Regio-selective formation of O-acyl/O-benzoyl hydroxamates by using a polymer supported reagent strategy

Article abstract of DOI:10.1081/SCC-120020206

Rapid, quantitative and regioselective O-acylation/O-benzoylation of hydroxamic acids has been carried using polymer supported hydroxamate anions and acetyl/benzoyl chloride under mild conditions. The isolation of unambiguous and pure products by si-mple

Full text of DOI:10.1081/SCC-120020206

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Regio-Selective Formation of O-Acyl/O-Benzoyl
Hydroxamates by Using a Polymer Supported Reagent
Strategy
A. S. Burungule a , S. P. Bondge a , S. B. Munde a , V. E. Bhingolikar a & R. A. Mane a
a Department of Chemistry , Dr. Babasaheb Ambedkar Marathwada University , Aurangabad,
India
Published online: 17 Aug 2006.
To cite this article: A. S. Burungule , S. P. Bondge , S. B. Munde , V. E. Bhingolikar & R. A. Mane (2003) Regio-Selective
Formation of O-Acyl/O-Benzoyl Hydroxamates by Using a Polymer Supported Reagent Strategy, Synthetic Communications:
An International Journal for Rapid Communication of Synthetic Organic Chemistry, 33:11, 1923-1927, DOI: 10.1081/
SCC-120020206
To link to this article: http://dx.doi.org/10.1081/SCC-120020206
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SYNTHETIC COMMUNICATIONSÕ
Vol. 33, No. 11, pp. 1923–1927, 2003
Regio-Selective Formation of O-Acyl/O-Benzoyl
Hydroxamates by Using a Polymer Supported
Reagent Strategy
A.S.Burungule, S.P.Bondge, S.B.Munde,
*
V.E.Bhingolikar, and R.A.Mane
Department of Chemistry, Dr. Babasaheb Ambedkar
Marathwada University, Aurangabad, India
ABSTRACT
Rapid, quantitative and regioselective O-acylation/O-benzoylation of
hydroxamic acids has been carried using polymer supported hydro-
xamate anions and acetyl/benzoyl chloride under mild conditions.
The isolation of unambiguous and pure products by simple work-up
is also an important feature of this method.
Key Words: O-Hydroxamates synthesis; Polymer supported
protocol.
*Correspondence: R. A. Mane, Department of Chemistry, Dr. Babasaheb
Ambedkar Marathwada University, Aurangabad 431 004 (M.S.), India; Fax:
+91-0240-2400291; E-mail: manera@indiatimes.com.
1923
DOI: 10.1081/SCC-120020206
Copyright & 2003 by Marcel Dekker, Inc.
0039-7911 (Print); 1532-2432 (Online)
www.dekker.com

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1924
Burungule et al.
The use of hydroxamic acids and their derivatives[1,2] as therapeutic
agents and analytical reagents is well established. Hydroxamic acids have
significant synthetic value as key intermediates for functional group
transformation. O-Acyl/O-tosyl hydroxamates are the key reactants
required for Lossen rearrangement.[1,3] The conventional way to obtain
O-acyl/O-tosyl hydroxamates is from the base catalysed acylation or
tosylation of the hydroxamic acids.[4] In this route there is possibility
of getting a mixture of O-acyl and N-acyl hydroxamates and the route
usually gives the O-acyl product with a moderate yield.
In view of the importance of the O-acyl hydroxamates and considering
the need to develop a regio-selective method of O-acylation of hydroxamic
acids, here we report a unique method based on a polymer supported
reagent strategy. Recently polymer bound nucleophiles (anions) have
been employed for a number of organic conversions[5–7] like alkylation,
arylation, sulphonation, oxidation, aldol condensation and thiocyanation.
Little attention has been paid towards the acylation by using polymer
bound nucleophile strategy.
Therefore we have made an attempt to develop a regio-selective
method for O-acylation of hydroxamic acids using a polymer supported
anion strategy. The required polymer supported anions i.e., hydroxamates
were obtained fromaqueous anion exchange of Amberlite 400 (chloride)
anion resin and potassium hydroxamates. The polymer-supported
hydroxamates thus obtained, on condensation with a stoichiometric
amount of acyl/benzoyl chloride in acetonitrile at room temperature,
gave O-acyl/benzoyl hydroxamates. This method has a number of
advantages;
1. Regio-selective and rapid O-acylation,
2. Excellent yields, and
3. Simple work-up to isolate the products.
EXPERIMENTAL
Amberlite IRA-400 (chloride form) was activated before use. The
potassiumsalts of hydroxamic acids were freshly prepared by following
literature procedure.[8] Spectroscopic grade acetonitrile was used.

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Formation of O-Acyl/O-Benzoyl Hydroxamates
1925
General Method for the Preparation of Polymer Supported
Hydroxamate Anions
Amberlite IRA-400 chloride form (5 g) was packed in column and
washed with 0.25 N aqueous potassiumsalt of benzohydroxamic acids
until complete removal of the chloride ions. The resin was then succes-
sively washed with water (100 mL), ethanol (25 mL) and finally with ether
(25 mL). The resin was dried azeotropically with toluene (dried at 50ꢀC in
vacuo for 2 h). The capacity of the benzohydroxamate anion supported
resin was found to be 1.5 mmol/g of dry resin.
General Method for the Synthesis of
O-Acyl/O-Benzoyl Hydroxamates
A mixture of the supported benzohydroxamate (5 mmol) and acetyl
chloride/benzoyl chloride (5 mmol) in acetonitrile (20 mL) was stirred in
a stoppered flask. The progress of the reaction was monitored by TLC.
Scheme 1.

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1926
Burungule et al.
Table 1. Physical characterization data.
ꢀ
Entry
R
R0
Time (min) Yield (%)
M.p. C (Lit)
1
C6H5
-CH3
-CH3
-CH3
-CH3
-CH3
-CH3
-CH3
-C6H5
-C6H5
7
91
90
94
92
91
92
90
89
91
90
92
90
126 (125)[9]
130 (129)[9]
2
4-CH3-C6H4
4-CH3O-C6H4
4-Cl-C6H4
C6H5CH2
10
11
12
10
10
12
10
12
12
10
10
3
136 (137)[10]
125 (123)[9]
4
5
152 (155)[10]
120 (121)[10]
112 (114)[10]
161–162 (164)[11]
160 (162)[11]
162 (162–164)[11]
120 (121–122)[12]
120 (123)[11]
6
3-CH3-C6H4
3-Cl-C6H4
C6H5
7
8
9
4-CH3-C6H4
10
11
12
4-CH3O-C6H4 -C6H5
-C6H5
-C6H5
C6H5CH2
3-CH3-C6H4
It was observed that the reaction was completed within seven minutes.
After completion of the reaction, the resin was removed by filtration and
washed with acetonitrile (2 ꢁ 10 mL). Distillation of solvent under
reduced pressure furnished the corresponding O-acyl/O-benzoyl benzo-
hydroxamate in high yield and in almost pure form. The products were
1
characterized by comparison of their melting points[9–12] and H NMR
spectra with those of authentic samples. The reaction path is depicted in
Sch. 1 and physical constants of the products are presented in Table 1.
ACKNOWLEDGMENT
Authors ASB and SBM, express their thanks to UGC, New Delhi
for the award of Teacher Fellowships. Authors are grateful to
Dr. P. P. Wadgaonkar, N. C. L., Pune and Dr. B. P. Bandgar, S.R.T.M.
University, Nanded for their valuable suggestions.
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1. Ludwig Bauer; Otto Exner. Angew. Chem. 1974, 13 (6), 376.
2. Ghosh, K.K. Indian J. Chem. 1997, 36B, 1089.
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1991, 689.

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Formation of O-Acyl/O-Benzoyl Hydroxamates
1927
4. Okawara, T.; Kanazawa, Y.; Yamaski, T.; Furukawa, M. Synthesis
1987, 2, 183 and references cited therein.
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