Microwave assisted deprotection of heterocyclic semicarbazones by quinolinium flurochromate

Article abstract of DOI:10.14233/ajchem.2017.20786

The regeneration of semicarbazone from 2,6-diphenyl piperidine-4-one semicarbazone (PPS) and its alkyl substituted derivatives (3, 3 and 5^th position) by quinolinium flurochromate (QFC) under microwave irradiation in the presence of montmorillonite K10 clay leads to the formation of ketone in a good yield.

Full text of DOI:10.14233/ajchem.2017.20786

Asian Journal of Chemistry; Vol. 29, No. 10 (2017), 2296-2298
ASIAN JOURNAL OF CHEMISTRY
https://doi.org/10.14233/ajchem.2017.20786
Microwave Assisted Deprotection of Heterocyclic Semicarbazones by Quinolinium Flurochromate
*
T. VIMALA , R. SANTHI and D. ANUSHA
PG and Research Department of Chemistry, Seethalakshmi Ramaswami College, Trichirappalli-620 002, India
*Corresponding author: E-mail: vimalsrc@gmail.com
Received: 17 May 2017; Accepted: 30 June 2017;
Published online: 31 August 2017;
AJC-18537
The regeneration of semicarbazone from 2,6-diphenyl piperidine-4-one semicarbazone (PPS) and its alkyl substituted derivatives (3, 3
th
and 5 position) by quinolinium flurochromate (QFC) under microwave irradiation in the presence of montmorillonite K10 clay leads to
the formation of ketone in a good yield.
Keywords: Piperidine 4-one semicarbazone, Quinolinium flurochromate, Microwave irradiation.
yields. The reagents have also been successfully applied to
the oxidation of selected alcohols and oxime to the corres-
ponding carbonyl compounds in dichloromethane solvent
under reflux condition [7]. The oxidation reactions have been
found to be smooth and gave the products in good yields [8].
Montmorillonite clay known as a Brønsted acid have a
great impact on organic synthesis [9,10]. These solid supports
with lamellar swelling structure and large surface area enhance
selectivity in synthetic organic chemistry. Avoiding organic
solvents during the reaction in organic synthesis lead to a clean,
efficient and economical technology [11-13]. In solid state
reaction, work-up is considerably simplified, cost is reduced and
increased amounts of reactants can be used in the same equipment.
Microwave chemistry is the science of applying micro-
wave radiation to chemical reactions. Microwave acts as high
frequency electric fields and generally heat any material
containing mobile electric charges, such as polar molecules
in a solvent or conducting ions in a solid. Regeneration of
carbonyl groups from semicarbazones can be accomplished
under microwave irradiation. Application of microwave
irradiation in chemical reactions is due to the fact that the
microwave approach contribute to the much provided reaction
conditions, higher chemical yield, lower energy usage and
formation of cleaner products and so deprotection of semicar-
bazones using microwave irradiation is a green process [14-16].
INTRODUCTION
Nitrogen derivatives of aldehydes and ketones such as
oximes and semicarbazones are highly crystalline compounds.
They constitute a very efficient method for the isolation,
purification and characterization of carbonyl compounds [1-3].
In contrast to oximes, little attention has been paid for the
conversion of semicarbazones into their carbonyl compounds
and the number of effective methods for this reaction mixture
remains quite limited. A number of procedures exist including
direct acid hydrolysis and acid catalyzed exchange with
pyruvic acid, levulic acid, etc. However, most of the procedures
used for this type of reaction require the use of solid support
or other axillaries, solvents for the extraction from the solid
supports, high temperature, long reaction time, expensive and
not readily available reagents and tedious work-up procedures.
Consequently, there is a demand for the development of this
process using readily available reagents, which operate under
extremely mild reaction conditions. Microwave irradiation is a
simple, rapid and efficient solvent free method for the depro-
tection of semicarbazones to carbonyl compounds [4].
Quinolinium flurochromate (QFC), in Cr(IV) oxidant
series is one of the efficient and interesting oxidizing agent
[
5]. Quinolinium flurochromate is found to have several advan-
tages over similar oxidizing agents due to its special charac-
teristics such as less acidity, better solubility in non-aqueous
solvents, shorter reaction times and forming products in high
yield. It behaves as two electron oxidant in majority of the
reactions so far studied. Bosh and Narasaiah [6] have reported
the conversion of C=N double bond of oximes, semicarba-
zones, tosyl hydrazones and N,N-dimethyl hydrazones to yield
the corresponding carbonyl compounds in good to excellent
EXPERIMENTAL
Quinoline was distilled at its boiling point. Chromium
trioxide, hydrofluoric acid, semicarbazide hydrochloride, silica
gel, dichloro methane, diethyl ether, petroleum ether,
montmorillonite clay K10 and ethyl acetate were used as such
(Analar grade).

Vol. 29, No. 10 (2017)
Microwave Assisted Deprotection of Heterocyclic Semicarbazones by Quinolinium Flurochromate 2297
Quinolinium flurochromate (QFC), a complex of chromic
acid, quinoline and hydrogen fluoride was prepared as suggested
by Murugesan and Pandurangan [5]. Chromium(VI) oxide (15 g:
Microwave irradiation process: 3-Alkyl-2,6-diphenyl
piperidin-4-one (2 mmol) semicarbazone was mixed with quinol-
inium flurochromate (4 mmol) with 2 g of montmorillonite
clay K10 and irradiated in microwave oven (LG. model No.
MH2043DW) for an appropriate time. The progress of the
reaction was monitored by thin layer chromatography. After
completion of the reaction the product recovered by passing
the reaction mixture through column chromatography of silica.
(200-300 mesh, eluted with mixture of petroleum ether and
ethyl acetate).
0.15 mol) was dissolved in water (25 mL) in a polythene beaker
and 40 % hydrofluoric acid (11.3 mL:0.23 mol) added to it
with stirring at room temperature. To this clear solution, distilled
quinoline (17.7 mL:0.15 mol) was added slowly with stirring.
The mixture was heated on a steam-bath for 0.5 h, then cooled
to room temperature and allowed to stand for 1 h. The bright
red-orange crystalline quinolinium flurochromate was isolated
by filtration and dried in vacuo for 1 h (m.p. 163 °Cand 162-
Separation of product by column chromatography: A
column of 5 × 1 cm was packed with silica gel by making slurry
with dichloromethane. It was dried in an oven and used for
163 °C) [5]. All semicarbazones were prepared from the
respective ketones by the reported procedure [17,18].
TABLE-1
Time of
irradiation (min)
m.p. (°C)
Substrate
Product
Yield (%)
Literature
Observed
N
NHCONH2
O
1
1
2
2
3
0
5
0
5
0
70
104
103
N
H
N
H5C6
C6H5
H5C6
C H
6
5
H
O
N
NHCONH2
CH3
CH3
90
90
90
75
80
86-87
85
N
H
N
H5C6
C6H5
H C
5
C H
6
6
5
H
O
N
NHCONH2
C2H5
C2H5
107
106
114
133
124
N
N
H C
C6H5
H5C6
C6H5
5
6
H
N
H
O
NHCONH2
CH3
CH3
CH3
CH3
114-115
133-134
125-126
N
N
H5C6
C6H5
H5C6
C H
6
5
H
N
H
O
NHCONH2
CH3
CH3
H C
H C
3
3
N
H
N
H5C6
C6H5
H5C6
C6H5
H
O
N
NHCONH2
CH(CH3)2
CH(CH3)2
30
N
H
N
H
H5C6
C H
H5C6
C6H5
6
5

2
298 Vimala et al.
Asian J. Chem.
eluting the products. The product dissolved in dichloromethane
and diethyl ether (9:1). After repeated eluting and washing
the fractions obtained were collected together and evaporated
to get the solid ketone.
ACKNOWLEDGEMENTS
The authors are gratefully acknowledge the financial
support provided by the University Grants Commission, New
Delhi, India to carry out this work.
RESULTS AND DISCUSSION
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