AN EFFICIENT OXIDANT FOR ORGANIC SUBSTRATES
637
3
,5-DmpzHCC, owing to its controlled acidity, was success-
etry of oxidation of alcohols, evidence for oxygen transfer, and the identity
of the reduced chromium species. Tetrahedron 1987, 43, 5389–5392.
. Corey, E.J.; Schmidt, G. Useful procedures for the oxidation of alcohols
involving pyridinium dichromate in aprotic media. Tetrahedron Lett. 1979,
ful in oxidizing acid-sensitive substrates. Thus, treatment of cit-
ronellol (entry 7) with DmpzHCC yielded citronellal in 94% iso-
lated yield. No isopulegone arising from acid promoted cationic
cyclization and further oxidation as in the case of unbuffered
pyridinium chlorochromate (PCC) was observed. This result
is believed to be a direct consequence of the far less pronounced
acidic character of the new reagent.
Significantly, oxidative deoximation of various oximes gave
corresponding carbonyl compounds with high yields (entries
2–14), thus providing an alternative pathway to the regener-
ation of carbonyl compounds from non-carbonyl substrates.
The selective protection and deprotection of carbonyl groups
frequently represent a key step in synthetic organic chemistry
and many reagents have been introduced over the years[ for
the purpose.
6
7
8
9
5
, 399–402.
. Chaudhuri, M.K.; Chettri, S.K.; Lyndem, S.; Paul, P.C.; Srinivas, P. Quino-
linium fluorochromate (QFC), C9H7NH[CrO3F]: An improved Cr(VI)-
oxidant for organic substrates. Bull. Chem. Soc. Jpn. 1994, 67, 1894–1898.
. Srinivasan, R.; Ramesh, C.V.; Madhulatha, W.; Balasubramanian, K. Oxi-
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[
18]
. Bora, U.; Chaudhuri, M.K.; Dey, D.; Kalita, D.; Kharmawphlang, W.; Man-
dal, G.C. 3,5-Dimethylpyrazolium fluorochromate(VI), C5H8N2H[CrO3F],
1
(
DmpzHFC): A convenient new reagent for oxidation of organic substrates,
Tetrahedron 2001, 57, 2445–2448.
0. Kassaee, M.Z.; Bekhradnia, A.R. Pyridinium sulfonate chlorochromate
VI), C5H5NSO3H [CrO3CI] (PSCC): A New reagent for oxidation of
1
(
19]
organic substrates. Phosphorous, Sulfur Silicon Relat. Elem. 2004, 179,
2025–2028.
1
1
1
1
1. Clarck, J.M.; Cullen, S.R.; Barlow, S.J.; Bastock, T.W. Environmentally
friendly chemistry using supported reagent catalysts: structure–property
relationships for clayzic. J. Chem. Soc. Perkin Trans. 1994, 2, 1117–1130.
2. Varma, R.S.; Dahiya, R.; Saini, R.K. Iodobenzene diacetate on alumina:
rapid oxidation of alcohols to carbonyl compounds in solventless system
using microwaves. Tetrahedron Lett. 1997, 38, 7029–7032.
3. Lou, J.D.; Zhu, L.H.; Pan, L.L.; Li, L.; Li, F.; Gao, C.L. Solvent-free
oxidation of secondary alcohols with chromium trioxide. Synth. React.
Inorg. Met.-Org. Chem. 2006, 36, 585–587.
Finally oxidation of fused ring hydrocarbons such as an-
thracene (entry 18) and phenanthrene (entry 19) gave 9,10-
anthraquinone and phenanthrene-9,10-quinone, respectively,
with good yields in reasonably short reaction times.
The reaction of triphenylphosphine (entry 20) with Dm-
pzHCC gave triphenylphosphine oxide in quantitative yields.
This provides clear-cut example of oxygen transfer reaction in-
volving DmpzHCC and the result may also be useful in defining
other related reactions.
4. Lou, J.D.; Wang, L.Z. An efficient and selective solvent-free oxidation of
alcohols. Chem. Pap. 2003, 57, 136–137.
In order to show the oxidative ability of this 15. Tajbakhsh, M.; Hosseinzadeh, R.; Sadatshahabi, M. Synthesis and appli-
cation of 2,6-dicarboxy pyridinium fluorochromate as a new solid-phase
reagent (DmpzHCC), we compared some of our re-
[
20,21]
[22,23]
oxidant. Synth. Commun. 2005, 35, 1547–1554.
sults with those of PCC,
PFC,
1-butyl-4-aza-1-
¨
1
6. Ozg u¨ n, B.; Yaylaoglu, A.; S¸ endil, K. 4-Benzylpyridinium fluorochromate:
[
24]
azoniabicyclo[2.2.2]octane chlorochromate (BAAOC), Dm-
an efficient and selective oxidant for organic substrates. Monat. Chemie
pzHFC,[ carried out under solvent-free conditions (Table 2).
25]
2
007, 138, 161–163.
¨
It has been found that this reagent has certain advantages 17. S¸ endil, K.; Ozg u¨ n, B. Quinoxalinium fluorochromate (QxFC): a new and
efficient reagent for the oxidation of alcohols in solution, under solvent-free
over similar oxidizing agents in terms of its controlled acid-
ity, chemoselectivity, amounts of oxidant, short reaction times
required, higher product yields, and milder conditions.
In conclusion, we have developed an efficient, solvent-free
method for the oxidation of alcohols, polycyclic aromatic hy-
drocarbons, and oximes that possesses significant advantages
over the existing methods such as simple procedure, easy reac-
tion workup, efficiency, high yields, and lack of solvent. Based
on all the results heretofore obtained it may be stated that Dm-
conditions and microwave irradiation. Phosphorous, Sulfur Silicon Relat.
Elem. 2006, 181, 959–964.
1
8. Nonaka, T.; Kanemoto, S.; Oshima, K.; Nozaki, H. Pyridinium fluorochro-
mate or benzyltrimethylammonium chlorochromate for selective oxidation
of alcohols. Bull. Chem. Soc. Jpn. 1984, 57, 2019–2020.
9. Greene, T.W.; Wuts, P.G.M. Protective Groups in Organic Synthesis, 2nd
edn.; Wiley: New York, 1999.
0. Salehi, P.; Firouzabadi, H.; Farrokhi, A.; Gholizadek, M. Solvent-free ox-
idations of alcohols, oximes, aldehydes and cyclic acetals by pyridinium
chlorochromate. Synthesis 2001, 15, 2273–2276.
1
2
pzHCC is an important addition to the species of oxidizing 21. Firouzabadi, H.; Gholizadeh, M. Solvent free oxidations of epoxides
and polycyclic aromatic hydrocarbons with chromium(VI)-based oxidants.
Zinc chlorochromate nonahydrate [Zn(CICrO3)2.9H2O] vs pyridinium
agents for the oxidation of organic substrates.
chlorochromate [PyCI CrO3H]. Malays. J. Chem. 2008, 10, 39–42.
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