S. Bhar, S. K. Chaudhuri / Tetrahedron 59 (2003) 3493–3498
3497
4.1. General experimental procedure for the oxidation of
alcohols
–CH CO–), 2.62 (4H, t, J¼7.7 Hz, –CH Ph–), 1.94–1.90
2
2
(2H, m, –CH –). Anal. Calcd for C H O C 80.55%, H
2
18 20 2
7.53%; Found C 80.69%, H 7.71%.
The alcohol (5 mmol) was added dropwise to the PCC-
Al O [prepared by adding activated neutral alumina (4.0 g)
4.2. Representative oxidation of alcohols using recycled
alumina
2
3
to a solution of PCC (1.62 g, 7.5 mmol) in dry acetone
followed by evaporation of solvent to get an orange-yellow
easy flowing powder] in ice-cold conditions (0–58C) with
stirring and then kept at room temperature till the reaction
was complete (as monitored by TLC). The product was
isolated almost in pure form by filtration chromatography of
the solid reaction mixture on a short plug of neutral alumina
using diethyl ether as eluent followed by evaporation of the
solvent under reduced pressure. It was further purified, if
required, by column chromatography over silica gel or
neutral alumina to yield the corresponding products as
mentioned in Tables 1 and 2. For solid alcohols ethereal
solution was added followed by immediate evaporation of
the solvent and then the process was followed as mentioned
above.
The alumina, recovered after the above-mentioned reactions
was washed with 4N sulfuric acid followed by aq. sodium
carbonate solution till neutral pH, dried and activated by
heating at 1808C at reduced pressure (0.01 mm). A solution
of benzhydrol (184 mg, 1 mmol) in minimum amount of
anhydrous diethyl ether was added to PCC (323 mg,
1.5 mmol) adsorbed on aforesaid recovered and activated
alumina (750 mg) and the solvent was removed instan-
taneously under reduced pressure at low temperature. The
reaction mixture was kept at room temperature with
occasional stirring for 2 hrs till the reaction was complete
(monitored by TLC). The product was isolated and purified
following the aforesaid method to yield benzophenone
(140 mg, 77%).
Most of the products are known compounds as substantiated
by appropriate references and they were easily identified
by their spectral (IR and H NMR) data. The spectral
data for alkyl alkanoates are presented here for ready
references.
4.2.1. Spectral data for 4-phenylbutan-1,4-olide. IR
21 1
1
(neat) 1774 cm ; H NMR (300 MHz, CDCl ) d 7.44–
3
7.18 (5H, m, aromatic-H), 5.47 (1H, dd, J ¼8.0 Hz, J ¼
1
2
1
3
6.3 Hz, –OCH–), 2.68–2.56. (4H, m, –CH –); C NMR
2
(75 MHz, CDCl ) d 177.00 (CvO of lactone), 139.40
(aromatic 48–C), 128.88, 128.56, 125.47 (other aromatic
C-Hs), 81.41 (O–C–H), 31.06, 29.11 (–CH -s of g-lactone
2
3
1
0a
4
column chromatography on silica gel (2% ethyl acetate-
.1.1. Heptyl heptanoate.
Colourless oil, purified by
21 1
hexane) yield 71%; IR 1740 cm ; H NMR (300 MHz,
ring). Anal. Calcd for C H O , C 74.05%, H 6.21%; found
1
0 10 2
CDCl ) d 4.06 (2H, t, J¼6.8 Hz, –OCH -), 2.29 (2H, t, J¼
C 74.29%, H 6.07%.
3
2
7
1
.5 Hz, –CH CO–), 1.63–1.54 (2H, m, –CH –), 1.30–
2 2
.26 (16H, m, –CH –), 0.9 (6H, t, J¼6.45 Hz, –CH )].
2
3
1
0b
4.1.2. Dodecyl dodecanoate. Colourless oil, purified by
column chromatography on silica gel (1% ethyl acetate-
Acknowledgements
21 1
hexane) yield 82%; IR 1740 cm ; H NMR (300 MHz,
CDCl ) d 4.05 (2H, t, J¼6.5 Hz, –OCH –), 2.28 (2H, t,
Financial support from CSIR, New Delhi [Grant No.
01(1673)/00/EMR-II dated 07-12-2000] is gratefully
acknowledged. Thanks to Mr N. Dutta of IACS for
necessary assistance.
3
2
J¼7.4 Hz, –CH CO–), 1.63–1.56 (2H, m, –CH –), 1.26–
2
2
1
.18 (36H, m, –CH –), 0.88 (6H, t, J¼6.8 Hz, –CH ).
2
3
1
0c
4.1.3. 3-Methyl-1-butyl 3-methylbutanoate. Colourless
oil, purified by column chromatography on silica gel (2%
2
1 1
ethyl acetate-hexane) yield 65%; IR 1740 cm ; H NMR
(
References
300 MHz, CDCl ) d 4.10 (2H, t, J¼6.8 Hz, –OCH –),
3
2
2
.18 (2H, d, J¼6.3 Hz, –CH CO–), 1.74–1.65 (1H, m,
1. (a) Hudlicky, M. Oxidations in Organic Chemistry; ACS
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2
(
(
(
CH ) CH–), 1.53–1.47 (1H, m, (CH ) CH–), 1.19–1.12
3
2
3 2
2H, m, CH –), 0.95 (6H, d, J¼6.3 Hz, (CH ) CH–), 0.92
2
3 2
6H, d, J¼6.6 Hz, (CH ) CH–).
3
2
1
984.
1
0d
4.1.4. 2-Methyl-1-propyl 2-methylpropanoate. Colour-
less oil, purified by column chromatography on silica gel
pentane) yield 68%; IR 1730 cm ; H NMR (300 MHz,
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2
1 1
(
CDCl ) d 3.84 (2H, d, J¼6.6 Hz, –OCH –), 2.54 (1H, hept,
3
2
J¼6.0 Hz, .CHCO–), 1.94–1.85 (1H, m, .CH–), 1.52
(
6H, d, J¼6.0 Hz, (CH ) CH–), 0.93 (6H, d, J¼6.6 Hz,
CH ) CH–).
3 2
3
2
(
4
. Cheng, Y. S.; Liu, W.-L.; Chen, S. Synthesis 1980, 223–224.
4.1.5. 3-Phenyl-1-propyl 3-phenylpropanoate. Colourless
oil, purified by column chromatography on silica gel (5%
5. (b) Hall, N. Science 1994, 266, 32–34. (b) Mizuno, N.;
Misono, M. Chem. Rev. 1998, 98, 199–217.
2
1 1
ethyl acetate-hexane) yield 76%; IR 1740 cm ; H NMR
300 MHz, CDCl ) d 7.29–7.17 (10H, m, aromatic-H),
6. (a) Ranu, B. C.; Bhar, S.; Chakrabarty, R.; Das, A. R.; Saha,
M.; Sarkar, A.; Chakraborty, R.; Sarkar, D. C. J. Indian Inst.
Sc.(special issue) 1994, 15–33. (b) Mignel, Y. R.; Brule’, E.;
(
3
4
.08 (2H, t, J¼6.5 Hz, –OCH –), 2.95 (2H, t, J¼7.8 Hz,
2