A. R. Hajipour et al. / Tetrahedron 58 +2002) 143±146
145
3. Conclusion
eluent 510:90). Pure carbonyl compounds were obtained in
75±100% yields 5Table 1).
In conclusion, in this study we have introduced a new
reagent for the oxidative cleavage of different types of
protected functional groups under non-aqueous and homo-
geneous conditions. The stability, easy preparation, high
selectivity of the reagent, easy work-up, mild reaction
conditions, and high yields of the products, make this
method a novel and useful one for oxidative deprotection
of trimethylsilyl and tetrahydropyranyl ethers to afford the
corresponding carbonyl compounds in acetonitrile in the
presence of aluminum chloride.
4.1.3. Oxidative deprotection of tetrahydropyranyl
ethers with BTPPC/AlCl3Ða general procedure. In a
round-bottomed ¯ask 525 mL) and a magnetic stirrer, a solu-
tion of tetrahydropyranyl ether 51 mmol) and AlCl3 50.03 g,
0.2mmol) in acetonitrile 510 mL) was prepared. BTPPC
50.44 g, 1 mmol) was added to the solution and stirred at
room temperature for 1±10 h. The reaction progress was
followed by TLC 5eluent: cyclohexane/ethylacetate: 8:2).
The reaction mixture was then cooled to room temperature
and the solid was then separated through a short pad of silica
gel and washed with acetonitrile 515 mL). The ®ltrate was
evaporated and the resulting crude material was puri®ed by
column chromatography on silica gel using a mixture of
ethyl acetate and hexane as eluent 510:90). Pure carbonyl
compounds were obtained in 30±100% yields 5Table 2).
4. Experimental
4.1. General
Trimethylsilyl ethers and tetrahydropyranyl ethers were
prepared according to described procedures.3a,14±16 All
yields refer to isolated products. The products were charac-
4.1.4. Oxidative deprotection of 1-ꢀ4-chlorophenyl)
ethanol trimethylsilyl ether with BTPPC/AlCl3Ða typi-
cal procedure. In a round-bottomed ¯ask 525 mL) equipped
with a re¯ux condenser and a magnetic stirrer, a solution of
1-54-chlorophenyl) ethanol trimethylsilyl ether 50.22 g,
1 mmol) and AlCl3 50.03 g, 0.2mmol) in acetonitrile
510 mL) was prepared. BTPPC 50.44 g, 1 mmol) was
added to the solution and was re¯uxed for 4 h. The reaction
progress was followed by TLC 5eluent: cyclohexane/ethyl-
acetate: 8:2). The reaction mixture was then cooled to room
temperature and the resulting solid was then separated
through a short pad of silica gel and washed with aceto-
nitrile 515 mL). Evaporation of the solvent gave 4-chloro-
acetophenone. The yield was 0.15 g 599%).1H NMR: d 2.6
5s, 3H), 7.4±7.7 5d, 2H, J6 Hz), 7.9±8.25d, 2H J6 Hz)
5Table 1).
1
terized by comparison with authentic samples 5IR and H
NMR spectra, melting and boiling points and TLC). All 1H
NMR spectra were recorded at 90 or 500 MHz in CDCl3 and
CCl4 relative to TMS 50.00 ppm), 13C NMR spectra were
recorded at 125 MHz in DMSO-d6 and IR spectra were
recorded on Shimadzu 435 IR spectrophotometer. All reac-
tions were carried out in acetonitrile under re¯ux conditions
or at room temperature The Tarbiat Modarres University,
Tehran, IR, Iran performed elemental analysis.
4.1.1. Preparation of benzyltriphenylphosphonium
chlorate ꢀ1) BTPPC. A solution of benzyltriphenyl-
phosphonium chloride 519.0 g, 49 mmol) in water
5100 mL) was prepared, then NaClO3 55.22 g, 49 mmol) in
water 5100 mL) was added dropwise to the above solution
and stirred for 1 h at room temperature. The resulting pre-
cipitate was ®ltered and washed with cooled distilled water
550 mL), and dried in a desiccator under vacuum over
calcium chloride to afford a white powder 519.25 g, 90%
yield), which decomposed at 181±1828C to a dark-brown
Acknowledgements
The authors are thankful of the Isfahan University of
Technology 5IUT), IR Iran and Center of Excellency in
Chemistry Research for ®nancial support.
1
material. H NMR: d 7.93±6.87 5m, 20 H), 4.7 5d, 2H,
J25.6 Hz, CH2±P). 13C NMR: d 135.28, 135.25, 134.32,
134.24, 131.07, 131.03, 130.19, 130.09, 128.99, 128.97,
128.69, 128.66, 127.45, 127.43, 118.01, 117.36, 29.68 5d,
J193 Hz, C±P). IR 5KBr): 1298, 1269, 1098, 1060, 700,
658, 590 cm21. Anal. Calcd for C25H22ClO3P: C, 68.73; H,
5.04%. Found: C, 68.90; H, 5.20%.
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