, 130.5, 130.0, 129.4, 129.0,
28.7, 125.4, 124.6, 124.3, 56.3, 36.8. HRMS calcd for
C H N O : 251.117889. Found: 251.11685.
1
C
1
6 15 2
4
. Experimental
0
stirring solution of 4,4 -dihydroxybenzophenone (2.14 g,
4
.1.3. 4,4 -(2-Bromoethoxy)benzophenone (4). To a
0
4
.1. General methods
1
0 mmol) in MEK (200 mL) was added K CO (3 g,
2 3
1
13
H NMR (300, 500 MHz) and C NMR (75, 125 MHz)
spectra were recorded on Bruker Avance 300 and 500 MHz
spectrometers. Unless otherwise indicated, all reagents and
solvents were obtained commercially and used without
22 mmol) followed by 1,2-dibromoethane (38 g, 200 mmol)
in one portion. The solution was heated to reflux for 5 h.
TLC indicated no starting material remained. The solution
was filtered through a plug of basic alumina, which was

S. C. Hubbard, P. B. Jones / Tetrahedron 61 (2005) 7425–7430
7429
washed with MEK (100 mL). The filtrate was concentrated
4.4. Method for sensitized photolysis of myrcene
to give a white solid (2.82 g, 6.6 mmol, 66%), which was
used without further purification. An analytically pure
sample of 4 was obtained by recrystallization from hot
To 10 mL [bmim][BF ] was added 15 mg of 2 (0.05 mmol)
4
and the solution stirred vigorously while being gently heated
until the sensitizer had dissolved. To the resulting solution
was added 125 mL of freshly distilled myrcene (100 mg,
0.74 mmol). The mixture was then evacuated on a high-
vacuum line (50 mTorr) for 30 min. The solution was then
irradiated with a medium pressure Hg lamp through Pyrex
1
ethanol. Mp 124–126 8C. H NMR (300 MHz, CDCl ) d
3
3
.68 (t, 4H, JZ6.6 Hz), 4.38 (t, 4H, JZ6.6 Hz), 6.98 (d, 4H,
13
JZ9.0 Hz), 7.78 (d, 4H, JZ9.0 Hz); C NMR (75 MHz,
CDCl ) d 194.2, 161.3, 132.3, 131.3, 114.2, 67.9, 28.6.
Anal. Calcd for C H Br O : C, 47.69; H, 3.77; Br, 37.33.
3
2
1
16
2 3
Found: C, 48.06; H, 3.72; Br, 36.99.
and a UO doped glass filter (lO350 nm) while being
2
vigorously stirred for 24 h. The photolysis mixture was
extracted three times with 15 mL of diethyl ether, the
combined organic extracts washed with 10 mL water and
conc. in vacuo to give the crude product.
0
4
.1.4. 4,4 -(2-(1-Methylimidazolium)ethoxy)benzophe-
none dibromide (3). To a stirring solution of 4 (2.28 g,
.4 mmol) in MEK (50 mL) was added 1-methylimidazole
7 mL, 84 mmol) in one portion. The solution was heated to
5
(
reflux for 72 h. Solvent was removed in vacuo to give a
gummy residue that was partitioned between EtOAc
Acknowledgements
(
50 mL) and water (100 mL). The layers were separated
and the aqueous layer washed repeatedly (5!50 mL) with
EtOAc. The aqueous layer was then dried in vacuo to give
an amorphous paste that was crystallized from ethanol/
S.C.H. thanks Wake Forest University and Glaxo-Wellcome
for Fellowship support. The authors thank the ACS Petroleum
Research Fund (PRF #37882-G4) and Wake Forest University
for financial support and D. Zuidema, R. Brinson and
M. Chervenak for help in preparing the manuscript.
1
EtOAc to give the desired salt (2.18 g, 3.68 mmol, 68%). H
NMR (300 MHz, CD OD) d 3.99 (s, 6H), 4.52 (m, 4H), 4.74
3
(
with CD OD)); C NMR (75 MHz, CD OD) d 196.2,
m, 4H), 7.11 (m, 4H), 7.71 (m, 8H), 9.18 (s, 2H, exchanges
1
3
3
3
1
62.8, 138.3, 133.0, 132.6, 125.0, 124.2, 115.5, 67.6, 36.7,
3.9. HRMS calcd for C H BrN O Na : 511.133928.
C
3
Found: 511.13426.
2
5
28
4 3
References and notes
4
.2. Method for photoisomerization of ionol
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1
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2
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To 10 mL [bmim][BF ] was added 16 mg of 2 (0.05 mmol)
4
and the solution stirred vigorously while being gently heated
until the sensitizer had dissolved. To the resulting solution
1
2
was added 5 (75 mg, 0.23 mmol). The mixture was then
evacuated on a high-vacuum line (50 mTorr) for 3 h. The
solution was then irradiated with a medium pressure Hg
lamp through Pyrex and a UO doped glass filter (lO
2
3
50 nm) while being vigorously stirred for 18 h. The
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of diethyl ether, the combined organic extracts washed with
1
0
0 mL water and conc. in vacuo to give 6 (65 mg,
.20 mmol, 87%). The H NMR spectrum for 6 isolated
1
from ionic liquid supported reactions matched exactly that
of 6 made by literature methods.
1
3

7430
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2