DDQ as a versatile reagent for oxidative cleavage of tosylhydrazones and oximes

Article abstract of DOI:10.1246/cl.2000.430

2,3-Dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) was found to be a very efficient oxidative reagent for the selective cleavage of tosylhydrazones and oximes of carbonyl compounds for the first time.

Full text of DOI:10.1246/cl.2000.430

430
Chemistry Letters 2000
DDQ as a Versatile Reagent for Oxidative Cleavage of Tosylhydrazones and Oximes
S. Chandrasekhar,* Ch. Raji Reddy, and M. Venkat Reddy
Indian Institute of Chemical Technology, Hyderabad 500007, India
(Received January 11, 2000; CL-000037)
2,3-Dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) was
found to be a very efficient oxidative reagent for the selective
cleavage of tosylhydrazones and oximes of carbonyl com-
pounds for the first time.
The title reagent namely DDQ has played an important role
as a reagent of choice in dehydrogenative aromatisation1 and in
deprotection of MPM ethers.2 This reagent is also found to be
an efficient catalyst in tetrahydropyranylation of alcohols3 and
dethioacetalisation of aldehydes.4 Our own interest in DDQ has
culminated in developing a new methodology for selective
deprotection of allyl ethers of primary alcohols5 and also a new
catalytic cycle of DDQ to DDHQ to DDQ is reported for depro-
tection of -OMPM ethers.6 While working on deprotection of
allyl ether of salicylaldehyde tosylhydrazone, we have observed
a clean cleavage of tosylhydrazone instead of expected allyl
ether cleavage in 95% yield (entry 7, Table 1). A careful litera-
ture survey has revealed that DDQ has previously never been
utilised for this important transformation. Interestingly few oxi-
dation reagents viz. Oxone,7 tert-butyl hydroperoxide,8 clay-
supported ferric nitrite,9 o-iodoxy benzoic acid (IBX),10 PCC-
11
H2O2, trimethylammonium chlorochromate,12 CrO3-
chlorotrimethylsilane13 performed this transformation to some
extent. Few acidic14 and basic reagents15 also are used for the
regeneration of carbonyl compounds from tosylhydrazones.
Almost all the above reagents cleaved oximes as well. Our
experience has revealed that DDQ also has effectively cleaved
tosylhydrazones and oximes to carbonyl compounds (Equation
1) in excellent yields (vide supra).16
The results pertaining to selective cleavage of tosylhydra-
zones and oximes are reported herein (Table 1). The substrates
studied include both aldehyde and keto derivatives. The over
oxidation prone benzaldehyde tosylhydrazone and oxime
allowed for a clean recovery of benzaldehyde without any
traces of benzoic acid formation (entry 1). Similarly cin-
namaldehyde derivative (entry 2) is subjected to cleavage con-
ditions with good success. Other aldehyde hydrazones
include furfural (entry 5), 2-O-allyl salicylaldehyde (entry 7)
and p-benzyloxybenzaldehyde (entry 8). Keto derivatives
namely, acetophenone hydrazone as well as oxime (entry 4),
benzylideneacetophenone-hydrazone (entry 6), p-O-tert-butyl-
dimethylsilylacetophenone (entry 10) were decently behaved
with over 80% yields. More complex 4-(3,4-dichlorophenyl)
tetrahydronaphthalone tosylhydrazone (entry 11) and sugar
hydrazone (entry 12) were also subjected to present cleavage
conditions to recover the parent carbonyl compounds in 80%
and 85% yields respectively. The oximes studied include cam-
Copyright © 2000 The Chemical Society of Japan

Chemistry Letters 2000
431
phor oxime (entry 13) and trimethoxybenzaldehyde oxime
(entry 14). It has been observed during the oxidative deprotec-
tion studies that the sensitive protective groups such as O-allyl
ether (entry 7), benzyl ether (entry 8), -OTHP ether (entry 9),
O-silyl ether (entry 10) and acetonide (entry 12) were stable.
In conclusion, DDQ is demonstrated as a versatile oxida-
tive reagent for selective deprotection of tosylhydrazones and
oximes of carbonyl compounds in high yields.17 The key fea-
ture of the present study is that sensitive over oxidation prone
substrates also being well responding to present protocol.
7
8
9
Y. H. Kim, J. C. Jung, and K. S. Kim, Chem. & Ind.,
1992, 31.
N. B. Barhate, A. S. Gajare, R. D. Wakharkar, and A.
Sudalai, Tetrahedron Lett., 38, 653 (1997).
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10 D. S. Bose, and P. Srinivas, Synlett, 1998, 977.
11 J. Drabowicz, Synthesis, 1980, 125.
12 C. G. Rao, A. S. Radhakrishna, B. B. Singh, and S. P.
Bhatnagar, Synthesis, 1983, 808.
13 J. M. Aizpurua, M. Juaristi, B. Lecea, and C. Palomo,
Tetrahedron, 41, 2903 (1985).
Two of us (CRR and MVR) thank CSIR, New Delhi for
financial assistance and SC for providing research grant (EMR-
0006).
14 a) R. B. Mitra, and B. G. Reddy, Synthesis, 1989, 694. b) J.
S. Yadav, P. K. Sasmal, and P. K. Chand. Synth.
Commun., 29, 3667 (1999) and references cited therein.
15 A. Kamal, M. Arifuddin, and V. N. Rao, Synth. Commun.,
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References and Notes:
1
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16 General Procedure: To a solution of tosylhydrazone or
oxime (3 mmoles) in CH2Cl2-H2O (8:2, 10 mL) was added
DDQ (5 mmoles) and stirred for given time (Table 1) at
room temperature. The reaction mixture was extracted with
CH2Cl2, washed with 10% NaHCO3 solution followed by
water and brine. The organic layer was dried (Na2SO4) and
evaporated in vacuo to afford the crude product which was
purified by column chromatography on silica gel.
2
3
4
5
6
K. Tanemura, T. Horaguchi, and T. Suzuki, Bull. Chem.
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1
17 All the products were characterized by H NMR, HRMS
and IR comparison with authentic samples in case of com-
mercially available carbonyl compounds.
IICT Communication No. 4383.