Bis(trimethylsilyl) Peroxide-Vanadyl Bis(acetylacetonate)1


[-]  · C16H32O7Si2V  · Bis(trimethylsilyl) Peroxide-Vanadyl Bis(acetylacetonate)  · (MW 443.54) (TMSO)2

[5796-98-5]  · C6H18O2Si2  · Bis(trimethylsilyl) Peroxide-Vanadyl Bis(acetylacetonate)  · (MW 178.38) VO(acac)2

[3153-26-2]  · C10H14O5V  · Bis(trimethylsilyl) Peroxide-Vanadyl Bis(acetylacetonate)  · (MW 265.16)

(reagent for the transposition of allylic and allenic alcohols)

Physical Data: Me3SiOOSiMe3: bp 40-41 °C/28 mmHg;2 VO(acac)2: mp 255 °C (dec).

Solubility: sol dichloromethane.

Preparative Method: prepared in situ from bis(trimethylsilyl) peroxide (colorless liquid) and VO(acac)2 (blue-green crystals).

Handling, Storage, and Precautions: bis(trimethylsilyl) peroxide is reported to be a reasonably stable, distillable liquid. Vanadyl acetylacetonate is air-sensitive and should be refrigerated under dry nitrogen or argon. See Bis(trimethylsilyl) Peroxide and Vanadyl Bis(acetylacetonate).

Isomerization of Primary and Secondary Allylic Alcohols.

The title reagent, prepared in situ by the addition of bis(trimethylsilyl) peroxide2,3 to a dichloromethane solution of vanadyl bis(acetylacetonate) (3:1), is effective in catalyzing the allylic transposition of both cyclic and acyclic primary and secondary allylic alcohols to tertiary allylic alcohols in good yields (eqs 1-3). The conversion of primary allylic alcohols to secondary allylic alcohols is less effective (eq 4). The reaction is catalytic in vanadyl bis(acetylacetonate) (10 mol %), and produces only the (E)-alkenes in the secondary alcohols studied. It is noteworthy that this reagent shows no propensity to give epoxides from the allylic alcohols, in contrast to the Sharpless epoxidation reagent, t-Butyl Hydroperoxide/VO(acac)2.4 MoO2(acac)2, with or without added Me3SiOOSiMe3, also catalyzes these allylic isomerizations but with inferior yields (e.g. 76% and 35%, respectively, for the transformation in eq 1).

Allylic isomerization of geraniol (or nerol) gives linalool (eq 5) in 68-70% yield, with only trace formation of a-terpineol. This evidence suggests that the isomerization does not proceed via a free allylic cation. Further support for a primarily suprafacial vanadium-assisted allylic rearrangement is provided in eq 6, where (S)-(-)-3-methyl-2-cyclohexen-1-ol (40% ee) gives (R)-(+)-1-methyl-2-cyclohexen-1-ol (29% ee), with retention of hydroxy facial orientation.

Isomerization of Secondary Allenic Alcohols.2

The VO(acac)2-Me3SiOOSiMe3 catalytic system also effects allylic transposition in a-allenic alcohols. (E)-4-Phenyl-3-buten-2-one is produced in 81% yield from the addition of 10 mol % of the catalyst to a dichloromethane solution of 1-phenyl-2,3-butadien-1-ol (eq 7). However, in substrates where both allylic and allenic rearrangement is possible, the allylic transposition dominates (eq 8). In this particular case, the use of the catalyst MoO2(acac)2 at 5 mol % is more effective in promoting the isomerization to either of the two products, and without the use of the bis(trimethylsilyl) peroxide.2 At 25 °C, MoO2(acac)2 gives 90% yield of the dienone (10 min), whereas at -78 °C, the allylic rearranged trienol product is formed in 94% yield (10 min).

1. Matsubara, S.; Takai, K.; Nozaki, H. TL 1983, 24, 3741.
2. Matsubara, S.; Okazoe, T.; Oshima, K.; Takai, K.; Nozaki, H. BCJ 1985, 58, 844.
3. Cookson, P. G.; Davies, A. G.; Fazal, N. JOM 1975, 99, C31.
4. For a review: Sheldon, R. A.; Kochi, J. Metal-Catalyzed Oxidations of Organic Compounds; Academic: New York, 1981; Chapter 9.

Bruce A. Barner

Union Carbide Corporation, South Charleston, WV, USA

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