Basic alumina as an efficient catalyst for preparation of semicarbazones in solvent free conditions

Article abstract of DOI:10.1002/jccs.200700189

An efficient and simple procedure for conversion of different classes of aldehydes and ketones into the corresponding semicarbazones with semicarbazide hydrochloride using basic alumina is studied.

Full text of DOI:10.1002/jccs.200700189

Journal of the Chinese Chemical Society, 2007, 54, 1337-1339
1337
Basic Alumina as an Efficient Catalyst for Preparation of Semicarbazones
in Solvent Free Conditions
Ali Reza Kiasat,a* Foad Kazemib and Mehdi Fallah Mehrjardia
aChemistry Department, College of Science, Shahid Chamran University, Ahvaz 61357-4-3169, Iran
bInstitute for Advanced Studies in Basic Sciences (IASBS), Zanjan 45195, Iran
An efficient and simple procedure for conversion of different classes of aldehydes and ketones into
the corresponding semicarbazones with semicarbazide hydrochloride using basic alumina is studied.
Keywords: Carbonyl; Aldehyde; Ketone; Semicarbazones; Basic alumina; Solvent free.
INTRODUCTION
Synthetic chemists continue to explore new methods
aldehydes and ketones with semicarbazide in the presence
of base or acid as catalyst.5-7 In 1999, a report by Hajipour
et al.6 outlined the application of SiO2/NaOH as a catalyst
for protection of carbonyl compounds as semicarbazone.
Very recently we reported protection of carbonyl groups as
semicarbazone using sodium acetate supported on silica
gel under solvent free conditions.7 Herein we report a solid
state method for synthesis of semicarbazone derivatives
from the corresponding aldehydes and ketones.
to carry out chemical transformations.1 One of these new
methods is to run reactions on the surface of solids. As the
surfaces have properties that are not duplicated in the solu-
tion or gas phase, entirely new chemistry may occur. Even
in the absence of new chemistry, a surface reaction may be
more desirable than a solution counterpart, because the re-
action is more convenient to run, or a high yield of product
is attained. For these reasons, synthetic surface organic
chemistry is a rapidly growing field of study.1
RESULTS AND DISCUSSION
Alumina (Al2O3) is a key industrial material with nu-
merous applications in refining and petrochemistry.2 This
metal oxide is widely used industrially as filler, adsorbent,
drying agent, catalyst, catalyst support and reagent. g-Alu-
mina is the transition alumina with a basic property most
commonly utilized to carry out surface organic chemistry.3
In contrast to clays and zeolites, this material does not con-
tain accessible channels or cavities and shows a large sur-
face area and highly porous exteriors available to sub-
strates.
It is shown that for efficient protection of a carbonyl
compound to the corresponding semicarbazone (Scheme
I), application of inorganic solid support is essential.
Among several mineral supports examined, basic alumina
was found to give the best results. The optimum molar ratio
of the substrate to the reagent is found to be 1:1.5.
Different types of aldehydes and ketones were sub-
jected to the protection as semicarbazone in the presence of
basic alumina under solvent free conditions. The process in
its entirety involves a simple mixing of aldehydes or ke-
tones and semicarbazide in the presence of basic alumina.
The mixture was then ground for the time specified in Table
1. As shown in Table 1, the isolated yields of the reactions
are good to excellent (74-90%) and the reaction times are
exceedingly short (4-10 min). It is proved that for rapid and
Protection of carbonyl compounds as semicarbazones
is of great interest to organic chemists as they are readily
prepared and highly stable compounds.4 Semicarbazones
are extensively used for purification and characterization
of carbonyl compounds.5 The most common method for the
preparation of semicarbazone derivatives is the reaction of
Scheme I

1338 J. Chin. Chem. Soc., Vol. 54, No. 5, 2007
Kiasat et al.
Table 1. Protection of carbonyl compounds as semicarbazones using basic alumina under solvent free
conditionsa,b
M.P.
Found
(lit.9)
Time Yield
No
Substrate
Product
(min) (%)
221
CH=NNHCONH2
CH=NNHCONH2
CH=NNHCONH2
CH=NNHCONH2
CHO
1
2
3
4
5
6
5
4
89
85
83
88
(222)
219
H3C
H3CO
Cl
H3C
CHO
(221)
212
H3CO
Cl
CHO
(210)
227
CHO
(230)
OH
CHO
OH
229
5
6
4
8
76
74
CH=NNHCONH2
(231)
NO2
NO2
242
(246)
CH=NNHCONH2
CHO
215
7
8
CH=CHCH=NNHCONH2
5
5
90
77
CH=CHCHO
(215)
200
CH=NNHCONH2
C(CH3)=NNHCONH2
CH2C(CH3)=NNHCONH2
CHO
(202)
O
O
198
9
10
8
74
87
COCH3
(198)
195
10
CH2COCH3
(198)
165
O
NNHCONH2
11
12
6
4
80
85
(166)
NNHCONH2
O
120
(122)
a. Yields refer to isolated products. b Products were characterized by comparison of their physical
data, IR, and NMR spectra with known samples.
clean conversion of carbonyl compounds to semicarba-
zones, addition of a few drops of t-BuOH and water in the
reaction media is essential. It can be emphasized that the re-
action is clean, the work-up is straightforward and, from

Preparation of Semicarbazones
J. Chin. Chem. Soc., Vol. 54, No. 5, 2007 1339
economical and environmental points of view, use of sol-
vent free conditions is favorable.
vent evaporated under reduced pressure to give the product
which was recrystallized from a suitable solvent and af-
forded the TLC and 1H NMR pure products in 74-90% iso-
lated yields.
In conclusion, we have demonstrated an efficient,
mild and novel protection methodology of carbonyl group
using semicarbazide hydrochloride in the presence of basic
alumina under solvent free conditions. We believe that the
present procedure provides an easy, mild, efficient, versa-
tile and general methodology for the protection of different
classes of carbonyl compounds, and we feel that it may be a
suitable addition to methodologies already present in the
literature.
Received January 29, 2007.
ACKNOWLEDGEMENT
Partial support for this work by Chamran University
Research Council is gratefully acknowledged.
EXPERIMENTAL
General
REFERENCES
Chemicals such as carbonyl compounds, semicarba-
zide hydrochloride and basic alumina were purchased from
the Fluka, Merck and Aldrich chemicals companies. All
products are known compounds and are identified by com-
parison of their physical and spectral data with those of au-
thentic samples.8 The purity determination of the products
and reaction monitoring were accomplished by TLC on sil-
ica gel polygram SILG/UV 254 plates.
1. Sharghi, H.; Sarvari, M. H. Tetrahedron 2002, 58, 10323.
2. Digne, M.; Sautet, P.; Raybaud, P.; Euzen, P.; Toulhoat, H. J.
Catal. 2004, 226, 54.
3. (a) Kabalka, G. W.; Pagni, R. M. Tetrahedron 1997, 53,
7999. (b) Parks, G. A. Chem. Rev. 1965, 65, 177.
4. Fieser, L. F.; Fieser, M. Reagents for Organic Synthesis;
John Wiley & Sons: New York, 1967; p 1000.
5. Vogel, A. I. Textbook of Practical Organic Chemistry; 4th
ed.; ELBS and Longman: London, 1978.
6. Hajipour, A. R.; Mohammadpoor-Baltork, I.; Bigdeli, M. J.
Chem. Res. 1999, 570 and references cited therein.
7. Kiasat, A. R.; Kazemi, F.; Mehrjardi, M. F. Asian J. Chem.
2005, 17, 2830.
General procedure for the protection of carbonyl
compounds as semicarbazones
Protection was carried out by mixing the carbonyl
compound (1 mmol), semicarbazide hydrochloride (1.5
mmol), basic alumina (2 g) and a few drops of t-BuOH and
water. The reaction mixture was ground for the time speci-
fied in the Table 1. The progress of the reaction was moni-
tored by TLC using ether-CCl4. On completion of the reac-
tion, the reaction mixture was poured into methanol (20
mL). The solid was filtered off by sinter glass and the sol-
8. Shriner, R. L.; Fuson, R. C. The Systematic Identification of
Organic Compounds; 5th ed.; John Wiley & Sons: New York,
1964.
9. Shriner, R. L.; Fuson, R. C.; Curtin, D. Y. The Systematic
Identification of Organic Compounds; 5th ed.; John Wiley &
Sons: New York, 1980.