Improving the Dakin Reaction by Using an Ionic Liquid Solvent

Jorge L. Zambrano; Romano Dorta

doi:10.1055/s-2003-40848

LETTER

Improving the Dakin Reaction by Using an Ionic Liquid Solvent

Jorge L. Zambrano*^a, Romano Dorta^b
^a Departamento de Química, Universidad Simón Bolivar, Valle de Sartenejas, Baruta, Caracas 1080-A, Venezuela
Fax: +58(2)129063961; e-Mail: jzambrano@usb.ve;
^b Centro de Química, Instituto Venezolano de Investigaciones Científicas (I.V.I.C.), Apartado 21827, Caracas 1020-A, Venezuela

Abstract

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Abstract

The oxidation of aromatic aldehydes to phenols (Dakin reaction) has been demonstrated to proceed readily on both activated and non-activated aldehydes in the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate ([BMI][PF₆], 1) with high selectivity, easy product separation and excellent chemical yields.

Key words

oxidations - phenols - aldehydes - ionic liquid - Dakin reaction

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Referenzen

References

1 Dakin HD. Org. Synth., Coll. Vol. 1 Wiley; New York: 1941. p.149

2 Matsumoto M. Kobayashi H. Hotta Y. J. Org. Chem. 1984, 49: 4740

3 Syper L. Synthesis 1989, 167

4 McKillop A. Sanderson WR. Tetrahedron 1995, 51: 6145

5 Roy A. Reddy KR. Mohanta PK. Ila H. Junjappa H. Synth. Commun. 1999, 29: 3781

6 For a recent review, see: Olivier-Bourbigou H. Magna L. J. Mol. Cat. A: Chem. 2002, 182-183: 419

7 Varma RS. Namboodivi VV. Chem. Commun. 2001, 643

8 Howart J. Hanlon K. Fayne D. McCormac P. Tetrahedron Lett. 1997, 38: 3097

9

CAS #: 2b [108-95-2], 3b [106-44-5], 4b [150-76-5], 5b [574-00-5], 6b [533-31-3], 7b [106-48-9].

10

Typical Procedure: To a solution of the aromatic aldehyde (1 mmol) in [BMI][PF₆] (1, 1 mL) was added boric acid
(3-5 mmol) with stirring, followed by sulfuric acid (0.1 mmol) and a solution of hydrogen peroxide (35%, 2 mmol). The resulting reaction mixture was stirred for 1-2 h at room temperature and then toluene (2 mL) was added. The two-phase liquid mixture was stirred and then allowed to stand. The toluene phase (upper phase) was decanted off and the ionic phase was extracted with a second portion of toluene (2 mL). The combined toluene layers were dried (MgSO₄) and then evaporated to give a yellowish solid. This solid was redissolved in CH₂Cl₂, filtered through a pad of silica gel (eluted with hexane/ethyl acetate 10:1), and dried in vacuo to afford a white-yellowish solid in 65-89% yield. The product was analyzed by ¹H NMR or GC-MS.