SnCl2-SiO2: A selective reagent for efficient regeneration of carbonyls from nitrogeneous derivatives

Article abstract of DOI:10.1081/SCC-120014982

Semicarbazones, Phenyl hydrazones, 2,4-DNP and Oxime derivatives are converted into corresponding carbonyl compounds, mostly in quantitative yield by stannous chloridesilica gel. This has general application to various nitrogeneous derivatives.

Full text of DOI:10.1081/SCC-120014982

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SnCl2–SiO2: A SELECTIVE REAGENT FOR EFFICIENT
REGENERATION OF CARBONYLS FROM NITROGENEOUS
DERIVATIVES
Nalin B. Das a , Bhagabat Nanda a & Amalendu Nayak a
a Regional Research Laboratory, Bhubaneswar, 751 013, India
Version of record first published: 16 Aug 2006.
To cite this article: Nalin B. Das , Bhagabat Nanda & Amalendu Nayak (2002): SnCl2–SiO2: A SELECTIVE REAGENT FOR
EFFICIENT REGENERATION OF CARBONYLS FROM NITROGENEOUS DERIVATIVES, Synthetic Communications: An International
Journal for Rapid Communication of Synthetic Organic Chemistry, 32:23, 3647-3651
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SYNTHETIC COMMUNICATIONS
Vol. 32, No. 23, pp. 3647–3651, 2002
SnCl2–SiO2: A SELECTIVE REAGENT FOR
EFFICIENT REGENERATION
OF CARBONYLS FROM
NITROGENEOUS DERIVATIVES
*
Nalin B. Das, BhagabatNanda,
and Amalendu Nayak
Regional Research Laboratory,
Bhubaneswar-751 013, India
ABSTRACT
Semicarbazones, Phenyl hydrazones, 2,4-DNP and Oxime
derivatives are converted into corresponding carbonyl
compounds, mostly in quantitative yield by stannous chloride–
silica gel. This has general application to various nitrogeneous
derivatives.
Nitrogeneous derivatives serve as important synthetic intermediates as
they are extensively used[1(a–d)] for purification, characterization and also
protection of carbonyl-containing molecules. Regeneration of the parent
carbonyl function is an important step in organic synthesis. Most of the
reported[2–15] methods for regeneration of carbonyl functions involve
*Corresponding author. E-mail: nbdas@rrlbhu.res.in
3647
DOI: 10.1081/SCC-120014982
Copyright & 2002 by Marcel Dekker, Inc.
0039-7911 (Print); 1532-2432 (Online)
www.dekker.com

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3648
DAS, NANDA, AND NAYAK
strongly, oxidative or reducing, hydrolysis under acidic or basic media or
stringent conditions or expensive reagents and or some times longer reaction
times. In continuation with our earlier studies on application of metal
reagent,[16(a–c)] we now report that SnCl2ꢀ2H2O–SiO2 is an excellent and
superior reagent system for the regeneration of carbonyl compounds from
their nitrogeneous derivatives in quantitative yields.
We have found that this reagent system has certain advantages
over other systems in terms of inexpensive, simple reagent and limited
reaction time required, chemoselective regeneration of carbonyl compounds.
The semicarbazones, phenyl hydrazones, 2,4-dinitrophenylhydrazones and
oximes of aromatic aldehydes and ketones, aliphatic aldehydes and ketones,
cyclic ketones and steroidal ketone react smoothly in this reaction condition
to give the corresponding aldehydes and ketones. This observation is quite
general.
R ¼ –NHCONH2; –NHC6H5; –2,4-DNP; –OH
Semicarbazones are tried with SnCl2ꢀ2H2O in THF alone under reflux
and the desemicarbazonation occurs in good yield. In contrast, the reaction
of phenylhydrazone, 2,4-dnp and oxime derivatives with SnCl2ꢀ2H2O/THF
does not regenerate the parent carbonyl compounds. The probable mechan-
ism for the reaction of semicarbazones only with stannous chloride, suggests
that the stannous (II) ion forms monocyclic chelating complex with semi-
carbazone through nitrogen and oxygen atoms and hydrolysis favors at the
imino bond of the complex to get carbonyl compounds. The regeneration of
carbonyl compounds of other nitrogeneous derivatives does not occur,
probably the formation of monocyclic chelating complex of stannous (II)
ion does not favor in this condition.
Whereas, the addition of SiO2 to SnCl2ꢀ2H2O/THF favors efficiently
the selective regeneration of corresponding carbonyl compounds of the
semicarbazone, phenylhydrazone, 2,4-dnp and oxime derivatives. However,
we speculate that the nitrogeneous compounds get absorbed on the SiO2
surface and the reactions get facilitated because of SiO2 acts as an activating
agent[18] for the substrates.
In conclusion we have developed an easy and convenient reaction
condition with very good yield in less time using in expensive reagents.
The results obtained are satisfactory and shows the new reagent system as
a valuable addition to the existing findings.

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SnCl2–SiO2: A SELECTIVE REAGENT
3649
Table 1. Regeneration of Carbonyl Compounds from Nitrogeneous Derivatives
with SnCl2Á2H2O–SiO2
Carbonyl
Compounds
Yield (%)b
Entry
Substratea
Semicarbazones of
Time (min)
1
2
3
4
5
6
7
8
Benzaldehyde
p-Chlorobenzaldehyde
Acetophenone
Benzophenone
Cyclohexanone
Dihydrocarvone
2-Octanone
45
60
30
30
30
45
30
45
86c
82d
92c
81d
85c
64c
78c
84c
Hexanal
2,4-Dinitrophenyl hydrazones of
Acetophenone
Benzophenone
Hexanal
Cyclohexanone
9
10
11
12
13
60
60
60
90
90
80c
78d
84c
82c
90d
5a-Cholestan-3-one
Phenylhydrazone of
Benzaldehyde
p-Chlorobenzaldehyde
Benzophenone
Heptanal
14
15
16
17
45
45
30
45
88c
90d
76d
80c
Oxime of
18
19
20
21
Benzophenone
Cyclohexanone
Heptanal
60
75
60
90
78d
80c
70c
86d
5a–Cholestan-3-one
aNitrogeneous derivatives of different carbonyl compounds; Yield refers to parent
carbonyl compounds; cPurification by distillation; dPurification by preparative
column chromatography (E.A. and P.E.) and crystallization from ethanol.
b
EXPERIMENTAL
Nitrogeneousderivativesareprepared[17] fromthecarbonylcompounds.
The products are characterized by m.p., b.p., spectral data and by direct
comparison with the authentic samples.

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3650
DAS, NANDA, AND NAYAK
General Procedure
Tin (II) chloride dihydrate (3 mmol) and silica gel (mesh 60–120)
(200 mg) were added separately to a solution of nitrogeneous derivatives
(1 mmol) in THF (10 mL) and the mixture was heated under reflux on a
water bath. The reaction was monitored by TLC for completion, Table 1.
The reaction mixture was filtered after cooling and filtrate was extracted
with dichloromethane. The extract was washed with water and brine and
dried (anhydrous Na2SO4). Evaporation of solvent under reduced pressure
furnished the crude product which, on purification by distillation and
chromatography, yielded the carbonyl compounds (Entries 1–21) in
64–92% yields.
ACKNOWLEDGMENT
We thank Dr. V.N. Misra, Director and Dr. Y. R. Rao, Head, F & M
Division, Regional Research Laboratory for their valuable suggestions and
for providing the necessary facilities for this work.
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SnCl2–SiO2: A SELECTIVE REAGENT
3651
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Received in the UK July 13, 2001

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