Surfactant/I2/water: An efficient system for deprotection of oximes and imines to carbonyls under neutral conditions in water

Article abstract of DOI:10.1021/jo0480287

(Chemical Equation Presented) I₂/surfactant/water system deprotecting oximes and imines to the corresponding carbonyl compounds under neutral conditions in water at 25-40°C with very high to excellent yields.

Full text of DOI:10.1021/jo0480287

8
9
Surfactant/I
2
/Water: An Efficient System
acid, pyruvic acid, etc. The oxidizing agents involve
10
11
12
for Deprotection of Oximes and Imines to
Carbonyls under Neutral Conditions in
Water
N
2
O
4
,
ozone, tert-butylhydroperoxide, KMnO
4
/alu-
13
mina, etc. The metallic salts involve thallium(III)
nitrate, chromium compounds such as chromium(II)
acetate,15 chromium(VI) species such as trimethylammo-
14
1
6
nium chlorochromate, chlorotrimethylsilane(chromi-
Pranjal Gogoi, Parasa Hazarika, and Dilip Konwar*
um),17 pyridinium chlorochromate, pyridinium chloro-
18
19
20
Organic Chemistry Division, Regional Research Laboratory,
Jorhat-785006, Assam, India
chromate-H
2 2
O ,
trimethylsilyl chlorochromate, bis(tri-
21
methylsilyl) chromate, supported and unsupported
chromium trioxide,22 and polymer supported CrO
. The
23
3
dkonwar @yahoo.co.uk
2
4
other reagentssbenzeneseleninic anhydride(PhSeO)
NaHSO
search for better reagents still continues.
2
O,
etc.smay be mentioned. And the
25
26
Received November 5, 2004
3
,
2 2 4
Na S O ,
13,27
However,
most of the reported methods though they are efficient,
are not free from drawbacks: for example, use of toxic
1
3
and hazardous transition metal oxidants, i.e., Mn,
17-23
5
14
Cr,
Ti, Th, and their problems associated with
waste disposal, use of strong Lewis and Bronsted acids,
6
7
11,16
low temperature,
involvement of longer reaction
time,18 low yield of products, difficulties in isolating the
products,19 and formation of over-oxidized products.
Therefore, development of a better reagent in water
under neutral condition is desirable.
24
12
I2/surfactant/water system deprotecting oximes and imines
to the corresponding carbonyl compounds under neutral
conditions in water at 25-40 °C with very high to excellent
yields.
In a previous communication, we reported deoxygen-
ation of nitrones to the corresponding imines catalyzed
by HI28 (generated from AlCl
3 2 2 3
‚6H O/NaI/H O/CH CN) in
hydrated media. The same system was used for the
dehydration of oximes to nitriles, the Beckmann rear-
rangements, and the Bischler-Napieralski reactions in
hydrated media. Recently, we reported selective oxidation
of alcohols to carbonyl compounds could be achieved with
In recent years, organic reactions conducted in aqueous
1
media have received much attention from chemists
29
2
because of concerns about the environment. Therefore,
organic reactions performed in aqueous media in the
presence of a homogeneous catalyst would be an ideal
methodology, provided the catalyst, preferably under
neutral conditions, shows high reactivity, versatility, and
solubility in water. Also, most organic reactants including
catalysts are insoluble in water, and the surfactants, due
(
(
8) Depuy, C. H.; Ponder, B. W. J. Am. Chem. Soc. 1959, 81, 4629.
9) Hershberg, E. B. J. Org. Chem. 1948, 13, 542.
(10) Shim, S. B.; Kim, K.; Kim, Y. H. Tetrahedron Lett. 1987, 28,
645.
3
(11) Erickson, R. E.; Andrulis, P. J., Jr.; Collins, J. C.; Lungle, M.
L.; Mercer, G. D. J. Org. Chem. 1969, 34, 2961.
to their hydrophobic and hydrophilic nature, form mi-
celles of the reactants and promote the reaction to occur
in water. On the other hand, protection-deprotection of
functional groups is a common and very essential process
(12) Barhate, N. B.; Gajare, A. S.; Wakharkar, R. D.; Sudalai, A.
Tetrahedron Lett. 1997, 38, 653.
(
13) Imanzadeh, G. H.; Hajipour, A. R.; Mallakpour, S. E. Synth.
Commun. 2003, 33, 735.
4
in multistep organic syntheses. The carbonyl compounds
(14) McKillop, A.; Hunt, J. D.; Naylor, R. D.; Taylor, E. C. J. Am.
Chem. Soc. 1971, 93, 4918.
protected by converting them to the corresponding oximes
and imines are deprotected after completing the essential
transformations to the parent carbonyl compounds by
using a number of efficient reagents in a reaction
(
(
15) Corey, E. J.; Richman, J. E. J. Am. Chem. Soc. 1970, 92, 5276.
16) Rao, C. G.; Radhakrishna, A. S.; Singh, B. B.; Bhatnager, S. P.
Synthesis 1983, 808.
(
17) Aizpurua, J. M.; Palomo, C. Tetrahedron Lett. 1983, 24, 4367.
18) Maloney, J. R.; Lyle, R. E.; Scovedra, J. E.; Lyle, G. G. Synthesis
(
sequence. The acidic reagents used for the deprotection
1
978, 212.
5
are aqueous TiCl
3
and acetic acid, nitrous acid (as well
(19) Drabowicz, J. Synthesis 1980, 125.
(20) Aizpurua, J. M.; Juaristi, M.; Lecea, B.; Palono, C. Tetrahedron
985, 41, 2903.
+
-
6
7
4
as nitrosonium salts such as NO , BF ), HCl, levulinic
1
(
21) Lee, J. G.; Kwak, K. H.; Hwang, J. P. Synth. Commun. 1992,
(1) (a) Grieco, P. A., Ed. Organic synthesis in water; Blackie
22, 2425.
Academic and Professional: London, UK, 1998. (b) Li, C.-J.; Chan, T.-
H. Organic Reactions in Aqueous Media; John Wiley & Sons: New
York, 1997. (c) Lindstrom, U. M. Chem. Rev. 2002, 102, 2751. (d)
Kobayashi, S.; Manabe, K. Acc. Chem. Res. 2002, 35, 209.
(22) (a) Hamal, S.; Mahto, S. K.; Gujurel, G. L. Indian J. Chem.,
Sect. B 1996, 35, 1116. (b) Pravin, M. B.; Bhushan, M. K. Tetrahedron
Lett. 1998, 39, 5867.
(23) Narayanan, N.; Balasubramaniam, T. R. J. Chem. Res., Synop.
1992, 4, 132.
(
2) Manabe, K.; Mori, Y.; Kobayaashi, S. Synlett 1999, 9, 1401.
3) Mori, Y. Micelles Theoretical and Applied; Plenum Press: New
(
(24) Barton, D. H. R.; Lester, D. J.; Ley, S. V. J. Chem. Soc., Chem.
Commun. 1977, 445.
York and London, 1992.
(
4) Greene, T. W. Protective Groups in Organic Synthesis; John Wiley
(25) Pines, S. H.; Chemerda, J. M.; Kozlowski, M. A. J. Org. Chem.
1966, 31, 3446.
&
Sons: New York, 1981.
(5) Timms, G. H.; Wildsmith, E. Tetrahedron Lett. 1971, 195.
6) (a) Doyle, M. P.; Wierenga. W.; Zaleta, M. A. J. Org. Chem. 1972,
(26) Pojer, P. M. Aust. J. Chem. 1979, 32, 201.
(27) (a) Khazaei, A.; Manash, A. A. Synthesis 2004, 1739. (b) Martin,
M.; Martinez, G.; Urpi, F.; Vilarrase, J. Tetrahedron Lett. 2004, 45,
5559 and references therein.
(28) Boruah, M.; Konwar, D. Synlett 2001, 6, 795.
(29) Boruah, M.; Konwar, D. J. Org. Chem. 2002, 67, 7138.
(
3
7, 1597. (b) Doyle, M. P.; Zaleta, M. A.; Deboer, J. E.; Wierenga. W.
J. Org. Chem. 1973, 38, 1663.
7) Corey, E. J.; Hopkins, P. B.; Kim, S.; Yoo, S.; Nambiar, K. P.;
Falck, J. R. J. Am. Chem. Soc. 1979, 101, 7131.
(
10.1021/jo0480287 CCC: $30.25 © 2005 American Chemical Society
1934
J. Org. Chem. 2005, 70, 1934-1936
Published on Web 01/29/2005

SCHEME 1
TABLE 1. Conversion of Oximes/Imines to Carbonyl
Compounds
the DMSO/N
it was shown that I
2
H
4
‚H
2
2
O/I
2
system in hydrated media and
to generate
could be reduced by N H
2 4
HI [in situ], and catalyze the oxidation process in the
presence of DMSO.30 Now, an alternate system for the
cleavage of the CdN bond catalyzed by I
on the hydrophobic and hydrophilic nature of a surfac-
tant, which would form micelles of I and oxime/imines
2
is devised based
2
in water and promote the deprotection process. Although
the application of surfactants as a reagent in organic
synthesis is well investigated,31 to the best of our
knowledge, its use as a promoter of I -catalyzed cleavage
2
of the CdN bond in water under neutral conditions is
not exploited. We now first report here an efficient
2
environmentally friendly catalytic system, surfactant/I /
water, for the deprotection of oximes and imines to
carbonyl compounds in water under neutral conditions
at 25-40 °C (Scheme 1).
Although the reaction of oximes/imines with a catalytic
amount of I
solubility of reactant and I
2
in water did not proceed at all (due to poor
in water), the addition of
2
surfactant (sodium dodecyl sulfate, SDS) to the reaction
mixture led to the formation of carbonyl compounds. For
example, 1 M of oxime/imines, 0.2 M of I , and 0.2 M of
2
sodium dodecyl sulfate (SDS) were mixed in water (10
mL) and the reaction mixture was stirred for a stipulated
time at 25-40 °C; after workup it produced the corre-
sponding carbonyl compounds with very good to excellent
yields [Table 1].
We found that this system did not produce iodoxime/
3
232-33
12
imidoyl iodide
or over oxidized product (acid) in
the reaction mixture. And it produced neither cis nor
trans halogenated products when cinnamaldehyde [entry
1
k] or furfuryl oximes [entry 1l] were used as substrates.
Both cis and trans isomers of oximes/imines were con-
verted smoothly to the corresponding carbonyl com-
pounds under the same reaction condition (in all cases
both cis and trans isomers of oximes/imines were used
as a mixture). The sterically less hindered ketoximes
[entry 1a-e] were successfully cleaved with faster rates
to the corresponding carbonyl compounds than sterically
more hindered ketoximes. We found that the rates as well
as yields of the reactions are dependent on the substit-
uents present on aryl or heteroaryl rings. The electron-
donating groups such as MeO, isobutyl, and Me on the
aromatic ring enhance the rate of the reaction [entry 1d,
1
g, and 1i]. Similarly, the aldoximes were converted to
the corresponding aryl aldehydes with excellent yields
a
Isolated yield. b Stirring at 25-40 °C. The structures of the
c
(
30) Gogoi., P.; Sarma, G. K.; Konwar, D. J. Org. Chem. 2004, 69,
153.
31) Manabe, K.; Limura, S.; Min, X.; Kobayashi, S. J. Am. Chem.
Soc. 2002, 124, 11971.
32) Patai, S., Ed.The Chemistry of Carbon-Nitrogen Double Bond;
John Wiley & Sones: London, UK, 1970; p 597.
1
compounds were determined by using H NMR, FTIR, and
elemental analyses and comparison with authentic samples.
5
33
(
(
[entry 1f-n]. Also, the reagent cleaved the imines to the
corresponding carbonyl compounds without forming any
iodinated side products. The temperature range of the
reaction was determined to be 25-40 °C.
(33) (a) Dictionary of Organic Compounds, 6th ed.; Chapman and
Hall: London, UK, 1996. (b) Donkor, I. O.; Gangjee, A.; Kisliuk, R. L.;
Gaumont, Y. J. Heterocycl. Chem. 1991, 28, 1651.
J. Org. Chem, Vol. 70, No. 5, 2005 1935

SCHEME 2
Experimental Section
General Procedure for Deprotection of Oximes to Car-
bonyl Compounds. In a 50-mL round-bottom flask, iodine (0.2
mmol), oxime (1 mmol), and surfactant (sodium dodecyl sulfate,
0
2
.2 mmol) in H O (15 mL) were added with stirring at room
temperature for 10 min, then the temperature of the reaction
mixture was raised to 40 °C and kept at this temperature for a
stipulated time with stirring. The progress of the reaction was
monitored by TLC. The product was extracted with diethyl ether
(
2 × 25 mL), the organic layer was washed with brine (2 × 15
mL), dried over anhydrous Na SO , concentrated, and purified
by column chromatography on SiO (60-120 mesh) with use of
2
4
2
an ethyl acetate/hexane mixture as eluent; distillation of the
solvent under reduced pressure gave carbonyl compounds.
4-Methoxybenzaldehyde (3g). 4-Methoxybenzaldehyde was
prepared from 4-methoxybenzaldoxime by using the general
Regarding the mechanism of the reaction, it is proposed
that the surfactant promotes micelle formation from
iodine and the oxime/imine in water, in which the
electrophilic iodine activates hydration of the carbon-
nitrogen double bond, possibly via an iodonium ion, that
suffers attack by water to form carbonyl compounds and
iodine in the reaction mixture [Scheme 2].
In conclusion, the salient features of the reaction are
the following: (1) Iodine is an efficient catalyst in the
presence of surfactant for the regeneration of carbonyl
compounds from oximes and imines. (2) The system does
not form iodoxime/imidoyl iodide or over-oxidized prod-
ucts (acids) in the reaction mixture. (3) The cleavage of
the CdN bond can be carried out in water under neutral
condition at 25-40 °C, eliminating toxic and acidic
reagents. (4) The workup procedure is simple and yields
are good to excellent.
procedure described above: 123 mg, (isolated yield; 90.4%) as a
1
liquid; H NMR (CDCl
7
3
, 60 MHz) δ 9.87 (s, 1H), 7.83 (d, 2H),
-
1
.0(d, 2H), 3.87 (s, 3H); FTIR (CHCl
3
) 1684 cm . Anal. Calcd
for C (136.15): C, 70.58; H, 5.92. Found: C, 70.58; H, 5.88.
8 8 2
H O
Acknowledgment. The authors acknowledge the
Director, Dr. P. G. Rao, the analytical division of RRL,
Jorhat, Assam, India, for their help. Also, P.G. thanks
CSIR, New Delhi for a grant of JRF fellowship.
Supporting Information Available: Characterization
1
data including H NMR, FTIR, and elemental analyses of all
the compounds. This material is available free of charge via
the Internet at http://pubs.acs.org.
JO0480287
1936 J. Org. Chem., Vol. 70, No. 5, 2005