Dichloro(ethoxy)oxovanadium(V)

[1801-77-0]  · C2H5Cl2O2V  · Dichloro(ethoxy)oxovanadium(V)  · (MW 182.91)

(Lewis acid capable of one-electron oxidation; effects oxidative cleavage and oxidative coupling reactions)

Physical Data: bp 32-34 °C/1 mmHg; yellow liquid;1 d204 1.47 g cm-3.

Solubility: sol most organic solvents such as alcohol, dichloromethane, hexane.

Preparative Method: VO(OEt)Cl2 is prepared by addition of ethanol to Vanadyl Trichloride.2

Handling, Storage, and Precautions: moisture sensitive; should be handled under dry inert atmosphere and refrigerated in the dark to prevent decomposition (orange fumes). Avoid breathing the vapor; skin irritant and corrosive. Use in a fume hood.

Introduction.

VO(OR)Cl2 (R = Et, i-Pr, etc.) are Lewis acids with one-electron oxidation capability, which effect oxidative transformations of carbonyl and organosilicon compounds in organic solvents. These oxovanadium(V) compounds have widely been used as catalysts in copolymerization.

Oxidation of Carbonyl Compounds.

The regioselective oxidative a-cleavage of cyclic ketones is catalyzed by VO(OEt)Cl2 in ethanol under oxygen to give diesters or keto esters (eq 1).2 The presence of a,b-unsaturation alters the reaction course. Oxidation of 2-cyclohexen-1-ones is induced by VO(OEt)Cl2 in ethanol, resulting in dehydrogenative aromatization to ethyl aryl ethers. An oxovanadium compound obtained from VO(OEt)Cl2 and Silver(I) Trifluoromethanesulfonate or Trimethylsilyl Trifluoromethanesulfonate is more efficient in the latter reaction.3 In the case of a,b-unsaturated ketones such as 2-cyclopenten-1-ones and 1-acetyl-1-cyclohexene, allylic oxidation is achieved to introduce an oxo or alkoxy group at the g-position as exemplified by the formation of 4-methyl-4-cyclopentene-1,3-dione (eq 2).4 2-Phenylglycine derivatives undergo the VO(OEt)Cl2-induced oxidative deamination and/or decarboxylation to give ethyl benzoate and ethyl phenylglyoxylate.5

Oxidative cleavage of cyclobutanone in the presence of Copper(II) Chloride or BrCCl3 affords ethyl 4-chloro- or ethyl 4-bromobutanoate (eq 3).6 1-Chlorooctan-4-one is produced upon addition of n-Butyllithium followed by oxidative fragmentation (eq 4). Conjugate addition of the ethoxycarbonylpropyl fragment occurs in the presence of electron-deficient alkenes such as acrylonitrile or methacrylonitrile (eq 5). The oxidative coupling of diketene and styrenes gives ethyl 2-methyl-4,5-dihydrofuran-3-carboxylates.7

Oxidation of Organosilicon Compounds.

Oxidative desilylation can be selectively performed by one-electron oxidation with VO(OEt)Cl2. Silyl enol ethers undergo VO(OEt)Cl2-induced oxidative dimerization and cross-coupling reactions, affording symmetrical and unsymmetrical 1,4-diketones (eq 6).8 Allylsilanes dimerize regioselectively to 1,4-dialkyl-1,5-hexadienes (eq 7).9

Related Reagents.

Copper(I) Trifluoromethanesulfonate; Lead(IV) Acetate; Silver(I) Oxide; Vanadyl Trichloride.


1. Funk, V. H.; Weiss, W.; Zeising, M. Z. Anorg. Allg. Chem. 1958, 296, 36.
2. Hirao, T.; Mori, M.; Ohshiro, Y. BCJ 1989, 62, 2399.
3. Hirao, T.; Mori, M.; Ohshiro, Y. JOC 1990, 55, 358; Hirao, T.; Mori, M.; Ohshiro, Y. CL 1991, 783.
4. Hirao, T.; Mikami, S.; Mori, M.; Ohshiro, Y. TL 1991, 32, 1741.
5. Hirao, T.; Ohshiro, Y. TL 1990, 31, 3917.
6. Hirao, T.; Fujii, T.; Miyata, S.-i.; Ohshiro, Y. JOC 1991, 56, 2264.
7. Hirao, T.; Fujii, T.; Ohshiro, Y. JOM 1991, 407, C1.
8. Fujii, T.; Hirao, T.; Ohshiro, Y. TL 1992, 33, 5823.
9. Fujii, T.; Hirao, T.; Ohshiro, Y. TL 1993, 34, 5601.

Yoshiki Ohshiro & Toshikazu Hirao

Osaka University, Japan



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