Generation of bis-Acyl ketals from esters and benzyl amines under oxidative conditions

Article abstract of DOI:10.1021/jo502903d

Treatment of benzylamines with esters at an elevated temperature are expected to give amides. However, in the presence of TBAI/TBHP, esters possessing a methylene carbon α-to oxygen with benzylamines provide bis-esters rather than the expected amides. Benzylamines under oxidative conditions generate less nucleophilic carboxylates, which couples at the sp³ C-H bonds of esters and cyclic ethers to give bis-acyl ketals and α-acyloxy ethers, respectively.

Full text of DOI:10.1021/jo502903d

Article
pubs.acs.org/joc
Generation of bis-Acyl Ketals from Esters and Benzyl Amines Under
Oxidative Conditions
Ganesh Majji, Suresh Rajamanickam, Nilufa Khatun, Sourav Kumar Santra, and Bhisma K. Patel*
Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati 781039, India
S
* Supporting Information
ABSTRACT: Treatment of benzylamines with esters at an
elevated temperature are expected to give amides. However, in
the presence of TBAI/TBHP, esters possessing a methylene
carbon α-to oxygen with benzylamines provide bis-esters
rather than the expected amides. Benzylamines under oxidative
conditions generate less nucleophilic carboxylates, which
couples at the sp3 C−H bonds of esters and cyclic ethers to give bis-acyl ketals and α-acyloxy ethers, respectively.
Scheme 1. Selectivity Achieved with Various Catalysts in the
Reactions of Benzylamine
INTRODUCTION
■
In the modern era of organic chemistry, the atom and step
economical synthesis of complex target molecules from simple
precursors via direct C(sp3)−H bond functionalization is of
paramount interest to both academia and industrial research.1
Thus, synthetic chemists continue to strive toward the
development of “ideal synthetic procedures” to directly
transform C−H bonds into other functional groups, which
could eventually be applied to the synthesis of natural
products.2 In this perspective, cross dehydrogenative coupling
(CDC) has played a vital role in the construction of a diverse
array of C−C and C−heteroatom bonds, by functionalizing C−
H bonds of all types.3 One of the extensively studied
approaches in this forum is the CDC strategy involving simple
solvents (i.e., alkylbenzenes, cyclic ethers, and cycloalkanes with
various coupling partners), most of which have ultimately lead
to the synthesis of esters via C(sp3)−H functionalization.4
Barring one example from our group, functionalization of α
sp3 C−H bond in ethyl acetate (ester) has been virtually
unexplored.5 Ethyl acetate is predominantly used as a solvent
and diluents because it is inexpensive and less toxic. Due to its
reactive nature toward various nucleophiles and its suscepti-
bility to hydrolysis, selective functionalization of esters in
general and ethyl acetate in particular is a challenging task.
Pertinent to this “solvent chemistry” in CDC reactions, recently
our group has developed a protocol for the synthesis of esters
via oxidative esterification of α sp3 C−H bond in ethyl acetate
with terminal alkenes and alkynes under metal-free conditions,
where alkenes and alkynes served as ArCOO- surrogates.5 It
would be exciting if one can explore the selective α sp3 C−H
functionalization of ethyl acetate as uncharted so far.
b, Scheme 1).7 Recently, alkenes and alkynes are also found to
be the surrogates of the ArCOO- group and have been utilized
for the bis-esterification of ethyl acetate.5 Further, when Pd is
used as the catalyst, benzylamine act as an aroyl (ArCO−)
source, while the use of Cu installs an aryl carboxy (ArCOO−)
group into ortho-directing substrates. Of late, metal free
combinations, viz., tetrabutylammonium iodide (TBAI)/
TBHP, are an efficient substitute to transition metals/oxidant
combinations. Thus, the reaction of benzylamine and ethyl
acetate under a metal-free oxidative condition is expected to
yield an amide or a bis-ester of ethyl acetate.5,8
Benzylamines are latent sources to aroyl (ArCO−) and aryl
carboxy (ArCOO−) groups.6,7 The Wu group has reported a
Pd catalyzed ortho-acylation of 2-phenylpyridine using benzyl-
amines, where it serve as ArCO- surrogates (path a, Scheme
1).6a Very recently our group has developed a copper-catalyzed
protocol for the o-benzoxylation of 2-phenylpyridines using
benzylamines as the arylcarboxy (ArCOO−) equivalents (path
Received: December 22, 2014
© XXXX American Chemical Society
A
DOI: 10.1021/jo502903d
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To seek an answer to the above possibilities, an initial
reaction was performed by reacting ethyl acetate (2 mL) and
benzylamine (1 mmol) in the presence of TBAI (20 mol %)
and oxidant TBHP (5−6 M in decane) (6 equiv) at 80 °C
(Table 1, entry 1). The outcome of this reaction was not
1, entry 2). Keeping all other parameters constant but
decreasing the quantity of TBHP from 6 to 5 equiv. or the
Bu4NI quantity from 20 to 10 mol %, a reduction in the
product yields (62% and 58%, respectively) (Table 1, entries
3−4) were found. No further improvement in the yield was
observed by either increasing the catalyst Bu4NI (30 mol %),
oxidant TBHP (7 equiv), or reaction temperature (100 °C)
(Table 1, entries 5−7). Other oxidants such as aq H2O2, di-tert
butyl peroxide (DTBP), benzoylperoxide, oxone, K2S2O8, and
DDQ were completely unproductive (Table 1, entries 8−13).
Surprisingly, no desired product could be obtained when other
halogen species such as Bu4NBr, I2, and KI (Table 1, entries
14−16) were used instead of Bu4NI. Control experiments
performed in the absence of either oxidant (TBHP) or catalyst
(Bu4NI) failed to achieve the desired transformation (Table 1,
entries 17−18). The byproducts formed in these reactions
(entries 8, 10−12, and 14−17) are benzaldehyde and benzoic
acid only. However, using oxidants such as DTBP (Table 1,
entry 9), DDQ (Table 1, entry 13) and in the absence of any
oxidant (Table 1, entry 18), benzylamine remained intact.
Benzaldehyde is generated in situ from benzylamine under
oxidative condition via the intermediacy of phenylmethanimine
and benzoic acid by the oxidation of performed benzaldehyde.
Therefore, the use of benzylamine (1 mmol), ethyl acetate (2
mL), Bu4NI (20 mol %), and aqueous TBHP (70% in water)
(6 equiv) at a temperature of 80 °C gave the best conversion
after 8 h (entry 2).
The above optimized condition was then implemented for
the oxidative esterification of ethyl acetate (a) using various
substituted benzylamines. The electron neutral −H (1) and
electron-donating substituents, viz., p-Me (2), p-OMe (3), 2,4-
di-OMe (4), as well as electron-withdrawing substituents, viz.,
p-F (5), p-Cl (6), p-Br (7), o-Cl (8), o-Br (9), m-Cl (10), and
m-CF3 (11) present in the phenyl ring of benzylamines were all
found to serve as ArCOO- surrogates providing the desired
double esters (i.e., unsymmetrical gem-diacylates (1a−11a) in
good to moderate yields as shown in Scheme 2). It was
observed that substituted benzylamines possessing electron-
withdrawing groups provided the corresponding products in
lower yields than those bearing electron-donating groups.
These results imply that the electronic effect of substituents on
the phenyl ring of benzylamines played a role in controlling the
product yields. This trend in reactivity is similar to our recent o-
benzoxylation of 2-phenylpyridine using benzylamines as
ArCOO- sources.7
The synthetic utility of this double esterification strategy was
further examined with another ester, n-propyl acetate (b),
having a methylene carbon α- to oxygen. When various
benzylamines (1), (3), and (6) were reacted with n-propyl
acetate (b) under identical reaction conditions, the desired
double esters (1b), (3b), and (6b) were obtained in similar
yields to that using ethyl acetate (a) (Scheme 2). Yet another
analogous ester n-butyl acetate (c) upon treatment with a set of
benzylamines (1), (3), and (6) produced their respective
desired double esters (1c), (3c), and (6c) in modest yields
(Scheme 2). Here again, the trends in the reactivity of
substituted benzylamines were found to be identical to those
observed for ethyl acetate (a). The use of allylamine in lieu of
benzylamine was not successful. Neither amidation nor ester
formation was observed when allyl amine was subjected under
the present reaction conditions with ethyl acetate as the allyl
amine remain intact. Interestingly, when α-methyl benzylamine
(12) was treated with ethyl acetate (a) under the present
a
Table 1. Screening of Reaction Conditions
b
entry catalyst (mol %)
oxidant (equiv)
temp (°C) yield (%)
1
Bu4NI (20)
Bu4NI (20)
Bu4NI (20)
Bu4NI (10)
Bu4NI (30)
Bu4NI (20)
Bu4NI (20)
Bu4NI (20)
Bu4NI (20)
Bu4NI (20)
Bu4NI (20)
Bu4NI (20)
Bu4NI (20)
Bu4NBr (20)
I2 (20)
TBHP (dec.) (6)
aq TBHP (6)
aq TBHP (5)
aq TBHP (6)
aq TBHP (6)
aq TBHP (7)
aq TBHP (6)
aq H2O2 (6)
DTBP (6)
80
80
80
80
80
80
100
80
80
80
80
80
80
80
80
80
80
80
32
69
62
58
68
65
64
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
PhCOOCOPh (6)
Oxone (6)
K2S2O8 (6)
DDQ (6)
aq TBHP (6)
aq TBHP (6)
aq TBHP (6)
aq TBHP (6)
−
KI (20)
−
Bu4NI (20)
a
Reaction condition: ethyl acetate (2 mL), benzylamine (1 mmol),
b
time 8 h. Isolated yield. nd = not detected.
amidation, rather it was further esterification of ethyl acetate
obtained (1a) in 32% yield (path c, Scheme 1). This
observation suggests incorporation of the ArCOO- group into
an ester where benzylamine serves as a source to the aryl
carboxy (ArCOO−) group. It may be mentioned here that
Wang et al. have reported a direct amidation of benzylamine
with N-substituted formamide via oxidative coupling in the
presence of I2/TBHP, where benzylamine is the aroyl
(ArCO−) equivalent.6b It has been observed earlier that the
same precursor may operate either as an aryl carboxy
(ArCOO−) or an aroyl (ArCO−) equivalent, depending
upon the nature of the metal catalyst used. For example,
benzylamine and alkylbenzene are both surrogates to ArCOO-
and ArCO- groups.6,7,9 Thus, generation of ArCOO- from
ArCH2NH2 and its subsequent incorporation into an ester
under a metal-free condition (TBAI) shows identical reactivity
to that of the Cu catalyst.7 Therefore, the present protocol for
the formation of a double ester via the α sp3 C−H bond
functionalization of ethyl acetate without affecting the existing
ester functionality is unexplored.
RESULTS AND DISCUSSION
■
Encouraged by this unique esterification of ester, further
optimization reactions were performed by varying reaction
parameters to attain the best yield of the product. Gratifyingly,
when the above reaction was performed using an aqueous
TBHP (70% in water) (6 equiv) in lieu of a decane solution of
the TBHP (5−6 M) product yield improved up to 69% (Table
B
DOI: 10.1021/jo502903d
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a b
,
scrutinize the feasibility of this protocol with cyclic ether (i.e.,
1,4-dioxane (d) having sp3 C−H bonds α- to an oxygen atom).
To demonstrate the practical utility of the above-mentioned
concept, benzylamine (1) was treated with 1,4-dioxane (d)
under the above optimized conditions. To our delight, the
product was found to be α-acyloxyether (1d) obtained in good
yield (74%). For the synthesis of α-acyloxyethers, in addition to
the traditional methods such as (i) addition of carboxylic acids
to alkenyl ethers,10 (ii) α-halo substitution of ethers with
carboxylic acids,11 (iii) esterification of hemiacetals with acids
or its derivatives,12 and (iv) complex routes comprising of a
two-step synthesis,13 several elegant CDC protocols have been
developed lately.14 Recently, our group has also developed two
CDC protocols, one involving a Cu-mediated solvent−solvent
coupling between alkylbenzenes and cyclic ethers,9a and the
other a metal free oxidative esterification of α sp3 C−H bonds
in cyclic ethers with terminal alkenes and alkynes.5 Proceeding
further toward the substrate exploration, 1,4-dioxane (d) was
reacted with a set of benzylamines having electron-donating
substituents such as p-Me (2), p-OMe (3), 2,4-di-OMe (4),
and electron-withdrawing substituents such as p-F (5), p-Cl
(6), p-Br (7), o-Cl (8), o-Br (9), and m-CF3 (11), all of which
provided the desired α-acyloxyethers (2d−9d and 11d) in
good-to-moderate yields (Scheme 4).
Scheme 2. Substrate Scope for Esterification of Esters
This approach was subsequently applied to other cyclic
ethers possessing a single oxygen [i.e., tetrahydropyran (e) and
tetrahydrofuran (f)]. Unlike in 1,4-dioxane (d), the oxidative
esterification of tetrahydropyran (e) and tetrahydrofuran (f)
with benzylamines (1), (2), and (6) were not so effective in
terms of yields, and they afforded α-acyloxy ethers (1e), (2e),
(6e), (1f), (2f), and (6f) in lower yields as shown in Scheme 3.
Due to the presence of eight equivalent sp3 C−H’s in 1,4-
dioxane (d), it gave better yields of product compared to four
such sp3 C−H’s containing substrates, tetrahydropyran (e) and
tetrahydrofuran (f), which may be possibly due to the statistical
reason. The oxidative esterification of 1,3-dioxolane with
benzylamines (1), (3), and (6) provided single regioisomer
(1g), (3g), and (6g), respectively, in good yields when the
reaction was performed at 120 °C (Scheme 4). Here the
esterification is taking place at the less acidic sp3 C−H bond
rather than at the more acidic sp3 C−H, which is possibly due
to the instability of the radical formed at the bridged head
methylene carbon.
a
Reaction conditions: benzylamine (1 mmol), ester (2 mL), TBAI
b
(0.2 mmol), and TBHP (6 mmol) at 80 °C. Isolated yields.
reaction condition, no amidation was observed. The reaction
gave a complex mixture from which two major products, viz.,
acetophenone (K) (15%) and 2-oxo-2-phenyl-N-(1-
phenylethyl)acetamide (N) (40%), could be isolated (Scheme
3). Under the reaction conditions, α-methyl benzylamine (12)
Scheme 3. Fate of α-Methyl Benzylamine
To elucidate a plausible mechanism for this coupling
reaction, several control experiments were carried out. Analysis
of the reaction mixture between 1,4-dioxane (d) and benzyl-
amine (1), along with the formation of the desired product,
revealed the presence of benzaldehyde and benzoic acid in the
medium, suggesting their intermediacy (Scheme 5). Formation
of benzaldehyde from benzylamine is expected to go via the
hydrolysis of the in situ generated imine, which, in turn, is
obtained by the oxidation of benzylamine.6b The benzaldehyde
so generated gets converted to benzoic acid under oxidative
conditions, which could be the possible source of the ArCOO-
group in these reactions.4a Product (1a) was obtained in 90%
yield when benzoic acid was reacted with ethyl acetate (a)
under the present reaction conditions, implying the coupling
partners are carboxylic acid and ethyl acetate.14a The presence
of a radical scavenger 2,2,6,6-tetramethylpyridine N-oxide
(TEMPO) considerably quenches the coupling reaction
between benzylamine (1) and ethyl acetate (a) giving <4%
yield of the expected product, indicating the radical nature of
is converted to acetophenone (K). Further reaction of
acetophenone with the in situ generated iodine gave α-
iodoacetophenone (L). Reaction of α-iodoacetophenone (L)
with α-methyl benzylamine (12) provided intermediate
product (M), which is rapidly oxidized to 2-oxo-2-phenyl-N-
(1-phenylethyl)acetamide (N) as shown in Scheme 3.
The successful oxidative esterifications of sp3 C−H bonds α-
to an oxygen atom in esters with benzylamines led us to
C
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a b
,
Scheme 4. Substrate Scope for α-Acyloxyether
a
b
c
Reaction conditions: benzylamine (1 mmol), cyclic ethers (1 mL), TBAI (0.2 mmol), TBHP (6 mmol) at 80 °C. Isolated yields. Reaction
performed at 120 °C.
benzaldehyde (B) (Scheme 5). Benzamide from possible
oxidation of the aminal formed between aldehyde (B) and
amine was not isolated from the reaction mixture. Furthermore,
subjection of the benzamide to the reaction conditions with
ethyl acetate gave rise to no coupling, ruling out the
intervention of a benzamide intermediate. Though benzalde-
hyde is generated in the reaction mixture, formation of
benzylschiff base adduct under these conditions was not
detected. If at all formed, it can possibly be hydrolyzed rapidly
back to corresponding aldehyde and amine. Subsequently, less
nucleophilic benzoate (D) is generated by the deprotonation of
benzoic acid (C). On the other hand, radical abstraction of α
sp3 C−H bond in ethyl acetate gives the radical intermediate
(E), which then undergoes a further single electron trans-
formation (SET) with iodine to give an oxonium species (F)
(Scheme 5). Finally, nucleophilic attack of benzoate ion (D) on
the α carbon of oxonium species (F) provided the double ester
(1a) (Scheme 5). A similar mechanism can be proposed
involving 1,4-dioxane instead of ester.
Scheme 5. Proposed Mechanism for Oxidative Esterification
CONCLUSION
■
In conclusion, treatment of benzylamines with esters possessing
α- sp3 C−H bond in the presence of TBAI/TBHP provided
bis-acyl ketals rather than amides. Symmetrical cyclic ethers
afforded a monoester; however, unsymmetrical cyclic ether
provided a single regioisomeric ester via sp3 C−H bond
functionalization. Benzylamine under oxidative condition
provided aryl carboxylic ion which is one of the coupling
partners in this solvent chemistry. A plausible reaction
the mechanism. The trapped TEMPO-ester (G) has been
isolated and characterized (see the Supporting Information).
Taking cues from the control experiments that were carried
out and from the literature reports,7,14a a possible mechanism as
shown in Scheme 5 has been proposed. Initially, benzylamine
(1) in the presence of TBAI/TBHP is converted to benzoic
acid (C) via the intermediacy of phenylmethanimine (A) and
D
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56.2, 88.9, 99.1, 104.9, 111.2, 134.3, 162.4, 163.2, 165.0, 169.2. IR
(KBr): 2943, 2843, 1744, 1723, 1609, 1577, 1506, 1421, 1253, 1031,
945, 836, 770 cm−1. HRMS (ESI): calcd for C13H16O6 (M + Na)+,
291.0845; found, 291.0840.
mechanism involving radical pathways has been suggested for
this CDC coupling.
1-Acetoxyethyl 4-Fluorobenzoate (5a). 1H NMR (400 MHz,
CDCl3): δ 1.61 (d, 3H, J = 5.6 Hz), 2.10 (s, 3H), 7.08−7.16 (m, 3H),
8.05−8.09 (m, 2H). 13C NMR (150 MHz, CDCl3): δ 19.9, 21.1, 89.3,
115.8 (d, J = 22.1 Hz), 125.8, 132.6, 132.7 (d, J = 9.0 Hz), 163.8, 166.3
(d, J = 252 Hz), 169.1. 19F NMR (564.7 MHz, CDCl3) δ −105.5. IR
(KBr): 2994, 2941, 1759, 1732, 1605, 1508, 1414, 1376, 1279, 1231,
1064, 1011, 946, 854, 767 cm−1. HRMS (ESI): calcd for C11H11FO4
(M + Na)+, 249.0539; found, 249.0546.
EXPERIMENTAL SECTION
■
General Information. All the reagents were commercial grade and
used without purification. Organic extracts were dried over anhydrous
sodium sulfate. Solvents were removed in a rotary evaporator under
reduced pressure. Silica gel (60−120 mesh size) was used for the
column chromatography. Reactions were monitored by TLC on silica
gel 60 F254 (0.25 mm). NMR spectra were recorded in CDCl3 with
1
tetramethylsilane as the internal standard for H NMR (400 and 600
1-Acetoxyethyl 4-Chlorobenzoate (6a). 1H NMR (400 MHz,
CDCl3): δ 1.60 (d, 3H, J = 5.6 Hz), 2.09 (s, 3H), 7.09 (q, 1H, J = 5.6
Hz), 7.41 (d, 2H, J = 8.8 Hz), 7.97 (d, 2H, J = 8.4 Hz). 13C NMR (100
MHz, CDCl3): δ 19.8, 21.0, 89.2, 127.9, 128.9, 131.4, 140.1, 163.8,
169.1. IR (KBr): 2924, 2854, 1759, 1732, 1595, 1488, 1376, 1275,
1227, 1067, 1012, 945, 759 cm−1. HRMS (ESI): calcd for C11H11ClO4
(M + Na)+, 265.0244; found, 265.0250.
MHz) and CDCl3 solvent as the internal standard for 13C NMR (100
and 150 MHz). 19F NMR spectra were recorded in CDCl3 with
CF3COOH as the internal standard (564.7 MHz). HRMS spectra
were recorded using the ESI mode (Q-TOF MS Analyzer). IR spectra
were recorded in KBr or neat.
General Procedure for the Synthesis of 1-Acetoxyethyl Benzoate
(1a). A mixture of Bu4NI (73.8 mg, 20 mol %), benzylamine (1) (107
mg, 1 mmol), and ethyl acetate (a) (2 mL) were taken in an oven-
dried round-bottom flask fitted with a refluxed condenser. To this
mixture, an aqueous solution of TBHP (70% in H2O) (857 μL, 6
equiv) was added, and the reaction mixture was heated at 80 °C for 8
h. The reaction mixture was cooled to room temperature and admixed
with ethyl acetate (20 mL). The ethyl acetate layer was washed
successively with a 5% solution of sodium bicarbonate (2 × 5 mL) and
a 5% solution of sodium thiosulfate (2 × 5 mL). The ethyl acetate
layer was dried over anhydrous Na2SO4, and the solvent was
evaporated under reduced pressure. The crude product was purified
over a column of silica gel and eluted with 97:3 hexane:ethyl acetate to
afford 1-acetoxyethyl benzoate (1a) (143.5 mg, 69% yield).
1-Acetoxyethyl 4-Bromobenzoate (7a). 1H NMR (600 MHz,
CDCl3): δ 1.60 (d, 3H, J = 4.8 Hz), 2.09 (s, 3H), 7.09 (q, 1H, J = 5.4
Hz), 7.58 (d, 2H, J = 7.8 Hz), 7.89 (d, 2H, J = 8.4 Hz). 13C NMR (150
MHz, CDCl3): δ 19.8, 21.0, 89.3, 128.4, 128.8, 131.5, 132.0, 164.0,
169.0. IR (KBr): 2996, 2935, 1759, 1732, 1590, 1484, 1397, 1374,
1275, 1226, 1068, 1009, 945, 847, 756 cm−1. HRMS (ESI): calcd for
C11H11BrO4 (M + Na)+, 308.9739; found, 308.9748.
1-Acetoxyethyl 2-Chlorobenzoate (8a). 1H NMR (600 MHz,
CDCl3): δ 1.61 (d, 3H, J = 6.0 Hz), 2.10 (s, 3H), 7.09 (q, 1H, J = 5.4
Hz), 7.31 (t, 1H, J = 7.2 Hz), 7.41−7.46 (m, 2H), 7.83 (d, 1H, J = 7.8
Hz). 13C NMR (150 MHz, CDCl3): δ 19.7, 21.0, 89.6, 126.8, 129.3,
131.4, 131.8, 133.2, 134.3, 163.7, 169.1; IR (KBr): 2927, 1760, 1635,
1599, 1438, 1374, 1294, 1253, 1224, 1077, 1041, 1010, 945, 867, 749
cm−1. HRMS (ESI): calcd for C11H11ClO4 (M+Na)+, 265.0244; found,
265.0240.
General Procedure for the Synthesis of 1,4-Dioxan-2-yl Benzoate
(1d). A mixture of Bu4NI (73.8 mg, 20 mol %), benzylamine (1) (107
mg, 1 mmol), and 1,4-dioxane (d) (1 mL) were taken in an oven-dried
round-bottom flask fitted with a refluxed condenser. To this mixture,
an aqueous solution of TBHP (70% in H2O) (857 μL, 6 equiv) was
added and the reaction mixture was heated at 80 °C for 8 h. The
reaction mixture was cooled to room temperature and admixed with
ethyl acetate (20 mL). The ethyl acetate layer was washed successively
with a 5% solution of sodium bicarbonate (2 × 5 mL) and a 5%
solution of sodium thiosulfate (2 × 5 mL). The ethyl acetate layer was
dried over anhydrous Na2SO4, and the solvent was evaporated under
reduced pressure. The crude product was purified over a column of
silica gel and eluted with (96:4, hexane/ethyl acetate) to afford 1,4-
dioxan-2-yl benzoate (1d) (154 mg, 74% yield).
1-Acetoxyethyl 2-Bromobenzoate (9a). 1H NMR (400 MHz,
CDCl3): δ 1.63 (d, 3H, J = 5.2 Hz), 2.12 (s, 3H), 7.09 (q, 1H, J = 5.2
Hz), 7.33−7.39 (m, 2H), 7.67 (d, 1H, J = 7.2 Hz), 7.81 (d, 1H, J = 8.0
Hz). 13C NMR (100 MHz, CDCl3): δ 19.7, 21.0, 89.7, 122.2, 127.4,
131.4, 131.8, 133.2, 134.7, 164.1, 169.1. IR (KBr): 2922, 1760, 1638,
1433, 1374, 1293, 1223, 1073, 1010, 945, 746, 699 cm−1. HRMS
(ESI): calcd for C11H11BrO4 (M + Na)+, 308.9739; found, 308.9743.
1-Acetoxyethyl 3-Chlorobenzoate (10a). 1H NMR (400 MHz,
CDCl3): δ 1.59 (d, 3H, J = 5.6 Hz), 2.08 (s, 3H), 7.07 (q, 1H, J = 5.6
Hz), 7.35−7.40 (m, 1H), 7.51−7.55 (m, 1H), 7.91 (d, 1H, J = 8.0 Hz),
8.05 (s, 1H). 13C NMR (100 MHz, CDCl3): δ 19.8, 21.0, 89.4, 128.2,
130.1, 130.2, 131.3, 133.7, 134.8, 163.6, 169.1. IR (KBr): 2923, 2081,
1760, 1735, 1635, 1426, 1374, 1290, 1259, 1223, 1068, 1010, 947, 746
cm−1. HRMS (ESI): calcd for C11H11ClO4 (M + Na)+, 265.0244;
found, 265.0238.
1
1-Acetoxyethyl Benzoate (1a). H NMR (400 MHz, CDCl3): δ
1.61 (d, 3H, J = 5.2 Hz), 2.09 (s, 3H), 7.12 (q, 1H, J = 5.2 Hz), 7.44 (t,
2H, J = 7.6 Hz), 7.58 (t, 1H, J = 7.6 Hz), 8.05 (d, 2H, J = 6.8 Hz). 13C
NMR (150 MHz, CDCl3): δ 19.9, 21.1, 89.2, 128.6, 129.5, 130.1,
133.6, 164.8, 169.2; IR (KBr): 2929, 2851, 1768, 1731, 1602, 1446,
1375, 1278, 1228, 1064, 1011, 945, 713 cm−1. HRMS (ESI): calcd for
C11H12O4 (M + Na)+, 231.0634; found, 231.0640.
1-Acetoxyethyl 3-(Trifluoromethyl)benzoate (11a). 1H NMR (400
MHz, CDCl3): δ 1.64 (d, 3H, J = 5.2 Hz), 2.12 (s, 3H), 7.14 (q, 1H, J
= 5.2 Hz), 7.61 (t, 1H, J = 7.6 Hz), 7.84 (d, 1H, J = 7.6 Hz), 8.24 (d,
1H, J = 7.6 Hz), 8.30 (s, 1H). 13C NMR (150 MHz, CDCl3): δ 19.8,
21.1, 89.6, 122.9, 124.7, 127.0 (t, J = 5.3 Hz), 129.4, 130.2 (t, J = 5.3
Hz), 130.5, 131.4 (q, J = 33.0 Hz), 133.3, 163.5, 169.1. 19F NMR
(564.7 MHz, CDCl3): δ −63.6; IR (KBr): 2926, 1762, 1620, 1445,
1375, 1335, 1260, 1223, 1171, 1130, 1071, 1011, 946, 756, 695 cm−1.
HRMS (ESI): calcd for C12H11F3O4 (M + Na)+, 299.0507; found,
299.0512.
1-Acetoxyethyl 4-Methylbenzoate (2a). 1H NMR (400 MHz,
CDCl3): δ 1.60 (d, 3H, J = 5.6 Hz), 2.09 (s, 3H), 2.41 (s, 3H), 7.10 (q,
1H, J = 5.6 Hz), 7.25 (d, 2H, J = 3.6 Hz), 7.93 (d, 2H, J = 8 Hz). 13C
NMR (100 MHz, CDCl3): δ 19.8, 21.1, 21.9, 89.1, 129.3, 130.1, 130.1,
144.4, 164.7, 169.1. IR (KBr): 2926, 2856, 1758, 1729, 1613, 1446,
1371, 1276, 1228, 1183, 1065, 1012, 945, 752, 699 cm−1. HRMS
(ESI): calcd for C12H14O4 (M + Na)+, 245.0790; found, 245.0783.
1
1
1-Acetoxyethyl 4-Methoxybenzoate (3a). H NMR (400 MHz,
1-Acetoxypropyl Benzoate (1b). H NMR (400 MHz, CDCl3): δ
CDCl3): δ 1.57 (d, 3H, J = 5.2 Hz), 2.06 (s, 3H), 3.83 (s, 3H), 6.89 (d,
2H, J = 8.8 Hz), 7.07 (q, 1H, J = 5.2 Hz), 7.97 (d, 2H, J = 8.8 Hz). 13C
NMR (100 MHz, CDCl3): δ 19.9, 21.1, 55.7, 89.1, 113.9, 121.9, 132.2,
164.0, 164.5, 169.2. IR (KBr): 2931, 2845, 1759, 1725, 1607, 1512,
1460, 1421, 1375, 1260, 1169, 945, 848, 769 cm−1. HRMS (ESI): calcd
for C12H14O5 (M + Na)+, 261.0739; found, 261.0731.
1.04 (t, 3H, J = 7.6 Hz), 1.91−1.98 (m, 2H), 2.10 (s, 3H), 7.01 (t, 1H,
J = 8.4 Hz), 7.43−7.48 (m, 2H), 7.56−7.60 (m, 1H); 8.05 (d, 2H, J =
8.8 Hz). 13C NMR (150 MHz, CDCl3): δ 7.9, 21.1, 26.8, 91.9, 128.7,
129.6, 130.1, 133.6, 164.9, 169.3. IR (KBr): 2978, 2939, 1760, 1732,
1602, 1452, 1373, 1276, 1222, 1117, 1018, 961, 711 cm−1. HRMS
(ESI): calcd for C12H14O4 (M + Na)+, 245.0790; found, 245.0783.
1
1-Acetoxyethyl 2,4-Dimethoxybenzoate (4a). 1H NMR (400
MHz, CDCl3): δ 1.58 (d, 3H, J = 5.6 Hz), 2.08 (s, 3H), 3.85 (s,
3H), 3.89 (s, 3H), 6.48−6.50 (m, 2H), 7.06 (q, 1H, J = 5.6 Hz), 7.88
(d, 1H, J = 8.0 Hz). 13C NMR (150 MHz, CDCl3): δ 19.9, 21.1, 55.7,
1-Acetoxypropyl 4-Methoxybenzoate (3b). H NMR (600 MHz,
CDCl3): δ 1.03 (t, 3H, J = 7.2 Hz), 1.91−1.93 (m, 2H), 2.09 (s, 3H),
3.86 (s, 3H), 6.92 (d, 2H, J = 9.0 Hz), 6.98 (t, 1H, J = 5.4 Hz), 8.00 (d,
2H, J = 8.4 Hz). 13C NMR (150 MHz, CDCl3): δ 7.9, 21.1, 26.9, 55.7,
E
DOI: 10.1021/jo502903d
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The Journal of Organic Chemistry
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91.7, 113.9, 121.9, 132.2, 164.0, 164.6, 169.3. IR (KBr): 2976, 2939,
2843, 1759, 1726, 1607, 1512, 1422, 1318, 1224, 1168, 1021, 961, 848,
769 cm−1. HRMS (ESI): calcd for C13H16O5 (M + Na)+, 275.0896;
found, 275.0902.
2951, 2870, 1725, 1606, 1509, 1453, 1362, 1284, 1148, 1092, 1067,
912, 884 cm−1.
1,4-Dioxan-2-yl 4-Chlorobenzoate (6d).14a 1H NMR (400 MHz,
CDCl3): δ 3.67−3.71 (m, 1H), 3.83−3.85 (m, 2H), 3.89−3.90 (m,
2H), 4.18−4.24 (m, 1H), 6.09 (t, 1H, J = 1.6 Hz), 7.44 (d, 2H, J = 8.4
Hz), 8.07 (d, 2H, J = 8.4 Hz). 13C NMR (150 MHz, CDCl3): δ 62.0,
66.3, 68.0, 90.2, 128.4, 129.0, 131.5, 140.1, 164.6. IR (KBr): 2924,
2855, 1726, 1594, 1260, 1155, 1090, 1012, 912, 881, 756 cm−1.
1,4-Dioxan-2-yl 4-Bromobenzoate (7d).14a 1H NMR (400 MHz,
CDCl3): δ 3.63−3.67 (m, 1H), 3.79−3.81 (m, 2H), 3.86 (d, 2H, J =
1.6 Hz), 4.14−4.20 (m, 1H), 6.06 (s, 1H), 7.57 (d, 2H, J = 8.4 Hz),
7.95 (d, 2H, J = 8.4 Hz). 13C NMR (100 MHz, CDCl3): δ 62.0, 66.3,
67.9, 90.3, 128.9, 131.6, 132.1, 164.8. IR (KBr): 2972, 2929, 2856,
1729, 1589, 1397, 1274, 1259, 1155, 1090, 1067, 1009, 911, 881, 757
cm−1.
1-Acetoxypropyl 4-Chlorobenzoate (6b). 1H NMR (600 MHz,
CDCl3): δ 1.03 (t, 3H, J = 7.2 Hz), 1.92−1.94 (m, 2H), 2.10 (s, 3H),
6.98 (t, 1H, J = 4.8 Hz), 7.42 (d, 2H, J = 6.6 Hz), 7.98 (d, 2H, J = 6.6
Hz). 13C NMR (150 MHz, CDCl3): δ 7.9, 21.0, 26.8, 92.0, 128.1,
129.0, 131.5, 140.2, 164.0, 169.3. IR (KBr): 2978, 2939, 1760, 1733,
1595, 1489, 1372, 1274, 1221, 1092, 1013, 850, 758 cm−1. HRMS
(ESI): calcd for C12H13ClO4 (M + Na)+, 279.0400; found, 279.0409.
1
1-Acetoxybutyl Benzoate (1c). H NMR (600 MHz, CDCl3): δ
0.97 (t, 3H, J = 7.2 Hz), 1.46−1.51 (m, 2H), 1.86−1.90 (m, 2H), 2.07
(s, 3H), 7.04 (t, 1H, J = 5.4 Hz), 7.41−7.45 (m, 2H), 7.56 (t, 1H, J =
7.2 Hz), 8.03 (d, 2H, J = 7.8 Hz). 13C NMR (150 MHz, CDCl3): δ
14.0, 17.1, 21.1, 35.6, 91.1, 128.7, 129.6, 130.1, 133.6, 164.9, 169.3. IR
(KBr): 2963, 2933, 2876, 1761, 1732, 1602, 1453, 1374, 1272, 1219,
1117, 1015, 802, 712 cm−1. HRMS (ESI): calcd for C13H16O4 (M +
Na)+, 259.0947; found, 259.0941.
1,4-Dioxan-2-yl 2-Chlorobenzoate (8d).14c 1H NMR (400 MHz,
CDCl3): δ 3.61−3.64 (m, 1H), 3.76−3.77 (m, 2H), 3.83−3.84 (m,
2H), 4.16−4.22 (m, 1H), 6.06 (s, 1H), 7.26−7.30 (m, 1H), 7.37−7.42
(m, 2H), 7.88 (d, 1H, J = 7.6 Hz). 13C NMR (100 MHz, CDCl3): δ
61.9, 66.1, 67.7, 90.5, 126.7, 129.5, 131.3, 131.9, 133.1, 134.1, 164.4. IR
(KBr): 2975, 2857, 2717, 1731, 1633, 1593, 1438, 1353, 1292, 1159,
1108, 1066, 1044, 1012, 911, 880 cm−1.
1-Acetoxybutyl 4-Methoxybenzoate (3c). 1H NMR (600 MHz,
CDCl3): δ 0.99 (t, 3H, J = 7.2 Hz), 1.47−1.51 (m, 2H), 1.87−1.89 (m,
2H), 2.09 (s, 3H), 3.86 (s, 3H), 6.91−6.94 (m, 2H), 7.04 (t, 1H, J =
5.4 Hz), 8.00 (d, 2H, J = 7.2 Hz). 13C NMR (150 MHz, CDCl3): δ
14.0, 17.1, 21.1, 35.6, 55.7, 90.9, 113.9, 122.0, 132.2, 164.0, 164.6,
169.3. IR (KBr): 2962, 2934, 2875, 1759, 1725, 1607, 1512, 1464,
1373, 1260, 1168, 1028, 847, 769 cm−1. HRMS (ESI): calcd for
C14H18O5 (M + Na)+, 289.1052; found, 289.1045.
1,4-Dioxan-2-yl 2-Bromobenzoate (9d).9a 1H NMR (600 MHz,
CDCl3): δ 3.63−3.66 (m, 1H), 3.77−3.79 (m, 2H), 3.83−3.88 (m,
2H), 4.19−4.23 (m, 1H), 6.06 (t, 1H, J = 1.8 Hz), 7.29−7.35 (m, 2H),
7.63−7.64 (m, 1H), 7.85−7.87 (m, 1H). 13C NMR (150 MHz,
CDCl3): δ 61.9, 66.2, 67.8, 90.7, 122.1, 127.4, 131.6, 131.9, 133.1,
134.6, 164.9. IR (KBr): 2971, 2924, 2852, 1734, 1581, 1387, 1276,
1255, 1159, 1093, 1069, 921, 871, 752 cm−1.
1-Acetoxybutyl 4-Chlorobenzoate (6c). 1H NMR (600 MHz,
CDCl3): δ 0.99 (t, 3H, J = 7.2 Hz), 1.46−1.51 (m, 2H), 1.88−1.89 (m,
2H), 2.09 (s, 3H), 7.03 (t, 1H, J = 5.4 Hz), 7.41−7.44 (m, 2H), 7.96
(d, 2H, J = 7.2 Hz). 13C NMR (150 MHz, CDCl3): δ 13.9, 17.1, 21.0,
35.5, 91.2, 128.1, 129.0, 131.5, 140.2, 164.0, 169.2. IR (KBr): 2963,
2933, 2876, 1760, 1732, 1595, 1488, 1372, 1219, 1173, 1013, 849, 685
cm−1. HRMS (ESI): calcd for C13H15ClO4 (M + Na)+, 293.0557;
found, 293.0549.
1,4-Dioxan-2-yl 3-(Trifluoromethyl)benzoate (11d). 1H NMR
(400 MHz, CDCl3): δ 3.67−3.70 (m, 1H), 3.82−3.84 (m, 2H),
3.89−3.90 (m, 2H), 4.17−4.24 (m, 1H), 6.10 (s, 1H), 7.60 (t, 1H, J =
8.0 Hz), 7.83 (d, 1H, J = 8.0 Hz), 8.29 (d, 1H, J = 8.4 Hz), 8.34 (s,
1H). 13C NMR (150 MHz, CDCl3): δ 62.1, 66.3, 67.9, 90.7, 122.9,
124.7, 127.0 (t, J = 4.2 Hz), 129.4, 130.2 (d, J = 6.0 Hz), 130.9, 131.4
(q, J = 32.7 Hz), 133.3, 164.2. 19F NMR (564.7 MHz, CDCl3): δ
−63.4. IR (KBr): 2924, 1730, 1636, 1449, 1333, 1251, 1166, 1128,
1071, 1016, 914, 879, 695 cm−1. HRMS (ESI): calcd for C12H11F3O4
(M + Na)+, 299.0507; found, 299.0501.
1,4-Dioxan-2-yl Benzoate (1d).14e 1H NMR (400 MHz, CDCl3): δ
3.64−3.68 (m, 1H), 3.80−3.82 (m, 2H), 3.83−3.88 (m, 2H), 4.18−
4.24 (m, 1H), 6.08 (s, 1H), 7.44 (t, 2H, J = 7.6 Hz), 7.57 (t, 1H, J =
7.2 Hz), 8.11 (d, 2H, J = 7.2 Hz). 13C NMR (150 MHz, CDCl3): δ
61.8, 66.1, 67.8, 89.8, 128.5, 129.8, 129.9, 133.4, 165.2. IR (KBr):
2971, 2925, 2856, 1726, 1602, 1452, 1258, 1155, 1065, 1018, 912, 880,
713 cm−1.
Tetrahydro-2H-pyran-2-yl Benzoate (1e).14a 1H NMR (400 MHz,
CDCl3): δ 1.58−1.77 (m, 3H), 1.81−1.99 (m, 3H), 3.72−3.75 (m,
1H), 3.94−4.01 (m, 1H), 6.23 (t, 1H, J = 3.2 Hz), 7.42 (t, 2H, J = 7.2
Hz), 7.54 (t, 1H, J = 7.2 Hz), 8.07 (d, 2H, J = 7.6 Hz). 13C NMR (100
MHz, CDCl3): δ 18.6, 25.0, 29.3, 63.2, 93.1, 128.4, 129.8, 130.3, 133.1,
165.2. IR (KBr): 2924, 2853, 1723, 1607, 1456, 1289, 1121, 709 cm−1.
Tetrahydro-2H-pyran-2-yl 4-Methylbenzoate (2e).14f 1H NMR
(600 MHz, CDCl3): δ 1.60−1.62 (m, 1H), 1.67−1.71 (m, 2H), 1.80−
1.95 (m, 3H), 2.39 (s, 3H), 3.71−3.74 (m, 1H), 3.94−3.98 (m, 1H),
6.21 (t, 1H, J = 2.0 Hz), 7.22 (d, 2H, J = 8.4 Hz), 7.95 (d, 2H, J = 8.4
Hz). 13C NMR (150 MHz, CDCl3): δ 18.8, 21.8, 25.2, 29.5, 63.4, 93.1,
127.7, 129.3, 129.9, 143.9, 165.4. IR (KBr): 2945, 2873, 1722, 1611,
1274, 1177, 1206, 1088, 1036, 943, 900, 871, 753 cm−1.
1,4-Dioxan-2-yl 4-Methylbenzoate (2d).14f 1H NMR (600 MHz,
CDCl3): δ 2.42 (s, 3H), 3.66−3.69 (m, 1H), 3.82−3.83 (m, 2H),
3.88−3.89 (m, 2H), 4.20−4.24 (m, 1H), 6.08 (s, 1H), 7.26 (d, 2H, J =
10.2 Hz), 8.02 (d, 2H, J = 8.4 Hz). 13C NMR (150 MHz, CDCl3): δ
21.7, 61.8, 66.1, 67.9, 89.7, 127.0 129.2, 130.0, 144.2, 165.2. IR (KBr):
2974, 2926, 2857, 1726, 1612, 1453, 1355, 1156, 1016, 912, 882, 755,
691, 577 cm−1.
1,4-Dioxan-2-yl 4-Methoxybenzoate (3d).14f 1H NMR (400 MHz,
CDCl3): δ 3.63−3.66 (m, 1H), 3.78−3.80 (m, 2H), 3.84−3.89 (m,
5H), 4.15−4.21 (m, 1H), 6.04 (s, 1H), 6.91 (d, 2H, J = 7.6 Hz), 8.05
(d, 2H, J = 8.4 Hz). 13C NMR (100 MHz, CDCl3): δ 55.6, 62.0, 66.3,
68.1, 89.7, 113.9, 122.2, 132.2, 164.0, 165.1. IR (KBr): 2971, 2929,
2855, 1723, 1607, 1511, 1458, 1421, 1257, 1168, 1087, 1021, 912, 881,
852, 771 cm−1.
Tetrahydro-2H-pyran-2-yl 4-Chlorobenzoate (6e).9a 1H NMR
(400 MHz, CDCl3): δ 1.59−1.67 (m, 1H), 1.72−1.77 (m, 2H), 1.83−
1.91 (m, 3H), 3.72−3.75 (m, 1H), 3.92−3.98 (m, 1H), 6.21 (s, 1H),
7.40 (d, 2H, J = 8.4 Hz), 8.00 (d, 2H, J = 8.4 Hz). 13C NMR (100
MHz, CDCl3): δ 18.8, 25.2, 29.4, 63.5, 93.6, 128.92, 128.97, 131.3,
139.8, 164.6. IR (KBr): 2944, 2871, 1725, 1593, 1272, 1206, 1089,
1016, 940, 898, 868, 758 cm−1.
1,4-Dioxan-2-yl 2,4-Dimethoxybenzoate (4d).14e 1H NMR (400
MHz, CDCl3): δ 3.62−3.65 (m, 2H), 3.76−3.78 (m, 2H), 3.82 (s,
3H), 3.86 (s, 3H), 4.16−4.22 (m, 2H), 6.02 (s, 1H), 6.45−6.48 (m,
2H), 7.93 (d, 1H, J = 8.4 Hz). 13C NMR (100 MHz, CDCl3): δ 55.7,
56.1, 62.0, 66.3, 68.1, 89.4, 99.1, 104.8, 111.7, 134.3, 162.1, 164.0,
164.9. IR (KBr): 2971, 2937, 2853, 1725, 1609, 1576, 1505, 1459,
1213, 1163, 1019, 911, 882, 770 cm−1.
Tetrahydrofuran-2-yl Benzoate (1f).14a 1H NMR (400 MHz,
CDCl3): δ 2.05−2.12 (m, 2H), 2.45−2.54 (m, 2H), 4.10−4.22 (m,
2H), 5.52 (s, 1H), 7.39−7.43 (m, 2H), 7.52−7.56 (m, 1H), 7.98−8.04
(m, 2H). 13C NMR (100 MHz, CDCl3): δ 28.7, 29.7, 67.1, 100.7,
128.6, 129.88, 129.93, 133.5, 166.2. IR (KBr): 2901, 1720, 1637, 1489,
1450, 1349, 1317, 1277, 1117, 1069, 1028, 958, 909, 713 cm−1.
Tetrahydrofuran-2-yl 4-Methylbenzoate (2f).14f 1H NMR (400
MHz, CDCl3): δ 2.03−2.09 (m, 2H), 2.36 (s, 3H), 2.43−2.52 (m,
2H), 4.08−4.21 (m, 2H), 5.51 (s, 1H), 7.18 (d, 2H, J = 8.4 Hz), 7.87
(d, 2H, J = 8.0 Hz). 13C NMR (100 MHz, CDCl3): δ 21.8, 28.6, 29.7,
67.0, 100.6, 127.1, 129.2, 129.9, 144.1, 166.3. IR (KBr): 2901, 2127,
1,4-Dioxan-2-yl 4-Fluorobenzoate (5d).14a 1H NMR (600 MHz,
CDCl3): δ 3.67−3.69 (m, 1H), 3.82−3.83 (m, 2H), 3.88−3.89 (m,
2H), 4.19−4.23 (m, 1H), 6.09 (s, 1H), 7.12−7.15 (m, 2H), 8.13−8.15
(m, 2H). 13C NMR (150 MHz, CDCl3): δ 61.8, 66.1, 67.8, 90.0, 115.7
(d, J = 21.8 Hz), 126.1, 132.5 (d, J = 9.3 Hz), 164.7 (d, J = 144 Hz),
166.9. 19F NMR (564.7 MHz, CDCl3): δ −105.5. IR (KBr): 2977,
F
DOI: 10.1021/jo502903d
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The Journal of Organic Chemistry
Article
1717, 1613, 1445, 1349, 1278, 1179, 1112, 1029, 958, 909, 842, 755,
691 cm−1.
Li, C.-J. Angew. Chem., Int. Ed. 2014, 53, 74. (e) Jia, F.; Li, Z. Org.
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Tetrahydrofuran-2-yl 4-Chlorobenzoate (6f). 1H NMR (400
MHz, CDCl3): δ 1.99−2.10 (m, 2H), 2.45−2.54 (m, 2H), 4.09−
4.23 (m, 2H), 5.51 (s, 1H), 7.36 (d, 2H, J = 8.0 Hz), 7.91 (d, 2H, J =
8.4 Hz). 13C NMR (100 MHz, CDCl3): δ 28.5, 29.6, 67.0, 100.6,
128.3, 128.9, 131.2, 140.0, 165.3. IR (KBr): 2943, 2906, 1718, 1593,
1486, 1402, 1344, 1276, 1107, 1032, 943, 889, 760 cm−1. HRMS
(ESI): calcd for C11H11ClO3 (M + Na)+, 249.0295; found, 249.0300.
1,3-Dioxolan-4-yl Benzoate (1g). 1H NMR (600 MHz, CDCl3): δ
4.12−4.19 (m, 2H), 5.16 (s, 1H), 5.21 (s, 1H), 6.59−6.60 (m, 1H),
7.45 (t, 2H, J = 7.8 Hz), 7.59 (t, 1H, J = 7.2 Hz), 8.05 (d, 2H, J = 7.8
Hz). 13C NMR (150 MHz, CDCl3): δ 71.0, 94.9, 96.2, 128.7, 129.7,
130.0, 133.7, 166.1. IR (KBr): 2926, 2881, 1729, 1602, 1452, 1316,
1269, 1167, 1069, 1024, 990, 870, 711 cm−1. HRMS (ESI): calcd for
C10H10O4 (M + Na)+, 217.0477; found, 217.0470.
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1,3-Dioxolan-4-yl 4-Methoxybenzoate (3g).14e 1H NMR (600
MHz, CDCl3): δ 3.83 (s, 3H), 4.07−4.14 (m, 2H), 5.12 (s, 1H), 5.16
(s, 1H), 6.53−6.54 (m, 1H), 6.89 (d, 2H, J = 9.0 Hz), 7.97 (d, 2H, J =
8.4 Hz). 13C NMR (150 MHz, CDCl3): δ 55.5, 70.8, 94.5, 95.9, 113.8,
121.9, 132.0, 163.9, 165.6. IR (KBr): 2970, 2882, 1719, 1607, 1512,
1422, 1318, 1260, 1169, 1028, 1087, 922, 769 cm−1.
1
1,3-Dioxolan-4-yl 4-Chlorobenzoate (6g). H NMR (600 MHz,
CDCl3): δ 4.10−4.17 (m, 2H), 5.14 (s, 1H), 5.19 (s, 1H), 6.56−6.57
(m, 1H), 7.41 (d, 2H, J = 6.6 Hz), 7.97 (d, 2H, J = 7.8 Hz). 13C NMR
(150 MHz, CDCl3): δ 70.9, 95.0, 96.2, 128.1, 129.0, 131.3, 140.2,
165.1. IR (KBr): 2975, 2881, 2782, 1731, 1594, 1488, 1402, 1269,
1169, 1038, 1014, 921, 851, 759 cm−1. HRMS (ESI): calcd for
C10H9ClO4 (M+Na)+, 251.0087; found, 251.0095.
2,2,6,6-Tetramethylpiperidin-1-yl Benzoate (G). 1H NMR (400
MHz, CDCl3): δ 1.16 (s, 6H), 1.31 (s, 6H), 1.48−1.52 (broad singlet,
1H), 1.61−1.64 (broad singlet, 2H), 1.71 (m, 3H), 7.50 (t, 2H, J = 7.6
Hz), 7.61 (t, 1H, J = 6.8 Hz), 8.11 (d, 2H, J = 7.2 Hz). 13C NMR (100
MHz, CDCl3): δ 17.1, 21.0, 32.1, 39.2, 60.5, 128.6, 129.7, 133.0, 166.5.
IR (KBr): 2974, 2934, 1749, 1540, 1378, 1255, 1176, 1081 cm−1.
HRMS (ESI): calcd for C16H23NO2 (MH+), 262.1807; found,
262.1812.
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Boice, G. N.; Qu, C.; Nelson, T. D.; McNamara, J. M. J. Org. Chem.
2005, 70, 4409.
1
2-Oxo-2-phenyl-N-(1-phenylethyl)acetamide (N). H NMR (400
MHz, CDCl3): δ 1.58 (d, 3H, J = 6.8 Hz), 5.13−5.20 (m, 1H), 7.35−
7.36 (m, 5H), 7.45 (t, 2H, J = 8.4 Hz), 7.60 (t, 1H, J = 7.6 Hz), 8.32
(d, 2H, J = 7.2 Hz). 13C NMR (100 MHz, CDCl3): δ 21.9, 49.3, 126.4,
127.9, 128.7, 129.0, 131.5, 133.5, 134.6, 142.4, 160.9, 187.8. IR (KBr):
3451, 2962, 2925, 2851, 1662, 1596, 1449, 1218, 1178, 1021, 744, 698
cm−1. HRMS (ESI): calcd. for C16H15NO2 (MH+), 254.1176; found,
254.1185.
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Joseph, J.; Kantam, M. L. RSC Adv. 2013, 3, 18283. (c) Zhang, S.;
Guo, L.-N.; Wang, H.; Duan, X.-H. Org. Biomol. Chem. 2013, 11, 4308.
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ASSOCIATED CONTENT
* Supporting Information
Spectral data for all compounds. This material is available free
of charge via the Internet at http://pubs.acs.org.
■
S
AUTHOR INFORMATION
Corresponding Author
*E-mail: patel@iitg.ernet.in.
■
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
B.K.P. acknowledges the support of this research by the
Department of Science and Technology (DST) (SB/S1/OC-
53/2013), New Delhi, and the Council of Scientific and
Industrial Research (CSIR) (02(0096)/12/EMR-II).
REFERENCES
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