S. K. Mohapatra et al. / Tetrahedron Letters 43 (2002) 8527–8529
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a few hours. Cetyltrimethylammonium chloride (CTAC;
25 wt% in water; Aldrich) was then added drop-wise and
the slurry was stirred for another 12 h. The pH was
maintained at 10 with a final (molar) gel composition of:
1
2
3
1
0.96
Al O :P O :0.08
CoO:0.5
(CTA) O:1.25
2
3
2
5
2
1
(TMA) O:70 H O. It was then transferred into a Teflon-
2
2
4
5
. Pasto, D. J. J. Am. Chem. Soc. 1979, 101, 6852.
. (a) Miyata, T.; Hirashima, T. Synthesis 1978, 834; (b)
Upadhya, T. T.; Ramaswamy, V.; Sabade, D. P.; Kat-
dure, D. P.; Sudalai, A. Chem. Commun. 1997, 1119; (c)
Kumbhar, P. S.; Sanchez-Valente, J.; Figueras, F. Tetra-
hedron Lett. 1998, 39, 2573; (d) Jyothi, T. M.; Raja, T.;
Talwar, M. B.; Sreekumar, K.; Rajagopal, R.; Rao, B. S.
Bull. Chem. Soc. Jpn. 2000, 73, 1425; (e) Sonavane, S. U.;
Jayaram, R. V. Synth. Commun. in press.
lined autoclave and heated at 373 K for 3 days for
crystallization. The resultant solid product (90% yield)
was washed repeatedly with distilled water, filtered and
dried at 343 K for 12 h. The sample was then calcined at
823 K for 1 h under flowing N , followed by 2 h in O .
2
2
12. XRD, TEM and ED studies of CoHMA indicate a
mesoporous hexagonal MCM-41 structure. Further, N
2
−1
2
sorption measurements (BET surface area; 931 m g ,
3
−1
pore volume; 0.44 cm g and pore size; 26 A.) support
,
6
7
8
. Mohapatra, S. K.; Selvam, P. Top. Catal. 2003, 22, 17, in
press.
. Kimura, T.; Sugahara, Y.; Kuroda, K. Chem. Mater.
the mesoporous nature of the sample. DRUV-VIS (triplet
absorption band at 540, 580 and 626 nm) and XANES
studies (Co-K pre-edge at 7710 eV) confirm the substitu-
tion and stabilization of Co(II) in the tetrahedral frame-
work. ICP-AES analysis shows 3.8 wt% Co in calcined
CoHMA.
1
999, 11, 508.
. (a) Kresge, C. T.; Leonowicz, M. E.; Roth, W. T.;
Vartuli, J. C.; Beck, J. S. Nature 1992, 359, 710; (b)
Selvam, P.; Bhatia, S. K.; Sonwane, C. G. Ind. Eng.
Chem. Res. 2001, 40, 3237.
13. In a typical reaction, KOH pellets (20 mmol) were dis-
solved in propan-2-ol (20 ml) to which substrate (20
mmol) was added along with 100 mg catalyst. The mix-
ture was then refluxed at 356 K for a few hours depend-
ing upon the nature of the substrate. The products were
analyzed using a gas chromatograph (Eshika) fitted with
OV-101 column.
9
. (a) Kapoor, M. P.; Raj, A. Appl. Catal. A 2000, 203, 311;
(b) Subrahmanyam, C.; Louis, B.; Fabio, R.;
Viswanathan, B.; Renken, A.; Varadarajan, T. K. Catal.
Commun. 2002, 3, 45; (c) Mohapatra, S. K.; Sahoo, B.;
Keune, W.; Selvam, P. Chem. Commun. 2002, 1466.
1
1
0. Thermogravimetric analysis of calcined CoHMA shows a
14. After the first reaction, the catalyst was recovered by
simple filtration, washed three times with acetone, acti-
vated at 773 K for 6 h and then the reaction was repeated
for the subsequent cycles.
2
5% weight loss indicating its acidic nature. This is well
supported by the temperature programmed desorption of
ammonia.
1. Dilute phosphoric acid (85%; Qualigens) and aluminium
isopropoxide (97%; Merck) were mixed under vigorous
stirring followed by the addition of aq. cobalt acetate
15. For a comparison, the reduction of nitrobenzene was also
carried out over CoO/ZrO (3.1 wt% Co). The reaction,
2
however, requires more catalyst (150 mg) and a longer
reaction time (5 h) to attain the maximum yield (86%)
indicating that the rate of hydride transfer is very slow.
In addition, the activity is lost significantly during recy-
cling studies (79% yield after the 6th recycle).
(99%; S.D. fine chemicals). The mixture was kept under
constant stirring at 343 K for 1 h and then tetramethyl
ammonium hydroxide (TMAOH; 25 wt% in water;
Aldrich) was added drop-wise and the mixture stirred for