Tetrahedron
Letters
Tetrahedron Letters 46 (2005) 1971–1973
Direct synthesis of carbonyl compounds from THP ethers with
IBX in the presence of b-cyclodextrin in water
M. Narender, M. Somi Reddy, V. Pavan Kumar, Y. V. D. Nageswar and K. Rama Rao*
Organic Chemistry Division-I, Indian Institute of Chemical Technology, Hyderabad 500 007, India
Received 9 December 2004; revised 27 January 2005; accepted 1 February 2005
Abstract—Water, an environmentally friendly reaction medium, has been utilized for the oxidative deprotection of tetrahydropy-
ranyl ethers 1 with IBX at room temperature in the presence of b-cyclodextrin to give the corresponding carbonyl compounds 2.
Ó 2005 Elsevier Ltd. All rights reserved.
There are many catalysts reported for the tetrahydro-
pyranylation of alcohols and the cleavage of tetrahydro-
pyranyl ethers to their parent alcohols,1 but the direct
synthesis of carbonyl compounds from tetrahydropyra-
nyl ethers is not widespread in the literature.2 However,
in view of the importance of oxidative deprotection of
THP ethers, a number of reagents have been studied
such as iron(III) nitrate with clay and montmorillonite
K-10,3 AgBrO3 and NaBrO3 in the presence of AlCl3,1
benzyltriphenylphosphonium peroxymonosulfate with
bismuth chloride,4 tetramethylammonium chloro-
chromate,5 PCC (pyridinium chlorochromate),2b
(nBuPPh3)2S2O8 (n-butyltriphenylphosphonium peroxo-
disulfate),6 CPCC (3-carboxypyridinium chlorochro-
mate),2c chromium(VI) oxide,7 etc. The utility of
chromium(VI) reagents in oxidative transformations is
compromised due to their inherent toxicity and the po-
tential danger in handling its complexes. Apart from
this, many of these methods have severe limitations such
as tedious work-up, long reaction times, low yields, high
temperatures and also the use of anhydrous organic sol-
vents, Lewis acid catalysts, expensive reagents, etc.
Thus, the introduction of new methods, inexpensive re-
agents and environmentally friendly reaction conditions
for such functional group transformations is still in
demand.
we explored the oxidative deprotection of THP ethers
using 2-iodoxybenzoic acid (IBX), which is a mild and
environmentally friendly oxidizing agent.
Amongst various oxidizing agents, IBX, a hypervalent
iodine reagent, attracted our attention due to its low
toxicity,9 ease of handling and moisture stability. We re-
port herein the utility of IBX for the direct synthesis of
carbonyl compounds from their corresponding THP
protected alcohols catalyzed by b-cyclodextrin in water
(Scheme 1).10 Cyclodextrins are cyclic oligosaccharides,
which exert microenvironmental effects. They promote
reactions by supramolecular catalysis through non-
covalent bonding as seen in enzymes.
The yields obtained were impressive ranging up to 96%.
No over-oxidation products were detected in the case of
aldehydes. The yields were diminished when a –NO2
group was present on the aromatic ring (Table 1, entry
6) due to a decrease in the nucleophilicity of the alco-
holic oxygen, since the reaction proceeds via nucleo-
philic attack of the alcoholic oxygen on IBX. Longer
reaction times had no impact on the yield. The yields
from THP ethers with an aromatic moiety were compar-
atively better than those from saturated THP ethers
In continuation of our investigations on organic reac-
tions catalyzed by b-cyclodextrin in aqueous medium,8
OTHP
O
β-CD, IBX
1
1
R
R
R
R
H2O, r.t.
1
2
Keywords: THP ethers; IBX; Oxidative deprotection; Carbonyl com-
pounds; b-Cyclodextrin; Water.
R=aryl; R1=H, alkyl, aryl
*
Corresponding author. Tel.: +91 40 2719 3164; fax: +91 40 2716
Scheme 1.
0040-4039/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2005.02.002