Oxidation of benzylic alcohols to carbonyls using tert-butyl hydroperoxide over pure phase nanocrystalline CeCrO3

Article abstract of DOI:10.1016/j.catcom.2013.05.019

Nanocrystalline phase pure CeCrO₃ was synthesized by a two step preparation method. The prepared material was characterized by techniques such as X-ray Diffraction (XRD), High Resolution Transmission Electron Microscopy (HR-TEM), EDX and SEM analysis. The catalytic activity of CeCrO₃ was investigated for the oxidation of benzylic alcohols to the corresponding carbonyls using TBHP as oxidant. Oxidation of several structurally diverse primary and secondary benzylic alcohols were studied with the CeCrO ₃/TBHP catalytic system. The catalyst exhibited significant catalytic activity and selectivity in most of the cases.

Full text of DOI:10.1016/j.catcom.2013.05.019

Oxidation of benzylic alcohols to carbonyls using tert-butyl hydroperoxide
over pure phase nanocrystalline CeCrO3
Anand S. Burange, Radha V. Jayaram, Rakesh Shukla, Avesh K. Tyagi
PII:
DOI:
Reference:
S1566-7367(13)00192-1
doi: 10.1016/j.catcom.2013.05.019
CATCOM 3514
To appear in:
Catalysis Communications
Received date:
Revised date:
Accepted date:
3 May 2013
22 May 2013
22 May 2013
Please cite this article as: Anand S. Burange, Radha V. Jayaram, Rakesh Shukla,
Avesh K. Tyagi, Oxidation of benzylic alcohols to carbonyls using tert-butyl hydroper-
oxide over pure phase nanocrystalline CeCrO3, Catalysis Communications (2013), doi:
10.1016/j.catcom.2013.05.019
This is a PDF file of an unedited manuscript that has been accepted for publication.
As a service to our customers we are providing this early version of the manuscript.
The manuscript will undergo copyediting, typesetting, and review of the resulting proof
before it is published in its final form. Please note that during the production process
errors may be discovered which could affect the content, and all legal disclaimers that
apply to the journal pertain.

ACCEPTED MANUSCRIPT
Oxidation of benzylic alcohols to carbonyls using tert-butyl hydroperoxide
over pure phase nanocrystalline CeCrO3
Anand S. Burangea, Radha V. Jayarama*, Rakesh Shuklab, Avesh K. Tyagib*
aDepartment of Chemistry, Institute of Chemical Technology, Mumbai – 400019, India.
bChemistry Division, Bhabha Atomic Research Centre, Mumbai – 400085, India
*Corresponding author. Tel.: + 91- 22 3361 2607; Fax: +91- 22 3361 1020.
Email: rv.jayaram@ictmumbai.edu.in , aktyagi@barc.gov.in
Abstract
Nanocrystalline phase pure CeCrO3 was synthesized by a two step preparation method. The
prepared material was characterized by techniques such as X-Ray Diffraction (XRD), High
Resolution Transmission Electron Microscopy (HR-TEM), EDX and SEM analysis. The
catalytic activity of CeCrO3 was investigated for the oxidation of benzylic alcohols to the
corresponding carbonyls using TBHP as oxidant. Oxidation of several structurally diverse
primary and secondary benzylic alcohols were studied with the CeCrO3/TBHP catalytic system.
The catalyst exhibited significant catalytic activity and selectivity in most of the cases.
Keywords: Selective oxidation, Perovskites, Heterogeneous catalyst, CeCrO3, benzylic alcohol
oxidation.
1

ACCEPTED MANUSCRIPT
1. Introduction
Oxidation of benzylic alcohols to carbonyls is a fundamental organic transformation for the
production of various intermediates in synthetic organic chemistry [1]. Conventional routes for
this transformation involves use of stoichiometric amounts of oxidants such as dichromate and
permanganate but these reagents are producing large volumes of solid waste leading to
environmental problems [2-4]. Supported noble metals such as palladium and gold have also
been reported for this conversion but these are not cost effective [5-7]. In view of the industrial
relevance of this reaction, development of green catalytic systems is a challenging research
arena. Many homogeneous and heterogeneous catalytic systems are reported as alternatives. This
includes many homogeneous catalytic systems [8-11], HNO3/Br2[12], FeBr3[13],
PDC/Adogen464[14], supported catalysts [15-20], PEEKWC microcapsules[21], CrO3[22], CrS-
2[23] and TEMPO-catalyzed H2O2/HBr/ionic liquid [bmim]PF6 system [24]
Most of these methods suffer from various disadvantages such as use of non benign
chemicals, non-recoverable homogeneous catalysts, less efficient and cost ineffective catalytic
systems etc. Thus the use of a heterogeneous catalyst system in the liquid phase remains as an
attractive approach for oxidation reactions. In the past few years, spinel and perovskites type
metal oxides have been extensively used as catalysts for various organic transformations [25-28].
These types of metal oxides have good thermal and chemical stability and can be employed for
wide range of temperatures in various reactions [29-31]. Selective oxidation of alcohols to
carbonyls using TBHP as oxidant over LaMO3 (M=Cr, Mn, Co, Ni, Fe) perovskites is recently
reported by us [32]. Herein we report the oxidation of benzylic alcohols to carbonyls using
TBHP as a clean oxidant with nano crystalline CeCrO3 catalyst.
2

ACCEPTED MANUSCRIPT
2. Experimental section
2.1. Synthesis of pure phase nano crystalline CeCrO3
Nanocrystalline CeCrO3 was synthesized by the reported two step method i.e. gel-combustion
method followed by reduction in presence of Zr sponge [33-34]. In a typical synthesis of
CeCrO3 catalyst, cerium nitrate (Ce(NO3)3•6H2O, 99.9% pure), chromium nitrate
(Cr(NO3)3•9H2O, 99.9% pure) and glycine (NH2CH2COOH) were used as starting materials. In
first step of synthesis, aqueous solutions of these reactants were mixed and thermally dehydrated
to form a gel. This upon auto-ignition produced a voluminous powder. The temperature of the
flame during auto-ignition was measured by a two color optical pyrometer (Reytek) (temperature
range 1273 - 3273 K). In second step, the powder was pelletized and then subjected to
calcination at 1223K in presence of Zr sponge in a vacuum- sealed quartz tube.
2.2. Material characterization
The XRD data of synthesized nanocrystalline CeCrO3 was obtained with a Philips X-ray
diffractometer (X’pert PRO) using Cu-Kα radiation. The flame temperatures were measured by a
two color optical pyrometer (Reytek) covering a temperature range from 1273 to 3273 K. The
powder was pelletized and calcined at 1223 K in a vacuum-sealed quartz tube (10–6 mbar) in the
presence of zirconium sponge wrapped in tantalum foil for 12 h. The preparation of samples for
TEM analysis involved sonication in ethanol for 5 minutes and deposition on a carbon coated
copper grid. The accelerating voltage of the electron beam was 200 kV. The extent and nature of
agglomeration were studied by particle size analyzer (Horiba, Model LA-500, Japan) based on
laser scattering technique. Powder sample were initially added to deionized water. The
microstructural features of samples were analyzed using a Scanning Electron Microscope
3

ACCEPTED MANUSCRIPT
(SERON, Model AIS-2100). Energy Dispersive X-ray microanalysis technique (Oxford, Model
INCA E350) was used to identify the elemental constituents on the sample. The suspension thus
obtained was sonicated and used for the laser scattering experiments. The yields of the products
of oxidation reaction were determined by GC analysis using a capillary column (Chemito 1000).
2.3 General procedure for oxidation reaction.
To a clean dry 10 mL round-bottomed flask containing 1 mmol of alcohol, 70% TBHP (3 mmol)
were added. This was followed by the addition of 10 mol% of CeCrO3 catalyst. The mixture was
sonicated for 5 min and then stirred at 90°C. The progress of the reaction was monitored by gas
chromatograph. After an appropriate time, the reaction mass was cooled and the catalyst was
separated by filtration. The yields of the products were based on GC analysis. The products were
identified by GC–MS analysis.
3. Results and discussion
3.1 Characterization of the pure phase nanocrystalline CeCrO3
The indexed powder X-ray diffraction pattern for the orthorhombic cell of the nanocrystalline
CeCrO3 is shown in Fig. 1. There was no detectable impurity phase in the XRD pattern. The
average crystallite size calculated for the different peaks from the Scherrer formula was around
40-45 nm.
Fig.1
TEM investigation further confirmed the crystallite size to be around 40 nm (Fig.2). The
agglomerate size of the CeCrO3 nano-powders measured by DLS was found to be 14.3μm after
ultrasonic treatment for about 10 minutes. Hence, it can be inferred that the agglomerates were
4

ACCEPTED MANUSCRIPT
relatively hard in nature. This hard agglomerate formation (Fig.3) was due to a local partial
sintering of the material during the auto-ignition process.
Fig.2
Fig. 3
SEM and EDX analysis was carried out on the sample to observe microstructural and
composition inhomogeneity. When two different phases with different mass compositions are
present in a sample, a contrast in the SEM image is observed. The absence of contrast in the
SEM images indicated that secondary phases are not present. EDX analysis (Fig.4) revealed that
compositional homogeneity was same at different points of analysis.
Fig.4
3.2 Catalytic activity of the synthesized CeCrO3
To explore the catalytic activity of CeCrO3, the oxidation of benzhydrol using TBHP as a clean
oxidant was chosen as the model reaction (Scheme 1) [35]. Effect of various parameters such as
catalyst loading, reactant/oxidant ratio, and temperature, solvent was studied in detail.
Scheme 1
Table 1
It can be seen from the Table 1 that no significant increase in conversion was observed beyond
three mmol of and hence this ratio of reactant/oxidant was used in further studies. It should also
be noted that no reaction occurred in the absence of TBHP (Table 1, Entry 1) and CeCrO3.
5

ACCEPTED MANUSCRIPT
The effect of solvent and temperature was studied for the oxidation of benzhydrol using TBHP
with 5 mol% CeCrO3 catalyst. Maximum activity was observed at reflux condition (Table 2,
Entry 3). In aromatic solvents like benzene (Table 3, Entry 4) and toluene (Table 3, Entry 5)
conversion was less. In DMSO 100% conversion was obtained in 7 h (Table 3, Entry 2). Hence
90°C and solvent DMSO were chosen for further studies.
With increase in concentration of the catalyst the conversion increased and 10% of the catalyst
was found to be optimum for the reaction (Table 4, Entry 3)
Table 2
Table 3
Table 4
To investigate the scope of CeCrO3/TBHP catalytic system, oxidation of various benzylic
alcohols was carried out under the optimized reaction conditions.
Table 5
Secondary benzylic alcohols like 1-phenylethanol and its derivatives (Table 5, Entry 1-3)
showed 100% conversion and 100% selectivity. Substituted benzhydrol (Table 5, Entry 4) also
showed 100% conversion with 100% selectivity. Primary benzylic alcohols produced the
corresponding carboxylic acid as a minor product under the same optimized reaction conditions.
Benzyl alcohol (Table 5, Entry 7) gave 100% conversion with 80% selectivity while 2-
chlorobenzyl alcohol and 4-bromobenzyl alcohol gave 100% conversion with 95% (Table 5,
Entry 6) and 92% (Table 5, Entry 8) selectivity respectively. It was observed that primary
benzylic alcohol with strong electron withdrawing group such as 2-nitrobenzyl alcohol (Table 5,
6

ACCEPTED MANUSCRIPT
Entry 5) did not form the carboxylic acid and showed 100% selectivity towards the carbonyl
compound. The oxidation of benzhydrol was also carried out with different oxidants such as
molecular oxygen and hydrogen peroxide under the conditions optimized with TBHP. However,
these oxidants were found to be least effective for this conversion under optimized reaction
conditions.
4. Conclusion
Nanocrystalline phase pure CeCrO3 was found to be an efficient catalyst for the oxidation of
benzylic alcohols with TBHP as a clean oxidant under ambient reaction conditions. The catalytic
system showed good substrate compatibility which makes the system an attractive alternative the
oxidation of various alcohols. The catalytic protocol exhibits high conversion and selectivity for
a variety of alcohols.
Acknowledgements
The author (A.S.B.) is thankful to UGC for providing Junior Research Fellowship (Green Tech -
JRF).
References
[1] T.Mallat, A. Baiker, Chem. Rev. 104 (2004) 3037–3058.
[2] G. Cainelli, G. Cardillo, Chromium Oxidants in Organic Chemistry, Springer-Verlag, Berlin,
1984.
[3] R.A. Sheldon, I.W.C.E. Arends, G.J.T. Brink, A. Dijksman, Acc. Chem. Res. 35 (2002) 774–
781.
[4] S. Dash, S. Patel, B.K. Mishra, Tetrahedron 65 (2009) 707–739.
7

ACCEPTED MANUSCRIPT
[5] D.I. Enache, J.K. Edwards, P. Landon, B. Solsona-Espriu, A.F. Carley, A.A. Herzing, M.
Watanabe, C.J. Kiely, D.W. Knight, G.J. Hutchings, Science 311 (2006) 362–365.
[6] J. Zhu, J.L. Figueiredo, J.L. Faria, Catal. Commun. 9 (2008) 2395–2397.
[7] X. Wang, H. Kawanami, S.E. Dapurkar, N.S. Venkataramanan, M. Chatterjee, T.
Yokoyama, Y. Ikushima, Appl. Catal. A: Gen. 349 (2008) 86–90.
[8] M.S. Yusubov, K. W. Chi, J.Y. Park, R. Karimov, V.V. Zhdankin, Tetrahedron Lett. 47
(2006) 6305–6308.
[9] R.A. Sheldon, I. Arends, G.T. Brink, A. Dijksman, Acc. Chem. Res. 35 (2002) 774–781.
[10] K.P. Peterson, R.C. Larock, J. Org. Chem. 63 (1998) 3185–3189.
[11] P.J. Figiel, J.M. Sobczak, Ziolkowski, Chem. Commun. (2004) 244–245.
[12] F. Minisci, O. Porta, F. Recupero, C. Punta, C. Gambarotti, M. Pierini, Synlett. (2004)
2203–2205.
[13] S.E. Martin, A. Garrone, Tetrahedron Lett. 44 (2003) 549–552.
[14] N. Delaval, S. Bouquillon, F. Henin, J. J. Muzart, Chem. Res., (Synop). (1999) 286–287.
[15] K. Krohn, I. Vinke, H. Adam, J. Org. Chem. 61 (1996) 1467–1472.
[16] N. Kakiuchi, Y. Maeda, T. Nishimura, S. Uemura, J. Org. Chem. 66 (2001) 6620–6625.
[17] W. H. Cheung, W.Y.Yu, W.P. Yip, N.Y. Zhu, C.M. Che, J. Org. Chem. 67 (2002) 7716–
7723.
[18] F. Wang, W. Ueda, Appl.Catal. A. 346 (2008) 155–163.
[19] C. Keresszegi, J.D. Grunwaldt, T. Mallat, A. Baiker, Chem. Commun. (2003) 2304–2305.
[20] X. Yang, X. Wang, C. Liang, W. Su, C. Wang, Z. Feng, C. Li, J. Qiu, Catal. Commun. 9
(2008) 2278–2281.
[21] M. G. Buonomenna, A. Figoli, I. Spezzano, E. Drioli, Catal. Commun. 9 (2008) 2209–2212.
8

ACCEPTED MANUSCRIPT
[22] J. Muzart, Tetrahedron Lett. 28 (1987) 2133–2134.
[23] N.B. Barhate, M. Sasidharan, A. Sudalal, Wakharkar, Tetrahedron Lett. 37 (1996) 2067–
2070.
[24] N. Jiang and A.J. Ragauskas, Tetrahedron Lett. 46 (2005) 3323–3326.
[25] A. Satyanarayana Reddy, Chinnakonda S. Gopinath, Satyanarayana Chilukuri, J. Catal. 243
(2006) 278–291.
[26] Andressa H. de Morais Batista a, Francisca S.O. Ramosa, Tiago P. Bragaa, Cleanio L.
Limab,1, Francisco F. de Sousab,1, Eduardo B.D. Barrosb,1, Josue M. Filhob,1, Aldenor S.
de Oliveirac,2, Jackson R. de Sousac,2, Antoninho Valentinia, Alcineia C. Oliveiraa, App.
Catal. A: Gen. 382 (2010) 148–157.
[27] K. Sreekumar , T. Mathew, B. M. Devassy, R. Rajgopal, R. Vetrivel, B.S. Rao, App. Catal.
A: Gen. 205 (2001) 11–18.
[28] A. S. Kulkarni, R. V. Jayaram., App. Catal. A: Gen. 252 (2003) 225–230.
[29] R. Sumathi, K. Johnson, B. Viswanathan, T.K. Varadarajan, Appl. Catal. A: Gen. 172
(1998) 15–22.
[30] M. Ilyas, M. Saeed, Int. J. Chem. React. Eng. 8 (2010) 1–19, A77.
[31] K.S.R.C. Murthy, J. Ghose, J. Catal. 147 (1994) 171–176.
[32] S. J. Singh, R. V. Jayaram., Synth. Commun. 42 ( 2012) 299–308,.
[33] R. Shukla, A. K. Bera, S. M. Yusuf, S. K. Deshpande, A. K. Tyagi, W. Hermes, M. Eul, R.
Pöttgen, J. Phys. Chem. C 113 (2009) 12663.
[34] R. Shukla, J. Manjanna, A. K. Bera, S. M. Yusuf, A. K. Tyagi, Inorg. Chem. 48 (2009)
11691
9

ACCEPTED MANUSCRIPT
[35] H. P. Mungse, S. Verma, N. Kumar, B. Sain and O. P. Khatri J. Mater. Chem., 22 (2012)
5427–5433
List of Caption for Schemes
Scheme 1. Oxidation of benzhydrol using tert-butyl hydroperoxide over CeCrO3 catalyst
List of Caption for Figure
Figure 1. Indexed XRD pattern of nanocrystalline CeCrO3
Figure 2. TEM micrographs of nanocrystalline CeCrO3
Figure 3. Agglomeration behavior of CeCrO3 powder
Figure 4. SEM and EDX data of CeCrO3
List of Caption for Tables
Table 1. Effect of mole ratio of TBHP in the oxidation of benzhydrol with CeCrO3 catalyst
Table 2. Effect of temperature on oxidation of benzhydrol
Table 3. Effect of solvent on the oxidation of benzhydrol with CeCrO3 catalyst
Table 4. Effect of amount of catalyst on oxidation of benzhydrol
Table 5. Oxidation of benzylic alcohols with TBHP and CeCrO3 catalyst
10

ACCEPTED MANUSCRIPT
Table 1
Effect of mole ratio of TBHP in the oxidation of benzhydrol with CeCrO3 catalysta
Entry
TBHP(mmoles)
% conversionb
1
2
3
4
5
--
1
2
3
4
00
32
49
67
70
Reaction conditions:
aBenzhydrol ( 1mmol), 70% TBHP (mmol), Catalyst: nano crystalline CeCrO3 (5 mol%) ;
Solvent ACN, Time (10h), Temperature (70°C)
b % conversion was determined by using GC
11

ACCEPTED MANUSCRIPT
Table 2
Effect of temperature on oxidation of benzhydrola
Entry Temperature(°C)
% Conversionb
1
2
3
70
80
67
80
Reflux
100
Reaction conditions:
aBenzhydrol ( 1mmol), 70% TBHP (3mmol), Catalyst: nano crystalline CeCrO3 (5 mol%) ;
Solvent ACN, Time (10h)
b% conversion was determined by using GC
12

ACCEPTED MANUSCRIPT
Table 3
Effect of solvent on the oxidation of benzhydrol with CeCrO3 catalyst
Entry
Solvent
ACNc
% Conversionb
Time (h)
1
2
3
4
5
6
100
100
100
80
8.5
7
DMSO
DMF
7.5
15
15
8
Benzenec
Toluene
85
c
CCl4
100
Reaction conditions:
aBenzhydrol ( 1mmol), 70% TBHP (3mmol), Catalyst: nano crystalline CeCrO3 (5 mol%)
;Temperature (90°C), Time (10h)
b% conversion was determined by GC analysis
cReflux condition
13

ACCEPTED MANUSCRIPT
Table 4
Effect of amount of catalyst on oxidation of benzhydrola
Entry
CeCrO3 (mol%)
Conversion(%)b
1
2
3
4
--
5
10
15
--
89
100
100
Reaction conditions:
aBenzhydrol ( 1mmol), 70% TBHP (3mmol), Catalyst: nano crystalline CeCrO3;Temperature
(90°C), Time (6h), Solvent (DMSO)
b% conversion was determined by using GC
14

ACCEPTED MANUSCRIPT
Table 5
Oxidation of benzylic alcohols with TBHP and CeCrO3 catalysta
Entry
1
Reactant
Product
Time
(h)
Conversion
(%)b
Selectivity
(%)b
6
100
100
100
100
2
3
5.5
5.5
5
100
100
100
100
4
5
6
7
6.5
6.5
7
100
100
100
100
95
80
8
6
100
92
a Reaction conditions:
Benzhydrol (1mmol), 70% TBHP (3mmol), Temperature 90°C, Catalyst: nano crystalline CeCrO3
(10mol %), Solvent (DMSO)
b% conversion was determined by using GC
15

ACCEPTED MANUSCRIPT
Scheme 1. Oxidation of benzhydrol using tert-butyl hydroperoxide over CeCrO3 catalyst
16

ACCEPTED MANUSCRIPT
Fig. 1 Indexed XRD pattern of nanocrystalline CeCrO3
14000
12000
10000
8000
6000
4000
2000
0
20
40
60
80
2 (degrees)
17

ACCEPTED MANUSCRIPT
Fig. 2 TEM micrographs of nanocrystalline CeCrO3
18

ACCEPTED MANUSCRIPT
Fig. 3 Agglomeration behavior of CeCrO3 powder
19

ACCEPTED MANUSCRIPT
Fig. 4 SEM and EDX data of CeCrO3
Average Ce
(in atom %)
20.15 (0.49)
Average Cr
(in atom %)
19.85 (0.71)
Average O
(in atom %)
60.00 (1.20)
(Numbers in the bracket gives the std. deviation)
20

ACCEPTED MANUSCRIPT
Graphical abstract
21

ACCEPTED MANUSCRIPT
Highlights

Nanocrystalline phase pure CeCrO3 was found to be an efficient catalyst for the oxidation of
benzylic alcohols.


Use of tert-butyl hydroperoxide (TBHP) and mild conditions makes the reaction greener.
The catalytic system showed good substrate compatibility which makes the system an
attractive alternative for the oxidation of various alcohols.

It is noteworthy to mention that to best of our knowledge, it is for the first time that CeCrO3
material has been used for catalytic oxidation system.
22