Transformation of primary benzyl amines to benzyl esters

Article abstract of DOI:10.1080/00397910500290581

Primary benzyl amines, upon treatment with aq. NaNO₂ and appropriate organic acids at 0-5°C, give their respective benzyl esters. Copyright Taylor & Francis, Inc.

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Transformation of Primary
Benzyl Amines to Benzyl Esters
a
a
Ramesh Naik & M. A. Pasha
a
Department of Chemistry, Central College Campus,
Bangalore University, Bangalore, India
Version of record first published: 22 Aug 2006.
To cite this article: Ramesh Naik & M. A. Pasha (2005): Transformation of Primary
Benzyl Amines to Benzyl Esters, Synthetic Communications: An International Journal
for Rapid Communication of Synthetic Organic Chemistry, 35:21, 2823-2826
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Synthetic Communications , 35: 2823–2826, 2005
Copyright # Taylor & Francis, Inc.
ISSN 0039-7911 print/1532-2432 online
DOI: 10.1080/00397910500290581
Transformation of Primary Benzyl
Amines to Benzyl Esters
Ramesh Naik and M. A. Pasha
Department of Chemistry, Central College Campus, Bangalore
University, Bangalore, India
Abstract: Primary benzyl amines, upon treatment with aq. NaNO
organic acids at 0–58C, give their respective benzyl esters.
2
and appropriate
Keywords: Benzyl amines, benzyl esters, carboxylic acids, NaNO2
INTRODUCTION
The transformation of benzyl amines into different functional groups is very
important in synthetic organic chemistry. A number of reactions have been
reported using secondary and tertiary benzyl amines to get a variety of
organic compounds. However, there are only a few transformations of
primary benzyl amines, which involve conversion of primary benzyl amines
into oximes by the methyltrioxorhenium (MTO)-catalyzed oxidation with
[
1]
[2]
H O
2
into imines using Fremy’s salt and into nitriles using tetrabutyl-
[
2
3]
ammonium peroxydisulfate catalyzed by nickel. Katritzky and coworkers
have demonstrated the indirect conversion of primary benzyl amines into
[
4,5]
[6]
benzyl chlorides, benzyl
respective halides, such as benzyl fluorides,
[7,8]
[9]
and benzyl iodides via pyrolysis of respective pyrylium,
bromides,
quinolium, or pyridinium salts.
Received in India May 25, 2005
Address correspondence to M. A. Pasha, Department of Chemistry, Central College
Campus, Bangalore University, Bangalore 560 001, India. E-mail: m_af_pasha@
yahoo.co.in
2
823

2824
R. Naik and M. A. Pasha
Scheme 1. Transformation of benzyl amines into benzyl esters.
In this communication, we report the conversion of primary benzyl
amines into benzyl esters by aqueous NaNO /carboxylic acids as shown in
Scheme 1.
2
Benzyl amine (1), aq. NaNO , and acetic acid initially at 0–58C and then
2
at room temperature gave benzyl acetate (Table 1, entry 1), which was
[
10]
identical to reported product.
Benzyl alcohol was also isolated from the
reaction mixture. To minimize hydrolysis of benzyl acetate, many reaction
conditions were tried. The optimal condition was the use of 2 equiv. of
water, 3 equiv. of acid, and 2 equiv. of NaNO (in minimum water) for
2
1 equiv of amine. Some representative primary benzyl amines with different
acids have been conveniently converted into corresponding benzyl ester
derivatives (Table 1). The use of CH CN for some solid carboxylic acids
3
was necessary for efficient transformation.
EXPERIMENTAL
TLC was performed on precoated aluminum plates with Merck silica gel 60
F-254 as the adsorbent. The developed plates were air dried and irradiated
with UV light. GC analysis was performed on a Shimadzu GC-MS QP
5050A instrument. IR spectra were recorded on Nicolet 400D FT-IR
1
spectrometer. The H NMR spectra were recorded on Bruker 400-MHz
spectrometer as CDCl solutions with TMS as internal standard.
3
General Procedure for the Conversion of Benzyl Amines
to Benzyl Esters
An ice-cold solution of NaNO (1.26 g, 18.6 mmol, in a minimum amount of
2
water) was added in a dropwise manner over a period of 15 min to a mixture of
benzyl amine (1 g, 9.3 mmol) in water (0.24 mL, 18.6 mmol) and acetic acid
(3.39 mL, 27.9 mmol) at 0–58C. After the addition, the reaction mixture
was allowed to attain room temperature, neutralized with sat. NaHCO , and
extracted with ether. The ether layer was washed with brine, dried over
anhyd. Na SO , filtered, and concentrated. The crude mixture was
3
2
4

Table 1. Conversion of benzyl amines into benzyl esters
Acid (2)
Time
(min)
Yield
a
(%) (3)
1
(R )
Entry
Substrate (1)
Product (3)
Benzylacetate
1
2
3
4
5
6
7
8
9
Benzylamine
Benzylamine
Benzylamine
CH
CH CH
Ar
3
20
20
25
25
20
25
30
20
22
25
25
25
22
25
80
82
2
3
Benzylpropionate
b
Benzylbenzoate
85
Benzylamine
Benzylamine
Benzylamine
(CH
CH
PhCH
4-NO Ph
2
)
2
CH
3
Benzylbutyrate
88
b
2
Cl
benzylchloroacetate
benzylphenylacetate
benzyl-4-nitrobenzoate
4-Methoxybenzylacetate
4-Nitrobenzylacetate
2-Nitrobenzylacetate
3-Nitrobenzylacetate
3-Chlorobenzylacetate
2-Hydroxybenzylacetate
2-Phenylethylacetate
85
90
b
3
b,c
Benzylamine
60
2
4-Methoxybenzylamine
4-Nitrobenzylamine
2-Nitrobenzylamine
3-Nitrobenzylamine
3-Chlorobenzylamine
2-Hydroxybenzylamine
2-Phenylethylamine
CH
CH
3
3
75
78
80
84
84
78
1
1
1
1
1
0
1
2
3
4
CH3
CH
CH
3
3
CH3
CH
c
3
65
a
b
c
Isolated yields.
CH CN used as cosolvent.
5% of alcohol recovered.
3
3

2826
R. Naik and M. A. Pasha
chromatographed on silica gel using EtOAc–pet. ether (1 : 9) as eluent to get
benzyl acetate (1.12 g; 80%).
ACKNOWLEDGMENT
Ramesh Naik acknowledges Bangalore University for financial assistance and
the Department of Organic Chemistry, Indian Institute of Science, Bangalore,
for recording the NMR spectra.
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