SCHEME 1
accessible and inexpensive among the CDs. â-CD was
used only in a catalytic amount (0.1 mmol of CD per
mmol of the alcohol). These reactions did not take place
in the absence of CD. All of the compounds were
characterized by mass, 1H NMR, and IR and by compari-
son with the known compounds.4,7
In these reactions, iodosobenzoic acid (IBA) obtained
from the reduction of IBX has been recycled by oxidation
to IBX.8 Cyclodextrin has also been recovered and reused.
In conclusion, we have presented an elegant and simple
methodology for the oxidation of a variety of alcohols
using IBX at room temperature with a water/acetone
mixture (86:14) as solvent under supramolecular cataly-
sis.
SCHEME 2
Exp er im en ta l Section
Ma ter ia ls. Alcohols were either purchased commercially or
synthesized as reported in the literature.9
by â-cyclodextrin (â-CD) using a water/acetone mixture
(86:14) as the solvent.
Gen er a l P r oced u r e for Oxid a tion . To a solution of â-cy-
clodextrin (0.1 mmol) in distilled water (15 mL) was added the
alcohol (1 mmol) in acetone (2 mL) followed by IBX (1 mmol) at
room temperature. The reaction mixture was stirred at room
temperature for 12 h, and then the product was extracted with
ethyl acetate (3 × 15 mL). The organic phase was dried over
anhydrous sodium sulfate and concentrated under vacuum. The
crude product thus obtained was purified by column chroma-
tography on silica gel (60-120 mesh) using ethyl acetate/hexane
(1:9) as eluent.
Cyclodextrins (CDs), which are cyclic oligosaccharides,
exert microenvironmental effects leading to selective
reactions. They catalyze reactions by supramolecular
catalysis through noncovalent bonding as seen in en-
zymes.
The reactions were carriedout by dissolving â-Cyclo-
dextrin in water at room temperature followed by the
addition of the alcohol. All the alcohols investigated gave
impressive yields ranging from 85% to 98% (Table 1). No
overoxidation to acids was observed in the case of
aldehyde products (entries 1-8, purities as assessed by
HPTLC >90%). Arylcarbinols gave comparatively better
yields than the aliphatic alcohols. This methodology is
also compatible in the presence of other functionalities
such as methoxy, methylenedioxy, nitro, hydroxy, and
alkene double bonds. This reaction is highly selective for
vicinaldiols in oxidizing only the secondary hydroxy group
R to the benzene ring (entries 13-16, Table 1). â-Cyclo-
dextrin was used as the catalyst because it is easily
After extraction with ethyl acetate, the reaction mixture was
filtered to isolate IBA, and the aqueous phase was lyophilized
to obtain the CD.
Ack n ow led gm en t. We thank Dr. J . S. Yadav for his
interest and CSIR, New Delhi, India, for a fellowship
to M.A.R.
Su p p or tin g In for m a tion Ava ila ble: Experimental data.
This material is available free of charge via the Internet at
http://pubs.acs.org.
J O026751W
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