An electrochemical method for carboxylic ester synthesis from N-alkoxyamides

Article abstract of DOI:10.1021/acs.joc.7b01473

An electrochemical method for the synthesis of carboxylic as well as hindered esters from N-alkoxyamides has been reported. The electrochemical reaction proceeds through constant current electrolysis (CCE) by taking advantage of the dual role of n-Bu₄NI (TBAI) as the redox catalyst as well as the supporting electrolyte. Besides providing mild reaction conditions, the present protocol is free from external oxidants and conducting salts, thereby generating nitrogen as the nonhazardous side product. Additionally, the developed procedure is highly advantageous due to its short reaction time, wide substrate scope, and gram-scale synthesis.

Full text of DOI:10.1021/acs.joc.7b01473

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Article
An Electrochemical Method for Carboxylic
Esters Synthesis from N-alkoxyamides
Kripa Subramanian, Subhash Laxman Yedage, and Bhalchandra Mahadeo Bhanage
J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.joc.7b01473 • Publication Date (Web): 05 Sep 2017
Downloaded from http://pubs.acs.org on September 5, 2017
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An Electrochemical Method for Carboxylic Esters Synthesis from
N-alkoxyamides
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Kripa Subramanian, Subhash L. Yedage and Bhalchandra M. Bhanage*
Department of Chemistry, Institute of Chemical Technology, Mumbai-400019, India
E-mail: bm.bhanage@ictmumbai.edu.in,bm.bhanage@gmail.com
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ABSTRACT: An electrochemical method for the synthesis of carboxylic as well as hindered
esters from N-alkoxyamides has been reported. The electrochemical reaction proceeds through
constant current electrolysis (CCE) by taking into advantage the dual role of n-Bu4NI (TBAI) as
the redox catalyst as well as the supporting electrolyte. Besides providing mild reaction
conditions, the present protocol is free from external oxidants and conducting salts thereby
generating nitrogen as the non-hazardous side product. Additionally, the developed procedure is
highly advantageous due to its short reaction time, wide substrate scope and gram scale
synthesis.
TOC Graphic
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INTRODUCTION
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Ester is an ubiquitous and key backbone in natural products and biologically active molecules
(Scheme 1).1 Classical methods reported for ester synthesis from various precursors were
through functional group inter conversions (FGI).2 However, the FGI of amides has always been
a challenge due to the presence of stable C-N bond.3
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Scheme 1. Biologically important esters
Traditionally, esterification of amides has been reported by acid/base2b mediated processes and
metal/enzyme catalysis.4 Amongst amides, N-alkoxyamides form a special class, useful for
synthesis of variety of esters. From N-alkoxyamides, esters have been synthesized using
Ce(NH4)2(NO2)6,5 NiO2.H2O,5 Ag2O,6 Pb(OAc)4,7,8 tBuOCl/NaN3,9 as catalysts. Subsequently,
Du and co-workers10 used stoichiometric amount of N-bromosuccinimide for the synthesis of
hindered esters and recently, Lan and Lei’s group reported11 the use of Ni(acac)2/DTBP and
Cu(OTf)2/DTBP for ester synthesis from amides (Scheme 2). Of late, taking into consideration
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the environmental aspects, we see an increasing demand for metal and oxidant free organic
synthesis, albeit such reactions were seldom performed in the past.
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Scheme 2. Previous reports and present work for ester synthesis from amides
It is well known that electrochemistry is one of the benign, energy efficient and thus sustainable
alternatives to conventional redox transformation of organic compounds12 wherein the electron
serves as a clean redox reagent thereby replacing stoichiometric reagents with electric current.
Furthermore, indirect/mediatedelectrosynthesis is a special approach in electroorganic synthesis
where a mediator12c,13 acts as both, an electron transfer agent as well as a redox catalyst thereby
avoiding reagent waste along with difficult separation procedures. Hence the utilization of
mediated electrolysis for the synthesis of esters from N-alkoxyamides seemed to be an attractive
alternative to the traditional oxidant/ metal catalyzed approach. Thus, in view of the fact that,
TBAI is an efficient catalyst14 as well as a supporting electrolyte15 in radical reactions, we
expected it to be the ideal candidate as metal-free redox catalyst in our reactions. Therefore,
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considering these advantages, we herein report metal and oxidant free electrochemical synthesis
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of carboxylic and hindered esters from N-alkoxyamides in the presence of TBAI using CCE.
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RESULTS AND DISCUSSION
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To explore the idea, we initially started with optimization of the reaction by using N-
methoxybenzamide 1a as the model substrate, a redox catalyst and a suitable solvent. CCE was
carried out in an undivided cell using Pt plate anode and Cu plate cathode. As shown in
Table 1, a series of experiments were carried out to study the effect of reaction parameters
like catalyst screening, catalyst loading, effect of solvents, electrode materials and
temperature on the yield of the desired product 2a. The progress of the reaction was
monitored by using TLC until the starting material was completely consumed.
Firstly, various metal-free redox catalysts were screened using N,N-dimethylformamide
(DMF) as the solvent and by passing maximum current possible in each case until the cut-
off voltage (10 V) was reached (Table 1, entries 1-8). Of these, TBAI provided superior
yield (85%) of the desired product 2a. The use of n-Bu4NBr also resulted in good yield
while other catalysts viz., KI, NaI, Me4NI and Et4NBr gave moderate yields of 2a
.
However, KCl had poor solubility in DMF leading to conductivity issues and thus
produced inferior yield of 2a. The use of molecular I2 as catalyst in 0.1 M
tertabutylammoniumhexafluoro phosphate (TBAPF6) as the electrolyte did not yield the
ester. In general, due to their better solubility in most of the organic solvents, quaternary
ammonium halides turned out to better catalysts than metal halides. Out of these
quaternary ammonium halides, TBAI proved to be ideal. Further more, since TBAI
provided necessary conductivity to the reaction mixture, additional conducting salts were
not necessary to carry out the reaction. It was observed that on passing 9 mA current (i.e.,
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current density of 1 mA cm-2) the time taken to obtain maximum yield was 90 minutes.
This is equivalent to passing 1 F mol-1 of electric charge which is same as the theoretical
amount required for maximum conversion. Thus, for further optimizations the reaction
time was fixed to be 90 minutes at a current density of 1 mA cm-2. Next, the effect of
catalyst loading viz., 5, 10, 15, 20 and 25 mol% of TBAI at constant reaction time was
monitored (Table 1, entries 8-12). Increasing the catalyst concentration from 5 to 10
mol% led to an increase in conductivity of the reaction mixture leading to a substantial
increase in the yield of 2a. Catalyst surge from 10 to 15 and then to 20 mol% led to a
gradual increase in yield and further increase of catalyst loading from 20 to 25 mol%
produced little effect on the yield of 2a. Therefore, the concentration of TBAI was fixed
to be 20 mol%, which resulted in 94% yield of 2a. The effect of solvents was noteworthy
(Table 1, entries 11, 13-16). Out of the various solvents screened, DMF was found to be
compatible since it yielded 94% of 2a. Dimethyl sulfoxide (DMSO) gave yields around
78% while C2H5OH and CH3CN gave poor yields of product. Toluene diminished the
conductivity of the system drastically and hence did not yield 2a. There was a significant
increase in yield when the temperature was increased from room temperature (30 °C) to
60 °C. Further on, we noticed a gradual increase in yield with rise in temperature up to 85
°C. Increase in temperature beyond 85 °C did not affect the yield of 2a (Table 1, entries
11, 17-20). Subsequently, the effect of various electrode materials were also investigated.
Changing the anode from platinum to graphite led to a wide reduction in yield of the ester
from 94% to 65% (Table 1, entry 21). Apart from copper, the other cathodes viz.
platinum, nickel and carbon were comparatively less active for the reaction (Table 1,
entries 22-24). From the above observations, we deduced the following optimal reaction
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conditions. The CCE of 0.5 mmol of N-methoxybenzamide at 1 mA cm-2 in an undivided
cell equipped with Pt plate anode and Cu plate cathode using 20 mol% of TBAI and 15
mL DMF at 85 °C for 90 minutes.
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Table 1. Optimization of Reaction Conditionsa
Catalyst
(mol %)
Temperature Time Current Yieldb
Entry
Solvent
(°C)
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85
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85
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85
85
85
85
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85
85
85
(min)
101
105
90
(mA)
(%)
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0
1
2
KI (10)
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
EtOH
CH3CN
DMSO
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6
NaI (10)
3
I2/TBAPF6 (10)
KCl (10)
9
4
105
115
101
146
90
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31
73
83
76
85
48
90
94
94
10
29
78
5
n-Me4NI (10)
n-Bu4NBr (10)
n-Et4NBr (10)
n-Bu4NI (10)
n-Bu4NI (5)
n-Bu4NI (15)
n-Bu4NI (20)
n-Bu4NI (25)
n-Bu4NI (20)
n-Bu4NI (20)
n-Bu4NI (20)
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5.5
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161
90
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90
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n-Bu4NI (20)
n-Bu4NI (20)
n-Bu4NI (20)
n-Bu4NI (20)
n-Bu4NI (20)
n-Bu4NI (20)
n-Bu4NI (20)
n-Bu4NI (20)
n-Bu4NI (20)
Toluene
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
85
30
60
80
90
85
85
85
85
90
90
90
90
90
90
90
90
90
1.5x10-3
n.r.
25
68
90
94
65
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64
42
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19
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21c
22d
23e
24f
aReaction conditions: N-methoxybenzamide (1a, 0.5 mmol), solvent (15 mL), bGC yield, anode-cathode
systems: cGraphite-Cu, dPt-Pt, ePt-Ni, fPt-C.
With the optimized conditions in hand, we investigated the scope and generality of the
reaction for various N-methoxybenzamide derivatives containing diverse functional
groups at the ortho-, meta- and para- positions of the phenyl ring. The results are
summarized in Table 2.
In general, electrochemical C-N bond cleavage and in situ thermal rearrangement of N-
methoxybenzamide gave 2a in 92% yield. It was observed that electron donating
substrates like -CH3, -OCH3, and tBu produced good yields of corresponding products 2b-
2e. But, hindered 2-methyl-N-methoxybenzamide resulted in lower yield of 2h (52%).
Meanwhile, α- and β- N-methoxynaphthamides were also tolerated to produce the
corresponding esters 2f (81%) and 2g (64%) respectively. The lower yield of the esters of
Table 2. Substrate scope for electrochemical esterification of N-methoxybenzamide under
standard conditionsa
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aN-methoxybenzamides 1a-1r (0.5 mmol), Pt-Cu electrode in an undivided cell, Yield of isolated
pure product.
N-methoxy-1-naphthamide compared to that of N-methoxy-2-naphthamide may be
attributed to the steric hindrance of the former. Next, weakly electron withdrawing groups
such as -Cl and -Br on the para- position resulted in good yields of 2i (81%) and 2j
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(76%). However, -Cl group in meta- position resulted in poor yield of 2k (44%) and –Cl
in –ortho position did not yield the ester 2l. But, a strongly electron withdrawing group
containing amide viz. N-methoxy-4-nitrobenzamide did not provide the respective ester
2m and herein the starting material was completely recovered. Interestingly, amides
containing external multiple bonds were transformed to the corresponding esters 2n
(80%) and 2o (78%) in good yields. Moreover, on replacing the phenyl ring of the amide
with a heterocyclic furan ring did not hinder the reaction thereby producing the
corresponding ester 2p in 83% yield. However, thiophenyl and pyridynyl N-
methoxyamides were stable to electrolysis and thus did not yield any ester (2q, 2r). To
further explore the substrate scope of N-alkoxyamides, various N-substituted benzamides
were also screened as shown in Table 3. It was noteworthy, that as the –OR chain length
on nitrogen decreased, the yield of the corresponding esters increased and thus the yield
of 4a (62%) was greater than that of 4b (58%) which inturn was greater than 4c (54%).
The N-substituted cyclohexylmethoxy and benzyloxy groups i.e., 3d-3f were well
tolerated to produce the respective esters 4d (65%), 4e (73%) and 4f (71%). Interestingly,
amides containing N-substituted allyloxy and propargyloxy groups were also transformed
to the corresponding esters 4g and 4h in good yields. Notably, when a cyanide containing
amide was subjected to optimal reaction conditions, the corresponding product 4i was not
obtained, thereby the starting material was recovered.
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We observed that when N-methoxyamides containing bulky R groups like phenyl
isobutyric or adamantine were electrolyzed, the corresponding esters 6a (83%) and 6b
(81%) were obtained in excellent yields but when R is a 2,6-disubstituted group the
corresponding ester 6c (38%) was obtained in low yield.
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Table 3. Substrate scope for electrochemical esterification of N-substituted benzamides
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under standard conditionsa
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aN-substitutedbenzamides 3a-3i (0.5 mmol), Pt-Cu electrode in an undivided cell, Yield of
isolated pure product.
Having successfully achieved the electrochemical transformation of N-alkoxyamides to
carboxylic esters, we applied this electrochemical protocol for the synthesis of hindered
esters. The synthesis of hindered esters has always been a challenge because bulky
substituents always hampered the process and thus not much reports10,16 could be found in
this regard. It is worth noting that we were able to successfully synthesize hindered esters
in moderate to good yields by applying the standard conditions of electrolysis as shown in
Table 4.
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Table 4. Substrate scope for electrochemical esterification of hindered N-alkoxyamides
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under standard conditionsa
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aN-alkoxyamides 5a-5f (0.5 mmol), Pt-Cu electrode in an undivided cell, Yield of isolated pure
product
It was interesting to observe that a bulky R’ group on the amide was also tolerated to
produce the corresponding ester 6d in 64% yield. Most delightedly, this protocol was also
applicable to amides bearing both bulky R and R’ groups as in 6e (61%) eventhough 6f
was not obtained.
Control experiments (Scheme 3) were carried out by stirring 0.5 mmol N-
methoxybenzamide with TBAI dissolved in DMF at 85 °C without passing electric
current.
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Scheme 3: Control experiments
Here, the product 2a was not obtained even after 24 hours of stirring. This indicated that
passing electric current is indispensable for the reaction to be feasible. Further, when
reactions were carried out under the standard conditions using N-methoxy-N-
methylbenzamide (1s) the corresponding product was not observed. Thus, it was
concluded that N-H bond is necessary for the reaction to be viable. Further, inorder to get
insights into the reaction mechanism, the electrolysis was performed under standard
conditions in the presence of 40 mol% of a radical scavenger viz.(2,2,6,6-
tetramethylpiperidin-1-yl)oxyl (TEMPO). Here only less than 6% of the ester 2a was
isolated. This indicated that the reaction proceeded via radical mechanism. Additionally,
the effect of visible light was also studied. It was found that visible light had no impact on
the yield of the desired product and the reaction proceeded smoothly even in the dark.
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As shown in Scheme 4, inorder to understand the mechanism further, we carried out cross
over experiments under standard electrolytic conditions by taking an equimolar mixture
of N-methoxy (1b) and N-benzyloxy (3e) benzamides.
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Scheme 4: Experiment to probe the proposed intramolecular reaction pathway
After electrolysis, a 50:50 mixture of the corresponding esters 2b and 4e were obtained
with an overall yield of 72% whereas the cross-coupled products 2t and 4j were not
observed. This experiment suggested that the process occurs through an intramolecular
mechanism.
Intending to establish the practicality of the protocol the electrochemical reaction of N-
methoxybenzamide for the synthesis of methyl benzoate was scaled upto gram scale
producing 71% yield under standard conditions as shown in Scheme 5.
Scheme 5: Electrochemical gram scale synthesis of ester from N-methoxyamide
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On the basis of the above observations and former literature reports,5-10 we propose a
plausible reaction mechanism for the electrochemical reaction as shown in Scheme 6.
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Initially, at the anode, the electrochemical oxidation of the iodide ion leads to the
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formation of an iodine radical which abstracts a proton from N-methoxybenzamide, 1a
and converts it to radical intermediate
2. Being active,
2 immediately undergo
dimerization to form the N-N homo dimer,
3
thereby liberating HI which further
undergoes oxidation to produce iodide ion and H+ and the catalytic cycle continues. The
H+ produced at the anode moves towards the cathode and the expected hydrogen
evolution is suppressed due to the presence of n-Bu4N+ ions which gets eventually
adsorbed on the cathode surface.17 Finally, dimer
rearrangement to produce the methyl ester
3 undergoes insitu thermal
4
.
Scheme 6: Plausible reaction mechanism
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In conclusion, we have developed an efficient electrochemical method for the cleavage of
C-N bond of amides for the syntheses of esters by using TBAI as the redox catalyst. The
reaction was performed by CCE in an undivided cell containing a platinum anode and
copper cathode using DMF as the solvent. The protocol was applicable for the synthesis
of a wide range of carboxylic esters and was feasible even for the synthesis of hindered
esters. The electrochemical reaction was scalable to gram level highlighting its
practicability. Hitherto, this is a novel and environmentally benign electrochemical
approach for the synthesis of esters from amides. This electrochemical protocol has the
following benefits: (a) it is free from metal catalysts or oxidizing agents, thereby
simplifying the workup and isolation process leading to a reduction in waste, (b) only
catalytic amount of TBAI is required, (c) no additional supporting electrolyte is required
as TBAI serves the purpose, (d) iodine and its salts have low toxicity and are safe as
compared to bromine and other transition-metal-based oxidation catalysts. Hence, TBAI
forms the ideal catalyst in this research.
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EXPERIMENTAL SECTION:
Instruments and reagents
The electrolysis was carried out using a regulated DC power supply generated by
MetrohmAutolab PGSTAT302N. NMR spectra were recorded with an Agilent
13
Technologies (1H NMR at 500 or 400 MHz, C NMR at 125 or 100 MHz) spectrometer.
The chemical shifts are reported in ppm relative to TMS as the internal standard and the
coupling constant in Hz. A GC-MS-QP 2010 instrument (Rtx-17, 30 m × 25 mm ID, film
thickness (df ) = 0.25 μm) (column flow 2 mL min−1, 80 °C to 240 °C at 10 °C min−1 rise)
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was used for the mass analysis. GC yields were obtained using Perkin Elmer Clarus 400
instruments with an ELITE-1 column. HRMS were recorded on a micromass ESI TOF
(time-of-flight) mass spectrometer. The IR spectra was recorded in ATR (Attenuated
Total Reflectance) mode by using Perkin Elmer Spectrum two FT-IR spectrometer. All
reactions were carried out in oven dried glass wares. Starting materials 1a–1r, 3a-3i and
4a-4f were synthesized according to reported procedures.18 Other chemicals and solvents
were obtained from commercial sources like Sigma Aldrich, Alfa Aesar, Spectrochem
and were used without further purification. Analytical TLC of products was performed
with 60F254 silica gel plates (0.25 mm thickness). Products were purified by column
chromatography with silica gel (60-120 mesh) using petroleum ether/EtOAc.
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General electrochemical procedure for the synthesis of esters from
N-alkoxyamides
A 25 mL peer shaped three necked undivided cell equipped with platinum plate (30mm x
15mm) anode and copper plate (30mm x 15mm) cathode was connected to a regulated
DC power supply. N-methoxybenzamide (0.5 mmol, 75.6 mg) and TBAI (0.05 mmol, 37
mg) dissolved in 15 mL DMF were then added into the cell. Electrolysis was carried out
under CCE of 1 mA cm-2 at 85 °C until the starting material was completely consumed as
determined by TLC. The mixture was constantly stirred during electrolysis. After
electrolysis, the reaction mixture was diluted with ethyl acetate and washed twice with
water. The organic layer was separated and dried over Na2SO4, filtered and concentrated
in vacuo. The product was then purified by column chromatography.
Methyl benzoate (2a)2g
The typical procedure was applied to N-methoxybenzamide 1a (0.50 mmol, 76 mg).
Silica gel chromatography (eluent: petroleum ether/ethyl acetate = 9.5/1) of the product
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2a afforded a colorless oil (63 mg, yield 92%): 1H NMR (400 MHz, CDCl3) δH/ppm 7.93
(d, J = 8.4 Hz, 2H), 7.44 – 7.36 (m, 1H), 7.34 – 7.23 (m, 2H), 3.76 (s, 3H). 13C NMR
(100 MHz, CDCl3) δC/ppm 166.8, 132.7, 130.1, 129.4, 128.2, 51.8. IR (ATR) ν (cm−1)
2952, 1718, 1435, 1272, 1109, 707. GCMS (EI, 70 eV) m/z (%) 136.05 (44.40), 106.05
(8.88), 105.05 (100), 77.00 (69.26), 50.95 (28.75).
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Methyl 4-methylbenzoate (2b)2g
The typical procedure was applied to N-methoxy-4-methylbenzamide 1b (0.50 mmol, 83
mg). Silica gel chromatography (eluent: petroleum ether/ethyl acetate = 9.5/1) of the
product 2b afforded a white crystalline solid (59 mg, yield 78%): 1H NMR (400 MHz,
CDCl3) δH/ppm 7.90 (d, J = 8.2 Hz, 2H), 7.21 (d, J = 7.2 Hz, 2H), 3.87 (s, 3H), 2.38 (s,
3H). 13C NMR (100 MHz, CDCl3) δC/ppm 167.2, 143.5, 129.6, 129.0, 127.4, 51.9, 21.6.
IR (ATR) ν (cm−1) 2925, 1721, 1434, 1275, 1106, 753. GCMS (EI, 70 eV) m/z (%)
150.05 (43.50), 120.05 (10.35), 119.05 (100), 91.05 (58.49), 77.00 (1.64), 50.95 (4.42).
Methyl 4-methoxybenzoate (2c)2g
The typical procedure was applied to N,4-dimethoxybenzamide 1c (0.50 mmol, 91 mg).
Silica gel chromatography (eluent: petroleum ether/ethyl acetate = 9.5/1) of the product
2c afforded a white solid (76 mg, yield 91%): 1H NMR (400 MHz, CDCl3) δH/ppm 7.74
(d, J = 8.1 Hz, 2H), 6.66 (d, J = 8.0 Hz, 2H), 3.63 (s, 3H), 3.56 (s, 3H). 13C NMR (100
MHz, CDCl3) δC/ppm 166.8, 163.3, 131.6, 122.5, 113.6, 55.4, 51.8. IR (ATR) ν (cm−1)
2952, 2843, 1705, 1426, 1280, 1104, 1020, 769. GCMS (EI, 70 eV) m/z (%) 166.00
(42.42), 136.05 (10.16), 135.05 (100), 107.00 (20.20), 91.95 (16.46), 77.00 (27.75), 63.95
(11.83).
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Methyl 4-(tert-butyl)benzoate (2d)2g
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The typical procedure was applied to 4-(tert-butyl)-N-methoxybenzamide 1d (0.50 mmol,
104 mg). Silica gel chromatography (eluent: petroleum ether/ethyl acetate = 9.5/1) of the
product 2d afforded a light yellow oil (67 mg, yield 70%): 1H NMR (400 MHz, CDCl3)
δH/ppm 7.93 (d, J = 8.5 Hz, 2H), 7.39 (d, J = 8.5 Hz, 2H), 3.84 (s, 3H), 1.28 (s, 9H). 13C
NMR (100 MHz, CDCl3) δC/ppm 166.9, 156.4, 129.4, 127.4, 125.2, 51.8, 34.9, 31.0. IR
(ATR) ν (cm−1) 2955, 1722, 1435, 1277, 1116, 775, 707. GCMS (EI, 70 eV) m/z (%)
192.00 (21.26), 178.05 (12.74), 177.05 (100), 161.05 (11.85), 149.05 (27.21), 115.00
(11.09), 105.00 (18.89), 91.00 (17.73), 77.00 (9.10), 58.95 (13.17).
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Methyl 3-methylbenzoate (2e)2g
The typical procedure was applied to N-methoxy-3-methylbenzamide 1e (0.50 mmol, 83
mg). Silica gel chromatography (eluent: petroleum ether/ethyl acetate = 9.5/1) of the
product 2e afforded a colorless oil (67 mg, yield 89%): 1H NMR (400 MHz, CDCl3)
δH/ppm 7.81 (d, J = 2.2 Hz, 1H), 7.79 (s, 1H), 7.28 (d, J = 4.3 Hz, 1H), 7.24 (dd, J = 7.7,
2.3 Hz, 1H), 3.85 (s, 3H), 2.33 (s, 3H). 13C NMR (100 MHz, CDCl3) δC/ppm 167.1,
138.0, 133.6, 130.0, 128.2, 126.6, 51.9, 21.1. IR (ATR) ν (cm−1) 2952, 1718, 1436, 1279,
1201, 1106, 743. GCMS (EI, 70 eV) m/z (%) 150.20 (41.11), 119.15 (100), 91.10
(61.80), 65.05 (19.09), 39.05 (7.40).
Methyl 2-naphthoate (2f)2e
The typical procedure was applied to N-methoxy-2-napthamide 1f (0.50 mmol, 101 mg).
Silica gel chromatography (eluent: petroleum ether/ethyl acetate = 9.5/1) of the product 2f
afforded a white solid (75 mg, yield 81%): 1H NMR (400 MHz, CDCl3) δH/ppm 8.60 (s,
1H), 8.05 (d, J = 8.7 Hz, 1H), 7.93 (d, J = 8.1 Hz, 1H), 7.86 (d, J = 8.2 Hz, 2H), 7.55 (m,
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2H), 3.97 (s, 3H). 13CNMR (100 MHz, CDCl3) δC/ppm 167.2, 135.5, 132.5, 131.0, 129.3,
128.2, 128.1, 127.7, 127.4, 126.6, 125.2, 52.2. IR (ATR) ν (cm−1) 1706, 1438, 1294,
1201, 1130, 768, 484. GCMS (EI, 70 eV) m/z (%) 186.00 (47.57), 156.00 (11.27), 155.00
(91.65), 127.05 (100), 101.00 (9.62), 77.05 (20.64), 63.15 (17.61), 51.00 (10.32).
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Methyl 1-naphthoate (2g)2e
The typical procedure was applied to N-methoxy-1-napthamide 1g (0.50 mmol, 101 mg).
Silica gel chromatography (eluent: petroleum ether/ethyl acetate = 9.5/1) of the product
2g afforded a colorless oil (60 mg, yield 64%): 1H NMR (400 MHz, CDCl3) δH/ppm 9.01
(d, J = 8.6 Hz, 1H), 8.18 (d, J = 7.3 Hz, 1H), 7.95 (d, J = 8.2 Hz, 1H), 7.83 (d, J = 8.2 Hz,
1H), 7.67 – 7.57 (m, 1H), 7.56 – 7.47 (m, 1H), 7.47 – 7.39 (m, 1H), 3.97 (s, 3H). 13C
NMR (100 MHz, CDCl3) δC/ppm 167.9, 133.8, 133.4, 131.4, 130.3, 128.6, 127.8, 127.0,
126.2, 125.9, 124.5, 52.1. IR (ATR) ν (cm−1) 2950, 1711, 1435, 1243, 1133, 778. GCMS
(EI, 70 eV) m/z (%) 185.95 (62.28), 155.00 (100), 127.05 (89.67), 101.00 (7.26), 77.00
(13.65), 63.10 (11.71), 50.95 (6.77).
Methyl 2-methylbenzoate (2h)2g
The typical procedure was applied to N-methoxy-2-methylbenzamide 1h (0.50 mmol, 83
mg). Silica gel chromatography (eluent: petroleum ether/ethyl acetate = 9.5/1) of the
product 2h afforded a colorless oil (39 mg, yield 52%): 1H NMR (400 MHz, CDCl3)
δH/ppm 7.85 (d, J = 8.2 Hz, 1H), 7.29 (d, J = 1.7 Hz, 1H), 7.15 (dd, J = 9.0, 5.3 Hz, 2H),
3.79 (s, 3H), 2.54 (s, 3H). 13C NMR (100 MHz, CDCl3) δC/ppm 167.8, 140.1, 131.8,
131.6, 130.5, 129.4, 125.6, 51.5, 21.6. IR (ATR) ν (cm−1) 2952, 1718, 1435, 1254, 1082,
735. GCMS (EI, 70 eV) m/z (%) 150.05 (59.43), 120.05 (9.36), 119.05 (100), 91.00
(89.65), 76.95 (9.73), 64.95 (34.61).
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Methyl 4-chlorobenzoate (2i)2g
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The typical procedure was applied to 4-chloro-N-methoxybenzamide 1i (0.50 mmol, 93
mg). Silica gel chromatography (eluent: petroleum ether/ethyl acetate = 9.5/1) of the
product 2i afforded a colorless oil (69 mg, yield 81%): 1H NMR (400 MHz, CDCl3)
δH/ppm 7.95 (d, J = 8.4 Hz, 2H), 7.39 (d, J = 7.7 Hz, 2H), 3.89 (s, 3H). 13C NMR (100
MHz, CDCl3) δC/ppm 166.1, 139.3, 130.9, 128.6, 128.5, 52.2. IR (ATR) ν (cm−1) 1675,
1400, 1276, 1090, 759, 522. GCMS (EI, 70 eV) m/z (%) 170.10, (30.46), 141.10 (32.38),
139.10 (100), 113.10 (13.13), 111.05 (40.31), 75.05 (25.11), 50.00 (10.87).
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Methyl 4-bromobenzoate (2j)2g
The typical procedure was applied to 4-bromo-N-methoxybenzamide 1j (0.50 mmol, 115
mg). Silica gel chromatography (eluent: petroleum ether/ethyl acetate = 9.5/1) of the
product 2j afforded a white solid (82 mg, yield 76%): 1H NMR (400 MHz, CDCl3)
δH/ppm 7.87 (d, J = 8.6 Hz, 2H), 7.56 (d, J = 8.6 Hz, 2H), 3.89 (s, 3H). 13C NMR (100
MHz, CDCl3) δC/ppm 166.3, 131.7, 131.1, 129.0, 128.0, 52.3. IR (ATR) ν (cm−1) 2950,
1714, 1581, 1433, 1190, 848, 755, 572. GCMS (EI, 70 eV) m/z (%) 213.85 (36.40),
184.85 (94.97), 182.85 (100), 156.90 (42.22), 154.90, (43.86), 135.00 (13.02), 104.00
(8.08), 76.00 (57.96), 75.00 (59.48), 73.95 (31.75), 49.95 (58.79).
Methyl 3-chlorobenzoate (2k)2e
The typical procedure was applied to 3-chloro-N-methoxybenzamide 1k (0.50 mmol, 93
mg). Silica gel chromatography (eluent: petroleum ether/ethyl acetate = 9.5/1) of the
product 2k afforded a colorless oil (38 mg, yield 44%): 1H NMR (400 MHz, CDCl3)
δH/ppm 7.99 (s, 1H), 7.89 (d, J = 7.5 Hz, 1H), 7.49 (d, J = 8.0 Hz, 1H), 7.41 – 7.29 (m,
1H), 3.90 (s, 3H). 13C NMR (100 MHz, CDCl3) δC/ppm 165.7, 134.4, 132.8, 131.8,
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129.56, 129.62, 127.6, 52.3. IR (ATR) ν (cm−1) 2925, 1726, 1437, 1256, 739, 674.
GCMS (EI, 70 eV) m/z (%) 170.05 (35.95), 141.00 (32.18), 139.00 (100), 112.95
(16.52), 110.95 (51.28), 74.95 (30.79), 49.95 (14.46).
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Methyl cinnamate (2n)10
The typical procedure was applied to N-methoxycinnamamide 1n (0.50 mmol, 89 mg).
Silica gel chromatography (eluent: petroleum ether/ethyl acetate = 9.5/1) of the product
2n afforded a light yellow oil (65 mg, yield 80%): 1H NMR (400 MHz, CDCl3) δH/ppm
7.67 (d, J = 16.0 Hz, 1H), 7.47 (d, J = 1.9 Hz, 2H), 7.34 (t, J = 1.5 Hz, 3H), 6.42 (d, J =
16.1 Hz, 1H), 3.77 (s, 3H). 13C NMR (100 MHz, CDCl3) δC/ppm 167.4, 144.8, 134.3,
130.3, 128.8, 128.0, 117.8, 51.6. IR (ATR) ν (cm−1) 2950, 1713, 1636, 1434, 1167, 766,
683. GCMS (EI, 70 eV) m/z (%) 162.00 (52.19), 161.00, (27.82), 156.00 (11.27), 155.00
(91.65), 131.00 (100), 103.00 (65.29), 76.95 (37.45), 50.95 (22.42).
Methyl-3-phenylpropiolate (2o)19
The typical procedure was applied to N-methoxy-3-phenylpropiolamide 1o (0.50 mmol,
88 mg). Silica gel chromatography (eluent: petroleum ether/ethyl acetate = 9.5/1) of the
product 2o afforded a pale yellow oil (62 mg, yield 78%): 1H NMR (500 MHz, CDCl3)
δH/ppm δ 7.58 – 7.52 (m, 2H), 7.44 – 7.32 (m, 3H), 3.81 (s, 3H). 13C NMR (125 MHz,
CDCl3) δC/ppm 154.4, 133.0, 130.7, 128.6, 119.5, 86.4, 80.4, 52.8. IR (ATR) ν (cm−1).
2954, 2224, 1708, 1434, 1285, 1168, 1003, 756, 688. GCMS (EI, 70 eV) m/z (%)195.95
(3.77), 165.00 (7.17), 160.00 (31.96), 130.05 (12.18), 129.10 (100), 102.05 (40.00),
101.05 (11.59), 75.00 (16.97), 51.00 (7.62).
Methyl furan-2-carboxylate (2p)20
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The typical procedure was applied to N-methoxyfuran-2-carboxamide 1p (0.50 mmol, 71
mg). Silica gel chromatography (eluent: petroleum ether/ethyl acetate = 9.5/1) of the
product 2p afforded a pale yellow liquid (52 mg, yield 83%): 1H NMR (500 MHz,
CDCl3) δH/ppm 7.54 (d, J = 1.0 Hz, 1H), 7.14 (dd, J = 3.6, 0.6 Hz, 1H), 6.47 (dd, J = 3.5,
1.7 Hz, 1H), 3.86 (s, 3H). 13C NMR (125 MHz, CDCl3) δC/ppm 159.1, 146.3, 144.5,
117.9, 111.8, 51.9. IR (ATR) ν (cm−1) 2956, 1722, 1476, 1299, 1116, 760. GCMS (EI, 70
eV) m/z (%) 126.05 (38.23), 96.05 (10.21), 95.05 (100), 68.00 (4.23), 67.00 (6.27).
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Ethyl benzoate (4a)4d
The typical procedure was applied to N-ethoxybenzamide 3a (0.50 mmol, 83 mg). Silica
gel chromatography (eluent: petroleum ether/ethyl acetate = 9.5/1) of the product 4a
afforded a colorless oil (47 mg, yield 62%): 1H NMR (400 MHz, CDCl3) δH/ppm 8.03 (d,
J = 6.9 Hz, 2H), 7.65 – 7.47 (m, 1H), 7.41 (dd, J = 8.3, 6.9 Hz, 2H), 4.35 (q, J = 7.1 Hz,
2H), 1.37 (t, J = 7.1 Hz, 3H). 13C NMR (100 MHz, CDCl3) δC/ppm 166.6, 132.8, 130.4,
129.5, 128.3, 60.9, 14.3. IR (ATR) ν (cm−1) 2982, 1714, 1451, 1270, 1174, 1106, 708.
GCMS (EI, 70 eV) m/z (%) 150.05 (28.24), 122.00 (47.27), 105.95 (14.34), 105.15
(100), 77.00 (69.95), 51.00 (31.44).
Propyl benzoate (4b)4d
The typical procedure was applied to N-propoxybenzamide 3b (0.50 mmol, 90 mg). Silica
gel chromatography (eluent: petroleum ether/ethyl acetate = 9.5/1) of the product 4b
afforded a colorless oil (48 mg, yield 58%): 1H NMR (400 MHz, CDCl3) δH/ppm 8.03 (d,
J = 7.0 Hz, 2H), 7.53 (t, J = 7.4 Hz, 1H), 7.42 (dd, J = 8.3, 7.0 Hz, 2H), 4.26 (t, J = 6.7
Hz, 2H), 1.77 (h, J = 7.3 Hz, 2H), 1.01 (t, J = 7.4 Hz, 3H). 13C NMR (100 MHz, CDCl3)
δC/ppm 166.7, 132.8, 130.5, 129.5, 128.3, 66.5, 22.1, 10.5. IR (ATR) ν (cm−1) 2970,
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1717, 1452, 1270, 1108, 709. GCMS (EI, 70 eV) m/z (%) 164.00 (3.15), 123.05 (75.99),
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122.05 (51.50), 105.95 (23.03), 105.15 (100), 77.00 (78.83), 51.00 (36.21), 41.05 (10.56).
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Butyl benzoate (4c)21
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The typical procedure was applied to N-butoxybenzamide 3c (0.50 mmol, 97 mg). Silica
gel chromatography (eluent: petroleum ether/ethyl acetate = 9.5/1) of the product 4c
afforded a colourless oil (54 mg, yield 61%): 1H NMR (500 MHz, CDCl3) 8.09 – 8.00
(m, 2H), 7.58 – 7.49 (m, 1H), 7.43 (t, J = 7.7 Hz, 2H), 4.32 (t, J = 6.6 Hz, 2H), 1.80 –
1.70 (m, 2H), 1.52 – 1.43 (m, 2H), 0.98 (t, J = 7.4 Hz, 3H). 13C NMR (125 MHz, CDCl3)
δC/ppm 166.7, 132.8, 130.5, 129.5, 128.3, 64.8, 30.8, 19.3, 13.8. IR (ATR) ν (cm−1) 2960,
2874, 1716, 1452, 1270, 1108, 1027, 707. GCMS (EI, 70 eV) m/z (%) 178.00 (2.29%),
123.15 (87.32%), 122.05 (28.00%), 106.10 (12.40%), 105.15 (100%), 79.05 (15.30%),
77.05 (64.59%), 56.05 (32.04%), 51.00 (20.73%), 41.00 (10.81%).
Cyclohexylmethyl benzoate (4d)4d
The typical procedure was applied to N-(cyclohexylmethoxy)benzamide 3d (0.50 mmol,
117 mg). Silica gel chromatography (eluent: petroleum ether/ethyl acetate = 9.5/1) of the
product 4d afforded a colorless oil (71 mg, yield 65%): 1H NMR (400 MHz, CDCl3)
δH/ppm 8.03 (dd, J = 8.4, 1.4 Hz, 2H), 7.64 – 7.48 (m, 1H), 7.42 (dd, J = 8.4, 7.0 Hz, 2H),
4.12 (d, J = 6.3 Hz, 2H), 1.86 – 1.62 (m, 5H), 1.41 – 0.83 (m, 6H). 13C NMR (100 MHz,
CDCl3) δC/ppm 166.6, 132.8, 130.5, 129.5, 128.3, 70.0, 37.2, 29.7, 26.4, 25.7. IR (ATR)
ν (cm−1) 2924, 2853,1717, 1450, 1268, 1176, 1113, 708. GCMS (EI, 70 eV) m/z (%)
218.15 (0.03), 123.00 (20.15), 105.00 (99.61), 96.10 (100), 81.05 (94.42), 77.00 (63.31),
68.05 (23.36), 67.05 (42.26), 55.05 (33.11), 54.05 (15.83), 51.00 (17.12), 41.05 (23.24).
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Benzyl benzoate (4e)4d
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The typical procedure was applied to N-(benzyloxy)benzamide 3e (0.50 mmol, 114 mg).
Silica gel chromatography (eluent: petroleum ether/ethyl acetate = 9.5/1) of the product
4e afforded a colorless oil (77 mg, yield 73%): 1H NMR (400 MHz, CDCl3) δH/ppm 8.12
– 8.05 (m, 2H), 7.60 – 7.51 (m, 1H), 7.49 – 7.31 (m, 5H), 5.37 (s, 3H). 13C NMR (100
MHz, CDCl3) δC/ppm 166.4, 136.0, 133.2, 130.1, 129.7, 128.6, 128.4, 128.2, 128.2, 66.7.
IR (ATR) ν (cm−1) 1716, 1451, 1266, 1175, 708. GCMS (EI, 70 eV) m/z (%) 212.00
(38.42), 194.00 (22.16), 167.05 (11.92), 105.95 (19.66), 105.15 (100), 91.05 (82.23),
79.05 (12.98), 77.00 (63.57), 65.05 (25.60), 51.00 (31.53), 39.00 (11.98).
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3-chlorobenzyl benzoate (4f)2f
The typical procedure was applied to N-((3-chlorobenzyl)oxy)benzamide 3f (0.50 mmol,
131 mg). Silica gel chromatography (eluent: petroleum ether/ethyl acetate = 9.5/1) of the
product 4f afforded a colorless oil (87 mg, yield 71%): 1H NMR (400 MHz, CDCl3)
δH/ppm 8.07 (d, J = 6.9 Hz, 2H), 7.56 (t, J = 7.4 Hz, 1H), 7.44 (t, J = 7.7 Hz, 3H), 7.30 (d,
J = 1.4 Hz, 3H), 5.32 (s, 2H). 13C NMR (100 MHz, CDCl3) δC/ppm 166.2, 138.0, 134.4,
133.2, 129.9, 129.8, 129.7, 128.4, 128.4, 128.1, 126.1, 65.7. IR (ATR) ν (cm−1) 1718,
1451, 1265, 1176, 1107, 709, 538. GCMS (EI, 70 eV) m/z (%) 245.90 (22.44), 127.00
(11.07), 125.00 (34.50), 105.95 (22.88), 89.00 (19.85), 105.15 (100), 77.00 (50.16), 51.00
(18.15).
Prop-2-en-1-yl benzoate (4g)22
The typical procedure was applied to N-(prop-2-en-1-yloxy)benzamide 3g (0.50 mmol, 89
mg). Silica gel chromatography (eluent: petroleum ether/ethyl acetate = 9.5/1) of the
product 4g afforded a colorless oil (60 mg, yield 74%): 1H NMR (400 MHz, CDCl3)
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δH/ppm 8.05 (d, J = 7.0 Hz, 2H), 7.61 – 7.49 (m, 1H), 7.42 (dd, J = 8.6, 6.9 Hz, 2H), 6.11
– 5.91 (m, 1H), 5.45 – 5.22 (m, 2H), 4.81 (d, J = 5.6 Hz, 2H). 13C NMR (100 MHz,
CDCl3) δC/ppm 166.2, 133.0, 132.2, 130.1, 129.6, 128.3, 118.2, 65.5. IR (ATR) ν (cm−1)
1717, 1649, 1452, 1266, 1176, 1108, 708. GCMS (EI, 70 eV) m/z (%) 162.00 (10.69),
117.05 (9.70), 105.95 (47.59), 105.05 (100), 77.00 (75.98), 51.00 (34.27), 50.00 (10.50),
41.00 (16.54), 39.00 (18.26).
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Prop-2-yn-1-yl benzoate (4h)23
The typical procedure was applied to N-(prop-2-yn-1-yloxy)benzamide 3h (0.50 mmol,
88 mg). Silica gel chromatography (eluent: petroleum ether/ethyl acetate = 9.5/1) of the
product 4h afforded a colorless oil (58 mg, yield 73%): 1H NMR (400 MHz, CDCl3)
δH/ppm 8.04 (d, J = 8.4 Hz, 2H), 7.53 (td, J = 7.4, 1.4 Hz, 1H), 7.41 (t, J = 7.0 Hz, 2H),
4.89 (d, J = 1.6 Hz, 2H), 2.51 (t, J = 2.4 Hz, 1H). 13C NMR (100 MHz, CDCl3) δC/ppm
165.7, 133.3, 129.8, 129.3, 128.4, 77.7, 75.1, 52.4. IR (ATR) ν (cm−1) 3296, 1720, 1452,
1262, 1095, 707, 568. GCMS (EI, 70 eV) m/z (%) 159.95 (12.92), 115.00 (24.70), 105.95
(42.58), 105.05 (100), 77.05 (79.87), 50.95 (43.83), 50.00 (14.39), 39.00 (24.75).
Methyl-2-methyl-2-phenylpropanoate (6a)24
The typical procedure was applied to N-methoxy-2-methyl-2-phenylpropanamide 5a
(0.50 mmol, 97 mg). Silica gel chromatography (eluent: petroleum ether/ethyl acetate =
9.5/1) of the product 6a afforded a white solid (74 mg, yield 83%): 1H NMR (500 MHz,
CDCl3) δH/ppm 7.5 – 7.16 (m, 5H), 3.66 (s, 3H), 1.61 (d, J = 1.6 Hz, 6H). 13C NMR (125
MHz, CDCl3) δC/ppm 177.3, 144.7, 128.4, 126.7, 125.6, 52.2, 46.5, 26.6. IR (ATR) ν
(cm−1) 2977, 1730, 1434, 1255, 1144, 697. GCMS (EI, 70 eV) m/z (%) 178.05 (21.95),
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120.15 (11.91), 119.15 (100), 103.05 (6.98), 91.10 (56.70), 77.05 (8.33), 51.00 (4.49),
41.00 (11.61).
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3r, 5r, 7r)-methyl adamantane-1-carboxylate (6b)10
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The typical procedure was applied to (3r, 5r, 7r)-N-methoxyadamantane-1-carboxamide
5b (0.50 mmol, 105 mg). Silica gel chromatography (eluent: petroleum ether/ethyl acetate
= 9.5/1) of the product 6b afforded a colourless oil (79 mg, yield 81%): 1H NMR (500
MHz, CDCl3) δH/ppm 3.62 (s, 3H), 1.98 (s, 3H), 1.86 (d, J = 3.0 Hz, 6H), 1.75 – 1.62 (m,
6H). 13C NMR (125 MHz, CDCl3) δC/ppm 178.2, 51.5, 40.6, 38.8, 36.5, 27.9. IR (ATR) ν
(cm−1) 2905, 2852, 1728, 1452, 1233, 1184, 1076. GCMS (EI, 70 eV) m/z (%) 194.10
(13.97), 136.20 (12.07), 135.20 (100), 107.10 (9.55), 93.10 (14.92), 79.05 (13.96), 41.00
(3.47).
Methyl-2,6-dimethoxybenzoate (6c)25
The typical procedure was applied to N,2,6-trimethoxybenzamide 5c (0.50 mmol, 106
mg). Silica gel chromatography (eluent: petroleum ether/ethyl acetate = 9.5/1) of the
product 6c afforded off white solid (37 mg, yield 38%): 1H NMR (500 MHz, CDCl3)
δH/ppm 7.27 (t, J = 8.5 Hz, 1H), 6.55 (d, J = 8.4 Hz, 2H), 3.90 (s, 3H), 3.80 (s, 6H). 13C
NMR (125 MHz, CDCl3) δC/ppm 167.1, 157.3, 131.1, 112.9, 103.9, 77.3, 77.0, 76.8,
56.0, 52.4. IR (ATR) ν (cm−1) 3006, 2921, 2850, 1731, 1594, 1475, 1251, 1104. GCMS
(EI, 70 eV) m/z (%) 196.00 (42.37), 166.00 (10.17), 165.00 (100), 150.05 (25.19), 136.05
(12.62), 122.00 (9.62), 107.00 (22.59), 79.00 (5.47), 77.00 (7.89), 51.00 (4.12).
Isobutyl benzoate (6d)4d
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The typical procedure was applied to N-isobutoxybenzamide 5d (0.50 mmol, 97 mg).
Silica gel chromatography (eluent: petroleum ether/ethyl acetate = 9.5/1) of the product
6d afforded a colourless oil (54 mg, yield 61%): 1H NMR (500 MHz, CDCl3) δH/ppm
8.10 – 8.02 (m, 2H), 7.58 – 7.50 (m, 1H), 7.46 – 7.40 (m, 2H), 4.11 (d, J = 6.6 Hz, 2H),
2.15 – 2.03 (m, 1H), 1.02 (d, J = 6.7 Hz, 6H). 13C NMR (125 MHz, CDCl3) δC/ppm
166.6, 132.8, 130.5, 129.5, 128.3, 71.0, 27.9, 19.2. IR (ATR) ν (cm−1) 2963, 2875, 1717,
1451, 1268, 1109, 1026, 708. GCMS (EI, 70 eV) m/z (%)178.05 (0.05%), 124.10
(8.37%), 123.15 (81.71%), 106.05 (14.43%), 105.15 (100%), 79.05 (7.67%), 77.05
(63.38%), 56.05 (45.73%), 51.00 (20.65%), 41.00 (12.11%).
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(
3r, 5r, 7r)-tert-butyl adamantane-1-carboxylate (6e)10
The typical procedure was applied to (3r, 5r, 7r)-N-(tert-butoxy)adamantane-1-
carboxamide 5e (0.50 mmol, 126 mg). Silica gel chromatography (eluent: petroleum
ether/ethyl acetate = 9.5/1) of the product 6e afforded a colourless oil (72 mg, yield 61%):
1H NMR (500 MHz, CDCl3) δH/ppm 2.02 (d, J = 3.2 Hz, 4H), 1.90 (d, J = 2.9 Hz, 8H),
1.83 (d, J = 2.9 Hz, 1H), 1.77 – 1.65 (m, 9H), 1.42 (s, 2H). 13C NMR (125 MHz, CDCl3)
δC/ppm 184.2, 40.5, 38.8, 38.5, 36.4, 28.0, 27.8. IR (ATR) ν (cm−1). 2905, 2852, 1695,
1453, 1247, 1169, 1079. GCMS (EI, 70 eV) m/z (%) 180.05 (4.84), 136.15 (11.57),
135.15 (100), 107.05 (9.06), 93.05 (13.68), 79.05 (12.57), 57.05 (6.22), 41.00 (3.85).
Procedure for the gram scale synthesis of methyl benzoate
A 250 mL round bottomed flask with detachable three neck lid equipped with a
cylindrical platinum gauze (d = h = 4.5 cm) anode and copper plate (4.5 cm x 6.0 cm)
cathode was connected to a regulated DC power supply. N-methoxybenzamide (7.0
mmol, 1.06 g) and TBAI (1.4 mmol, 2.6 g) dissolved in 150 mL DMF were then added
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into the cell. Electrolysis was carried out under CCE of 1 mA cm-2 at 85 °C for 90
minutes until 1 F mol-1 charge was consumed. The mixture was constantly stirred during
electrolysis. After electrolysis, the reaction mixture was diluted with ethyl acetate and
washed thrice with water. The organic layer was separated and dried over Na2SO4,
filtered and concentrated in vacuo. The product was then purified by column
chromatography.
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ASSOCIATED CONTENT
Supporting Information
Copies of 1H and 13C NMR spectra
AUTHOR INFORMATION
Corresponding Author
E-mail: bm.bhanage@ictmumbai.edu.in.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGEMENTS
K. S. is thankful to the University Grants Commission of India (UGC) for providing the
Basic Scientific Research (BSR) fellowship. S. L. Y. is thankful to the Council of
Scientific and Industrial Research (CSIR), Govt. of India, for providing the Senior
Research Fellowship (SRF).
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