P. Wang et al. / Tetrahedron Letters 54 (2013) 533–535
535
nient for oxidizing both primary and secondary alcohols as other
methods reported in the literature. Additional investigations will
focus on the extension of this catalytic system.
Acknowledgments
This work was supported by the National Basic Research Pro-
gram of China (No. 2011CB933503). H. Hu is grateful to China Post-
doctoral Science Foundation funded project (No. 2012M511645)
and NSFC (No. 21202058) for their financial support.
Supplementary data
Scheme 1. Proposed reaction mechanism of alcohol oxidation by chloramine-T
with ZnBr as catalyst.
2
References and notes
1
.
.
Smith, M. B.; March, J. March’s Advanced Organic Chemistry: Reactions,
Mechanisms, and Structure, 5th ed.; Wiley-Interscience: New York, 2001.
(a) Brink, G.-J. T.; Arends, I. W. C. E.; Sheldon, R. A. Science 2000, 287, 1636–1639;
1
-phenylethanols. We also tested some substituted diphenylc-
2
arbinols (Table 4, entries 22 and 23). In the case of 4-methyl-
benzhydrol, its corresponding ketone was obtained in high
yield.
(
b) Mallat, T.; Baiker, A. Chem. Rev. 2004, 104, 3037–3058; (c) Zhan, B.-Z.;
Thompson, A. Tetrahedron 2004, 60, 2917–2935.
3
.
.
(a) Dess, D. B.; Martin, J. C. J. Org. Chem. 1983, 48, 4155–4156; (b) Li, P.; Majireck,
M. M.; Korboukh, I.; Weinreb, S. M. Tetrahedron Lett. 2008, 49, 3162–3164.
(a) Omura, K.; Swern, D. Tetrahedron 1978, 34, 1651–1660; (b) McConnell, J. R.;
Hitt, J. E.; Daugs, E. D.; Rey, T. A. Org. Process Res. Dev. 2008, 12, 940–945.
On the basis of the above results and mechanism reported in the
4
9
literature, a plausible reaction mechanism is shown in Scheme 1.
Initially, coordination of alcohols to zinc bromide results in facili-
tating the cleavage of the hydroxyl bond. Then chloramine-T
successively reacts with alcohols to afford the intermediate 3.
Finally, the decomposition of the intermediate 3 into carbonyl
compounds proceeds in a concerted manner. Therefore, complexa-
tion of the oxygen atom of the alcohols with zinc should accelerate
the cleavage of the O–H bond and the hydrogen transfer in the
presence of zinc bromide.
In conclusion, an efficient procedure for the conversion of alco-
2
hols into the corresponding carbonyl compounds using ZnBr /chlo-
ramine-T system has been developed. Primary and secondary
alcohols are rapidly oxidized without overoxidation to carboxylic
acids. This novel method makes use of very easily available and
cheaper reagents under mild conditions. It seems to be as conve-
5. Wu, X.-F. Tetrahedron Lett. 2012, 53, 3397–3399.
6
7
.
.
Campbell, M. M.; Johnson, G. Chem. Rev. 1978, 78, 65–79.
(a) Kitagawa, H.; Mukaiyama, T. Chem. Pharm. Bull. 2002, 50, 1276–1279; (b)
Cao, H. T.; Grée, R. Tetrahedron Lett. 2009, 50, 1493–1494; (c) Li, S.-J.; Wang, Y.-G.
Tetrahedron Lett. 2005, 46, 8013–8015.
8.
General procedure for oxidation of alcohols: A CH
3
CN solution of diphenylcarbinol
1
(1 mmol), ZnBr (45 mg, 0.2 mmol), and chloramine-T (282 mg, 1 mmol) was
2
placed in a three necked flask with a reflux condenser. After the mixture was
stirred under reflux for 1.5 h, it was quenched by adding water and the resulting
mixture was extracted with AcOEt. Removal of the solvent under reduced
pressure gave the crude product, which was purified by column
chromatography on silica gel (n-hexane/AcOEt = 8/1) to give benzophenone 2
(173 mg, 95% yield). 1H NMR (300 MHz, CDCl ) d (ppm) 7.46–7.51 (m, 4H), 7.57–
3
7
1
2
.62 (m, 2H), 7.80–7.82 (m, 4H). 13C NMR (75 MHz, CDCl
32.3, 137.4, 196.5. ESI-MS: calcd [M+Na] for C13
05.0628. All other carbonyl derivatives have spectral data in agreement with
3
) d (ppm) 128.1, 129.9,
H10ONa: 205.0624, found:
+
authentic samples and/or with literature data.
9.
Hassan, Y. I.; Saeed, N. H. M. E-J. Chem. 2012, 9, 642–649.