Triethylsilyl Hydrotrioxide


[101631-06-5]  · C6H16O3Si  · Triethylsilyl Hydrotrioxide  · (MW 164.31)

(alkene oxidation, dioxetane formation1)

Preparative Methods: addition of Triethylsilane (2 equiv) to a cold (-78 °C), saturated methylene chloride solution of Ozone (ca. 0.04 M) results in discharge of the color with formation of triethylsilyl hydrotrioxide within 45 s.2

Handling, Storage, and Precautions: is prepared in solution immediately before use. In methylene chloride at -78 °C, the half-life of the reagent has been estimated to be a few minutes.2 Precautions appropriate for reactions which utilize or generate peroxides should be used.

Alkene Oxidation Reactions.

The reaction of triethylsilane with ozone and use of the intermediate triethylsilyl hydrotrioxide in oxidation reactions have been described. Initial oxidation reactions reported included the formation of the 9,10-endoperoxide from 9,10-dimethylanthracene (eq 1), and an allylic hydroperoxide from 2,3-dimethyl-2-butene (eq 2). Researchers also observed a near-IR emission from triethylsilyl hydrotrioxide as it decomposed at -60 °C, consistent with generation of singlet oxygen.2 Other workers have characterized triethylsilyl hydrotrioxide by NMR spectroscopy and and measured the kinetics of its decomposition in deuterated acetone.3

Subsequent work examined the use of triethylsilyl hydrotrioxide in alkene oxidations and found it to be effective in oxidative cleavage of unactivated terminal and internal alkenes into carbonyl fragments, and in formation of 1,2-dioxetanes from vinyl aromatics and vinyl ethers.1,4-6 The results of this research indicated that the reaction proceeds via direct interaction of the alkene and triethylsilyl hydrotrioxide without the intermediacy of singlet oxygen. Allylbenzene reacted with triethylsilyl hydrotrioxide followed by Lithium Aluminum Hydride reduction to give 2-phenylethanol (eq 3). The same sequence of reactions gave 1-nonanol and 1,9-nonanediol in 64% and 74% yield, respectively, from methyl oleate (eq 4).1 It has been noted in the cleavage of alkenes by triethylsilyl hydrotrioxide that the presence of an ether or ester function in the molecule results in improved yields, even when the oxygen function is remote from the double bond. Addition of diethyl ether or ethyl acetate does not improve the reactions of unsaturated hydrocarbons.5

In the case of an enol ether derivative (eq 5), reaction with triethylsilyl hydrotrioxide produced an intermediate dioxetane which was cleaved to give 3-phenylpropionaldehyde upon warming. In contrast, reaction of the same enol ether with photochemically generated singlet oxygen proceeded via an ene pathway. After hydrolysis, this gave an a,b-unsaturated aldehyde in 37% yield.1

Reaction of triethylsilyl hydrotrioxide with a keto vinyl ether and subsequent rearrangement of the dioxetane intermediate resulted in formation of the 1,2,4-trioxane product in 58% overall yield (eq 6).5 This model system for the naturally occurring antimalarial artemisin was similarly prepared in 48% yield using singlet oxygen.7 Both singlet oxygen and triethylsilyl hydrotrioxide have been used in the synthesis of a regiospecifically oxygen-18 labeled model system.6

1. Posner, G. H.; Webb, K. S.; Nelson, W. M.; Kishimoto, T.; Seliger, H. H. JOC 1989, 54, 3252.
2. Corey, E. J.; Mehrotra, M. M.; Khan, A. U. JACS 1986, 108, 2472.
3. Koenig, M.; Barrau, J.; Hamida, N. B. JOM 1988, 356, 133.
4. Posner, G. H.; Weitzberg, M.; Nelson, W. M.; Murr, B. L.; Seliger, H. H. JACS 1987, 109, 278.
5. Posner, G. H.; Oh, C. H.; Milhous, W. K. TL 1991, 32, 4235.
6. Posner, G. H.; Oh, C. H. JACS 1992, 114, 8328.
7. Jefford, L. W.; Verlarde, J.; Bernardinelli, G. TL 1989, 30, 4485.

Charles G. Caldwell

Merck Research Laboratories, Rahway, NJ, USA

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