Rate enhancements due to ultrasound in isoquinolinium dichromate and isoquinolinium chlorochromate catalyzed chlorination of aromatic compounds in presence of KHSO4/KCl

Article abstract of DOI:10.14233/ajchem.2018.20963

Chlorination of aromatic compounds underwent magnificent rate accelerations in isoquinolinium dichromate and isoquinolinium chlorochromate catalyzed chlorination of aromatic hydrocarbons in the presence of KCl and KHSO₄. Reaction times reduced highly significantly from 4-5 h in conventional protocol to 30-40 min under sonication, followed by high yields of monochloro derivatives as products with high regioselectivity.

Full text of DOI:10.14233/ajchem.2018.20963

Asian Journal of Chemistry; Vol. 30, No. 1 (2018), 167-170
A
SIAN
J
OURNAL OF HEMISTRY
C
https://doi.org/10.14233/ajchem.2018.20963
Rate Enhancements Due to Ultrasound in Isoquinolinium Dichromate and Isoquinolinium
Chlorochromate Catalyzed Chlorination of Aromatic Compounds in Presence of KHSO4/KCl
1,*
2,3
2
1
K.C. RAJANNA , A. SAMBASHIVA RAO , I.E. CHAKRAVARTHI and K. RAJENDAR REDDY
1Department of Chemistry, Osmania University, Hyderabad-500 007, India
2Department of Chemistry, Rayalaseema University, Kurnool-518 007, India
3Department of Chemistry, Maturi Venkata Subba Rao Engineering College, Hyderabad-500 007, India
*Corresponding author: E-mail: kcrajannaou@yahoo.com
Received: 9 August 2017;
Accepted: 31 October 2017;
Published online: 30 November 2017;
AJC-18670
Chlorination of aromatic compounds underwent magnificent rate accelerations in isoquinolinium dichromate and isoquinolinium
chlorochromate catalyzed chlorination of aromatic hydrocarbons in the presence of KCl and KHSO4. Reaction times reduced highly
significantly from 4-5 h in conventional protocol to 30-40 min under sonication, followed by high yields of monochloro derivatives as
products with high regioselectivity.
Keywords: Chlorination, Aromatic compounds, Isoquinolinium chlorochromate, Isoquinolinium dichromate, Sonication.
secondary alcohols under mild conditions. It oxidized vicinal
and non-vicinal diols to the corresponding α-hydroxy carbonyl
compounds. Recently, we have accomplished the use of isoquino-
linium dichromate and isoquinolinium chlorochromate as efficient
catalysts to trigger oxidative bromination and iodination of
aromatic hydrocarbons with KBr/KI and KHSO4 under acid-
free conditions. Reaction times reduced highly significantly
under sonication, followed by corresponding monobromo deri-
vatives in very good yield with high regioselectivity [21]. Encou-
raged by this protocol we have embarked on exploring the
possibility of isoquinolinium chlorochromate (IQCC) and
isoquinolinium dichromate (IQDC) as catalysts to achieve
oxidative chlorination of aromatic compounds with various
functional groups such as phenols, anilines and acetanilides.
We also wish to explore the use of ultrasound to assist IQCC
and IQDC mediated chlorination reactions with a view to acce-
lerate chemical reactions for achieving better yields as well as
improving the greenery of reaction protocols. Earlier reviews
and publications in this field [22-32] proved the importance
of ultrasonically assisted organic synthesis and also highlighted
that sonication using ultrasound is not only simple, but also
satisfies both economical and environmental demands, as
recommended by Anastas and Warner in the green chemistry
formulations [33].
INTRODUCTION
Like several other electrophilic aromatic substitution reactions,
chlorination of aromatic compounds is also an evergreen and
prominent synthetic protocol because of its uses in the synthesis
of diversified aromatic compounds such as aromatic ethers
and thioethers, amines, arylhydrazines, benzonitriles, fluoro-
aromatic, silylated aromatic hydrocarbons and many more
functionalities [1-3]. Reagents such as molecular chlorine [4],
sulfuryl chloride [5], alkyl and acyl hypochlorites [6], inorganic
chlorides [7], m-CPBA/18-crown-6/KCl [8], NaBO3/Na2WO4/
KCl [9], H2O2/NH4VO3/KCl [10], N-chlorosuccinimide [11],
benzyltrimethyl ammonium tetrachloroiodate (BTMAICl4)
[12], dichlorinemonoxide [13], PhICl2 in trifluoroacetic acid [14],
N-chloroamines [15], N-chloroamides and N-chlorosulfonamides
[16]. Many of the reported methods have some limitations such
as use of strong and non-selective chlorinating agents, toxic and
expensive reagents, low yields and long reaction times. In some
protocols, after completion of the reaction, large amount of acid
waste is drained through the outlets of laboratories and indus-
tries. Oxychlorination methods were among some such protocols
through which one can address few issues and also achieve
smooth chlorination [17,18]. Onium halochromates and onium
dichromates were among the few most effective reagents, which
could be used for oxidation as well as oxyhalogenation of organic
compounds [19]. Srinivasan et al. [20] synthesiszed isoquino-
linium dichromate (a new oniumdichromate) which proved
as a versatile reagent for selective oxidation of primary and
EXPERIMENTAL
All chemicals used were of synthesis grade reagents and
procured from Merck, S.D. Fine orAvra Chemicals. Isoquino-

168 Rajanna et al.
Asian J. Chem.
linium dichromate (IQDC) and isoquinolinium chlorochromate
(IQCC) were prepared as reported method [20,21].
IQCC or IQDC/KCl
(ii) DCE/sonication)
Generalprocedureforconventionalchlorinationreactions:
Organic compound (10 mmol) potassium chloride (KCl 10
mmol) and (1 mmol) Cr(VI) reagent (IQCC or IQDC) and solvent
(aq. acetontrile or DCE) were taken in a clean round bottom
flask. About 50 mg of KHSO4 is also added to the contents of
reaction flask and the reaction mixture is refluxed for about 4-5 h
at 50-60 ºC till the completion reaction, as ascertained by thin
layer chromatography (TLC). The reaction mixture is then treated
with 5% sodium thiosulphate solution followed by the addition
of ether. The aqueous layer was separated from the ether layer.
The ether is evapourated from organic layer under vacuum,
and purified with column chromatography using chloroform:
n-hexane (9:1) as eluent to get pure chlorinated aromatic compound
as product [2,3].
General procedure for ultrasonically assisted chlorination
reactions: The general procedure for ultrasonically assisted
chlorination reaction is largely similar to the preceeding conven-
tional method.After mixing the reactants in a clean round bottom
flask, is placed in an ultrasound assited sonicator and sonicated
at room temperature till the reaction is completed (about 30-
40 min). Progress of the reaction was monitored by TLC
technique. Work up procedure after completion of the reaction
mixture is similar to as described above.
Y
Y
X
X
Cl
IQCC or IQDC/KCl
(i) DCE/Reflux
where Y = OH, NH2 and NHCOCH3
X = ED or EW group
Scheme-I: IQDC and IQCC triggered chlorination of aromatic compounds
cation the reaction times are drastically reduced to about 30 to
40 min followed by considerable yield enhancements. The
products of these reactions were characterized by spectroscopic
and physical data with authentic samples and found to be
satisfactory with literature reports [2,3]. The yields of major
products are given in Table-1.
Spectroscopic data of some synthesized compounds:
1
4-Chlorophenol: H NMR (400 MHz, CDCl3) δ 7.24-
7.17 (m, 2H, Ph), 6.77-6.74 (m, 2H, Ph), 5.27 (s, 1H, OH);
HRMS (ESI-TOF) m/z: calcd. for C6H5OCl 127.0029, found
126.9956.
2-Methoxy-4-chlorophenol: 1H NMR (400 MHz, DMSO-
d6) δ 9.20 (s, 1H, OH), 6.95 (d, J = 2.0 Hz, 1H, Ph), 6.79-6.75
(m, 2H, Ph), 3.78 (s, 3H, OCH3); HRMS (ESI-TOF) m/z: calcd.
for C7H6O2Cl 157.0135, found 157.0056.
RESULTS AND DISCUSSION
The chlorination reactions of aromatic compounds were
conducted using isoquinolinium dichromate (IQDC)/KCl and
isoquinolinium chlorochromate (IQCC)/KCl combinations in
aqueous KHSO4 under mineral acid free conditions. Described
methods worked out well for an array of functionalities such
as phenols, anilines or acetanilides (Scheme-I).
Each reaction is repeated at least half a dozen times and
the reaction times are reproducible with an accuracy of 5 min.
The chlorination of aromatic compounds required 4-5 h under
conventional conditions at reflux temperatures, but under soni-
2-Chloro-4-methoxyphenol: 1H NMR (400 MHz, DMSO-
d6) δ 9.55 (s, 1H, OH), 6.94-6.90 (m, 2H, Ph), 6.76 (dd, J =
3.2, 8.8 Hz, 1H, Ph), 3.69 (s, 3H, OCH3); HRMS (ESI-TOF)
m/z: calcd. for C7H6ClO2 157.0135, found 157.0059.
4-Chloro-3-methylphenol: 1H NMR (400 MHz, DMSO-
d6) δ 9.51 (s, 1H, OH), 7.16 (d, J = 2.4 Hz, 1H, Ph), 6.74 (d, Hz,
1H, Ph), 6.62 (dd, , 8.8 Hz, 1H, Ph), 2.24 (s, 3H, CH3); HRMS
(ESI-TOF) m/z: calcd. for C7H6ClO 141.0185, found 141.0116.
TABLE-1
OXIDATIVE CHLORINATION OF AROMATIC HYDROCARBONS
Reaction time Conventional: 4-5 h; Sonication: 30-40 min
Conventional yield (%)
Product
Sonication yield (%)
KCl/IQCC KCl/IQDC
71 70
S. No.
Substrate
KCl/IQCC
70
KCl/IQDC
68
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
Phenol
4-Chloro Phenol
o-Cresol
p-Cresol
m-Cresol
4-Chloro phenol
2-Chloro phenol
4-Bromo phenol
1,4-Dihydroxy benzene
1-Naphthol
4-Chloro-2-methylphenol
2-Chloro-4-methylphenol
4-chloro-3-methylphenol
2,4-Dichloro phenol
65
65
66
55
60
69
70
60
66
69
68
59
62
66
76
68
71
63
68
59
69
68
71
70
69
62
68
71
63
64
69
72
71
73
65
70
60
70
69
70
77
70
2,4-Dichloro phenol
59
61
4-Bromo-2-chloro phenol
2-Chloro benzene-1,4-diol
2-Chloro-1-naphthol
60
71
69
66
74
73
Benzaldehyde
3-Chloro benzaldehyde
70
73
1-(3-OH phenyl)ethanone 1-(3-OH-4-chloro phenyl)ethanone
62
66
4-NO2 phenol
4-NO2-2-chloro phenol
5-Chloro-2-OH-benzaldehyde
3-Chloro-4-OH-benzaldehyde
2-Chlorotoluene
65
55
65
69
69
59
69
70
2-OH benzaldehyde
4-OH benzaldehyde
Toluene
2-OH-benzoic acid
2-OH-aniline
3-Chloro-6-OH- benzoic acid
3-Chloro-4-OH-aniline
3,4-di-Cl-acetophenone
69
66
71
70
68
67
4-Cl-acetophenone

Vol. 30, No. 1 (2018)
Rate Enhancements Due to Ultrasound in Isoquinolinium Dichromate and Isoquinolinium Chlorochromate 169
3-Chloro-5-hydroxy benzaldehyde: 1H NMR (400 MHz,
DMSO-d6) δ 10.93 (s, 1H), 10.23 (s, 1H), 7.60 (d, Hz, 1H,
Ph), 7.54 (dd, , 8.8 Hz, 1H, Ph), 7.05 (d, Hz, 1H, Ph); HRMS
(ESI-TOF) m/z: calcd. for C7H4ClO2 154.9978, found 154.9898.
4-Chloro-2-methylphenol: 1H NMR (400 MHz, DMSO-
d6) δ 9.52 (s, 1H, OH), 7.10 (d, Hz, 1H, Ph), 7.01 (dd, , 8.4 Hz,
1H, Ph), 6.78 (d, Hz, 1H, Ph), 2.11 (s, 3H, CH3); HRMS (ESI-
TOF) m/z: calcd. for C7H6OCl 141.0185, found 141.0107.
4-Chloro-2-nitroaniline:Yellow orange powder; 1H NMR
(400 MHz, DMSO) δ 7.90 (d, J = 2.42 , 1H, Ar), δ 7.28 (dd,
J = 9.20, 2.24, 1H, Ar), δ 7.06 (d, J = 9.22, 1H,Ar) δ 7.55 (bs,
1H, NH2) ppm; MS (APCI): calcd. for C6H5N2O2Cl [M]+
172.57, found 172 [M]+.
Y
Y
[(IQH)OCrO3Cl]
(IQH)O
O
Cl
R
Cr
H
R
O
Y
O
where R = EWG/EDG;
Y = Functional group
[(IQH)+(OHCrO3)-]
R
Cl
Scheme-II
3-Chloro-4-hydroxybenzaldehyde: Light brown powder;
1H NMR (400 MHz, DMSO) δ 9.78 (s, 1H, CHO), δ 7.81 (d,
J = 1.80 Hz, 1H, Ar), δ 7.64 (dd, J = 8.40, 1.80 Hz, 1H, Ar),
δ 7.12 (d, J = 8.32 Hz, 1H,Ar) ppm; MS: calcd. For C7H5O2Cl
[M]+ 156,5, found 155 [M-1]+.
and its protonated form (IQHOCr(OH)Cl)+, by capturing H+
from the dissociated bisulfate species, according to the following
equilibria:
+ ZZX
+
1
(5)
(IQHOCrO2Cl) + H
(IQHOCr(OH)OCl)
YZZ
5-Chlorosalicylic acid: White crystals; H NMR (400
MHz, DMSO) δ 9.05 (s, 1H, OH), δ 7.79 (d, J = 2.52 Hz, 1H,
Ar), δ 7.38 (dd, J = 8.80, 2.52 Hz, 1H, Ar), δ 6.91 (d, J = 8.88
Hz, 1H, Ar) ppm; MS: calcd. for C7H5O3Cl [M]+ 172, found
171.
The protonated chromium(VI) species thus formed
(IQHOCr(OH)OCl)+ being a stronger electrophile, may further
react with chloride ion to afford [IQHOCr(OH)(OCl)Cl] species,
since the reactions are conducted in excess KCl.
We have also tried to to explain the mechanism of IQDC/
KCl mediated chlorination reaction. It is well established in
earlier reports that in aquoues acidic media K2Cr2O7 or Cr(VI)
exists in several reactiveforms, such as HCrO4−, H2CrO4, [HCrO3]+
and HCrO3B (where B = HSO4−, ClO4− or Cl−) [34,35]. On the
basis of fact that quinolinium dichromate (QDC) is related to
K2Cr2O7, we have formulated similar types of reactive species
with quinolinium ion background [36]. Further, it is also of
interest to note that isoquinolinium dichromate (IQDC) resembles
the structure of quinolinium dichromate (QDC), following
species could be considered according to the following equilibria:
− ZZX
[IQHOCr(OH)OCl]+ +Cl
[IQHOCr(OH)(OCl)Cl]
(6)
YZZ
Finally, aromatic substrates undergo mono chlorination
through the attack of Cl+ of [IQHOCr(OH)(OCl)Cl] on the
aromatic ring as shown Scheme-III.
Y
Y
[IQHOCr(OH)(OCl)Cl]
(IQH)O
R
Cl
OH
O
Cr
H
R
Cl
where R = EWG/EDG;
Y = Functional group
−
(1)
ZZX
(IQH) Cr O + H O
2[(IQH) + (HCrO ) ]
YZZ
2
2
7
2
4
As the reactions are conducted in presence of aqueous
KHSO4 medium, it is more likely that the bisulfate ion dissociates
to give (H+) creating mild acid reaction conditions. Protons (H+)
thus released could be used to protonate IQDC, leading to the
formation of active [(IQH)+(HCrO4)−] (IQ bound chromic acid)
species.
[IQHOCr(OH)(OH)Cl]
Y
R
Cl
Scheme-III
SO2− + H+
ZZX
(2)
HSO
4 YZZ
4
The observed rate enhancements in ultrasonically assisted
reactions could be explained due to cavitation, a physical process
that creates, enlarges implodes gaseous and vaporous cavities
in an ultrasonically assisted (irradiated) liquid. Cavitation
induces very high local temperatures in the reaction mixture
and enhances mass transfer [20-29].
+
+ ZZX
(IQH)+ (HCr2O4 )− + H
[(IQH)CrO ] + H O
(3)
YZZ
3
2
Active species thus formed may further react with chloride
ion to afford [(IQH)CrO3Cl] species, since the reactions are
conducted in excess KCl.
− ZZX
[(IQH)CrO3 )+ + Cl
[(IQH)OCrO Cl]
2
(4)
Conclusion
YZZ
Finally, aromatic substrates undergo mono chlorination
through the formation of cyclic intermediate with aromatic
compound as shown in Scheme-II.
On the other hand, the most plausible mechanism in IQCC
triggered reactions could be proposed by formulating isoquinol-
inium chlorochromate (IQCC) in the lines of other onium halo-
chromate species [37-40]. Since the reactions are studied in
aqueous KHSO4 medium, IQCC could exists as (IQHOCrO2Cl)
In summary, isoquinolinium chlorochromate (IQCC) and
isoquinolinium dichromate (IQDC) as cost-effective catalysts
to trigger chlorination of aromatic compounds in presence of
KCl and small amount of KHSO4 is successfully explored.
The use of mineral acid is completely avoided in these protocols.
Reaction times drastically reduced from 4-5 h (in conventional)
to 30-40 min under sonication. The reactions occurred under
mild and under environmentally safe conditions with simple

170 Rajanna et al.
Asian J. Chem.
15. (a) J.R. Lindsay Smith, L.C. McKeer and J.M. Taylor, J. Chem. Soc.,
Perkin Trans. 2, 1529 (1989);
work up at room temperature. Thus, it is believed that the
developed protocols are one of the important contributions in
the area of chlorination reactions.
https://doi.org/10.1039/P29890001529.
(b) J.R. Lindsay Smith, L.C. McKeer and J.M. Taylor, J. Chem. Soc.,
Perkin Trans. 2, 385 (1988);
REFERENCES
https://doi.org/10.1039/P29880000385.
(c) J. R. Lindsay Smith, L.C. McKeer, and J.M. Taylor, J. Chem. Soc.,
Perkin Trans. 2, 1537 (1989);
https://doi.org/10.1039/P29890001537.
1. (a) P.B.D. De la Mare, Electrophilic Halogenation, Cambridge University
Press: Cambridge (1976).
(b) R. Taylor, Electrophilic Aromatic Substitution, Wiley: Chichester,
pp. 362 (1990).
(c) Ullmann’s Encyclopedia of Industrial Chemistry,Wiley-VCH,Weinheim,
edn 6 (1998).
16. P. Bovonsombat and E. Mcnelis, Synthesis, 237 (1993);
https://doi.org/10.1055/s-1993-25839.
17. (a) E.B. Merkushev, Synthesis, 923 (1988);
https://doi.org/10.1055/s-1988-27758.
2. (a) N. Narender, P. Srinivasu, S.J. Kulkarni and K.V. Raghavan, Synth.
Commun., 32, 279 (2002);
(b) J.K. Stille, Angew. Chem. Int. Ed. Engl., 25, 508 (1986);
https://doi.org/10.1002/anie.198605081.
(c) A. Suzuki, Pure Appl. Chem., 63, 419 (1991);
https://doi.org/10.1351/pac199163030419.
https://doi.org/10.1081/SCC-120002013.
(b) N. Narender, K.V.V. Krishna Mohan, P. Srinivasu, S.J. Kulkarni
and K.V. Raghavan, Indian J. Chem., 43B, 1335 (2004).
3. (a) H.A. Muathen, Monatsh. Chem., 130, 1493 (1999);
https://doi.org/10.1007/s007060050309.
18. (a) A. Bachki, F. Foubelo and M. Yus, Tetrahedron, 50, 5139 (1994);
https://doi.org/10.1016/S0040-4020(01)90424-7.
(b) G.A. Olah, Q. Wang, G. Sandford and G.K. Surya Prakash, J. Org.
Chem., 58, 3194 (1993);
(b)Y. Xiong, H. Duan, X. Meng, Z. Ding and W. Feng, J. Chem., Article
ID 2960414 (2016);
https://doi.org/10.1155/2016/2960414.
(c) K.H. Chung, H.J. Kim, H.R. Kim, and E.K. Ryu, Synth. Commun.,
20, 2991 (1990);
https://doi.org/10.1021/jo00063a052.
(c) B. Akhlaghinia and M. Rahmani, Turk. J. Chem., 33, 67 (2009).
(d) J. March, Advanced Organic Chemistry, Wiley-Interscience, New
York, edn 4 (2000).
https://doi.org/10.1080/00397919008051517.
4. (a) R.H. Huston and A.H. Neeley, J. Am. Chem. Soc., 57, 2176 (1935);
https://doi.org/10.1021/ja01314a040.
19. (a) S. Patel and B.K. Mishra, Tetrahedron, 63, 4367 (2007);
https://doi.org/10.1016/j.tet.2007.02.073.
(b) B. Tamami and A.R. Kiasat, Iran. Polym. J., 6, 273 (1997).
(c) A.F. Luzzio and F.S. Guziec Jr., Org. Prep. Proced. Int., 20, 533 (1988);
https://doi.org/10.1080/00304948809356301.
(b) D.R. Harvey and R.O.C. Norman, J. Chem. Soc., 3604 (1961);
https://doi.org/10.1039/jr9610003604.
20. R. Srinivasan, S. Akila, J. Caroline and K. Balasubramanian, Synth.
Commun., 28, 2245 (1998);
https://doi.org/10.1080/00397919808007040.
21. A.S. Rao, K.C. Rajanna, K.R. Reddy and S. Kulkarni, Synth. React. Inorg.
Met.-Org. Nano-Met. Chem., 46, 832 (2016);
https://doi.org/10.1080/15533174.2014.989596.
22. S.V. Ley and C.M.R. Low, Ultrasound in Synthesis, Springer, Berlin,
(1989).
23. W.T. Richards and A.L. Loomis, J. Am. Chem. Soc., 49, 3086 (1927);
https://doi.org/10.1021/ja01411a015.
24. T.J. Mason and J.P. Lorimer, Sonochemistry: Theory, Applications and
Uses of Ultrasound in Chemistry, John Wiley & Sons, NewYork (1988).
25. T.J. Mason, Chem. Soc. Rev., 26, 443 (1997);
https://doi.org/10.1039/cs9972600443.
26. K.S. Suslick, Ultrasound: Its Chemical, Physical and Biological Effects,
VCH, New York (1988).
5. (a) M. Hojo and R. Masuda, Synth. Commun., 5, 169 (1975);
https://doi.org/10.1080/00397917508064104.
(b) L. Delaude and P. Laszlo, J. Org. Chem., 55, 5260 (1990);
https://doi.org/10.1021/jo00305a023.
6. (a) M. Anbar and D. Ginsburg, Chem. Rev., 54, 925 (1954);
https://doi.org/10.1021/cr60172a002.
(b) D. Ginsburg, J. Am. Chem. Soc., 73, 2723 (1951);
https://doi.org/10.1021/ja01150a084.
(c) K. Smith, M. Butters, W.E. Paget and B. Nay, Synthesis, 1155 (1985);
https://doi.org/10.1055/s-1985-31461.
(d) I. Lengyel, V. Cesare and R. Stephani, Synth. Commun., 28, 1891
(1998);
https://doi.org/10.1080/00397919808007021.
(e) K. Smith, M. Butters and B. Nay, Synthesis, 1157 (1985);
https://doi.org/10.1055/s-1985-31462.
7. (a) D. Masilamani and M.M. Rogic, J. Org. Chem., 46, 4486 (1981);
https://doi.org/10.1021/jo00335a033.
27. V. Singh, K.P. Kaur, A. Khurana and G.L. Kad, Resonance, 3, 56 (1998);
https://doi.org/10.1007/BF02836081.
(b) M. Srebnik, R. Mechoulam and I.Yona, J. Chem. Soc., Perkin Trans. I,
1423 (1987);
28. T.J. Mason, Chemistry with Ultrasound, Elsevier Science Publishers
Ltd., London (1990).
https://doi.org/10.1039/p19870001423.
(c) E.M. Kosower, W.J. Cole, G.-S. Wu, D.E. Cardy and G.J. Meisters,
J. Org. Chem., 28, 630 (1963);
29. T.J. Mason and D. Peters, Practical Sonochemistry: Power Ultrasound
Uses andApplications, Hoorwood Publishing, Chichester, edn 2 (2003).
30. M.A. Margulis, Advances in Sonochemistry, JAI Press, London, vol. 1,
p. 49 (1990).
https://doi.org/10.1021/jo01038a007.
31. H. Fillion and J.L. Luche, ed.: J.L. Luche, Selected Experiments, In:
Synthetic Organic Sonochemistry, Plenum, NewYork, Chap. 9 (1998).
32. R. Cella and H.A. Stefani, Tetrahedron, 65, 2619 (2009);
https://doi.org/10.1016/j.tet.2008.12.027.
33. P.T. Anastas and J.C. Warner, Green Chemistry: Theory and Practice
Oxford University Press; New York (1998).
34. K.B. Wiberg, Oxidations in Organic Chemistry, PartA,Academic Press,
New York (1965).
35. D. Benson, Mechanisms of Oxidation by Metal Ions, Elsevier, New
York (1976).
(d) H. Lübbecke and P. Boldt, Tetrahedron, 34, 1577 (1978);
https://doi.org/10.1016/0040-4020(78)80185-9.
8. N. Usami, K. Kobana, H.Yoshida, T. Kimura, K. Watanabe, H.Yoshimura
and I. Yamamoto, Chem. Pharm. Bull. (Tokyo), 46, 1462 (1998);
https://doi.org/10.1248/cpb.46.1462.
9. B.P. Bandgar and N.J. Nigal, Synth. Commun., 28, 3225 (1998);
https://doi.org/10.1080/00397919808004426.
10. V.R. Hegde, G.C.G. Pais, R. Kumar, P. Kumar and B. Pandey, J. Chem. Res.
(S), 62 (1996).
11. (a) Y. Goldberg and H. Alper, J. Mol. Catal., 88, 377 (1994);
https://doi.org/10.1016/0304-5102(93)E0278-O.
(b) F.L. Lambert, W.D. Ellis and R.J. Parry, J. Org. Chem., 30, 304 (1965);
https://doi.org/10.1021/jo01012a512.
12. S. Kajigaeshi,Y. Shinmasu, S. Fujisaki and T. Kakinami, Bull. Chem. Soc.
Jpn., 63, 941 (1990);
36. J.N. Reddy, S. Giridhar, K.C. Rajanna and P.K. Saiprakash, Transition
Met. Chem., 21, 105 (1996);
https://doi.org/10.1007/BF00136537.
37. D. Sharma, P. Pancharia, K. Vadera and P.K. Sharma, J. Sulfur Chem.,
32, 315 (2011);
https://doi.org/10.1080/17415993.2011.587519.
38. D. Sharma, P. Panchariya, P. Purohit and P.K. Sharma, Oxid. Commun.,
35, 821 (2012).
https://doi.org/10.1246/bcsj.63.941.
13. F.D. Marsh, W.B. Farnham, D.J. Sam and B.E. Smart, J. Am. Chem. Soc.,
104, 4680 (1982);
39. S. Panwar, S. Pohani, P. Swami, S. Vyas and P.K. Sharma, Eur. Chem. Bull.,
https://doi.org/10.1021/ja00381a032.
2, 904 (2013).
14. L.J. Andrews and R.M. Keefer, J. Am. Chem. Soc., 82, 5823 (1960);
https://doi.org/10.1021/ja01507a014.
40. L. Mathur and A. Choudhary, Asian J. Chem., 26, 2597 (2014);
https://doi.org/10.14233/ajchem.2014.15753.