F. Rajabi / Tetrahedron Letters 50 (2009) 395–397
397
Table 3
Reusability of catalyst 1 in the acetylation of benzyl alcohol with Ac
Supplementary data
2
O
Run no.
Yield (%)
Time (min)
1
99
45
2
99
45
3
99
45
4
99
45
5
98
60
6
98
60
7
95
60
8
95
60
9
90
90
10
86
120
Supplementary data (copies of thermogravimetric analysis, sur-
face analysis (nitrogen adsorption/desorption experiments), and
diffuse reflectance fourier transform infrared spectroscopy of cata-
Preparation of cobalt(II) catalyst 1: The preparation of the cata-
lyst is straightforward and is analogous to the procedure described
in Ref. 46 with slight modification. Salicylaldehyde (2 mmol,
References and notes
1.
Green, T. W.; Wuts, P. C. M. Protective Groups in Organic Synthesis, 3rd ed.;
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0
.244 g) was added to excess absolute MeOH, to which 3-amino-
2.
Kocienski, P. J. Protecting Groups; Thieme: Stuttgart, 1994.
propyl (trimethoxy)silane (2 mmol, 0.352 g) was then added. The
solution instantly became yellow due to imine formation. After
3. Steglich, W.; Hofle, G. Angew. Chem., Int. Ed. Engl. 1969, 8, 981.
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5.
6.
7.
Scriven, E. F. V. Chem. Soc. Rev. 1983, 12, 129.
3
2 2
h, cobalt(II) acetate, Co(OAc) Á2H O (1 mmol, 0.248 g), was added
Tomohumi, S.; Kousaburo, O.; Takashi, O. Synthesis 1991, 1141.
Orita, A.; Tanahashi, C.; Kakuda, A.; Otera, J. Angew. Chem., Int. Ed. 2000, 39,
2877.
to the solution, and the mixture was stirred for a further 3 h to al-
low the new ligands to complex the cobalt and a color change from
pink to olive green was observed. Mesoporous silica (average pore
diameter 60 Å, 3 g) was activated by refluxing in concentrated
hydrochloric acid (6 M) and then washed thoroughly with deion-
ized water and dried before undergoing chemical surface modifica-
tion. Hydrated mesoporous silica was then added, and the mixture
was stirred overnight. The solvent was removed using a rotary
evaporator, and the resulting olive green solid dried at 80 °C over-
night. The final product was washed with MeOH and water until
the washings were colorless. Further drying of the solid product
was carried out in an oven at 80 °C for 8 h (Scheme 1). The loading
8.
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1
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1
1
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2
À1
17. Kamal, A.; Khan, M. N. A.; Reddy, K. S.; Srikanth, Y. V. V.; Krishnaji, T.
achieved was about 0.3 mmol g , as determined from the 11.5%
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loss in mass between 200 and 600 °C, as well as atomic absorption
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analysis of the HNO
the surface area as 197 m /g (Kieselgel 60 has a surface area of
3
-digested material. Surface analysis showed
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4
58 m /g) and the catalyst has a single point total pore volume
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3
3
of 0.461 cm /g, compared to 0.69 cm /g for the support. This indi-
cates that supporting the complex brings about a substantial
reduction in surface area, possibly due to pore blockage from the
bulky silane limiting access to some very narrow-entrance pores
in the material. The infrared spectrum of the catalyst showed the
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Eur. J. Org. Chem. 2003, 4611.
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À1
expected bands,47 including a distinctive band at 1561 cm due
2
to C@N stretching, which is lowered in frequency on complexation
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General procedure for the acetylation of alcohols and phenols:
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5 mmol) was added supported cobalt(II) catalyst 1 (0.01 mmol,
.33 g) and the mixture was stirred at 50 °C. After completion
a
solution of substrate (1 mmol) and acetic anhydride
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(
0
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of the reaction (TLC), the reaction mixture was filtered and the
catalyst rinsed with acetic anhydride and dichloromethane and
thus recovered. The organic layer was washed with saturated
NaHCO and water, and dried over anhydrous Na SO . Evapora-
3 2 4
tion of the solvent under reduced pressure gave the almost pure
acetates.
35. Joseph, J. K.; Jain, S. L.; Sain, B. J. Mol. Catal. A: Chem. 2007, 267, 108.
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4
4
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4
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Acknowledgment
44. Rajabi, F.; Clark, J. H.; Karimi, B.; Macquarrie, D. J. Org. Biomol. Chem. 2005, 5,
25.
7
4
4
5. Rajabi, F.; Karimi, B. J. Mol. Catal. A: Chem. 2005, 232, 95.
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The author thanks the Payame Noor University for partial finan-
cial support of this work.