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S. Pääkkönen et al. / Tetrahedron Letters 51 (2010) 6695–6699
Table 3
Oxidation of aromatic secondary alcohols using cyclic microwave heating with variable reaction times and temperatures
Entry
Time (min)
Temperature (°C)
Irradiation power (W)
Alcohol (%)
Reaction products (%)a,b
Brominated side products
Product
O
OH
O
1
Br
135c
10
30
5
rt
—
15
15
70 to 10
70 to 10
—
6
3
5
2
100
94
93
95
97
—
—
4
—
1
33–35
33–35
60
10
60
OH
O
O
O
Br
2
3
4
Br
Trace
—
Trace
Trace
6
135
10
20
40
3
rtc
—
15
15
15
70 to 10
70 to 10
—
—
—
—
—
—
>99
ꢁ100
ꢁ98
ꢁ98
94
Trace
Trace
2
2
—
7
33–35
33–35
33–35
60
5
60
85
8
OH
O
O
O
OH
OH
Br
Br
Br
Br
1
—
—
3
135
5
10
15
3
rtc
—
15
15
15
70 to 10
70 to 10
—
17
—
—
18
—
95
81
97
>92
49
68
2
2
2
3
4
6
8
—
—
—
—
19
16
33–35
33–35
33–35
60
—
—
<1
7
1
—
5
60
8
O
OH
O
Br
Cl
Cl
Cl
—
—
—
—
—
2
135
5
10
15
5
rtc
—
15
15
15
70 to 10
70 to 10
—
17
12
6
3
—
100
83
88
94
97
98
33–35
33–35
33–35
60
10
60
a
Reaction procedure: 2-butanol (1 mmol) and a mixture of NaBr (2 equiv): NaBrO3 (1 equiv) were added to a microwave reactor tube and 10% acid (H2SO4, 3 equiv of H+)
was added.31
The product distribution was analyzed by GC–MS.29
b
c
Room temperature reactions (not microwave); the acid was added over 135 min.18
5. Hayes, B. L. Microwave Synthesis, Chemistry at the Speed of Light; CEM
Publishing: USA, 2002.
We believe that this new heating technique should be amenable
to other reactions which are sensitive to side reactions or increased
reaction temperatures.
6. Bai, L.; Wang, J.-X. Curr. Org. Chem. 2005, 9, 535–553.
7. Larhed, M.; Moberg, C.; Hallberg, A. Acc. Chem. Res. 2002, 35, 717–727.
8. Polshettiwar, V.; Varma, R. S. Acc. Chem. Res. 2008, 41, 629–639.
9. Habermann, J.; Ponzi, S.; Ley, S. V. Mini-Rev. Org. Chem. 2005, 2, 125–
137.
Acknowledgment
10. Deshayes, S.; Liagre, M.; Loupy, A.; Luche, J. L.; Petit, A. Tetrahedron 1999, 55,
10851–10870.
11. Perreux, L.; Loupy, A. Tetrahedron 2001, 57, 9199–9223.
12. Loupy, A.; Petit, A.; Hamelin, J.; Texier-Boullet, F.; Jacquault, P.; Mathé, D.
Synthesis 1998, 1213–1234.
This work was supported financially by the Inorganic Materials
Chemistry Graduate Program and Tauno Tönning Foundation.
Supplementary data
13. Lew, A.; Krutzik, P. O.; Hart, M. E.; Chamberlin, A. R. J. Comb. Chem. 2002, 4, 95–
105.
14. Lidström, P.; Tierney, J.; Wathey, B.; Westman, J. Tetrahedron 2001, 57, 9225–
9283.
15. Li, C. J.; Chen, L. Chem. Soc. Rev. 2006, 35, 68–82.
16. Dallinger, D.; Kappe, C. O. Chem. Rev. 2007, 107, 2563–2591.
17. Wei, W.; Keh, C. C. K.; Li, C.-J.; Varma, R. S. Clean Techn. Environ. Policy 2004, 6,
250–257.
Supplementary data (NMR spectra and ESI-TOF or ES-MS spec-
tral characterization of the ketone products) associated with this
article can be found, in the online version, at doi:10.1016/
18. Pääkkönen, S.; Pursiainen, J.; Lajunen, M. Synth. Commun. 2010, 41,
References and notes
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