Sodium borohydride-solid LiClO4: An effective reagent for reducing aldehydes and ketones in aprotic solvent

Article abstract of DOI:10.1080/00397910500186177

An efficient and simple method for the reduction of aldehydes, ketones and acid chlorides has been accomplished by using NaBH₄-solid LiClO ₄ in mild conditions at ambient temperature with complete chemoselectivity in reduction of α,β-unsaturated aldehydes and ketones. The reaction is fast with high yield and simple workup. Copyright Taylor & Francis, Inc.

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Sodium Borohydride–Solid
LiClO : An Effective Reagent
4
for Reducing Aldehydes and
Ketones in Aprotic Solvent
a
a
Azim Ziyaei Halimjani & Mohammad R. Saidi
a
Department of Chemistry, Sharif University of
Technology, Tehran, Iran
Version of record first published: 18 Aug 2006
To cite this article: Azim Ziyaei Halimjani & Mohammad R. Saidi (2005): Sodium
Borohydride–Solid LiClO : An Effective Reagent for Reducing Aldehydes and Ketones
4
in Aprotic Solvent, Synthetic Communications: An International Journal for Rapid
Communication of Synthetic Organic Chemistry, 35:17, 2271-2276
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Synthetic Communications , 35: 2271–2276, 2005
Copyright # Taylor & Francis, Inc.
ISSN 0039-7911 print/1532-2432 online
DOI: 10.1080/00397910500186177
Sodium Borohydride–Solid LiClO4:
An Effective Reagent for Reducing
Aldehydes and Ketones in Aprotic Solvent
Azim Ziyaei Halimjani and Mohammad R. Saidi
Department of Chemistry, Sharif University of Technology, Tehran, Iran
Abstract: An efficient and simple method for the reduction of aldehydes, ketones and
4 4
acid chlorides has been accomplished by using NaBH –solid LiClO in mild conditions
at ambient temperature with complete chemoselectivity in reduction of a,b-unsaturated
aldehydes and ketones. The reaction is fast with high yield and simple workup.
Keywords: Lithium perchlorate, reduction, sodium borohydride
INTRODUCTION
Sodium borohydride is the most frequently used hydride. This is a good
reagent for reduction because it is mild and inexpensive and has application
for a wide range of reduction processes in comparison with other reagents
such as LiAlH and B H . It is capable of the reduction of aldehydes and
4
2 6
ketones to alcohols and imines or iminium salts to amines in a protic
[1]
solvent. It is quite clear that the reducing capacity of the borohydride is
[2]
markedly affected by the metal ion present in the borohydride complex.
Various methods for enhancement of reactivity and selectivity of NaBH
4
[
3]
[4]
[5]
such as NaBH -ZrCl ,
NaBH -SnCl ,
NaBH -CeCl ,
[8]
NaBH4-
MnCl2, NaBH -Al O , and NaBH –amberlyst in aprotic, protic, and
4
4
4
2
4
3
[6]
[7]
4
2
3
4
[9]
[BMim] PF6 have been reported in the literature for the reduction of
aldehydes and ketones.
Received in the U.K. December 16, 2004
Address correspondence to Mohammad R. Saidi, Department of Chemistry, Sharif
University of Technology, P.O. Box 11365-9516, Tehran, Iran. Fax: þ98-21-601-
2
983; E-mail: saidi@sharif.edu
2
271

2
272
RESULTS AND DISCUSSION
Our research is mainly devoted to the use of lithium perchlorate for different
A. Z. Halimjani and M. R. Saidi
[
10]
organic transformations.
We now report a facile reduction of aldehydes,
ketones, and acid chloride by NaBH /LiClO at room temperature in aceto-
4
4
nitrile as an aprotic solvent (Scheme 1).
Many different aldehydes and ketones are reduced by this method. The
results are shown in Table 1.
Lithium perchlorate is a catalyst or activator for the reduction of aldehydes,
ketones, and acid chlorides because of (1) its Lewis acid character for activation
of carbonyl groups for nucleophilic attack and (2) its capability to change the
NaBH to LiBH , which is more powerful reagent for reduction.
4
4
We also found that NaBH /LiClO is a chemoselective reagent for
4
4
reduction of a,b-unsaturated aldehydes and ketones to prepare allylic
To show the chemoselectivity of this reagent, reduction of some
[11]
alcohols.
a,b-unsaturated aldehydes and ketones are studied (Table 2, entries 6–10).
This reagent is a very powerful tool for selective 1,2-reduction of a,b-
unsaturated aldehydes and ketones for preparation of the corresponding
allylic alcohols in high yields. In addition, direct conversion of acid chlorides
into the corresponding alcohols is a useful reaction and some hydride
[
12]
reagents have been used for this purpose.
Table 2 (entries 1–5) shows a
series of acid chlorides, which are efficiently converted to their corresponding
alcohols in excellent yields. It should be mentioned that without using LiClO4,
the reductions are taking place with much longer reaction times. Also, this
strategy is a powerful tool to attain very simple workup procedures.
When the reduction of an aldehyde or ketone is carried out in the presence
of styrene oxide, the corresponding alcohol from aldehyde or ketone is formed
under these reaction conditions with the starting styrene oxide (Scheme 2).
Therefore, with this method, it would be possible to reduce an aldehye or
ketone in the presence of an epoxide ring.
EXPERIMENTAL
General Procedure for the Reduction of Aldehydes, Ketones, Acid
Chloride, and a,b-Unsaturated Aldehydes and Ketones
In a 50-mL flask, a carbonyl compound (3 mmol) and lithium perchlorate
(3 mmol, 0.32 g) were dissolved in acetonitrile (5 mL). Sodium borohydride
Scheme 1.

Sodium Borohydride–Solid LiClO4
Table 1. Reduction of aldehydes and ketones by NaBH
2273
/LiClO
4 4
a
Reaction time
(min)
Yield
(%)
Entry
Substrate
PhCHO
1
2
15
10
96
98
3
10
92
4
5
20
15
90
95
6
15
93
7
8
9
20
20
15
20
15
95
80
95
90
98
1
1
0
1
1
1
2
3
15
15
92
98
91
1
1
4
5
20
b
(2)-Camphor
5 (h)
69
a
b
Isolated yields.
Exo/Endo 2 : 1.
(
6 mmol, 0.22 g, for aldehyde and ketone; 8 mmol, 0.3 g for acid chloride and
a,b-unsaturated aldehyde and ketone) was added slowly with stirring over a
period of 5 min. The reaction was stirred for corresponding time given in
Tables 1 and 2. Then, water (10 mL) was added. After 5 min, the product

2274
A. Z. Halimjani and M. R. Saidi
Table 2. Reduction of unsaturated carbonyl compounds and acid chlorides by
NaBH /LiClO
4
4
a
Reaction time
(min)
Yield
(%)
Entry
1
Substrate
Product
40
95
2
3
25
25
93
90
PhCOCl
2
PhCH OH
4
40
87
5
6
30
20
93
95
7
15
93
8
9
15
15
15
85
60
85
1
0
a
Isolated yields.
was extracted with dichloromethane (3 ꢀ 10 mL) and dried over Na SO , and
2
4
the solvent was removed by using a rotary evaporator to give the correspond-
ing alcohols.
In conclusion, we have developed a general and efficient method for
reduction of aldehydes and ketones to their corresponding alcohols using
NaBH /LiClO in aprotic solvent. The notable advantages of this procedure
4
4
Scheme 2.

Sodium Borohydride–Solid LiClO4
2275
are (1) general applicability to a wide range of aldehydes, ketones, and
acid chlorides (aliphatics and aromatics); (2) chemoselective reduction of
a,b-unsaturated aldehydes and ketones to their corresponding allylic
alcohols; (3) a simple procedure with easy workup and high yields of the
product; and (4) carboxylic acids, esters, nitro, halide, and C 55 C double
bonds are not disturbed during the course of the reduction.
ACKNOWLEDGMENTS
We are grateful to the research council of Sharif University for financial
support.
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