Oxidation of benzyl alcohols, benzyl halides, and alkylbenzenes with oxone

Article abstract of DOI:10.1016/j.tet.2012.09.028

Oxidation of benzyl alcohols, benzyl halides, and alkylbenzenes to their corresponding oxidation products has been shown to be accomplished directly with oxone. The methodology that involves mere stirring/heating of the reactants and oxone in acetonitrile/water (1:1, v/v) is simple and practical, but is limited to substrates that do not contain sensitive functionalities and heteroaromatic rings.

Full text of DOI:10.1016/j.tet.2012.09.028

Tetrahedron 68 (2012) 9763e9768
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journal homepage: www.elsevier.com/locate/tet
Oxidation of benzyl alcohols, benzyl halides, and alkylbenzenes with oxone
*
Keshaba Nanda Parida, Samik Jhulki, Susovan Mandal, Jarugu Narasimha Moorthy
Department of Chemistry, Indian Institute of Technology, Kanpur 208016, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 5 May 2012
Received in revised form 3 September 2012
Accepted 5 September 2012
Available online 11 September 2012
Oxidation of benzyl alcohols, benzyl halides, and alkylbenzenes to their corresponding oxidation prod-
ucts has been shown to be accomplished directly with oxone. The methodology that involves mere
stirring/heating of the reactants and oxone in acetonitrile/water (1:1, v/v) is simple and practical, but is
limited to substrates that do not contain sensitive functionalities and heteroaromatic rings.
Ó 2012 Elsevier Ltd. All rights reserved.
1. Introduction
hydrocarbons using oxone and point out limitations with the use of
oxone.
Oxidation of primary alcohols to corresponding aldehydes/car-
boxylic acids and secondary alcohols to ketones is a much visited
chemistry, and can be accomplished with a number of organic and
transition metal-based oxidation reagents.1 In our laboratories, we
have recently shown that alcohols can be conveniently oxidized
with modified IBXs2a,b as well as with precursor iodo-acids cata-
lytically in the presence of oxone as a terminal oxidant.2c We sur-
mised that benzyl halidesdlike those of benzyl alcoholsdshould
be possible to be converted to the carbonyl compounds using iodo-
acid as a catalyst and oxone as a co-oxidant; indeed, we showed
some time ago that primary and secondary halides can be con-
verted to aldehydes and ketones using IBX in DMSO at high tem-
peratures.3 In our attempts to obviate the use of DMSO as a solvent
and to develop a catalytic protocol, we discovered that oxone itself
is effective in some of the oxidations. Oxone is a mild, inexpensive,
easy-to-handle, and environmentally benign oxidation reagent that
has found extensive application in organic synthesis.4 It has largely
been employed as a co-oxidant in the presence of a catalyst for
a variety of oxidative transformations.2c,5 There are only a few re-
ports in which oxone has been directly employed for
oxidations.6e12 Given that oxone is largely employed as a co-
oxidant, exploration of its true potential in oxidations directly
was deemed necessary. It is ironical that IBX has emerged as
2. Results
In our initial attempts to optimize the reaction conditions for
oxidation of p-bromobenzyl bromide to the corresponding car-
boxylic acid using o-iodobenzoic acid and oxone in acetonitrile/
water, we discovered from a control experiment that oxone itself
performs the oxidation at reflux conditions. From solvent screening
studies, CH3CN/H2O (1:1) mixture was reckoned to be the best
combination to examine the oxidation of a range of substrates.
Thus, both benzyl chlorides and bromides were found to be con-
verted to their corresponding carboxylic acids when heated at
reflux with 3e5 equiv of oxone in acetonitrile/water (entries 1e7,
Table 1).
TLC monitoring of the reactions indicated that the reactions in
all cases proceeded through the intermediacy of aldehydes, which
subsequently underwent oxidation to the carboxylic acids with
oxone, vide infra. It should be noted that the oxidation of aldehydes
to acids with oxone in DMF is a well-established synthetic pro-
tocol.13 A similar attempt with the oxidation of secondary benzyl
bromide, namely 1-bromo-4-(1-bromoethyl)benzene, in refluxing
acetonitrile/water revealed that the oxidation completed within
10 min; product analysis showed that the corresponding
a-bro-
a
fantastic oxidation reagent than its triacetate, namely
moketone formed as a side product along with the major expected
ketone in 85% yield (Eq. 1). When the reaction was conducted
at room temperature, the reaction was found to be clean
affording the ketone, i.e., 4-bromoacetophenone, primarily. Thus,
secondary benzyl halides containing both electron-donating
as well as electron-withdrawing groups were found to be oxidized;
the substrate with electron-withdrawing group was found to un-
dergo completion over a longer period and at reflux conditions, cf.
Table 1 (entries 8e11).
DesseMartin periodinane. Now, we seem to realize that oxone itself
is great, at least for some oxidations, than IBX, which is produced by
oxidation of o-iodobenzoic acid with oxone. Herein, we report the
oxidation of benzyl alcohols, benzyl halides, and aromatic
* Corresponding author. Tel.: þ91 512 2597438; fax: þ91 512 2597436; e-mail
address: moorthy@iitk.ac.in (J.N. Moorthy).
0040-4020/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tet.2012.09.028

9764
K.N. Parida et al. / Tetrahedron 68 (2012) 9763e9768
Table 1
may arise from radical-mediated reactions. In principle, oxone may
undergo dissociation upon thermolysisdlike H2O2dto produce
hydroxyl radicals that lead to complicated reaction mixtures; al-
ternative pathway involving the formation of dioxirane and sub-
sequent reactions with it is ruled out, since dioxirane is produced
in basic pH conditions.14
Oxidation of primarya and secondaryb benzyl halides using oxone
Entry
Substrate
Equiv/time
(h)
Product
Isolated
yield (%)
1
3/5
98
In our experiments with oxidation of alcohols, we observed
that the reaction of 3-phenylpropanol with oxone led to a complex
mixture of products as revealed by TLC, which made us wonder if
oxone performs the benzylic oxidation along the lines of KMnO4 as
well as the oxidation of aromatics; replacement of transition
metal-based oxidation chemistry for alkylbenzenes with a green
reagent such as oxone was deemed impressive. Thus, when
substituted toluenes were heated at reflux in the presence of
3e6 equiv of oxone for 36 h, the corresponding acids were indeed
isolated, cf. Table 3. While the yield of the acid was remarkable in
the case of p-bromotoluene (entry 1), the reactions of all other
electron-poor arenes were found to be rather sluggish (entries
2e6); the isolated yields of the acids were 48e64%. Oxidation of
naphthalene led to trans-o-carboxycinnamic acid in 56% isolated
yield together with 1,4-naphthoquinone in 34% yield (entry 7). The
formation of o-carboxycinnamic acid may occur via initial epoxi-
dation of the C1eC2 double bond followed by ring opening to af-
ford 2-hydroxynapthalene, which has been reported to yield o-
carboxycinnamic acid upon treatment with peracetic acid.15 Oxi-
dation of anthracene afforded bianthronyl16 in 55% isolated yield;
of course, 9,10-anthraquinone was also isolated in 23% yield (entry
8). While fluorene underwent a very sluggish reaction to afford
fluorenone, its acyclic analog, i.e., diphenylmethane, was found to
react better yielding benzophenone in good isolated yields (entries
9 and 10).
X = H
2
3
4
5
Br
NO2
CN
Cl
3/15
5/24
4/12
3/9
98
74c
73d
96
6
7
4/12
5/24
85
80e
8
0.6/1.8
85
X = H
9
10
11
Br
Cl
NO2
0.6/1
0.6/1.8
1.2/5.5
92
97
93f
a
Reactions were run at reflux in 1:1 (v/v) acetonitrile/water mixture.
Unless mentioned otherwise, the reactions were run at rt in 1:1 (v/v) acetoni-
trile/water mixture.
Starting material (14%) was recovered.
Formation of unidentified nonpolar compound was also observed, which
seemed to account for loss of the starting material.
Starting material (3%) was recovered.
The reaction was performed at reflux conditions. p-Nitrobenzoic acid was iso-
lated as a side product in 5% yield.
b
c
d
e
f
Buoyed by the facile oxidation of both primary and secondary
benzyl halides with oxone, we investigated the oxidation of pri-
mary and secondary benzyl alcohols using oxone in CH3CN/H2O at
reflux. As shown in Table 2, a variety of benzyl alcohols were
converted to the corresponding carbonyl compoundseketones in
the case of secondary alcohols (entries 10e14, Table 2) and acids
(entries 1e6) in the case of primary alcohols; yields of the isolated
products are quantitative for alcohols with the exception of elec-
3. Mechanism of oxidation
To gain insights into the mechanism of oxidation of benzyl
halides, progress of the reaction was monitored by 500 MHz 1H
NMR spectroscopy with an attempt to observe the intermediate en
route to the oxidation product. The 1H NMR spectral profiles for the
reaction of p-bromobenzyl bromide, a representative case, in 80:20
mixture of acetonitrile-d3/D2O in the presence of 3 equiv of oxone
revealed the formation of aldehyde in small amounts (Fig. 1), which
converted rapidly to the acid. At higher conversions after 24 h, the
1H NMR spectra revealed the formation of a small amount of
benzyl alcohol, which isn’t observed in the initial stages. Thus, the
primary benzyl halide seemingly undergoes oxidation rather
slowly to the aldehyde, which is in turn oxidized rapidly to the
acid. The reason as to why the alcohol shows up only after a longer
reaction time should be explicable from the following consider-
ations: it is well established that oxone decomposes with time in
the acidic medium.17 Thus, the unreacted benzyl halide, after a few
tron-poor substrates (entries 3 and 6). Benzyl alcohol with a-car-
boxy group and benzil were found to undergo oxidation to benzoic
acid in high isolated yields (entries 15 and 16). The oxidation of
aliphatic alcohols led to surprising results. While the oxidation of
dodecyl alcohol and 2-octyloxyethanol led to an intractable mix-
ture, that of the secondary cyclooctanol gave rise to octanedi-
carboxylic acid in 60% isolated yield (entries 7, 9, and 18). In
contrast, cholestanol was almost recovered intact after 36 h (entry
17). Oxidation of cyclohexyl methanol yielded adipic acid in 57%
isolated yield (entry 8). We believe that the products in these cases

K.N. Parida et al. / Tetrahedron 68 (2012) 9763e9768
9765
Table 2
Table 3
Oxidation of primary and secondary alcohols using oxonea
Oxidation of aromatic hydrocarbons using oxonea
Entry
Substrate
Equiv/time
(h)
Product
Yieldb
(%)
Entry
Substrate
Equiv/time
(h)
Product
Yield
(%)
Me
1
3/9.5
93
1
3/5.5
96
X
X = p-Br
X = H
2
3
4
5
Br
NO2
CN
Cl
3/12
5/24
3/13
4/20
94
92c
99
2
3
4
5
6
p-NO2
p-CN
o-NO2
m-CO2H
p-CO2H
5/24
5/36
6/24
5/36
5/36
61b
50c
48d
64e
56f
COOH
X
99
6
5/24
74d
7
8
9
5/36
5/36
56g
7
8
5/36
5/36
de
57
55h
9
5/36
2/1
de
5/36
5/36
18i
72j
10
62f
X = H
11
12
13
Cl
Br
NO2
2/1.2
2/2
4/20
86
95
93
10
a
Oxidations were run in acetonitrile/water mixture (1:1, v/v) at reflux.
Starting material (24%) was recovered.
Starting material (43%) was recovered.
Starting material (34%) was recovered.
Starting material (26%) was recovered.
14
15
5/22.5
6/30
95
85
97
b
c
d
e
f
Starting material (38%) was recovered.
Starting material (5%) was recovered and 34% 1,4-naphthoquinone was
g
obtained.
16
17
8/48
5/36
h
Starting material (3%) was recovered and 9,10-anthraquinone was obtained in
23% isolated yield.
i
Cholestanol
dg
Starting material (71%) was recovered.
Starting material (17%) was recovered.
j
18
5/36
60
Supplementary data). It is not yet clear to us as to what this signal
indeed corresponds to.
a
Insofar as the mechanism of oxidation of alcohols is con-
cerned, we believe that the strongly acidic conditions noted above
may facilitate the SN1 ionization via protonation, cf. Scheme 1,
such that the subsequent steps are similar to those of benzyl
halides. 500 MHz 1H NMR monitoring of the reaction reveals
formation of the aldehyde in small amounts with rapid formation
of the acids, cf. Fig. 1. The ionization appears to be rate-
determining as revealed from rather slow oxidation, for exam-
ple, of p-nitrobenzyl alcohol (entry 3, Table 2). In this respect, it is
worth mentioning that Wu et al. reported the oxidation of various
primary and secondary alcohols by oxone in the presence of AlCl3
as an additive in water.18 Quite explicably, the role of AlCl3 in this
instance must be to generate HCl, which facilitates ionization of
the alcohols.
All reactions were run in at reflux in 1:1 (v/v) acetonitrile-water mixture.
Isolated yields, unless mentioned otherwise.
Starting material (4%) was recovered.
Starting material (14%) was recovered.
An intractable product mixture was observed.
b
c
d
e
f
Starting material (21%) was recovered.
No reaction was observed with starting compound recovered almost
g
quantitatively.
hours, may slowly undergo hydrolysis to the benzyl alcohol in the
absence of active oxone to account for the formation of small
amounts of the alcohol. Based on the medium employed, namely
acetonitrile/water (50:50), we believe that the oxidation of benzyl
halides proceeds via SN1 mechanism, Scheme 1. The sluggish re-
action with electron-poor substrates and relatively shorter reaction
times for secondary benzyl bromides are consistent with the
rate-determining ionization followed by attack of the oxone to
yield the ketone. It is noteworthy that one observes a singlet at ca.
4. Limitations with oxone as a direct oxidation reagent
d
6.9. We presumed that it possibly corresponds to the addition
Given the cheap cost and environmentally benign attributes,
oxone should in principle constitute a sought-after oxidation re-
agent. For benzyl halides, activated benzyl alcohols and some of the
alkylarenes as those shown in Tables 1e3, oxone is indisputably
product between the aldehyde and oxone, cf. Scheme 1. However,
independent 1H NMR monitoring of the reaction of 4-
bromobenzaldehyde did not yield
a similar signal (Fig. S2,

9766
K.N. Parida et al. / Tetrahedron 68 (2012) 9763e9768
Fig. 1. 1H NMR monitoring of oxidation of p-bromobenzyl alcohol (left) and p-bromobenzyl bromide (right) in CD3CN/D2O (4:1) with oxone (3 equiv) at reflux. (a) Before addition of
oxone, (b) after 1 h of shaking at rt for alcohol and heating at reflux for benzyl bromide, (c) after 2.5 h of heating, (d) after 4.5 h of heating at reflux, and (e) after 24 h of heating at
reflux for benzyl bromide.
were found to be quite messy. It has been shown that oxone
reacts with pyridines and sulfides to give N-oxides9a and sulf-
oxides/sulfones,6 respectively; presumably, the double bonds
in furans react with oxone.13
5. Conclusions
In conclusion, we have found that oxone can be employed di-
rectly for oxidation of a number of benzyl halides. In an analogous
manner, activated primary and secondary alcohols are shown to be
converted to the corresponding acids and ketones, respectively.
Based on the medium employed for the reaction and different rates
of oxidations observed for differently-substituted substrates, SN1
mechanism has been proposed for the oxidation of benzyl alcohols
and benzyl halides. Aromatics and alkylaromatics are also found to
undergo oxidation to yield products in respectable yields. Although
the methodology reported herein is simple and practical, it suffers
from certain limitations.
Scheme 1. Mechanism of oxidation of benzyl halides and benzyl alcohols.
6. Experimental section
6.1. General
a good reagent. However, we note several limitations with the use
Solvents were distilled prior to use and double distilled water
was used for the reaction. All the reactions were carried out in an
open atmosphere without any precaution. The products were iso-
lated by column chromatography with silica gel of 100e200 mm
particle size. NMR spectra were recorded with 400 and 500 MHz
spectrometers.
of oxone, which are enumerated below:
ꢀ Oxone is known to decompose at low pH.17 The saturated so-
lution of oxone is strongly acidic (pH ca. 3.0), and the amount of
oxone that is decomposed increases with duration of the re-
action. Thus, for substrates that react poorly, the reactions tend
to be too sluggish as is evident for the oxidation of p-nitro-
benzyl alcohol (entry 3, Table 2).
ꢀ For unreactive aliphatic alcohols, the reactions are likely to
proceed via radical pathways leading to intractable mixtures of
products.
ꢀ Substituted arenesdunless very reactive to oxone oxida-
tiondyield side chain oxidation products competitively.
ꢀ The reactions of p-methoxy-substituted benzene derivatives,
i.e., p-methoxytoluene, p-methoxybenzyl alcohol, p-methox-
ybenzyl halides, etc., with oxone led to competitive reactions
yielding intractable mixtures of products. We believe that
these substrates initially afford p-quinonemethides that sub-
sequently react under the employed conditions of the reaction
to yield mixtures.19 Further, the reactions of alkylated hetero-
aromatic compounds such as pyridines, thiophenes, furans, etc.
6.2. General procedure for oxidation of benzyl halides, alco-
hols, and aromatic hydrocarbons
To 16 mL of acetonitrile/water (1:1 v/v) mixture was added
0.5e1.2 mmol of the starting compound. The contents were heated
at reflux with introduction of oxone (cf. entries for each case) in-
crementally over the entire duration of the reaction. For secondary
benzyl halides, the reactions were run at room temperature. The
progress of the reaction in each case was monitored by TLC analysis.
After completion of the reaction, the reaction mixture was cooled to
room temperature and the organic matter was extracted with ethyl
acetate. The combined organic extract was dried over anhyd
Na2SO4 and concentrated in vacuo. Short pad silica gel column
chromatography of the residue led to isolation of the pure product.

K.N. Parida et al. / Tetrahedron 68 (2012) 9763e9768
9767
6.2.1. o-Nitrobenzoic acid.20 Colorless solid; Rf (10% CH3OH/EtOAc)
0.31; 1H NMR (CDCl3, 400 MHz)
7.73e7.68 (m, 2H), 7.92e7.86 (m, 2H).
137.6, 145.1, 168.1, 168.7. ESI-MSþ m/z calcd for C10H8O4Na 215.0320
[MþNaþ], found 215.0327.
d
6.2.2. p-Bromobenzoic acid.2c Colorless solid; Rf (50% EtOAc/pet.
6.2.17. Naphthalene-1,4-dione.30 Yellow solid; Rf (5% EtOAc/pet.
ether) 0.48; 1H NMR (CDCl3, 500 MHz)
d
7.62 (d, J¼8.55 Hz, 2H),
ether) 0.5; 1H NMR (CDCl3, 400 MHz)
d 6.98 (s, 2H), 7.74e7.77 (m,
7.96 (d, J¼8.55 Hz, 2H).
2H), 8.07e8.09 (m, 2H).
6.2.3. o-Bromobenzoic acid.21 Colorless solid; Rf (50% EtOAc/pet.
ether) 0.49; 1H NMR (CDCl3, 500 MHz)
7.38e7.43 (m, 2H), 7.72(d,
J¼8.2 Hz, 1H), 8.02 (dd, J1¼7.3 Hz, J2¼2.1 Hz, 1H).
6.2.18. Bianthronyl.16 Yellow solid; Rf (17.5% EtOAc/pet. ether) 0.57;
mp 265e268 ꢁC (lit. 256e258 ꢁC); IR (KBr, cmꢂ1) 2923, 2852, 1661,
d
1597, 1463, 1319; 1H NMR (CDCl3, 400 MHz)
d 4.78 (s, 1H),
6.86e6.88 (m, 2H), 7.41e7.43 (m, 4H), 7.92e7.95 (m, 2H). ESI-MSþ
m/z calcd for C28H19O2Na 387.1385 [MþNaþ], found 387.1385.
6.2.4. p-Cyanobenzoic acid.22 Colorless solid; Rf (50% EtOAc/pet.
ether) 0.19; 1H NMR (DMSO-d6, 500 MHz)
8.07 (d, J¼8.6 Hz, 2H).
d
7.98 (d, J¼8.6 Hz, 2H),
6.2.19. Anthracene-9,10-dione.31 Yellow solid; Rf (5% EtOAc/pet.
ether) 0.54; 1H NMR (CDCl3, 400 MHz)
d 7.80e7.82 (m, 4H),
6.2.5. p-Nitrobenzoic acid.2c Colorless solid; Rf (10% CH3OH/EtOAc)
8.31e8.33 (m, 4H).
0.32; 1H NMR (CDCl3, 400 MHz)
J¼8.8 Hz, 2H).
d
8.27 (d, J¼8.8 Hz, 2H), 8.33 (d,
6.2.20. Isophthalic acid.32 Colorless solid; Rf (10% CH3OH/EtOAc)
0.23; 1H NMR (DMSO-d6, 500 MHz)
7.63 (t, J¼7.6 Hz, 1H), 8.16 (dd,
J1¼7.8 Hz, J2¼1.6 Hz, 2H), 8.48 (s, 1H).
d
6.2.6. p-Fluorobenzoic acid.23 Colorless solid; Rf (50% EtOAc/pet.
ether) 0.46; 1H NMR (CDCl3, 500 MHz)
8.12e8.15 (m, 2H).
d
7.15 (t, J¼8.8 Hz, 2H),
6.2.21. Octane-1,8-dicarboxylic acid.33 Colorless solid; Rf (10%
CH3OH/EtOAc) 0.23; mp 128e130 ꢁC (lit. 133e135 ꢁC); 1H NMR
(acetone-d6, 500 MHz)
(t, J¼7.45 Hz, 4H).
d 1.36e1.38 (m, 4H), 1.59e1.62 (m, 4H), 2.29
6.2.7. p-Bromoacetophenone.2c Colorless solid; Rf (10% EtOAc/pet.
ether) 0.43; 1H NMR (CDCl3, 500 MHz)
d
2.58 (s, 3H), 7.60 (d, J¼8.
5 Hz, 2H), 7.82 (d, J¼8.5 Hz, 2H).
6.2.22. Adipic acid.34a Colorless solid; Rf (10% MeOH/EtOAc) 0.24;
mp 146e148 ꢁC (lit. mp 147.5e149 ꢁC);34b 1H NMR (acetone-d6,
6.2.8. 2-Bromo-1-(4-bromophenyl)ethanone.24 Colorless solid; Rf
500 MHz)
d 1.63e1.67 (m, 4H), 2.30e2.35 (m, 4H).
(10% EtOAc/pet. ether) 0.6; 1H NMR (CDCl3, 400 MHz)
d 4.4 (s, 2H),
6.2.23. Benzene-1,4-dicarboxylic acid.32 Colorless solid; Rf (10%
7.64 (d, J¼8.5 Hz, 2H), 7.85 (d, J¼8.5 Hz, 2H).
CH3OH/EtOAc) 0.2; 1H NMR (DMSO-d6, 500 MHz)
d 8.03 (s, 4H),
6.2.9. Acetophenone.2c Colorless liquid; Rf (10% EtOAc/pet.
ether) 0.59; 1H NMR (CDCl3, 400 MHz)
2.61 (s, 3H), 7.46
12.7 (br s, 2H).
d
(t, J¼7.3 Hz, 2H), 7.54e7.59 (m, 1H), 7.96 (dd, J1¼8.5 Hz,
J2¼1.4 Hz, 2H).
Acknowledgements
6.2.10. Benzoic acid.2c Colorless solid; Rf (25% EtOAc/pet. ether)
J.N.M. is thankful to the Department of Science and Technology,
India for generous financial support. K.N.P., S.M., and S.J. thank CSIR
for their research fellowships.
0.37; 1H NMR (CDCl3, 400 MHz)
d
7.49 (t, J¼7.8, 2H), 7.62 (t,
J¼7.8 Hz, 1H), 8.12 (d, J¼7.3 Hz, 2H).
6.2.11. Benzophenone.25 Colorless solid; Rf (10% EtOAc/pet. ether)
Supplementary data
0.45; 1H NMR (CDCl3, 400 MHz)
7.48 (t, J¼7.8 Hz, 4H), 7.59 (t,
J¼7.3 Hz, 2H), 7.8 (d, J¼8.2 Hz, 4H).
d
1H and 13C NMR spectral reproductions for the products of ox-
idations and 1H NMR monitoring of the oxidations. Supplementary
data associated with this article can be found in the online version,
at http://dx.doi.org/10.1016/j.tet.2012.09.028.
6.2.12. p-Nitroacetophenone.2c Straw-yellow solid; Rf (17.5% EtOAc/
pet. ether) 0.45; 1H NMR (CDCl3, 400 MHz)
d 2.68 (s, 3H), 8.11 (d,
J¼8.7 Hz, 2H), 8.31 (d, J¼8.7 Hz, 2H).
References and notes
6.2.13. p-Chloroacetophenone.26 Colorless solid; Rf (10% EtOAc/pet.
ether) 0.53; 1H NMR (CDCl3, 400 MHz)
d
2.59 (s, 3H), 7.43 (d,
1. Tojo, G.; Fernandez, M. In Oxidation of Alcohols to Aldehydes and Ketones; Tojo, G.,
Ed.; Springer ScienceþBusiness Media: New York, NY, 2006.
J¼8.3 Hz, 2H), 7.89 (d, J¼8.3 Hz, 2H).
2. (a) Moorthy, J. N.; Senapati, K.; Singhal, N. Tetrahedron Lett. 2009, 50, 2493; (b)
Moorthy, J. N.; Senapati, K.; Parida, K. N. J. Org. Chem. 2010, 75, 8416; (c)
Moorthy, J. N.; Senapati, K.; Parida, K. N.; Jhulki, S.; Sooraj, K.; Nair, N. N. J. Org.
Chem. 2011, 76, 9593.
6.2.14. p-Chlorobenzoic acid.27 Colorless solid; Rf (25% EtOAc/pet.
ether) 0.39; 1H NMR (CDCl3, 400 MHz)
(d, J¼8.3 Hz, 2H).
d
7.45 (d, J¼8.3 Hz, 2H), 8.04
3. Moorthy, J. N.; Singhal, N.; Senapati, K. Tetrahedron Lett. 2006, 47, 1757.
4. He, W. Synlett 2006, 3548.
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6.2.16. o-Carboxycinnamic acid. Colorless solid; Rf (10% MeOH/
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