Base-Promoted Amidation and Esterification of Imidazolium Salts via Acyl C-C bond Cleavage: Access to Aromatic Amides and Esters

Article abstract of DOI:10.1021/acs.joc.8b02567

Imidazolium salts have been effectively employed as suitable acyl transfer agents in amidation and esterification in organic synthesis. The weak acyl C(O)-C imidazolium bond was exploited to generate acyl electrophiles, which further react with amines and alcohols to afford amides and esters. The broad substrate scope of anilines and benzylic amines and base-promoted conditions are the benefits of this route. Interestingly, phenol, benzylic alcohols, and a biologically active alcohol can also be subjected to esterification under the optimized conditions.

Full text of DOI:10.1021/acs.joc.8b02567

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Article
Base-Promoted Amidation and Esterification of Imidazolium Salts via
Acyl C-C bond Cleavage: An Access to Aromatic Amides and Esters
Shanmugam Karthik, Karthick Muthuvel, and Thirumanavelan Gandhi
J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.joc.8b02567 • Publication Date (Web): 25 Dec 2018
Downloaded from http://pubs.acs.org on December 25, 2018
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Base-Promoted Amidation and Esterification of Imidazolium Salts via Acyl
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C-C bond Cleavage: An Access to Aromatic Amides and Esters
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Shanmugam Karthika, Karthick Muthuvela and Thirumanavelan Gandhi*a
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Department of Chemistry, School of Advanced Sciences, VIT University, Vellore, Tamil Nadu
- 632014, India.
E-mail: velan.g@vit.ac.in
Me
O
O
R2
R2
O
N
R2-NH2
R2-OH
N
O
H
N
R1
(37 examples)
R1
(25 examples)
I
Me
R1
(stable acyl source - isolated as solids)
R1 = Aryl/Hetero-aryl
R2 = Aryl/Ar-alkyl/Alkyl
Abstract. Imidazolium salts are effectively employed as a suitable acyl transfer agent in
amidation and esterification in organic synthesis. The weak acyl C(O)-C imidazolium bond
was exploited to generate acyl electrophiles which on further reacts with amines and alcohols
to afford amides and esters. The broad substrate scope of anilines and benzylic amines, and
base-promoted conditions are the benefits of this route. Interestingly, phenol, benzylic
alcohols, and biologically active alcohol can also be subjected to esterification under the
optimized conditions.
Introduction. Amides are common and highly notable linkage prevalent in nature as a
backbone of proteins.1 The high stability of amides favors them as a key constituent in
biological compounds, active pharmaceutical agents, and agrochemicals.2 Their profound
resistance to hydrolysis makes them ubiquitous in polymers3 and functional materials.4
Conventionally, amides are accessible by direct condensation of carboxylic acids and amines.
Alternatively, there are numerous non-classical methods in generating amides by utilizing
stoichiometric coupling reagents,5 carboxylic acid surrogates,6 amine surrogates,7 alkenes or
alkynes aminocarbonylation,8 cross-dehydrogenating coupling of aldehydes with amines by
visible light photoredox catalysis9 and NHC catalyzed direct oxidative amidation of
aldehydes.10 The split and union of the C-C bond are fundamental steps witnessed and
manipulated by the chemists with great fervor, due to its potential applicability both in
academics and industry.11 Widely, the C-C bond cleavages
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Scheme 1 a) Synthesis of Esters and Amides a-c (previous work) b) Imidazolium Salts as a
Stable Acyl Transfer Agent in Amidation and Esterification d (this work).
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CH3
RCOSC2H5
CH3
N
(R = C6H5)
O
N
Li
i)
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N
O
RCONH-n-Pr
N
R
-78 °C, THF
N
a)
X
(R = C6H5/c-C6H11)
CH3
Okamoto's
work
R
ii)
CH3-X
R = C6H5; X = I
R = n-hexyl; X = I
R = c-C6H11; X = CH3SO3O
RCOOH
(R = C6H5)
RCOOCH3
(R = C6H5/n-hexyl)
O
N
N
DBU, THF, rt
I
N
O
Ph
O
NH2
Studer's
work
t-Bu
t-Bu
NH2
OH
b)
Ph
H
O
O
t-Bu
t-Bu
O
CyNH2
MeOH
O
P
Cy
O
O
Ar
N
tBu
tBu
H
N
N
O
ZnAr2, CH2Cl2
40 °C, 2 h
Ar
(1 example)
c)
Ogoshi's
work
N
N
O
OTf
OTf
Ar
OMe
(1 example)
O
R2
O
Cl
R2-NH2
N
H
R1
O
N
R1
i)
(37 examples)
O
N
N
This work
d)
N
ii)
CH3I
R2
O
I
R2-OH
R1
(stable acyl source-isolated
as solids)
R1
(25 examples)
R1 = Aryl/Hetero-aryl
R2 = Aryl/Ar-alkyl/Alkyl
were achieved in strained and unstrained ring systems by employing transition metal
catalysts.12 In the myriad of C-C bond cleavage, acyl C(O)-C bond cleavage attract great
attention in organic synthesis owing to its simple and convenient transformation towards useful
derivatives.13 Recently, the acyl group revealed to be a promising electrophile which reacts
efficiently with amines catalyzed by acid, base, oxidizing agent and transition metals to afford
amides.14 Strategically, functional groups are converted into their salts and employed as a
suitable transfer agent for various organic transformations. This methodology found to be very
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attractive owing to their facile leaving ability, air, and thermal stability. In this context,
ammonium salts especially benzylic were successfully utilized in Buchwald-Hartwig, Kumada,
Negishi, and Suzuki coupling reactions.15 Similarly, diazonium,16 iodonium,17 phosphonium,18
pyridinium,19 silanolate20 and sulphonium21 salts play a vital role in offering necessary
electrophiles. From the acylation viewpoint, azoles such as pyrrole,22 pyrazole,23 triazole,24
and imidazoles25 have been explored both in metal and metal-free conditions via a C(O)-N
cleavage. Very recently, Beutner and co-workers elegantly utilized in situ generated N-acyl
imidazolium salts for challenging amide bond formations via C(O)-N cleavage.26 However,
the precedence of using C-acyl imidazolium salts as a bench stable acylating agent via C(O)-C
cleavage is scarce.
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Okamoto research group revealed the synthesis of C-acyl imidazolium salts by the
reaction of (1-methyl-1H-imidazol-2-yl)lithium with amide to yield C-acyl imidazoles
followed by quaternization with methyl iodide or dimethyl sulphate (Scheme 1a).27 Studer and
co-workers have disclosed the oxidation of aldehydes to esters from in situ generated acyl
triazolium and imidazolium salts (Scheme 1b).28 The same group has reported the utilization
of α,β-unsaturated acyl azolium salts in the synthesis of pyranones and pyridinones.29 In related
research, Ogoshi group has effectively utilized the imidazolium carbene to generate carboxylic
phosphinic mixed anhydride from CO2, which further effected to amide and ester via acyl
imidazolium intermediate (Scheme 1c).30 Unfortunately, all the reported methods suffer from
certain shortcomings. Thus, we envisioned a straightforward, mild base-promoted, amidation
and esterification of stable acyl imidazolium salts via C(O)-C bond cleavage (Scheme 1d). The
synthesis of C-acyl imidazoles was accomplished by following Bildstein31 and Meggers32
literatures and it avoids the usage of organolithium reagents.29 The novelty of this methodology
resides on;
i) Evading air and moisture sensitive carbenes as a catalyst,33 and non-green, expensive
oxidants34 and organometallic reagents for the coupling reaction.27,35
ii) Precluding multistep process.36
iii) Acyl imidazolium salts are inexpensive, and they can be prepared easily.
iv) The wide range of substrate scope especially aromatic, benzylic amines and aromatic,
benzylic alcohols can be studied.
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Results and Discussion
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We commenced our exploration with 2-benzoyl-1,3-dimethyl-1H-imidazol-3-ium iodide 1 (1.5
equiv) as an electrophilic acyl source, 4-butylaniline 2 (1.0 equiv) as a coupling partner, K2CO3
(1.5 equiv) as a base in CH3CN (1 mL) at room temperature for 18 h (Table 1). This resulted
in the formation of N-(4-butylphenyl)benzamide 3ad in 20% yield (entry 1). Replacement of
TBAB and DMF in place of K2CO3 and CH3CN respectively resulted in 15 and 25% yield of
3ad (entries 2 and 3). The elevation of temperature from rt to 80 °C (14 h) improves the yield
of 3ad (65%) (entry 4). Screening of bases NaOH, Cs2CO3 and Et3N were not promising
(entries 5-7), and K2CO3 was found to be the best.
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Table 1. Optimization of the Reaction with Acylimidazolium Salta
O
NH2
O
base/solvent
N
I
N
H
Me
+
temperature/time
N
Me
3ad
1a
2a
Entry Base/additive Solvent
Temp
(°C)
Yieldb
(%)
1
K2CO3
TBAB
K2CO3
K2CO3
NaOH
Cs2CO3
Et3N
CH3CN
CH3CN
DMF
rt
20c
15c
25c
65
5
2
rt
3
rt
4
DMF
DMF
80
80
80
80
100
80
80
80
80
5
6
DMF
50
31
67d
33
8
7
DMF
8
K2CO3
-
DMF
9
DMF
10
11
12
K2CO3
K2CO3
K2CO3
ethanol
toluene
DMF
-
34e
Reaction conditions: a1a (1.5 equiv), 2a (1.0 equiv), K2CO3 (1.5 equiv), DMF (1 mL), 80 °C,
b
c
d
e
14 h (entries 4-7). isolated yields. rt 18 h, 100 °C, 18 h, with 1a (1.0 equiv). TBAB:
Tetrabutylammonium bromide; DMF: N, N-Dimethylformamide.
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Furthermore, the increase in reaction temperature and time to 100 °C and 18 h respectively
shown a slight improvement in the yield of 3ad (entry 8). Notably, the absence of base reduces
the yield of 3ad to 33% (entry 9). Replacing the solvent DMF with ethanol and toluene hamper
the reaction (entries 10 and 11). With 1a (1 equiv) the yield of 3ad drops to 34%. Thus, the
optimized reaction condition for base promoted amidation of acyl imidazolium salt is 1 1.5
equiv, 2 1 equiv, K2CO3 1.5 equiv, in DMF (1 mL) at 80 °C for 14 h. Encouraged by the
optimized conditions, we explored the substrate scope of amidation reaction with various
amines (Table 2). Aniline possessing alkyl substituents at meta 3ab and para 3ac sites afforded
better yields of amidation product as compared with unsubstituted 3aa. Predictably, sterically
hindered 3ae and multi-substituted aniline 3af results in poor yield. Methoxy group positioned
at meta 3ag and para 3ah showed an improved yield of 58% and 67% respectively.
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Table 2. Substrate Scope of Aromatic and Aliphatic Aminesa,b
O
O
R2
K2CO3, DMF
80 oC
N
I
N
R2 NH2
+
H
N
R1
R1
3
2
1
Me
O
O
O
O
N
Me
N
H
N
N
Me
H
H
H
3ad, 65%
3aa, 52%
O
3ac, 53%
3ab, 51%
Me
Me
O
O
O
O
N
H
Me
N
H
Me
N
H
O
N
H
Me
Me
3ag, 58%
3ah, 67%
3ae, 10%
3af, 26%
Br
NO2
O
Me
O
O
O
N
H
N
H
Me
N
H
N
H
Me
3aj, ND
O
3ak, 92%
O
3al, 30%
O
3ai, 19%
O
F
N
H
Me
N
H
Me
N
H
Me
N
H
Me
S
F
NO2
3ap, 26%
3ao, 35%
O
3am, 31%
O
3an, 33%
O
N
O
N
N
H
Me
N
O
MeO
3ar, 58%
3as, 60%
3at, 50%
3aq, 20%
Reaction conditions: a1 (1.5 equiv), 2 (1.0 equiv), K2CO3 (1.5 equiv), DMF (1 mL), 80 °C, 14
b
h. Isolated yields.
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Electron-withdrawing 4-Br 3ai exhibited reduced yield (19%) whereas 4-NO2 3aj derivate was
not detected. Strikingly, aliphatic amines afforded the maximum yield of 3ak (92%). Next,
we turned our attention to various substituted acyl imidazolium salts. On the contrary to the
above observation, methyl substrate 3al displayed lower in yield (30%) and electron-
withdrawing substrates 3am-3ao resulted in slightly improved yield (31%-35%). Heterocyclic
thiophenyl substrate moderate the yield of 3ap (26%). Electron rich -OCH3 group at para
position of acyl imidazolium salts further decreases the yield of 3aq to 20%. Notably, cyclic
secondary amines such as pyrrolidine 3ar (58%), piperidine 3as (60%) and morpholine 3at
(50%) reacts efficiently to afford the amides. Then, we examined the reactivity of ar-alkyl
amines in the amidation reaction (Table 3). Benzylamine 3au and its electron-donating
congeners 3av & 3aw offers maximum yields (80%-90%). Halogen substituents 4-F 3ax and
4-Cl 3ay on the phenylic group reduce the yields (75%-77%). α-Methylbenzyl amine and 2-
picolylamine reacted smoothly to offer 3az and 3ba in 79% and 65% yields respectively. The
reaction proceeded cleanly with phenethyl amine derivatives 3ca (91%) and 3da (93%).
Substituted acyl imidazolium salts such as 3-Me, 4-Me and 4-F tolerate the reaction conditions
to offer amidation product 3ea, 3fa, and 3ga in 78%, 75%, and 81% yield respectively.
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Table 3. Substrate Scope of Benzylic amines
O
O
R2
K2CO3, DMF
80 oC
N
I
N
R2 NH2
+
H
N
R1
R1
3
2
1
Me
Me
F
O
O
O
O
N
H
O
N
N
H
N
H
H
3ax, 75%a
3aw, 90%a
3au, 80%a
Cl
3av,82%a
N
O
O
O
O
N
H
N
H
N
H
Me
N
H
3ay, 77%a
3ba, 65%a
3ca, 91%a
3az 79%a
O
N
H
O
O
O
Me
N
H
N
H
N
H
Me
F
OCH3
3ga, 81%b
3fa, 75%b
3da, 93%a
3ea, 78%b
b
aThe reactions were executed at 80 °C for 1 h. The reactions were executed at 80 °C for 3 h.
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Esters constitutes major subunits prevalent in natural products, pharmaceuticals,
polymers and functional materials.37 The well-established synthetic routes to prepare ester
involve acid chlorides,38 acids39 and acid anhydrides40 with alcohols. Besides, esters were
accessible from amides,41 methyl ketones,42 nitriles,43 allylic group,44 ethers45 and amino
acids.46 The synthesis of esters via acyl transfer from stable imidazolium salts is in its infancy.
Usually, this approach avoids consumption of concentrated acids, ionic liquids, harmful and
expensive metal salts. We applied our optimized reaction conditions in synthesizing the esters
using acyl imidazolium salts 1a with alcohol 4a in the presence of K2CO3 as a base at 80 °C,
for 14 h (Table 4). To our delight, phenols undergo esterification smoothly to afford 5aa in
25% of yield. Phenols with ortho, meta, and para-methyl substituents gave the corresponding
esters 5ab-5ad in 26%-28% yields. 4-Chlorophenol and 2-naphthol diminish the yield of 5ae
and 5af to 19% and 13% respectively. Conversely, functionalized acyl imidazolium salts
possessing 3-Me, 4-Me and 4-F were all compatible, give 5ag, 5ah, and 5ai in similar yield
(18%-25%).
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Table 4. Substrate Scope of Phenolsa,b
O
OH
O
N
I
K2CO3, DMF
O
+
R2
80 o
C
N
R1
R1
R2
5
4
1
O
O
O
O
O
O
Me
Me
5ac 26%
5aa, 25%
5ab, 26%
Cl
Me
O
O
O
O
O
O
5af, 13%
5ae, 19%
5ad, 28%
O
O
O
O
O
O
Me
F
Me
5ag, 20%
5ah, 18%
5ai, 25%
Reaction conditions: a1 (1.5 equiv), 4 (1.0 equiv), K2CO3 (1.5 equiv), DMF, (1 mL), 80 °C,
14 h. bIsolated yields.
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Furthermore, the applicability of this protocol was realized for benzylic alcohol substrates
(Table 5). Notably, simple benzylic alcohol 5aj, 4-Me 5ak, and 4-MeO 5al confer the esters
in improved yields of 70%-76%. Benzylic alcohols having halogen substituents such as 4-F,
4-Cl, 2,4-dichloro gave the desired products 5am, 5an, and 5ao respectively in good yields
(62%-65%). Evidently, highly electron-withdrawing -NO2 substituent at ortho and para
position deteriorates the yield of 5ap and 5aq in 53% and 49% respectively. Pertinently, 3-
pyridine 5ar, naphthyl 5as, diphenyl 5at and anthracenyl derivatives 5au result in low yield of
product (51%-67%). Acyl imidazolium derivative possessing 3-Me, 4-Me and 2-F react
amicably to yield 5av, 5aw, and 5ax (68%-65%). Biologically active cholesterol ester 5ay can
be synthesized in 10% of isolated yield by using this strategy.
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Table 5. Substrate Scope of Benzyl Alcohols and Cholesterol
R2
OH
O
O
N
I
K2CO3, DMF
80 oC
O
+
N
R1
R1
R2
5
1
4
Me
F
Me
O
O
O
O
O
O
O
O
O
5am, 65%a
NO2
5al, 76%a
5ak,72%a
Cl
5aj, 70%a
Cl
O
O
O
O
Cl
O
O
NO2
O
O
5an, 67%a
5ao, 62%a
5ap, 53%a
5aq, 49%a
N
O
O
O
O
O
O
5ar, 52%a
5as, 55%a
OMe
Me
5at, 67%a
Me
O
O
Me
Me
H
F
O
O
O
Me
H
O
H
H
R
O
5au, 51%a
5av, R = 3-CH3 , 68%b
5aw, R = 4-CH3, 65%b
5ax, 65%b
Bz
5ay, 10%c
b
aThe reactions were executed at 80 °C, 1 h. 80 °C for 3 h. c80 °C for 14 h.
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To get further insights into the reaction pathway selectivity studies were executed.
Intermolecular competition reaction between benzyl alcohol 4j and benzyl amine 2u with C-
benzoyl imidazolium iodide 1a was studied. It was found that 2u are more reactive as
compared to its alcoholic counterpart 4j to substantiate nucleophilic addition across acyl C-C
bond (Scheme 2a); The intermolecular competitive reaction between phenol 4a and aniline 2a
with 1a also revealed its innate nucleophilicity (Scheme 2b); The higher reactivity of aliphatic
amine 2k than aromatic amine 2a is elucidated by their intermolecular competition reaction
with 1a (Scheme 2c);
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Scheme 2. Control Experiments (a-d) and Scale-up (e) Studies
a) Intermolecular competition reaction of benzylic nucleophiles
OH
NH2
O
O
N
I
K2CO3, DMF
X
N
under optimized
conditons
3au
5aj
, X = NH
, X = O
3au 5aj
:
= 7:3
2u
1a
4j
b) Intermolecular competition reaction of aromatic nucleophiles
O
OH
NH2
O
X
N
I
K2CO3, DMF
N
under optimized
conditions
5aa
3aa
, X = O
, X = NH
5aa 3aa
:
= 1:9
4a
2a
1a
c) Intermolecular competition reaction of aliphatic and aromatic nucleophiles
O
O
NH2
K2CO3, DMF
NH2
R
N
N
H
under optimized
conditions
N
I
3ak 3aa
:
= 9:1
3ak
3aa
, R = butyl
, X = phenyl
2k
1a
2a
d) Selectivity of amines in amidation
O
NH
O
N
NH2
K2CO3, DMF
N
+
H
N
under optimized
conditions
N
H
I
7aa, 51%
6a
1a
(preferential reactivity of aliphatic amine vs indole)
e) Scale-up approach
O
O
R
N
K2CO3, DMF
under optimized
X
R-X
N
conditions
I
3ak,
3au
5aj,
R = butyl; X = NH, 80%,
, R = benzyl; X = NH, 69%
R = benzyl; X = OH, 53%
2k, 2u, 4j
(0.5 g each)
1a
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The compound possessing two different amine functionalities have been chosen such as 2-(1H-
indol-3-yl)ethan-1-amine 6a (scheme 2d) where selectively primary amidated product 7aa was
observed (51% yield). This is owing to the easy availability and high reactivity of aliphatic
primary amine group –(CH2CH2NH2) to couple with acyl electrophiles. But, in case of indole-
NH, the secondary amine is involved in extended conjugation with benzene ring to lowers its
reactivity with 1a. From these competition experiments, it is proved that these substrates (C-
acyl imidazolium salts) can be efficiently used in the synthetically advantageous level of
selectivity towards amines and alcohols. Besides, this optimized condition can be scaled-up
(Scheme 2e). Additionally, the 1a was used as an acylating agent for the substrate having
binucleophilic centers (ex: -NH2 and OH) to yield 8aa-11aa in 20%-56% (Scheme 3).
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Scheme 3. Acylation of Binucleophilic Centers
N
H
O
O
H2N
N
N
OH
OH
H
OH
O
O
N-(2-hydroxyphenyl)
O
11aa
, 56%
N
benzamide,
(1-benzoylpiperidin-4-yl)methyl
8aa,
N
benzoate,
20%
OH
O
O
I
1a
N
H
N
H
OH
OH
H2N
OH
N-(4-hydroxyphenyl)
10aa,
N-(2-hydroxyethyl)
benzamide,
48%
9aa,
benzamide,
49%
H2N
Intriguingly, these acyl imidazolium salt 1a can be efficiently used as an acyl source for the
reaction with carbon nucleophiles such as 1-methylindolin-2-one 12a to furnish (Z)-3-
(hydroxy(phenyl)methylene)-1-methylindolin-2-one 13aa in 61% of yields (Scheme 4). This
method offers a direct and straightforward way to acylate carbon nucleophiles. Further,
optimization of reaction conditions and substrate scope studies are in progress in our research
group.
Scheme 4. Acylation with Carbon Nucleophiles
OH
O
N
N
PdCl2(Xantphos) (5 mol%)
KOt-Bu (2.1 equiv.)
O
O
N
10
N
Dioxane, 80 °C, 16 h
CH3
CH3
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Recently, Szostak47 and Zeng48 group proposed a base-promoted pathway for transamidation
of amides via formation of tetrahedral transition state. Based on this observation a possible
reaction pathway is proposed for amidation and esterification of imidazolium salts (Scheme 5).
Initially, nucleophilic addition of amines or alcohols to the regio selectively activated acyl
imidazolium salts 1 in the presence of K2CO3 furnishes tetrahedral transitions state A. Further,
site-selective fissure of C(O)-C bond delivers amidation and esterification outputs. This
pathway is promoted thermodynamically by easy leaving ability and poor nucleophilic nature
of imidazolium unit as compared with participating amines or phenols.
Scheme 5. Proposed Mechanism for Acyl C-C bond Cleavage of Imidazolium Salts with
Nucleophiles
O
O
N
I
R2
K2CO3, DMF
Y
R2
Y
+
N
Y = NH2; R = aryl/ar-alkyl/butyl
Y = OH; R = aryl/ar-alkyl
R1
R1
3
1
2
N
K2CO3
Site-selective
H
R2
Y
Scission of C-C
bond
N
2
I
OH
(Confirmed by HRMS)
Addition
of nucleophile
N
YR2
N
I
R1
Formation of
tetrahedral
state
A
Conclusions
In conclusion, the feeble nature of C(O)-C bond of acyl imidazolium salts has been exploited
for the augmentation of a highly regioselective amidation and esterification of aryl, ar-alkyl
and alkyl amine and alcohols under base promoted conditions. This protocol reveals the
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benefits such as low-cost, simple in operation, wide range of substrate scopes of anilines,
benzylic amines, and butylamine. Fascinatingly, this procedure can be extended into
esterification of substituted phenols, benzylic alcohols. Selectivity studies deal with a
preferential attack of aliphatic amines and competition experiments discuss the high
nucleophilicity of nitrogen donor than oxygen.
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Experimental Section
General Experimental Information
Unless otherwise mentioned all the reactions were carried out in screw capped reaction tubes
(8 mL) under an inert atmosphere of nitrogen. Anhydrous solvents (THF, CHCl3) purchased
from commercial sources and used without further purification. Chemicals were purchased
from Sigma-Aldrich, Alfa Aesar, AVRA. Thin layer chromatography was done by using
market available TLC plates with eluents hexanes-ethyl acetate and chloroform wherever
1
required with monitoring the reaction under UV radiation. H NMR spectra were recorded on
Bruker spectrometer (400 MHz) and are reported in units ppm (parts per million) relative to
the signals for residual chloroform (7.26 ppm) and DMSO (2.54 ppm) in the deuterated solvent.
13C NMR spectra were recorded on Bruker spectrometer (100 MHz) and are reported in ppm
relative to deuterated chloroform (77.23 ppm) and DMSO (39.52 ppm) with tetramethyl silane
as an internal standard. Coupling constants (J) are reported in Hz; splitting patterns are
assigned s = singlet, d = doublet, t = triplet, q = quartet, br = broad signal. High-resolution
mass spectra (HRMS) were performed as EI analyzer mode.
General procedure for the synthesis of acyl imidazolium salts (1a-1g) with
characterization data
A 100 mL round bottom flask equipped with a stir bar was charged with 1-methylimidazole A
(500 mg, 1.0 equiv), DMAP (4 mg, 1 mol %), placed under a positive pressure of nitrogen.
Chloroform (10 mL) was added with stirring followed by addition of Et3N (1230 mg, 2 equiv)
at 0 °C was done. Benzoyl chloride (939 mg, 1.1 equiv) was added dropwise at 0 °C and the
reaction mixture was stirred for 12 h at room temperature. After the indicated time, the reaction
mixture was diluted with water (100 mL), extracted with chloroform (15 mL Χ 2) and
concentrated. The crude material was purified by column chromatography on silica gel with
chloroform or hexanes-ethyl acetate (70:30 v/v) as eluent, to yield (1-methyl-1H-imidazol-2-
yl)(phenyl)methanone (B) as pale-yellow oil. Then, B (0.5 g, 1 equiv) was taken in 2 mL of
Dioxane in a screw capped reaction tube of 15 mL capacity and CH3I (20 equiv) was added
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and the reaction mixture was heated at 70 °C, for 16 h. The precipitated solid was filtered and
washed with dioxane (3 mL), followed by hexanes (25 mL) to give the imidazolium benzoyl
derivatives 1a-1g.
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8
9
2-Benzoyl-1,3-dimethyl-1H-imidazol-3-ium iodide, 1a.27 Pale yellow solid, 0.77 mg, 88%
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of yield, m.p. 192-194 °C. H NMR (400 MHz, DMSO-d6) δ 8.03 (s, 2H), 7.95 (d, J = 8.0 Hz,
2H), 7.87 (t, J = 7.6 Hz, 1H), 7.69 (t, J = 7.6 Hz, 2H), 3.80 (s, 6H). 13C{1H} NMR (100 MHz,
DMSO-d6) δ 180.9, 138.9, 136.5, 135.1, 130.8, 130.0, 125.9, 37.9.
1,3-Dimethyl-2-(4-methylbenzoyl)-1H-imidazol-3-ium iodide, 1b. Pale brown solid,
1
0.675g, 79% of yield, m.p. 186-188 °C. H NMR (400 MHz, DMSO-d6) δ 8.01 (s, 2H), 7.86
(d, J = 8.4 Hz, 2H), 7.50 (d, J = 8.0 Hz, 2H), 3.79 (s, 6H), 2.46 (s, 3H). 13C{1H} NMR (100
MHz, DMSO-d6) δ 180.4, 147.9, 139.1, 132.6, 131.0, 130.7, 125.7, 37.7, 22.0. HRMS (ESI-
QTOF) m/z: [M - I]+ Calcd for C13H15N2O 215.1179; found 215.1171.
2-(2-Fluorobenzoyl)-1,3-dimethyl-1H-imidazol-3-ium iodide, 1c. Grey solid, 0.414 g, 49%
of yield, m.p. 150-152 °C. 1H NMR (400 MHz, DMSO-d6) δ 8.06 (s, 2H), 7.95-7.91 (m, 2H),
7.54-7.49 (m, 2H), 3.85 (s, 6H). 13C{1H} NMR (100 MHz, DMSO-d6) δ 176.7, 161.1 (d, 1JC-
F = 255.9 Hz), 138.6 (d, 3JC-F = 9.3 Hz), 132.5, 126.2 (d, 4JC-F = 3.2 Hz), 126.1, 124.0 (d, 3JC-F =
9.4 Hz), 117.7 (d, 2JC-F = 20.6 Hz), 37.8. 19F{1H} NMR (376 MHz, DMSO-d6 ) δ -113.9. HRMS
(ESI-QTOF) m/z: [M - I]+ Calcd for C12H12FN2O 219.0928; found 219.0923.
2-(4-Fluorobenzoyl)-1,3-dimethyl-1H-imidazol-3-ium iodide, 1d. Brown solid, 0.43 g, 51%
1
of yield, m.p. 195-197 °C. H NMR (400 MHz, DMSO-d6) δ 8.06-8.05 (m, 2H), 8.03 (s, 2H),
7.55-7.51 (m, 2H), 3.81 (s, 6H). 13C{1H} NMR (100 MHz, DMSO-d6) δ 179.5, 166.9 (d, 1JC-
F = 255.0 Hz), 138.6, 134.3 (d, 3JC-F = 10.1 Hz), 131.9 (d, 4JC-F = 2.7 Hz), 125.9, 117.3 (d, 2JC-F =
22.5 Hz), 37.9. 19F{1H} NMR (376 MHz, DMSO-d6) δ -100.8. HRMS (ESI-QTOF) m/z: [M
- I]+ Calcd for C12H12FN2O 219.0928; found 219.0922.
1,3-Dimethyl-2-(3-nitrobenzoyl)-1H-imidazol-3-ium iodide, 1e. Bright yellow solid,
0.523g, 65% of yield, m.p. 200-202 °C. (synthesis imidazolium salt was carried out in
acetonitrile instead of dioxane). 1H NMR (400 MHz, DMSO-d6) δ 8.06-8.05 (m, 2H), 8.35 (d,
J = 7.6 Hz, 1H), 8.08 (s, 2H), 7.96 (t, J = 8.0 Hz, 1H), 3.83 (s, 6H). 13C{1H} NMR (100 MHz,
DMSO-d6) δ 179.4, 148.5, 137.9, 136.7, 131.6, 129.8, 126.5, 124.9, 38.4. HRMS (ESI-QTOF)
m/z: [M - I]+ Calcd for C12H12N3O3 246.0873; found 246.0864.
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1,3-Dimethyl-2-(thiophene-2-carbonyl)-1H-imidazol-3-ium iodide, 1f. Pale yellow solid,
1
0.39 g, 46% of yield, m.p. 170-172 °C. H NMR (400 MHz, DMSO-d6) δ 8.50 (d, J = 4.4 Hz,
1H), 8.11-8.01 (m, 3H), 7.43 (t, J = 4.0 Hz, 1H), 3.86 (s, 6H). 13C{1H} NMR (100 MHz,
DMSO-d6) δ 172.0, 142.3, 140.8, 138.9, 130.6, 125.6, 37.5. HRMS (ESI-QTOF) m/z: [M -
I]+ Calcd for C10H11N2OS 207.0587; found 207.0580.
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2-(4-Methoxybenzoyl)-1,3-dimethyl-1H-imidazol-3-ium iodide, 1g.30 Brown solid, 0.55g,
1
66% of yield, m.p. 180-182 °C. H NMR (400 MHz, DMSO-d6) δ 7.99 (s, 2H), 7.94 (d, J =
8.0 Hz, 2H), 7.20 (d, J = 8.0 Hz, 2H), 3.93 (s, 3H), 3.79 (s, 6H). 13C{1H} NMR (100 MHz,
DMSO-d6) δ 178.8, 166.2, 139.5, 133.7, 127.7, 125.4, 115.6, 56.6, 37.4.
General Procedure for Amidation from Imidazolium Salts via C-C bond Cleavage with
Characterization Data
An oven-dried 8 mL vial equipped with a stir bar was charged with 2a (50 mg, 1 equiv), 1a
(264 mg, 1.5 equiv), potassium carbonate (111 mg, 1.5 equiv) in DMF (1 mL). The reaction
mixture was placed in a preheated oil bath at 80 °C and stirred for 14 h. After the indicated
time, the solvent was evaporated, and the crude material was purified by column
chromatography on silica gel with n-hexane-ethyl acetate or hexanes–diethyl ether as eluent,
to yield the title compound.
N-phenylbenzamide, 3aa.49 Pale yellow solid, 54 mg, 52% of yield (hexanes/diethyl ether,
1
90:10 v/v). H NMR (400 MHz, CDCl3) δ 7.79 (d, J = 7.2 Hz, 2H), 7.57 (d, J = 8.0 Hz, 2H),
7.46 (t, J = 7.6 Hz, 1H), 7.39 (t, J = 6.8 Hz, 2H), 7.28 (t, J = 8.0 Hz, 2H), 7.08 (t, J = 7.6 Hz,
1H). 13C{1H} NMR (100 MHz, CDCl3) δ 165.8, 137.9, 135.0, 131.8, 129.1, 128.8, 127.0,
124.6, 120.3.
N-(m-tolyl)benzamide, 3ab.50 Pale brown solid, 49 mg, 51% of yield (hexanes/diethyl ether,
1
90:10 v/v). H NMR (400 MHz, CDCl3) δ 8.02 (s, 1H), 7.79 (d, J = 8.0 Hz, 2H), 7.42-7.30 (m,
5H), 7.11 (t, J = 7.6 Hz, 1H), 6.86 (d, J = 7.6 Hz, 1H), 2.22 (s, 3H). 13C{1H} NMR (100 MHz,
CDCl3) δ 164.9, 137.9, 136.9, 133.9, 130.7, 127.8, 127.6, 126.0, 124.3, 120.0, 116.4, 20.4.
N-(p-tolyl)benzamide, 3ac.49 Grey solid, 56 mg, 53% of yield (hexanes/diethyl ether, 90:10
1
v/v). H NMR (400 MHz, CDCl3) δ 7.79 (d, J = 7.2 Hz, 2H), 7.73 (s, 1H), 7.47-7.38 (m, 5H),
13
7.10 (d, J = 8.0 Hz, 2H), 2.27 (s, 3H). C{1H} NMR (100 MHz, CDCl3) δ 165.7, 135.3, 135.1,
134.3, 131.8, 129.6, 128.8, 127.0, 120.3, 20.9.
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N-(4-butylphenyl)benzamide, 3ad.49 Off-white solid, 54 mg, 65% of yield (hexanes/diethyl
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ether, 90:10 v/v). H NMR (400 MHz, CDCl3) δ 7.79 (d, J = 7.6 Hz, 2H), 7.74 (s, 1H), 7.47-
7.38 (m, 5H), 7.10 (d, J = 8.0 Hz, 2H), 2.52 (t, J = 7.6 Hz, 2H), 1.54-1.48 (m, 2H), 1.32-1.23
(m, 2H), 0.85 (t, J = 7.2 Hz, 3H). 13C{1H} NMR (100 MHz, CDCl3) δ 165.7, 139.4, 135.5,
135.1, 131.8, 128.9, 128.8, 127.0, 120.3, 35.1, 33.7, 22.3, 13.9.
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N-(2-isopropylphenyl)benzamide, 3ae.51 Grey solid, 9 mg, 10% of yield (hexanes/diethyl
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ether, 90:10 v/v). H NMR (400 MHz, CDCl3) δ 7.91 (d, J = 7.2 Hz, 2H), 7.84 (d, J = 7.2 Hz,
1H), 7.80 (s, 1H), 7.61-7.50 (m, 3H), 7.37-7.23 (m, 3H), 3.17-3.10 (m, 1H), 1.31 (d, J = 6.8
Hz, 6H). 13C{1H} NMR (100 MHz, CDCl3) δ 166.0, 140.6, 135.0, 134.2, 131.8, 128.9, 127.1,
126.5, 126.2, 125.7, 124.8, 28.2, 23.0.
N-(3,5-dimethylphenyl)benzamide, 3af.52 Grey solid, 24 mg, 26% of yield (hexanes/diethyl
1
ether, 90:10 v/v). H NMR (400 MHz, CDCl3) δ 7.87 (d, J = 7.2 Hz, 2H), 7.56-7.45 (m, 3H),
7.30 (s, 2H), 6.81 (s, 1H), 2.32 (s, 6H). 13C{1H} NMR (100 MHz, CDCl3) δ 165.8, 138.8,
137.8, 135.1, 131.7, 128.7, 128.4, 127.0, 126.3, 118.1, 21.4.
N-(3-methoxyphenyl)benzamide, 3ag.49
Pale brown solid, 53 mg, 58% of yield
1
(hexanes/diethyl ether, 85:15 v/v). H NMR (400 MHz, CDCl3) δ 8.02 (s, 1H), 7.87 (d, J = 7.2
Hz, 2H), 7.57-7.45 (m, 4H), 7.26 (d, J = 8.0 Hz, 1H), 7.13 (d, J = 8.0 Hz, 1H), 6.73 (d, J = 8.0
Hz, 1H), 3.83 (s, 3H). 13C{1H} NMR (100 MHz, CDCl3) δ 166.1, 160.2, 139.3, 134.9, 131.8,
129.7, 128.7, 127.1, 112.5, 110.5, 105.9, 55.3.
N-(4-methoxyphenyl)benzamide, 3ah.49 Grey solid, 61 mg, 67% of yield (hexanes/diethyl
1
ether, 85:15 v/v). H NMR (400 MHz, DMSO-d6) δ 10.14 (s, 1H), 7.96 (d, J = 7.6 Hz, 2H),
7.69 (d, J = 8.4 Hz, 2H), 7.59-7.50 (m, 3H), 6.93 (d, J = 8.8 Hz, 2H), 3.71 (s, 3H). 13C{1H}
NMR (100 MHz, DMSO-d6) δ 170.3, 160.7, 140.3, 137.4, 136.6, 133.6, 132.8, 127.2, 118.9,
60.4.
N-(4-bromophenyl)benzamide, 3ai.53 Grey solid, 15 mg, 19% of yield (hexanes/diethyl
1
ether, 90:10 v/v). H NMR (400 MHz, DMSO-d6) δ 10.37 (s, 1H), 7.95 (d, J = 6.8 Hz, 2H),
13
7.77 (d, J = 8.8 Hz, 2H), 7.60-7.52 (m, 5H). C{1H} NMR (100 MHz, DMSO-d6) δ 166.1,
139.0, 135.1, 132.1, 131.9, 128.8, 128.1, 122.7, 115.8.
N-butyl benzamide, 3ak.49 Colorless oil, 111 mg, 92% of yield. (0.5 g batch yielded 0.96 g)
1
(hexanes/diethyl ether, 90:10 v/v). H NMR (400 MHz, CDCl3) δ 7.68 (d, J = 7.2 Hz, 2H),
7.40 (t, J = 7.2 Hz, 1H), 7.33 (t, J = 7.6 Hz, 2H), 6.22 (s, 1H), 3.39-3.34 (m, 2H), 1.55-1.48 (m,
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2H), 1.37-1.28 (m, 2H), 0.87 (t, J = 7.2 Hz, 3H). 13C{1H} NMR (100 MHz, CDCl3) 167.6,
5
6
134.8, 131.2, 128.5, 126.8, 39.8, 31.7, 20.2, 13.8.
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9
N-(4-butylphenyl)-4-methylbenzamide, 3al.54 Pale brown solid, 26 mg, 30% of yield
1
(hexanes/diethyl ether, 90:10 v/v). H NMR (400 MHz, CDCl3) δ 7.69 (d, J = 8.0 Hz, 2H),
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7.66 (s, 1H), 7.46 (d, J = 8.0 Hz, 2H), 7.21 (d, J = 8.0 Hz, 2H), 7.10 (d, J = 8.4 Hz, 2H), 2.52
(t, J = 7.6 Hz, 2H), 2.35 (s, 3H), 1.54-1.48 (m, 2H), 1.31-1.25 (m, 2H), 0.85 (t, J = 7.6 Hz, 3H).
13C{1H} NMR (100 MHz, CDCl3) δ 165.7, 142.3, 139.2, 135.6, 132.2, 129.4, 128.9, 126.9,
120.2, 35.1, 33.7, 22.3, 21.5, 13.9.
N-(4-butylphenyl)-2-fluorobenzamide, 3am.55
Grey solid, 28 mg, 31% of yield
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(hexanes/diethyl ether, 90:10 v/v). H NMR (400 MHz, CDCl3) δ 8.35-8.27 (m, 1H), 8.10 (t,
J = 8.0 Hz, 1H), 7.49-7.43 (m, 3H), 7.24 (t, J = 7.2 Hz, 1H), 7.11 (d, J = 8.4 Hz, 2H), 2.53 (t,
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J = 7.6 Hz, 2H), 1.54-1.50 (m, 2H), 1.29-1.25 (m, 2H), 0.85 (t, J = 7.2 Hz, 3H). C{1H} NMR
(100 MHz, CDCl3) δ 161.6, 159.9 (d, 1JC-F = 258.1 Hz), 139.6, 135.3, 133.6 (d, 3JC-F = 9.3 Hz),
132.3, 128.9, 125.1 (d, 4JC-F = 3.2 Hz), 120.6, 116.2 (d, 2JC-F = 24.9 Hz), 35.1, 33.7, 22.3, 13.9.
19F{1H} NMR (376 MHz, CDCl3) δ -113.3.
N-(4-butylphenyl)-4-fluorobenzamide, 3an.55
Grey solid, 29 mg, 33% of yield
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(hexanes/diethyl ether, 90:10 v/v). H NMR (400 MHz, CDCl3) δ 7.80-7.77 (m, 2H), 7.77 (s,
1H), 7.43 (d, J = 8.4 Hz, 2H), 7.10-7.03 (m, 4H), 2.52 (t, J = 7.6 Hz, 2H), 1.55-1.47 (m, 2H),
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1.30-1.24 (m, 2H), 0.85 (t, J = 7.2 Hz, 3H). C{1H} NMR (100 MHz, CDCl3) δ 164.8 (d, 1JC-F
= 250.1 Hz), 164.7, 139.5, 135.3, 131.2 (d, 4JC-F = 3.0 Hz), 131.4 (d, 3JC-F = 8.9 Hz), 128.9, 120.4,
115.8 (d, 2JC-F = 21.8 Hz), 35.1, 33.6, 22.3, 13.9. 19F{1H} NMR (376 MHz, CDCl3) δ -107.6.
N-(4-butylphenyl)-3-nitrobenzamide, 3ao.55
Brown solid, 35 mg, 35% of yield
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(hexanes/diethyl ether, 80:20 v/v). H NMR (400 MHz, CDCl3) δ 8.61 (s, 1H), 8.30 (d, J = 7.2
Hz, 1H), 8.17 (d, J = 7.2 Hz, 1H), 8.03 (s, 1H), 7.60 (t, J = 8.0 Hz, 1H), 7.47 (d, J = 8.0 Hz,
2H), 7.11 (d, J = 8.0 Hz, 2H), 2.52 (t, J = 7.6 Hz, 2H), 1.55-1.47 (m, 2H), 1.30-1.24 (m, 2H),
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0.85 (t, J = 7.2 Hz, 3H). C{1H} NMR (100 MHz, CDCl3) δ 163.3, 148.2, 140.1, 136.7, 134.8,
133.4, 130.0, 129.1, 126.2, 121.9, 120.6, 35.1, 33.6, 22.3, 13.9.
N-(4-butylphenyl)thiophene-2-carboxamide, 3ap.56 Brown solid, 22 mg, 26% of yield
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(hexanes/diethyl ether, 90:10 v/v). H NMR (400 MHz, CDCl3) δ 7.64 (s, 1H), 7.54 (d, J = 3.2
Hz, 1H), 7.46-7.41 (m, 3H), 7.10-7.02 (m, 3H), 2.52 (t, J = 7.6 Hz, 2H), 1.55-1.47 (m, 2H),
1.30-1.24 (m, 2H), 0.85 (t, J = 7.2 Hz, 3H). 13C{1H} NMR (100 MHz, CDCl3) δ 159.9, 139.4,
135.1, 130.6, 128.9, 128.4, 127.8, 120.3, 35.1, 33.6, 22.3, 13.9.
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N-(4-butylphenyl)-4-methoxybenzamide, 3aq.57 Off-white solid, 18 mg, 20% of yield
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(hexanes/diethyl ether, 80:20 v/v). H NMR (400 MHz, DMSO-d6) δ 10.0 (s, 1H), 7.95 (d, J
= 8.4 Hz, 2H), 7.65 (d, J = 8.4 Hz, 2H), 7.15 (d, J = 8.0 Hz, 2H), 7.05 (d, J = 8.4 Hz, 2H), 3.83
(s, 3H), 2.54 (t, J = 7.6 Hz, 2H), 1.58-1.50 (m, 2H), 1.33-1.27 (m, 2H), 0.90 (t, J = 7.2 Hz,
3H). 13C{1H} NMR (100 MHz, DMSO-d6) δ 165.1, 162.3, 137.8, 137.4, 129.9, 128.7, 127.5,
120.8, 114.0, 55.9, 34.7, 33.7, 22.2, 14.3.
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Phenyl(pyrrolidine-1-yl)methanone, 3ar.58 Pale yellow oil, 70 mg, 58% of yield
(hexanes/ethyl acetate, 90:10 v/v). 1H NMR (400 MHz, CDCl3) δ 7.51-7.49 (m, 2H), 7.45-
7.42 (m, 3H), 3.46 (t, J = 6.8 Hz, 2H), 3.35 (t, J = 6.8 Hz, 2H), 1.89-1.82 (m, 2H), 1.81-1.76
(m, 2H). 13C{1H} NMR (100 MHz, CDCl3) δ 168.6, 137.7, 130.1, 128.6, 127.4, 49.3, 46.3,
26.4, 24.3.
Phenyl(piperidin-1-yl)methanone, 3as.59
Pale yellow oil, 65 mg, 60% of yield
(hexanes/ethyl acetate, 90:10 v/v). 1H NMR (400 MHz, CDCl3) δ 7.31 (s, 5H), 3.63 (s, 2H),
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3.26 (s, 2H), 1.60 (s, 4H), 1.44 (s, 2H). C{1H} NMR (100 MHz, CDCl3) δ 170.4, 136.5,
129.4, 128.4, 126.8, 48.8, 43.1, 29.7, 26.5, 25.6.
Morpholino(phenyl)methanone, 3at.58 colorless liquid, 53 mg, 50% of yield (hexanes/ethyl
acetate, 90:10 v/v). 1H NMR (400 MHz, CDCl3) δ 7.34 (s, 5H), 3.69-3.38 (m, 8H). 13C{1H}
NMR (100 MHz, CDCl3) δ 170.5, 135.3, 129.9, 128.6, 127.1, 66.9, 48.2, 42.6.
N-benzyl benzamide, 3au.47 Off-white solid, 78 mg, 80% of yield (hexanes/ethyl acetate,
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80:20 v/v). (0.5 g batch yielded 0.680 g). H NMR (400 MHz, CDCl3) δ 7.71 (d, J = 8.0 Hz,
2H), 7.41 (t, J = 6.4 Hz, 1H), 7.33 (t, J = 7.6 Hz, 2H), 7.27-7.21 (m, 5H), 6.49 (s, 1H), 4.54 (d,
J = 2.8 Hz, 2H). 13C{1H} NMR (100 MHz, CDCl3) δ 167.4, 138.2, 134.4, 131.6, 128.8, 128.6,
127.9, 127.6, 126.9, 44.1.
N-(4-methylbenzyl)benzamide, 3av.60 Off- white solid, 75 mg, 82% of yield (hexanes/ethyl
acetate, 80:20 v/v). 1H NMR (400 MHz, CDCl3) δ 7.69 (d, J = 7.6 Hz, 2H), 7.41 (t, J = 7.2 Hz,
1H), 7.32 (t, J = 7.6 Hz, 2H), 7.69 (d, J = 8.0 Hz, 2H), 7.07 (d, J = 7.6 Hz, 2H), 6.41 (s, 1H),
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4.50 (d, J = 5.6 Hz, 2H), 2.26 (s, 3H). C{1H} NMR (100 MHz, CDCl3) δ 167.3, 137.3, 135.2,
134.5, 131.5, 129.4, 128.6, 127.9, 126.9, 43.9, 21.1.
N-(4-methoxybenzyl)benzamide, 3aw.61 Off-white solid, 79 mg, 90% of yield (hexanes/ethyl
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acetate, 80:20 v/v). H NMR (400 MHz, CDCl3) δ 7.80 (d, J = 7.6 Hz, 2H), 7.52-7.40 (m, 3H),
7.28 (d, J = 7.6 Hz, 2H), 6.88 (d, J = 8.4 Hz, 2H), 6.60 (s, 1H), 4.57 (d, J = 5.6 Hz, 2H), 3.80
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(s, 3H). 13C{1H} NMR (100 MHz, CDCl3) δ 167.4, 159.1, 134.4, 131.5, 129.3, 128.6, 126.9,
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114.5, 55.3, 43.6.
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N-(4-fluorobenzyl)benzamide, 3ax.62 Grey solid, 68 mg, 75% of yield (hexanes/ethyl acetate,
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80:20 v/v). H NMR (400 MHz, CDCl3) δ 7.80 (d, J = 8.0 Hz, 2H), 7.42 (t, J = 6.4 Hz, 1H),
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7.33 (t, J = 7.6 Hz, 2H), 7.22 (t, J = 6.4 Hz, 2H), 6.93 (t, J = 8.0 Hz, 2H), 6.58 (s, 1H), 4.50 (d,
J = 5.6 Hz, 2H). 13C{1H} NMR (100 MHz, CDCl3) δ 167.4, 162.2 (d, 1JC-F = 244.1 Hz), 134.2,
134.1 (d, 4JC-F = 2.9 Hz), 131.7, 129.5 (d, 3JC-F = 8.1 Hz), 128.6, 126.9, 115.6 (d, 2JC-F = 21.4 Hz),
43.3. 19F{1H} NMR (376 MHz, CDCl3) δ -114.9.
N-(4-chlorobenzyl)benzamide, 3ay.63 Off-white solid, 66 mg, 77% of yield (hexanes/ethyl
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acetate, 80:20 v/v). H NMR (400 MHz, CDCl3) δ 7.70 (d, J = 7.6 Hz, 2H), 7.41 (t, J = 7.2
Hz, 1H), 7.33 (t, J = 7.6 Hz, 2H), 7.23-7.20 (m, 2H), 6.93 (t, J = 8.4 Hz,2H), 6.58 (s, 1H), 4.50
(d, J = 5.6Hz, 2H). 13C{1H} NMR (100 MHz, CDCl3) δ 167.4, 163.4, 161.0, 134.2, 131.6,
129.5, 128.6, 126.9, 115.7, 115.5, 43.3.
N-(1-phenylethyl)benzamide, 3az.64 Off white-solid, 73 mg, 79% of yield (hexanes/ethyl
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acetate, 80:20 v/v). H NMR (400 MHz, CDCl3) δ 7.68 (d, J = 7.6 Hz, 2H), 7.39 (t, J = 6.8
Hz, 1H), 7.33-7.24 (m, 6H), 7.18 (t, J = 7.2 Hz, 1H), 6.43 (s, 1H), 5.27-5.20 (m, 1H), 1.50 (d,
J = 6.8 Hz, 3H). 13C{1H} NMR (100 MHz, CDCl3) δ 166.6, 143.2, 134.6, 131.5, 128.7, 128.5,
127.4, 126.9, 126.3, 49.2, 21.7.
N-(pyridin-2-ylmethyl)benzamide, 3ba.62
Off-white solid, 63 mg, 65% of yield
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(hexanes/ethyl acetate, 80:20 v/v). H NMR (400 MHz, CDCl3) δ 8.48 (d, J = 4.0 Hz, 1H),
7.80 (d, J = 8.4 Hz, 2H), 7.71 (s, 1H), 7.62 (t, J = 7.6 Hz, 1H), 7.42-7.29 (m, 4H), 7.15 (t, J =
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7.2 Hz, 1H), 4.69 (d, J = 5.2 Hz, 2H). C{1H} NMR (100 MHz, CDCl3) δ 167.4, 156.3, 148.7,
137.2, 134.3, 131.5, 128.5, 127.1, 122.3, 122.6, 44.7.
N-phenethyl benzamide, 3ca.65 Off-white solid, 84 mg, 91% of yield (hexanes/ethyl acetate,
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80:20 v/v). H NMR (400 MHz, CDCl3) δ 7.72 (d, J = 7.2 Hz, 2H), 7.50 (t, J = 7.2 Hz, 1H),
7.42 (t, J = 7.6 Hz, 2H), 7.35 (t, J = 7.6 Hz, 2H), 7.27 (t, J = 7.2 Hz, 3H), 6.30 (s, 1H), 3.76-
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3.71 (m, 2H), 2.95 (t, J = 6.8 Hz, 2H). C{1H} NMR (100 MHz, CDCl3) δ 167.5, 138.9, 134.7,
131.4, 128.8, 128.7, 128.6, 126.8, 126.6, 41.2, 35.7.
N-(4-methoxyphenethyl)benzamide, 3da.66 Off-white solid, 78 mg, 93% of yield
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(hexanes/ethyl acetate, 70:30 v/v). H NMR (400 MHz, CDCl3) δ 7.72 (d, J = 7.2 Hz, 2H),
7.49 (t, J = 7.2 Hz, 1H), 7.41 (t, J = 7.6 Hz, 2H), 7.17 (d, J = 8.4 Hz, 2H), 6.88 (d, J = 8.8 Hz,
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2H), 6.28 (s, 1H), 3.81 (s, 3H) 3.72-3.67 (m, 2H), 2.89 (t, J = 6.8 Hz, 2H). C{1H} NMR (100
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MHz, CDCl3) δ 167.5, 158.3, 134.7, 131.4, 130.9, 129.8, 128.6, 126.8, 114.1, 55.3, 41.3, 34.8.
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N-benzyl-3-methylbenzamide, 3ea.67 Pale brown solid, 82 mg, 78% of yield (hexanes/ethyl
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acetate, 80:20 v/v). H NMR (400 MHz, CDCl3) δ 7.54 (s, 1H), 7.48 (t, J = 4.8 Hz, 1H), 7.28-
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7.21 (m, 7H), 6.39 (s, 1H), 4.56 (d, J = 5.6 Hz, 2H), 2.30 (s, 3H). 13C{1H} NMR (100 MHz,
CDCl3) δ 167.6, 138.5, 138.3, 134.4, 132.3, 128.8, 127.9, 127.6, 123.9, 44.1, 21.4.
N-benzyl-4-methylbenzamide, 3fa.68 Off-white solid, 78 mg, 75% of yield (hexanes/ethyl
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acetate, 80:20 v/v). H NMR (400 MHz, CDCl3) δ 7.61 (d, J = 8.0 Hz, 2H), 7.28-7.20 (m, 5H),
7.15 (d, J = 8.0 Hz, 2H), 6.32 (s, 1H), 4.57 (d, J = 5.6 Hz, 2H), 2.31 (s, 3H). 13C{1H} NMR
(100 MHz, CDCl3) δ 167.3, 142.0, 138.3, 131.5, 129.3, 128.8, 127.9, 127.6, 126.9, 44.1, 21.4.
N-benzyl-4-fluorobenzamide, 3ga.69 Grey-solid, 87 mg, 81% of yield (hexanes/ethyl acetate,
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80:20 v/v). H NMR (400 MHz, CDCl3) δ 7.74-7.70 (m, 2H), 7.28-7.22 (m, 5H), 7.02 (t, J =
8.4 Hz, 2H), 6.36 (s, 1H), 4.55 (d, J = 5.6 Hz, 2H). 13C{1H} NMR (100 MHz, CDCl3) δ 166.3,
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164.7(d, JC-F = 244.1 Hz), 138.03, 130.5 (d, JC-F = 3.0 Hz), 129.3 (d, JC-F = 8.9 Hz), 128.8,
127.9, 127.7, 115.7 (d, 2JC-F = 21.7 Hz), 44.2. 19F{1H} NMR (376 MHz, CDCl3) δ -108.0.
General Procedure for Esterification from Imidazolium Salts via C-C bond Cleavage with
Characterization Data
An oven-dried 8 mL vial equipped with a stir bar was charged with 4a (1 equiv), 1a (1.5 equiv),
potassium carbonate (1.5 equiv) in DMF (1 mL). The reaction mixture was placed in a
preheated oil bath at 80 °C and stirred for 14 h. After the indicated time, the solvent was
evaporated, and the crude material was purified by column chromatography on silica gel with
n-hexane-ethyl acetate or hexanes–diethyl ether as eluent, to yield the title compound.
Phenyl benzoate, 5aa.40 Off-white solid, 31 mg, 25% of yield (hexanes/ethyl acetate, 90:10
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v/v). H NMR (400 MHz, CDCl3) δ 8.14 (d, J = 7.2 Hz, 2H), 7.57 (t, J = 7.6 Hz, 1H), 7.44 (t,
J = 7.6 Hz, 2H), 7.36 (t, J = 8.0 Hz, 2H), 7.21 (d, J = 7.2 Hz, 1H), 7.14 (d, J = 7.2 Hz, 2H).
13C{1H} NMR (100 MHz, CDCl3) δ 165.2, 150.9, 133.6, 130.2, 129.5, 128.6, 125.9, 121.7.
o-Tolyl benzoate, 5ab.70 Colorless oil, 25 mg, 26% of yield (hexanes/ethyl acetate, 90:10 v/v).
1H NMR (400 MHz, CDCl3) δ 8.15 (d, J = 7.2 Hz, 2H), 7.57 (t, J = 7.6 Hz, 1H), 7.44 (t, J =
7.6 Hz, 2H), 7.22-7.17 (m, 2H), 7.13-7.02 (m, 2H), 2.17 (s, 3H). 13C{1H} NMR (100 MHz,
CDCl3) δ 164.8, 149.5, 133.6, 131.2, 130.2, 128.6, 127.0, 126.1, 122.0, 16.3.
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m-Tolyl benzoate, 5ac.71 Colorless oil, 25 mg, 26% of yield (hexanes/ethyl acetate, 90:10
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v/v). H NMR (400 MHz, CDCl3) δ 8.12 (d, J = 7.2 Hz, 2H), 7.57 (t, J = 7.6 Hz, 1H), 7.43 (t,
J = 7.6 Hz, 2H), 7.23 (t, J = 7.6 Hz, 1H), 7.02-6.93 (m, 3H), 2.31 (s, 3H). 13C{1H} NMR (100
MHz, CDCl3) δ 165.3, 150.9, 139.7, 133.5, 130.2, 129.2, 128.6, 126.7, 122.3, 118.6, 21.3.
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p-Tolyl benzoate, 5ad.70 Off white solid, 27 mg, 28% of yield (hexanes/ethyl acetate, 90:10
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v/v). H NMR (400 MHz, CDCl3) δ 8.12 (d, J = 7.2 Hz, 2H), 7.57 (t, J = 7.6 Hz, 1H), 7.43 (t,
J = 7.6 Hz, 2H), 7.15 (d, J = 8.0 Hz, 2H), 7.01 (d, J = 8.4 Hz, 2H), 2.31 (s, 3H). 13C{1H}
NMR (100 MHz, CDCl3) δ 165.4, 148.7, 135.5, 133.5, 130.2, 130.0, 128.5, 121.4, 20.9.
4-Chlorophenyl benzoate, 5ae.72 Yellow oil, 17 mg, 19% of yield (hexanes/ethyl acetate,
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90:10 v/v). H NMR (400 MHz, CDCl3) δ 8.12 (d, J = 7.2 Hz, 2H), 7.58 (t, J = 7.6 Hz, 1H),
7.45 (t, J = 7.6 Hz, 2H), 7.32 (d, J = 8.8 Hz, 2H), 7.10 (d, J = 8.8 Hz, 2H). 13C{1H} NMR (100
MHz, CDCl3) δ 164.9, 149.4, 133.8, 131.3, 130.2, 129.6, 128.6, 123.1.
Naphthalen-2-yl benzoate, 5af.72 Off-white solid, 11 mg, 13% of yield (hexanes/ethyl
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acetate, 90:10 v/v). H NMR (400 MHz, CDCl3) δ 8.19 (d, J = 7.6 Hz, 2H), 7.85-7.75 (m, 3H),
7.63-7.57 (m, 2H), 7.49-7.41 (m, 4H), 7.30-7.28 (m, 1H). 13C{1H} NMR (100 MHz, CDCl3)
δ 168.0, 151.1, 133.8, 133.7, 131.5, 130.2, 129.6, 129.5, 128.6, 127.8, 127.7, 126.6, 125.7,
121.3, 118.7.
Phenyl-3-methylbenzoate, 5ag.73 Colorless oil, 22 mg, 20% of yield (hexanes/ethyl acetate,
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90:10 v/v). H NMR (400 MHz, CDCl3) δ 7.94-7.92 (m, 2H), 7.37-7.30 (m, 4H), 7.21-7.12
(m, 3H) 2.37 (s, 3H). 13C{1H} NMR (100 MHz, CDCl3) δ 165.4, 151.0, 138.4, 134.4, 130.7,
129.5, 128.5, 127.3, 125.9, 121.8, 21.3.
Phenyl-4-methylbenzoate, 5ah.74 Colorless oil, 20 mg, 18% of yield (hexanes/ethyl acetate,
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90:10 v/v). H NMR (400 MHz, CDCl3) δ 8.13 (d, J = 8.4 Hz, 2H), 7.46 (t, J = 7.6 Hz, 2H),
7.35-7.23 (m, 5H), 2.48 (s, 3H). 13C{1H} NMR (100 MHz, CDCl3) δ 165.3, 151.0, 144.4,
130.2, 129.5, 129.3, 126.8, 125.8, 121.8, 21.8.
Phenyl-4-fluorobenzoate, 5ai.74 Off-white solid, 28 mg, 25% of yield (hexanes/ethyl acetate,
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90:10 v/v). H NMR (400 MHz, CDCl3) δ 8.27-8.24 (m, 2H), 7.46 (t, J = 5.6 Hz, 2H), 7.33-
7.19 (m, 5H). 13C{1H} NMR (100 MHz, CDCl3) δ 166.1 (d, 1JC-F = 253.4 Hz), 164.2, 150.9,
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132.9 (d, JC-F = 9.4 Hz), 129.5, 126.02, 125.8 (d, JC-F = 2.9 Hz), 121.6, 115.9 (d, JC-F = 21.9
Hz). 19F{1H} NMR (376 MHz, CDCl3) δ -104.4.
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Benzyl benzoate, 5aj.75 Colorless oil, 68 mg, 70% of yield. (0.5 g batch yielded 0.520 g)
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(hexanes/ethyl acetate, 95:05 v/v). H NMR (400 MHz, CDCl3) δ 8.12 (d, J = 7.2 Hz, 2H),
7.46 (t, J = 7.2 Hz, 1H), 7.50- 7.37 (m, 7H), 5.41 (s, 2H). 13C{1H} NMR (100 MHz, CDCl3) δ
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4-Methylbenzyl benzoate, 5ak.75 Colorless oil, 80 mg, 72% of yield (hexanes/ethyl acetate,
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95:05 v/v). H NMR (400 MHz, CDCl3) δ 7.97 (d, J = 7.0 Hz, 2H), 7.43 (t, J = 7.2 Hz, 1H),
7.33-7.23 (m, 4H), 7.09 (d, J = 8.0 Hz, 2H), 5.22 (s, 2H), 2.25 (s, 3H). 13C{1H} NMR (100
MHz, CDCl3) δ 166.5, 138.2, 133.1, 133.0, 130.3, 129.7, 129.3, 128.4, 128.4, 66.7, 21.3.
4-Methoxybenzyl benzoate, 5al.75 Off-white solid, 66 mg, 76% of yield (hexanes/ethyl
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acetate, 90:10 v/v). H NMR (400 MHz, CDCl3) δ 7.98 (d, J = 7.2 Hz, 2H), 7.46 (t, J = 7.2
13
Hz, 1H), 7.36-7.30 (m, 4H), 7.09 (d, J = 7.8 Hz, 2H), 5.22 (s, 2H), 3.75 (s, 3H). C{1H} NMR
(100 MHz, CDCl3) δ 166.5, 159.7, 132.9, 130.3, 130.1, 129.7, 128.3, 128.2, 113.9, 66.6, 55.3.
4-Fluorobenzyl benzoate, 5am.75 Colorless oil, 59 mg, 65% of yield (hexanes/ethyl acetate,
1
90:10 v/v). H NMR (400 MHz, CDCl3) δ 7.98 (d, J = 7.2 Hz, 2H), 7.46 (t, J = 7.2 Hz, 1H),
7.33-7.30 (m, 4H), 6.95 (t, J = 8.2 Hz, 2H), 5.21 (s, 2H). 13C{1H} NMR (100 MHz, CDCl3) δ
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165.1 (d, JC-F = 246.1 Hz), 161.4, 133.1, 131.9 (d, JC-F = 3.3 Hz), 130.2 (d, JC-F = 8.1 Hz),
2
130.0, 129.7, 128.4, 115.6 (d, JC-F = 21.6 Hz), 66.0. 19F{1H} NMR (376 MHz, CDCl3) δ -
113.6.
4-Chlorobenzyl benzoate, 5an.76 Yellow oil, 57 mg, 67% of yield (hexanes/ethyl acetate,
90:10 v/v). 1H NMR (400 MHz, CDCl3) δ 7.96 (d, J = 7.2 Hz, 2H), 7.46 (t, J = 7.2 Hz, 1H),
7.33-7.23 (m, 6H), 5.21 (s, 2H). 13C{1H} NMR (100 MHz, CDCl3) δ 166.3, 134.6, 134.2,
133.2, 129.9, 129.7, 129.6, 128.8, 128.5, 65.9.
2,4-Dichlorobenzyl benzoate, 5ao.77 Grey solid, 49 mg, 62% of yield (hexanes/ethyl acetate,
1
90:10 v/v). H NMR (400 MHz, CDCl3) δ 7.99 (d, J = 7.2 Hz, 2H), 7.46 (t, J = 7.2 Hz, 1H),
13
7.38-7.34 (m, 4H), 7.19-7.16 (m, 1H), 5.33 (s, 2H). C{1H} NMR (100 MHz, CDCl3) δ 165.1,
133.7, 133.4, 132.2, 131.4, 129.6, 128.7, 128.4, 127.4, 126.2, 62.4.
2-Nitrobenzyl benzoate, 5ap.78 Pale yellow solid, 44 mg, 53% of yield (hexanes/ethyl acetate,
1
90:10 v/v). H NMR (400 MHz, CDCl3) δ 8.07-8.01 (m, 3H), 7.62-7.50 (m, 3H), 7.45-7.38
(m, 3H), 5.71 (s, 2H). 13C{1H} NMR (100 MHz, CDCl3) δ 165.9. 147.6, 133.8, 133.4, 132.4,
129.8, 129.6, 128.9, 128.8, 128.6, 125.1, 63.4.
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4-Nitrobenzyl benzoate, 5aq.77 Yellow solid, 40 mg, 49% of yield (hexanes/ethyl acetate,
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85:15 v/v). H NMR (400 MHz, CDCl3) δ 8.18 (d, J = 8.2 Hz, 2H), 8.01 (d, J = 7.6 Hz, 2H),
7.53 (t, J = 8.2 Hz, 3H), 7.40 (t, J = 8.2 Hz, 2H), 5.39 (s, 2H). 13C{1H} NMR (100 MHz,
CDCl3) δ 166.1. 147.7, 143.4, 133.5, 129.7, 129.5, 128.6, 128.3, 123.9, 65.2.
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Pyridin-3-ylmethyl benzoate, 5ar.79 Pale brown liquid, 50 mg, 52% of yield (hexanes/ethyl
1
acetate, 90:10 v/v). H NMR (400 MHz, CDCl3) δ 8.18 (d, J = 1.6 Hz, 1H), 8.59 (d, J = 4.8
Hz, 1H), 8.06 (d, J = 7.2 Hz, 2H), 8.79 (d, J = 7.6 Hz, 1H), 7.58-7.31 (m, 4H), 5.38 (s, 2H).
13C{1H} NMR (100 MHz, CDCl3) δ 166.2, 149.6, 136.0, 133.3, 131.7, 129.7, 128.5, 123.5,
64.1.
Naphthalen-1-ylmethyl benzoate, 5as.76 Off-white solid, 45 mg, 55% of yield (hexanes/ethyl
1
acetate, 90:10 v/v). H NMR (400 MHz, CDCl3) δ 8.18 (d, J = 8.4 Hz, 1H), 8.09 (d, J = 8.0
13
Hz, 2H), 7.95-7.90 (m, 2H), 7.68-7.42 (m, 7H), 5.86 (s, 2H). C{1H} NMR (100 MHz, CDCl3)
δ 166.5, 133.8, 133.0, 131.8, 131.5, 130.1, 129.8, 129.4, 128.8, 128.4, 127.5, 126.7, 126.0,
125.3, 123.7, 65.2.
Benzhydryl benzoate, 5at.80 Colorless oil, 52 mg, 67% of yield (hexanes/ethyl acetate, 90:10
1
v/v). H NMR (400 MHz, CDCl3) δ 8.06 (d, J = 7.2 Hz, 2H), 7.40 (t, J = 7.2 Hz, 1H), 7.39-
7.16 (m, 12H), 7.04 (s, 1H). 13C{1H} NMR (100 MHz, CDCl3) δ 165.6, 140.3, 133.2, 130.2,
129.8, 128.6, 128.5, 127.9, 127.2, 77.4.
Anthracen-9-ylmethyl benzoate, 5au.81 Pale yellow solid, 38 mg, 51% of yield
1
(hexanes/ethyl acetate, 90:10 v/v). H NMR (400 MHz, CDCl3) δ 8.42 (s, 1H), 8.34 (d, J = 9.2
13
Hz, 2H), 7.95-7.89 (m, 4H), 7.51-7.23 (m, 7H), 6.29 (s, 2H). C{1H} NMR (100 MHz, CDCl3)
δ 166.8, 133.0, 131.4, 131.2, 129.8, 129.3, 129.1, 128.3, 126.7, 126.3, 125.2, 124.0, 59.4.
4-Methoxybenzyl-3-methylbenzoate, 5av.82
Colorless oil, 63 mg, 68% of yield
1
(hexanes/ethyl acetate, 90:10 v/v). H NMR (400 MHz, CDCl3) δ 7.89-7.87 (m, 2H), 7.42-
7.28 (m, 4H), 6.94 (d, J = 8.8 Hz, 2H), 5.31 (s, 2H), 3.84 (s, 3H), 2.41 (s, 3H). 13C{1H} NMR
(100 MHz, CDCl3) δ 166.7, 159.6, 138.1, 133.7, 130.2, 130.1, 128.2, 126.8, 113.9, 66.5, 55.3,
21.3.
4-Methoxybenzyl-4-methylbenzoate, 5aw.83
Colorless oil, 59 mg, 65% of yield
1
(hexanes/ethyl acetate, 90:10 v/v). H NMR (400 MHz, CDCl3) δ 7.97 (d, J = 8.0 Hz, 2H),
7.41 (d, J = 8.8 Hz, 2H), 7.24 (d, J = 8.0 Hz, 2H), 6.94 (d, J = 8.8 Hz, 2H), 5.31 (s, 2H), 3.84
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(s, 3H), 2.42 (s, 3H). 13C{1H} NMR (100 MHz, CDCl3) δ 166.6, 159.6, 143.6, 130.0, 129.7,
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129.0, 128.3, 127.5, 113.9, 66.4, 55.3, 21.7.
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Benzyl-2-fluorobenzoate, 5ax.84 Colorless oil, 65% of yield (hexanes/ethyl acetate, 90:10
1
v/v). H NMR (400 MHz, CDCl3) δ 7.86 (t, J = 7.2 Hz, 1H), 7.43-7.35 (m, 3H), 7.30-7.22 (m,
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3H), 7.10-7.01 (m, 2H), 5.29 (s, 2H). 13C{1H} NMR (100 MHz, CDCl3) δ 164.2 (d, 4JC-F = 3.6
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3
Hz), 162.0 (d, JC-F = 258.5 Hz), 135.8, 134.6 (d, JC-F = 9.0 Hz), 132.2, 128.6, 128.3, 128.1,
124.0 (d, 4JC-F = 4.0 Hz), 118.7 (d, 3JC-F = 9.7 Hz), 117.1 (d, 2JC-F = 22.3 Hz), 66.9.
(3S,8S,9S,10R,13R,14S,17R)-10,13-Dimethyl-17-((R)-6-methylheptan-2-yl)-
2,3,4,7,8,9,10,11,12,13,14,15,16,17-tetradecahydro-1H-cyclopenta[a]phenanthren-3-yl
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benzoate, 5ay.85 Colorless solid, 6 mg, 10% of yield (hexanes/ethyl acetate, 90:10 v/v). H
NMR (400 MHz, CDCl3) δ 7.97 (d, J = 6.8 Hz, 2H), 7.47 (t, J = 8.4 Hz, 1H), 7.35 (t, J = 8.0
Hz, 2H), 5.34 (d, J = 3.6 Hz, 1H), 4.82-4.76 (m, 1H), 2.39 (d, J = 7.6 Hz, 2H), 1.48 (m, 26H),
0.93 (s, 3H), 0.85 (d, J = 6.4 Hz, 3H), 0.79 (dd, J = 6.8, 2.0 Hz, 6H), 0.61 (s, 3H). 13C{1H}
NMR (100 MHz, CDCl3) δ 164.9, 138.6, 131.7 129.8, 128.5, 127.2, 121.8, 73.6, 55.7, 55.1,
49.0, 41.3, 38.7, 38.5, 37.2, 36.0, 35.6, 34.8, 30.9, 28.7, 28.3, 27.2, 26.8, 23.3, 22.8, 21.8, 21.5,
20.0, 18.3, 10.8.
N-(2-(1H-indol-3-yl) ethyl) benzamide, 7aa.86 Off-white solid 42 mg, 51% of yield
1
(hexanes/ethyl acetate, 75:25 v/v). H NMR (400 MHz, CDCl3) δ 10.82 (s, 1H), 8.64 (t, J =
6.8 Hz, 1H). 7.87 (d, J = 8.0 Hz, 2H), 7.60 (d, J = 8.0 Hz, 1H), 7.52-7.45 (m,3H), 7.36 (d, J =
8.0 Hz, 1H), 7.19 (s,1H), 7.08 (t, J = 8.0 Hz, 1H), 6.99 (t, J = 8.0 Hz, 1H), 3.58-3.53 (m,2H),
13
2.96 (t, J = 8.0 Hz, 2H). C{1H} NMR (100 MHz, CDCl3) δ 166.6, 136.7, 135.2, 131.5, 128.7,
127.7, 127.6, 123.1, 121.4, 118.8, 118.7, 112.4, 111.8, 40.7, 25.6.
(1-benzoylpiperidin-4-yl)methyl benzoate, 8aa,87 Off-white solid, 28 mg, 20%
1
(hexanes/ethyl acetate, 90:10 v/v). H NMR (400 MHz, DMSO-d6) δ 7.98 (d, J = 7.2 Hz, 2H),
7.67 (t, J = 7.6 Hz, 1H), 7.54 (t, J = 7.6 Hz, 2H), 7.45-7.43 (m, 3H), 7.39-7.36 (m, 2H), 4.52
(bs, 1H), 4.18 (d, J = 6.4 Hz, 2H), 3.60 (bs, 1H), 3.06 (bs, 1H), 2.80 (bs, 1H), 2.09-1.71 (m,
4H), 1.29-1.26 (m, 1H). 13C{1H} NMR (100 MHz, DMSO-d6) δ 169.4, 166.1, 136.8, 133.8,
130.2, 129.8, 129.6, 129.3, 128.8, 127.1, 68.8, 47.3, 35.6, 29.3, 28.6.
N-(2-hydroxyethyl)benzamide, 9aa,88 Brown liquid, 66 mg, 49 % (hexanes/ethyl acetate,
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90:10 v/v). H NMR (400 MHz, DMSO-d6) δ 8.44 (s, 1H), 7.86 (d, J = 7.2 Hz, 2H), 7.51 (t, J
= 7.6 Hz, 1H), 7.44 (t, J = 7.6 Hz, 2H), 3.52 (t, J = 6.4 Hz, 2H), 3.41(bs, 1H), 3.35 (t, J = 6.4
13
Hz, 2H). C{1H} NMR (100 MHz, DMSO-d6) δ 166.8, 134.9, 131.5, 128.6, 127.6, 60.2, 42.6.
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N-(4-hydroxyphenyl)benzamide, 10aa,89 Brown flakes, 46 mg, 48% (hexanes/ethyl acetate,
90:10 v/v). 1H NMR (400 MHz, DMSO-d6) δ 10.02 (s, 1H), 9.25 (s, 1H), 7.93 (d, J = 7.2 Hz,
2H), 7.58-7.49 (m, 5H), 6.74 (d, J = 8.2 Hz, 2H); 13C{1H} NMR (100 MHz, DMSO-d6) δ 165.4,
154.2, 135.6, 131.7, 131.1, 128.7, 127.9, 122.7, 116.1, 115.4.
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N-(2-hydroxyphenyl)benzamide, 11aa,90 Brown solid, 54 mg, 56% (hexanes/ethyl acetate,
90:10 v/v). 1H NMR (400 MHz, DMSO-d6) δ 9.76 (s, 1H), 9.53 (s, 1H), 7.98 (d, J = 7.6 Hz,
2H), 7.69 (d, J = 7.6 Hz, 1H), 7.62-7.52 (m, 3H), 7.05 (t, J = 8.0 Hz, 1H), 6.93 (d, J = 8.0 Hz,
1H), 6.84 (t, J = 7.8 Hz, 1H). 13C{1H} NMR (100 MHz, DMSO-d6) δ 165.7, 149.8, 134.8,
132.1, 128.9, 127.9, 126.1, 124.6, 119.5, 116.4.
(Z)-3-(hydroxy(phenyl)methylene)-1-methylindolin-2-one, 13aa.91 pale yellow solid, 52
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mg, 61% (hexanes/ethyl acetate, 90:10 v/v). H NMR (400 MHz, CDCl3) δ 7.71 (d, J = 6.4
13
Hz, 2H), 7.49-7.44 (m, 3H), 7.11 (t, J = 7.6 Hz, 2H), 6.87-6.80 (m, 2H), 3.32 (s, 3H). C{1H}
NMR (100 MHz, CDCl3) δ 172.0, 170.9, 139.1, 134.1, 131.3, 128.6, 128.4, 125.9, 121.8, 121.5,
119.7, 108.3, 101.4, 25.8.
ASSOCIATED CONTENT
Supporting Information
1
13
19
Isolated C-acyl imidazolium salts and the H, C and F NMR spectra. This material is
available free of charge via the Internet at http:// pubs.acs.org.
AUTHOR INFORMATION
Corresponding Author
* E-mail: velan.g@vit.ac.in
Acknowledgements
This work is supported by the DST-SERB (EMR/2016/005461), and SEED Grant, VIT
University, Vellore. S.K. acknowledges UGC, India, for SRF [no. F.2-4/2011(SA-I) dated
22.07.2017]. We thank Ramdas Sreedharan for his support and VIT-SIF and IITM-SAIF for
instrument facilities.
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