(NO3)3CeBrO3: Solvent-free oxidation of alcohols and deprotection and oxidative deprotection of trimethylsilyl ethers

Article abstract of DOI:10.1080/00397910500297362

Trinitratocerium(IV) bromate (TNCB) can be used as an efficient reagent for oxidation of alcohols and deprotection and oxidative deprotection of trimethylsilyl ethers under solvent-free conditions. Copyright Taylor & Francis, Inc.

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(NO3)3CeBrO3: Solvent‐Free
Oxidation of Alcohols and
Deprotection and Oxidative
Deprotection of Trimethylsilyl
Ethers
Farhad Shirini a , Majid Esm‐Hosseini b & Zoha Hejazi
a b
a Department of Chemistry, College of Science,
Guilan University, Rasht, Iran
b Department of Chemistry, College of Science,
Urmia University, Urmia, Iran
Published online: 22 Aug 2006.
To cite this article: Farhad Shirini , Majid Esm‐Hosseini & Zoha Hejazi (2005):
(NO3)3CeBrO3: Solvent‐Free Oxidation of Alcohols and Deprotection and Oxidative
Deprotection of Trimethylsilyl Ethers, Synthetic Communications: An International
Journal for Rapid Communication of Synthetic Organic Chemistry, 35:22, 2913-2919
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Synthetic Communicationsw, 35: 2913–2919, 2005
Copyright # Taylor & Francis, Inc.
ISSN 0039-7911 print/1532-2432 online
DOI: 10.1080/00397910500297362
(NO3)3CeBrO3: Solvent-Free Oxidation
of Alcohols and Deprotection and Oxidative
Deprotection of Trimethylsilyl Ethers
Farhad Shirini
Department of Chemistry, College of Science, Guilan University,
Rasht, Iran
Majid Esm-Hosseini
Department of Chemistry, College of Science,
Urmia University, Urmia, Iran
Zoha Hejazi
Department of Chemistry, College of Science, Guilan University,
Rasht, Iran and Department of Chemistry, College of Science,
Urmia University, Urmia, Iran
Abstract: Trinitratocerium(IV) bromate (TNCB) can be used as an efficient reagent for
oxidation of alcohols and deprotection and oxidative deprotection of trimethylsilyl
ethers under solvent-free conditions.
Keywords: Alcohols, deprotection, oxidation, trinitratocerium (IV) bromate, solvent-
free conditions
Cerium(IV)-based reagents are among the most widely used lanthanide
reagents in organic chemistry. These reagents are used for such purposes as
Received in the UK February 18, 2005
Address correspondence to Farhad Shirini, Department of Chemistry, College of
Science, Guilan University, Rasht, 41335-1914, Iran. E-mail: shirini@guilan.ac.ir;
fshirini@yahoo.com
2913

2914
F. Shirini, M. Esm-Hosseini, and Z. Hejazi
Scheme 1.
oxidation,[1–4] one-electron transfer reactions,[5–7] coupling of substituted
benzenes,[8] and so forth.
Recently we have reported the synthesis and application of
trinitratocerium(IV) bromate in the oxidation of benzyl alcohols and
acyloins in refluxing acetonitrile.[9] Although the yields of the obtained
Table 1. Oxidation of alcohols using TNCB under solvent-free conditions
Entry
Substrate
Product
T(h)
Yield (%)a
1
2
PhCH2OH
PhCHO
0.33
0.5
0.42
0.42
0.42
1
95
95
92
90
95
90
80
92
95
90
95
92
95
90
92
90
85
2-BrC6H4CH2OH
2-ClC6H4CH2OH
4-ClC6H4CH2OH
2-MeC6H4CH2OH
2-NO2C6H4CH2OH
4-NO2C6H4CH2OH
4-Me3CC6H4CH2OH
PhCH(OH)CH3
2-BrC6H4CHO
2-ClC6H4CHO
4-ClC6H4CHO
2-MeC6H4CHO
2-NO2C6H4CHO
4-NO2C6H4CHO
4-Me3CC6H4CHO
PhCOCH3
3
4
5
6
7
3
8
0.42
0.42
0.8
0.8
0.3
0.5
0.5
0.5
0.33
1.5
9
10
11
12
13
14
15
16
17
PhCH(OH)CH2OH
PhCH2CH(OH)CH3
Cyclohexanol
PhCOCHO
PhCH2COCH3
Cyclohexanone
(2)-Menthone
2-Adamantanone
Camphor
(2)-Menthol
2-Adamantanol
Borneol
2-(2-Pyridyl)ethanol
PhCH55CHCH2OH
2-(2-Pyridyl)ethanol
PhCH55CHCHO
aIsolated yields.
Table 2. Comparison of some of the results obtained by the oxidation of alcohols with
TNCB in solution (1)[9] and under solvent-free conditions (2)
(1)
(2)
Yield
Yield Oxidant/
Oxidant/
substrate
Entry
Substrate
T(h)
(%)
substrate
T(h)
(%)
1
2
3
PhCH2OH
PhCH(OH)CH3
Cyclohexanol
2.5
2.5
—
92
82
—
4
6
0.33
0.42
0.3
95
95
92
1
1
1
—

(NO3)3CeBrO3
2915
Scheme 2.
carbonyl compounds using this reagent are relatively high, the method suffers
from disadvantages such as inability of the reagent to oxidize aliphatic
alcohols,[10] long reaction times, and relatively high oxidant-to-substrate ratio.
In view of this and in according to our experience in solvent-free
reactions,[11–13] we decided to overcome these disadvantages by conducting
the previous reactions in the absence of solvent. Herein, we report that
TNCB is able to oxidize the alcohols efficiently under solvent-free conditions
(Scheme 1).
Different types of alcohols, including primary and secondary benzylic and
aliphatic, were efficiently oxidized to their corresponding aldehydes and
Table 3. Solvent-free deprotection of trimethylsilyl ethers with TNCB
Entry
Substrate
Product
T (min) Yield (%)a
1
2
PhCH2OTMS
PhCH2OH
2-BrC6H4CH2OH
4-ClC6H4CH2OH
5
2
95
90
92
80
80
85
95
90
80
92
75
95
92
2-BrC6H4CH2OTMS
4-ClC6H4CH2OTMS
4-Me3CC6H4CH2OTMS
2-NO2C6H4CH2OTMS
4-NO2C6H4CH2OTMS
4-MeOC6H4CH2OTMS
3
5
4
4-Me3CC6H4CH2OH
2-NO2C6H4CH2OH
4-NO2C6H4CH2OH
4-MeOC6H4CH2OH
5
5
1
6
5
7
5
8
4-PhCH2OC6H4CH2OTMS 4-PhCH2OC6H4CH2OH
2-MeC6H4CH2OTMS
Ph2CHOTMS
1
9
2-MeC6H4CH2OH
Ph2CHOH
1
10
11
12
13
5
PhCOCH(OTMS)Ph
PhCH2 CH2CH2OTMS
PhCH2CH(OTMS)CH3
PhCOCH(OH)Ph
PhCH2 CH2CH2OH
PhCH2CH(OH)CH3
10
1
5
14
15
1
1
95
92
16
17
1
1
95
82
Me3COTMS
Me3COH
aIsolated yield.

2916
F. Shirini, M. Esm-Hosseini, and Z. Hejazi
ketones in good to high yields in the absence of solvent at 908C (Table 1).
Overoxidation of the products was not observed using this method.
To show the efficiency of this method we have compared some of the
results with some of those obtained by TNCB in solution (Table 2).[9]
As shown in Table 2, by omitting the solvent, the reaction time and
the oxidant-to-substrate ratio were reduced and the need for solvent is
avoided.
Our investigations also indicated that deprotection and direct oxidative
deprotection of trimethylsilyl ethers to their corresponding alcohols or
carbonyl compounds have been achieved efficiently in the presence of
TNCB under solvent-free conditions (Scheme 2).
The pathway of the reaction is quite dependent upon the temperature,
the reaction times, and the oxidant-to-substrate ratio. Deprotection occurs at
room temperature and in the presence of 0.5 molar equivalents of the
reagent in few minutes (Table 3). The direct oxidative deprotection is
performed using 1 molar equivalent of the reagent at 908C with longer
reaction times (Table 4).
To illustrate the efficiency of the proposed method, Table 5 compares
some of the results obtained by our method with some of those reported in
the literature.[14,15]
Table 4. Oxidative deprotection of trimethylsilyl ethers with TNCB under solvent-
free conditions
Entry
Substrate
Product
PhCHO
T (h)
Yield (%)a
1
2
PhCH2OTMS
0.33
0.7
97
95
92
97
80
95
92
95
96
95
95
92
2-BrC6H4CH2OTMS
4-ClC6H4CH2OTMS
4-Me3CC6H4CH2OTMS
2-NO2C6H4CH2OTMS
4-NO2C6H4CH2OTMS
4-MeOC6H4CH2OTMS
4-PhCH2OC6H4CH2OTMS
2-MeC6H4CH2OTMS
Ph2CHOTMS
2-BrC6H4CHO
4-ClC6H4CHO
4-Me3CC6H4CHO
2-NO2C6H4CHO
4-NO2C6H4CHO
4-MeOC6H4CHO
4-PhCH2OC6H4CHO
2-MeC6H4CHO
Ph2CHO
3
0.33
0.7
4
5
0.5
6
0.83
0.83
0.33
0.33
0.25
0.5
7
8
9
10
11
12
PhCH2 CH2CH2OTMS
PhCH2CH(OTMS)CH3
PhCH2 CH2CHO
PhCH2COCH3
0.7
13
14
0.4
0.7
98
95
aIsolated yield.

Table 5. Comparison of some of the results obtained by the oxidative deprotection of trimethylsilyl ethers with TNCB (1), with some of those
reported by [(NO3)3Ce]2CrO4 (2)[14] and benzyltriphenylphosphonium chlorate (3)[15]
(1)
(2)
(3)
Oxidant/
substrate
Yield
(%)
Oxidant/
substrate
Yield
(%)
Oxidant/
substrate
Yield
(%)
Entry
Substrate
Product
H
H
H
1
2
3
PhCH2OTMS
Ph2CHOTMS
Ph(CH2)2CH2OTMS
PhCHO
Ph2CO
Ph(CH2)2CHO
1
1
1
0.33
0.25
0.5
97
95
95
2
0.5
3
85
85
80
1
1
1
0.25
0.3
100
95
4.5
6
5
10
85

2918
F. Shirini, M. Esm-Hosseini, and Z. Hejazi
In conclusion, in this study we have developed a mild, efficient, and
excellent yielding method for oxidation of alcohols and deprotection and
direct oxidative deprotection of trimethylsilyl ethers. In addition, solvent-
free reaction conditions, high reaction rates, and easy and clean workup are
worthy advantages of the present method.
EXPERIMENTAL
Chemicals were purchased from Fluka, Merck, and Aldrich Chemical
Companies. Trimethylsilyl ethers were prepared according to the described
procedures.[16–18] All products are known compounds; they are identified
by comparison of their physical data and IR and NMR spectra with those of
authentic samples. All yields refer to the isolated products. The purity deter-
mination of the substrates and reaction monitoring were accompanied by TLC
on silica-gel polygram SILG/UV 254 plates.
Oxidation of Alcohols and Trimethylsilyl Ethers to Their
Corresponding Carbonyl Compounds: General Procedure
A mixture of the substrate (1 mmol) and TNCB (1 mmol, 0.454 g) was shaken
in an oil bath (908C) for the specified time (Tables 1 and 4). The progress of
the reaction was monitored by TLC. The reaction mixture was triturated
with CH2Cl2 (5 mL) and filtered, and the solid residue was washed with
CH2Cl2 (3 mL). Evaporation of the solvent followed by column chromato-
graphy on silica gel gave the corresponding carbonyl compounds in good to
high yields.
Deprotection of Trimethylsilyl Ethers to Their Corresponding
Alcohols: General Procedure
A mixture of the substrate (1 mmol) and TNCB (0.5 mmol, 0.227 g) was
shaken at room temperature for the specified time (Table 5). The progress
of the reaction was monitored by TLC. The reaction mixture was triturated
with CH2Cl2 (5 mL) and filtered, and the solid residue was washed with
CH2Cl2 (3 mL). Evaporation of the solvent followed by column chromato-
graphy on silica gel gave the corresponding carbonyl compounds in good to
high yields.
ACKNOWLEDGMENT
We are thankful to the Guilan University Research Council for partial support
of this work.

(NO3)3CeBrO3
2919
REFERENCES
.
1. Shirini, F.; Azadbar, M. R. [(NO3)3 Ce]3 H2IO6: As a veratile and efficient reagent
for cleavage of carbon O nitrogen double bonds under heterogeneous and non-
aqueous conditions. Synth. Commun. 2001, 31, 3775.
2. Al-Haq, N.; Sullivan, A. C.; Wilson, R. H. Oxidation of alcohols using cerium(IV)
alkyl phosphonate modified silica. Tetrahedron Lett. 2003, 44, 769.
3. Laali, K. K.; Herbert, M.; Cushnyr, B.; Bahatt, A.; Terrano, D. Benzylic oxidation
of aromatics with cerium(IV) triflate; synthetic scope and mechanistic insight.
J. Chem. Soc., Perkin Trans. 2001, 1, 578.
4. Imamoto, T.; Koide, Y.; Hiayama, S. Cerium(IV) trifluoromethanesulfonate as a
strong oxidizing agent. Chem. Lett. 1990, 1445.
5. Iranpoor, N.; Mohammadpoor-Baltork, I.; Shirini, F. Cerric ammonium nitrate, as
an efficient catalyst for mild and selective opening of epoxides in the presence of
water, thiols and acetic acid. Tetrahedron 1991, 47, 9861.
6. Iranpoor, N.; Shirini, F. Tris[trinitrato Ce(IV)]paraperiodate, as an efficient hetero-
geneous catalyst for alcoholysis, acetolysis, and hydrolysis of epoxides. Synth.
Commun. 1994, 24, 1959.
7. Iranpoor, N.; Shekarriz, M.; Shirini, F. Highly efficient, regio- and stereoselective
ring opening of epoxides with Ce(OTf)4. Synth. Commun. 1998, 28, 347.
8. Iranpoor, N.; Shekarriz, M. Homocoupling of substituted benzenes to symmetrical
biaryls with mercury(II) in the presence of cerium(IV). J. Chem. Res., Synop. 1999,
442.
9. Shirini, F.; Tajik, H.; Aliakbar, A.; Akbar, A. Oxidation of benzyl alcohols and
acyloins with (NO3)3CeBrO3. Synth. Commun. 2001, 31, 767.
10. Akbar, A. Guilan University: Iran, 2000, M.Sc. Thesis.
11. Shirini, F.; Zolfigol, M. A.; Pourhabib, A. Efficient cleavage of carbon–nitrogen
double bonds under solvent-free conditions. Synth. Commun. 2002, 32, 2837.
12. Shirini, F.; Zolfigol, M. A.; Mallakpour, B.; Mohammadpoor-Baltork, I.;
Mallakpour, S. E.; Hajipour, A. R. Solvent-free oxidation of thiols by
(NH4)2Cr2O7 in the presence of Mg(HSO4)2 and wet SiO2. J. Chem. Res., Synop.
2003, 1, 28.
13. Shirini, F.; Zolfigol, M. A.; Mohammadi, K. Silica sulfuric acid as a mild and
efficient reagent for the acetylation of alcohols in solution and under solvent-
free conditions. Bull. Korean Chem. Soc. 2004, 25, 325.
14. Firouzabadi, H.; Shirini, F. Bis[trinitrato cerium (IV)] chromate; [(NO3)3 Ce]2
.
CrO4 vs trinitrato cerium(IV) chromate dihydrate; [(NO3)3Ce] CrO4 2H2O in
the oxidation of trimethylsilyl ethers. Synth. Commun. 1996, 26, 649.
15. Hajipour, A. R.; Mallakpour, S. E.; Mahammadpoor-Baltork, I.; Malakoutikhah, M.
Benzyltriphenylphosphonium chlorate (BTPPC) as a new and mild reagent for
oxidative deprotection of trimethylsilyl and tetrahydropyranyl ethers of benzylic
alcohols under non-aqueous conditions. Tetrahedron. 2002, 58, 143.
16. Karimi, B.; Golshani, B. Mild and highly efficient method for the silylation of
alcohols using hexamethyldisilazane catalyzed by iodine under nearly neutral
reaction conditions. J. Org. Chem. 2000, 65, 7228.
17. Firouzabadi, H.; Karimi, B. Zinc chloride–catalyzed silylation of alcohols and
phenols by hexamethyldisilazane. A highly chemoselective reaction. Synth.
Commun. 1993, 23, 1633.
18. Shirini, F.; Zolfigol, M. A.; Mohammadi, K. A mild and efficient method for
chemoselective silylation of alcohols using hexamethyldisilazane in the presence
of silica chloride. Phosphorus, Sulfur, Silicon Relat. Elem. 2003, 178, 1567.