Ritter reactions between alcohols and acetonitrile mediated by the conducting polymer poly-(3,4-ethylenedioxy thiophene) (Pedot)

Article abstract of DOI:10.1080/00397911.2013.775592

Herein, we report new reactivity of the conducting polymer, poly-(3,4-ethylenedioxy thiophene) (PEDOT), where PEDOT mediates a Ritter reaction between alcohols and acetonitrile. The yields were variable and in most cases competitive with results obtained using sulfuric acid. Attempts at a stoichiometric reaction between benzonitrile and diphenylmethanol are also reported herein. Finally, described here are preliminary mechanistic studies that suggest PEDOT is behaving as an alcohol-selective or specific Lewis acid. Taylor & Francis Group, LLC.

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Ritter Reactions between Alcohols and
Acetonitrile Mediated by the Conducting
Polymer Poly-(3,4-ethylenedioxy
Thiophene) (PEDOT)
John G. D'Angelo a , Jeremy A. Cody b , Christian Larrabee b , Danica
J. Ostrander a , Kyle W. Rugg b & Donna Mamangun c
a Department of Chemistry , Alfred University , Alfred , New York ,
USA
b School of Chemistry and Materials Sciences , Rochester Institute of
Technology , Rochester , New York , USA
c Department of Chemistry , University of Connecticut , Storrs ,
Connecticut , USA
Accepted author version posted online: 18 Jun 2013.Published
online: 04 Sep 2013.
To cite this article: John G. D'Angelo , Jeremy A. Cody , Christian Larrabee , Danica J. Ostrander ,
Kyle W. Rugg & Donna Mamangun (2013) Ritter Reactions between Alcohols and Acetonitrile Mediated
by the Conducting Polymer Poly-(3,4-ethylenedioxy Thiophene) (PEDOT), Synthetic Communications:
An International Journal for Rapid Communication of Synthetic Organic Chemistry, 43:23, 3224-3232,
DOI: 10.1080/00397911.2013.775592
To link to this article: http://dx.doi.org/10.1080/00397911.2013.775592
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Synthetic Communications1, 43: 3224–3232, 2013
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397911.2013.775592
RITTER REACTIONS BETWEEN ALCOHOLS AND
ACETONITRILE MEDIATED BY THE CONDUCTING
POLYMER POLY-(3,4-ETHYLENEDIOXY THIOPHENE)
(PEDOT)
John G. D’Angelo,1 Jeremy A. Cody,2 Christian Larrabee,2
Danica J. Ostrander,1 Kyle W. Rugg,2 and Donna Mamangun3
1Department of Chemistry, Alfred University, Alfred, New York, USA
2School of Chemistry and Materials Sciences, Rochester Institute of
Technology, Rochester, New York, USA
3Department of Chemistry, University of Connecticut, Storrs,
Connecticut, USA
GRAPHICAL ABSTRACT
Abstract Herein, we report new reactivity of the conducting polymer, poly-(3,4-
ethylenedioxy thiophene) (PEDOT), where PEDOT mediates a Ritter reaction between
alcohols and acetonitrile. The yields were variable and in most cases competitive with results
obtained using sulfuric acid. Attempts at a stoichiometric reaction between benzonitrile and
diphenylmethanol are also reported herein. Finally, described here are preliminary mechan-
istic studies that suggest PEDOT is behaving as an alcohol-selective or specific Lewis acid.
Supplementary materials are available for this article. Go to the publisher’s online
edition of Synthetic Communications1 for full experimental and spectral details.
Keywords Alcohol; amide; conducting polymer; PEDOT; Ritter
INTRODUCTION
Recently, the conducting polymer poly-(3,4-ethylenedioxy-thiophene)
(PEDOT) (1, Fig. 1)[1] was reported to initiate formation of homoethers from
alcohols with small amounts of oxidation to the corresponding ketone or aldehyde[2]
Friedel–Crafts alkylations of benzene and toluene with alcohols[3] and cyclodehydra-
tions of acyclic sugars[4]—suggesting acid-like behavior. Other conjugated polymers
have also been used to mediate chemical reactions, such as protonated polyaniline
2ꢀ
ꢀ
salts with counteranions such as SO4 or NO3 for the tetrahydropyranylation of
alcohols;[5] protonated polyaniline salts with counteranions such as SO42ꢀ, Clꢀ, or
Received December 20, 2012.
Address correspondence to John G. D’Angelo, Department of Chemistry, Alfred University, One
Saxon Drive, Alfred, NY 14802, USA. E-mail: dangelo@alfred.edu
3224

POLYMER-MEDIATED RITTER REACTIONS
3225
Figure 1. Chemical structure of PEDOT employed in this study. The polymer is a repeating trimer unit
containing a single positive charge counterbalanced by one triflate counterion.
NO3 for transesterification reactions;[6] protonated polyaniline salts with SO42ꢀ, a
ꢀ
counteranion for acetal formation and deprotection;[7] polypyrrole with Pd(0) or
Pd(II) to hydrogenate nitrobenzene to aniline;[8] and polypyrrole-based heteropoly
acid catalysts for eliminations and oxidations on alcohols.[9] These and other reac-
tions employing modified conjugated polymers were recently reviewed.[10] In each
of the aforementioned cases, acids such as H2SO4 or other additives are added to
the polymer or incorporated into the polymer backbone. In contrast, for the reac-
tions using PEDOT,[2–4] including those described herein, no such acids are added
during or after polymerization, suggesting that these reactions are somehow
mediated by PEDOT.
The use of PEDOT to initiate reactions is advantageous as a heterogeneous
catalyst, which permits ease of purification, workup, and potential recycling. Because
PEDOT does not have functionality bound to it (i.e., amines or sulfonic acid) the
mode of reaction should prove to be different, and those differences should result
in chemoselectivity to the alcohol functionality and synthetically viable reactivity
differences among 1ꢁ, 2ꢁ, and 3ꢁ alcohols. Additionally, an improved fundamental
understanding of PEDOT’s ability to catalyze reactions such as the Ritter reaction
may result in the development of novel polymer catalysts with lower preparation cost
and perhaps improved selectivity.
Because PEDOT and other polymeric reagents are used as heterogeneous
mixtures, we turned our attention to exploring the utility of PEDOT in mediating
chemical transformations of alcohols traditionally initiated by Lewis and=or protic
acids. Subsequently, we discovered that when alcohols are treated with PEDOT in
acetonitrile at reflux, a Ritter reaction occurs between the alcohol and acetonitrile
to furnish the corresponding acetamide.
The Ritter reaction (Scheme 1)[11,12] generates amides=amide-protected amines
from a carbocation, a nitrile, and lactams in cases where reaction occurs intramole-
cularly. The currently accepted mechanism involves nucleophilic attack of the cation
by the nitrile with subsequent nucleophilic attack of the intermediate nitrilium ion
by the conjugate base of the mediating acid to furnish an imidate.[13] The resulting
imidate is then hydrolyzed to give the amide product. Substrates for the Ritter
reaction have included alcohols, halides, and alkenes, with the concurrent treatment
of the substrate with an appropriate Lewis or protic acid, typically employing a
strongly ionizing solvent such as acetic acid. The use of catalysts (Lewis and protic
acids) to mediate Ritter reactions was recently reviewed.[14] Recently, it has been

3226
J. G. D’ANGELO ET AL.
Scheme 1. General Ritter reaction.
shown that silica[15,16] or polymer-supported[17] acids as well as ionic liquids[18] are
effective at mediating these reactions as well.
DISCUSSION
To simultaneously explore the scope of our PEDOT protocol and compare the
results to more traditional conditions, we separately treated the alcohols in this study
with Amberlyst-15, H2SO4, and PEDOT in acetonitrile at reflux as described in
Scheme 2 and Table 1. The Amberlyst and sulfuric acid–mediated Ritter reactions
generated amides 4 in good yields in cases where the carbocation intermediate was
stabilized (Table 1, entries 1–4, 6, and 7). In all cases studied, sulfuric acid–mediated
reactions had faster rates of conversion then the Amberlyst-mediated reactions. The
substrate cyclohexanol (3j) was converted in poor yields to amide 4j, with the major
by-product being cyclohexene, as observed by gas chromatography–mass spec-
trometry (GCMS). It is reasonable to conclude that in cases of alcohols that have
b-hydrogens available for elimination the appropriate alkene is the major by-product,
although not isolated in the current study because of their low boiling points (Table 1,
entries 5, 6, 8, and 9). In alcohol substrates where elimination is not possible, the
yields increase significantly. Additionally, with primary alcohols 3a, 3h, and 3i
observed by-products were the acylated alcohols, benzyl acetate, and iso-butyl acetate
and butyl acetate, respectively, in reactions with H2SO4.
The PEDOT-mediated Ritter reactions provide greater yields of amides 4 in
each case where the amide was observed with PEDOT (Table 1, entries 2, 3, and
7). Interestingly, the reactivity of PEDOT seems orthogonal to the traditional Ritter
conditions for the tertiary alcohols. For instance, triphenylmethanol (3d) provides
trace quantities of amide 4d found by GCMS, along with the reduction product,
triphenyl methane, and small amounts of what appears to be a product consistent
with spectral data for 9-phenylfluorene. Mediation by Amberlyst and H2SO4
provided yields of 96 and 87% of the desired amide 4d, respectively. These differences
suggest that the alcohol -OH may need to coordinate with the PEDOT in order to
react. This accounts for the reduced activity with PEDOT because the traditional
acids liberate an electrophilic Hþ, whereas interactions with PEDOT must overcome
a steric approach to the positively charged polymer backbone to react. We are parti-
cularly excited about the 1-adamantanol case (Table 1, entry 7), which furnished
Scheme 2. General Ritter reaction performed.

POLYMER-MEDIATED RITTER REACTIONS
3227
Table 1. Summary of results with H2SO4, Amberlyst, and PEDOT-mediated
reactions of alcohols with acetonitrile
Entry
1
Alcohol 3
Initiator
Isolated yield of 4 (%)
Amberlyst
H2SO4
PEDOT
12
63
<1
2
Amberlyst
H2SO4
PEDOT
40
48
70
3
4
5
6
7
Amberlyst
H2SO4
PEDOT
70
85
91
Amberlyst
H2SO4
PEDOT
96
87
<1
Amberlyst
H2SO4
PEDOT
<1
14
Not detected
Amberlyst
H2SO4
PEDOT
44
66
Not detected
Amberlyst
H2SO4
PEDOT
48
53
83
8
9
Amberlyst
H2SO4
PEDOT
Not detected
Not detected
Not detected
Amberlyst
H2SO4
PEDOT
<1
<1
Not detected
10
Amberlyst
H2SO4
PEDOT
<1
18
Not detected
amide 4g in very good yield (>80%) with PEDOT and more modest 48 and 53% yields
with Amberlyst and H2SO4, respectively. We found that this reaction proceeded far
more slowly than all of the others with PEDOT, taking ꢂ32 h to reach a point of
no further consumption of alcohol by GCMS with an isolated yield of 83%. This
longer reaction time is consistent with the premise that sterics may hinder the
approach of the alcohol to the polymer, further supporting this mode of reactivity
over one that involves Hþ. Secondary alcohols 3e and 3j suffered from poor reactivity
with Amberlyst and H2SO4 and no observed reactivity with PEDOT (Table 1, entries

3228
J. G. D’ANGELO ET AL.
5 and 10). Of note is the poor reactivity of benzyl alcohol (3a) compared to
1-naphthalene methanol (3b) with PEDOT. In the case of 1-naphthalene methanol
(Table 1, entry 2) nearly all of the alcohol was consumed in the reaction with PEDOT
after ꢂ4 h, furnishing, after purification, the desired amide in 70% isolated yield. This
observed reactivity of PEDOT is consistent with previous reports where Friedel–
Crafts reactions with 1-naphthalene methanol proceeded better than benzyl alcohol
in benzene at reflux.[3] It is possible that the greater conversion observed for the
naphthyl system compared with the benzyl system, when using PEDOT, may be
due to the naphtyl system interacting more favorably with the PEDOT than benzyl
alcohol or trityl alcohol. The case of diphenylmethanol (Table 1, entry 3) was the
most efficient PEDOT-mediated reaction. After only 3 h, all of the starting material
was completely consumed by GCMS, giving rise to a single product that corre-
sponded to amide 4c in 91% isolated yield after purification.
We next investigated if this reaction could be performed with more complex
nitriles in a nonnitrile solvent (Scheme 3). After a survey of solvents, we identified
nitromethane as a suitable solvent for this purpose. Again, as with acetonitrile, we
compared the results obtained using PEDOT with a more traditional initiator, sulfu-
ric acid (Table 2). Although the PEDOT conditions are unoptimized, we demonstrate
here that PEDOT can be used as a mediator in a Ritter reaction between alcohols and
nitriles in nonnitrile solvents. We were surprised to find the oxidation product, 8,
become the major product in the 2.0 eq. case (Table 2, entry 2). Using 5 equivalents
of benzonitrile, the major product shifts to the desired amide 6, though the yield
(22%) is far inferior to that from H2SO4 (88%). It is unclear at this time whether
the increased equivalence of nitrile in this case (Table 2, entry 4 vs 2) is somehow che-
mically responsible for the decrease in yield of 8. Previous studies showed oxidation to
be a minor pathway.[2] The source of the oxidation by-products of PEDOT reactions
with alcohols remains unknown, but is interesting that polypyrrole-based heteropoly
acid catalysts have been used for the oxidation of alcohols.[9] It is also noteworthy
that the reaction with PEDOT yielded significantly less hydrolysis product of the
nitrile to the primary amide, compared to H2SO4, as would be expected, which further
emphasizes the chemoselectivity of PEDOT.
In an attempt to demonstrate the selectivity of PEDOT for alcohols and inves-
tigate the mechanism, we, in separate reactions, also attempted a reaction between
styrene and benzyl chloride with PEDOT in refluxing acetonitrile. In both cases,
after 2 h, no reaction was observed by GCMS. Based on our experience from moni-
toring our reactions, if the reaction were going to furnish product, 2 h is enough time
to generate detectable product. Furthermore, PEDOT appears to preferentially react
with alcohols in the presence of alkenes, as seen when we attempted the tetrahydro-
pyranylation of 1-naphthalene methanol using PEDOT in benzene along with
3,4-dihydro-2H pyran, under reflux. The major products of this chemical reaction
were found by GC=MS to be di-1-naphthylenemethyl ether and the Friedel–Crafts
Scheme 3. Stoichiometric Ritter reaction performed.

POLYMER-MEDIATED RITTER REACTIONS
3229
Table 2. Stoichiometric Ritter reactions between diphenyl methanol and benzonitrile mediated by
PEDOT and H2SO4
Isolated yield (% based on 3c)
Isolated yield (% based on 5)
Equivalence
of 5
Entry
Initiator
3c
6
8
9
5
7
1
2
3
4
2
2
5
5
H2SO4
PEDOT
H2SO4
ND
ND
ND
ND
73
8
3a
<1a
8
ND
20b
18
5b
46
12
38
6
21b
ND
12b
88
22
ND
6
PEDOT
a8 and 9 were not separated during purification. Ratios as determined by 1H NMR integration are 4:1 of
8/9 (% calculated).
b5 and 8 were obtained as an inseparable mixture. Ratios as determined by 1H NMR integration are 2:1
of 5/8 for entries 2 and 4 (% calculated).
Note. ND, not detected.
alkylation product between the putative 1-naphthyl cation and benzene. By contrast,
when using Amberlite IRE-50(H) as the initiator, the major product was the desired
tetrahydropyranyl ether according to GCMS, similar to polyaniline salts loaded with
H2SO4 and HNO3.[5] Thus, PEDOT appeared to prefer to react with the naphthalene
methanol, rather than the 3,4-dihydro-2H pyran, whereas the Amberlite IRE-50(H)
preferred to react with the pyran. These results demonstrate that PEDOT reacts at
least selectively and perhaps specifically with alcohols and not halides or alkenes.
In another reaction, we reacted a 1:1 mixture of cyclohexanol and 1-naphthalene
methanol in acetonitrile. In this case, only N-1-naphthalenemethyl acetamide and
unreacted cyclohexanol along with very small amounts of unreacted 1-naphthalene-
methanol were observed. This result is important because it insinuates a selectivity of
PEDOT for aromatic over aliphatic alcohols under these reaction conditions,
which may be taken advantage of in total synthesis by eliminating the need for pro-
tection and deprotection steps. We are currently exploring the selectivity to include
developing more complex systems, including diols, to further evaluate this potential
selectivity.
EXPERIMENTAL
Example of Method A: Ritter Reactions Mediated by Sulfuric Acid
with Acetonitrile as Solvent
Sulfuric acid (0.80 mL, 15.0 mmol) was added dropwise to a parallel reactor
vial containing diphenylmethanol (1.00 g, 5.43 mmol) and acetonitrile (20.0 mL,
383 mmol). The reaction was stirred at reflux until the alcohol was consumed (mon-
itored by GCMS) and then quenched with sodium bicarbonate (saturated, 25 mL).
The resulting mixture was extracted with ethyl acetate (3 ꢃ 15 mL) and the combined
organics were washed with brine (saturated, 18 mL), dried over magnesium sulfate,
filtered, and concentrated in vacuo to give the crude reaction products, which were
purified by radial chromatography to give N-benzhydrylacetamide (4c) as a white
solid (1.02 g, 85%).

3230
J. G. D’ANGELO ET AL.
Example of Method B: Ritter Reactions Mediated by Amberlyst-15
with Acetonitrile as Solvent
Amberlyst-15 hydrogen form (1.81 g) was added to a parallel reactor vial
containing diphenylmethanol (1.00 g, 5.43 mmol) and acetonitrile (20.0 mL). The
reaction was stirred at reflux for 72 h and then filtered to remove Amberlyst. The
filtrate was diluted with 25 mL water and quenched with sodium bicarbonate
(saturated, 2 mL). The aqueous was then extracted with ethyl acetate (3 ꢃ 15 mL)
and the combined organics were washed with brine (saturated, 18 mL), dried over
magnesium sulfate, filtered, and concentrated in vacuo to give N-benzhydrylaceta-
mide (4c) as a white solid (0.85 g, 70%).
General Method C: Ritter Reactions Mediated by PEDOT with
Acetonitrile as Solvent
PEDOT (200 mg) was added to a round-bottomed flask containing acetonitrile
(25 mL) and the alcohol (1.00 mmol). The reaction was stirred at reflux until the
alcohol was consumed (monitored by GCMS), filtered, and concentrated in vacuo
to give the crude reaction products, which were purified by flash chromatography
when warranted.
General Method D: Stoichiometric Ritter Reactions Mediated by
Sulfuric Acid with Nitromethane as Solvent
Sulfuric acid (0.60 mL, 10.9 mmol) was added to a parallel reactor vial contain-
ing diphenylmethanol (1.00 g, 5.43 mmol), nitromethane (20 mL), and benzonitrile
(variable). The reaction was stirred at 86 ꢁC for 3 h until the limiting reagent was
consumed (monitored by GCMS). Upon cooling to rt, the reaction was quenched
with sodium bicarbonate (saturated, 20 mL). The resulting mixture was extracted
with ethyl acetate (3 ꢃ 20 mL) and the combined organics were washed with brine
(50%, 20 mL), dried over magnesium sulfate, filtered, and concentrated in vacuo to
give the crude reaction products. The off-white solid was purified by flash chromato-
graphy (2% ethyl acetate=hexanes to 100% ethyl acetate) to give the products.
General Method E: Stoichiometric Ritter Reactions Mediated by
PEDOT with Nitromethane as Solvent
PEDOT (150 mg) was added to a parallel reactor vial containing diphenyl-
methanol (138 mg, 0.75 mmol), nitromethane (8 mL), and benzonitrile (variable).
The reaction was stirred at reflux for 3 h until the limiting reagent was consumed
(monitored by GCMS). Upon cooling to rt, the reaction was filtered and washed with
dichloromethane to recover PEDOT, and then the filtrate was filtered and washed
with dichloromethane through Celite. The filtrate was concentrated in vacuo to give
the crude reaction products. The residue was purified by flash chromatography (2%
ethyl acetate=hexanes to 100% ethyl acetate) to give the products.

POLYMER-MEDIATED RITTER REACTIONS
3231
N-Benzhydrylacetamide (4c)
1HNMR (300 MHz, CDCl3): d 7.36–7.20 (m, 10H), 6.32 (br d, J ¼ 8.1 Hz, 1H),
6.23 (d, J ¼ 8.1 Hz, 1H), 2.01 (s, 3H); 13CNMR (75 MHz, CDCl3): d 169.4, 141.6,
128.9, 127.4, 127.5, 57.0, 23.2; MS (EI): m=z ¼ 225 (Mþ); cf. spectrum reported.[19]
SUPPORTING INFORMATION
1
Full experimental details with H and 13C NMR reports can be found via the
Supplementary Content section of this article’s Web page.
CONCLUSIONS AND FUTURE WORK
We have shown that the conducting polymer PEDOT mediates a Ritter reaction
between activated alcohols and nitriles. Although the mechanism by which PEDOT
mediates this reaction is still under investigation, the work herein and ongoing
suggests that it is behaving as a chemoselective Lewis acid that prefers to react with
alcohols. Moreover, with the unreactivity of styrene in mind, coupled with the result
of the experiment with the tetrahydropyranylation, it appears that the reaction is not
initiated by putative small quantities of trifilic acid embedded in or adsorbed by the
polymer that could have been produced during the polymerization. For the same rea-
son, we do not think that we are generating trifilic acid during the reaction and there-
fore argue that the PEDOT is behaving as a Lewis acid. This hypothesis is further
supported by the sluggish reactions with 1-adamantanol and virtual lack of reactivity
with triphenyl methanol, which is likely a steric effect. If triflic acid were somehow
present, Hþ would be the reactive unit and there would be little to no influence of
steric hindrance around the alcohol OH.
Given the number of natural and pharmaceutical products that contain an
amide or amine moiety, further exploration of the PEDOT-mediated Ritter reactions
is warranted. Using a survey of nitriles in nonnitrile solvents we hope to generate a
method that converts an activated alcohol chemoselectively in the presence of other
moieties such as unprotected alcohols, alkenes, and halides to amides=amide-
protected amines. Additionally, further exploration of PEDOT’s ability to mediate
other reactions employing alcohol substrates is under way. We also have begun
studies that examine the polymer before and after the reaction. We anticipate that this
will lead to the generation of lower cost reactive conducting polymers.
REFERENCES
1. Morvant, M. C.; Reynolds, J. R. Synthetic Metals 1998, 92, 57–61.
2. D’Angelo, J. G.; Sawyer, R.; Kumar, A.; Onorato, A.; McCluskey, C.; Delude, C.;
Vollenweider, L.; Reyes, N.; French, R.; Warner, S.; Chou, J.; Stenzel, J.; Sotzing, G.;
Smith, M. B. J. Poly. Sci: Part A: Polym. Chem. 2007, 45, 2328–2333.
3. D’Angelo, J. G.; Kumar, A.; Onorato, A.; Delude, C. J.; Sotzing, G. A.; Smith, M. B.
Polymer. 2007, 48, 4328–4336.
4. Onorato, A.; Pavlik, C.; Invernale, M. A.; Berghorn, I. D.; Sotzing, G. A.; Morton, M. D.;
Smith, M. B. Carbohydr. Res. 2011, 346, 1662–1670.
5. Palaniappan, S.; Amamath, C. A. New J. Chem. 2002, 26, 1671–1674.

3232
J. G. D’ANGELO ET AL.
6. Palaniappan, S.; Chandra-Shekhar, R. Polym. Adv. Technol. 2004, 15, 140–143.
7. Palaniappan, S.; Narender, P.; Saravan, C.; Jayathirtha-Rao, V. Synth. Lett. 2003, 12,
1793–1796.
8. Huang, S. W.; Neoh, K. G.; Shih, C. W.; Lim, D. S.; Kang, E. T.; Han, H. S.; Tan, K. L.
Synth. Metals 1998, 96, 117–122.
9. Turek, W.; Lapkowski, M.; Debiec, J.; Krowiak, A. Appl. Surf. Sci. 2005, 252, 847–852.
10. Palaniappan, S.; John, A. Curr. Org. Chem. 2008, 12, 98–117.
11. Ritter, J. J.; Minieri, P. P. J. Am. Chem. Soc. 1948, 70, 4045–4048.
12. Ritter, J. J.; Kalish, J. J. Am. Chem. Soc. 1948, 70, 4048–4050.
´
13. Kurti, L.; Czako, B. Strategic Applications of Named Reactions in Organic Synthesis;
¨
Elsevier Academic Press: Burlington, MA, 2005; pp. 382–383.
´
14. Guerinot, A.; Reymond, S.; Cossy, J. Eur. J. Org. Chem. 2012, 2012, 19–28.
15. Tamaddon, F.; Tavakoli, F. J. Mol. Catal. A: Chem. 2011, 337, 52–55.
16. Yadav, J. S.; Subba-Reddy, B. V.; Pandurangam, T.; Jayasudan-Reddy, Y.; Gupta, M. K.
Catal. Commun. 2008, 9, 1297–1301.
17. Lakouraj, M. M.; Makhtary, M. Montash. Chem. 2009, 140, 53–56.
18. Kalhambkar, R. G.; Waters, S. N.; Laali, K. K. Tetrahedron Lett. 2011, 52, 867–871.
19. Katkar, K. V.; Chaudhari, P. S.; Akamanchi, K. G. Green Chem. 2011, 13, 835–838.