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Partial Oxidation of Alkenylsilanes with Ozone: A Novel Stereoselective Approach to the Diol and Triol Derivatives
08 February 2008 (online)
The reaction of alkenylsilanes with ozone provides synthetically versatile β-hydroxy or α-formyl silyl peroxides in good yield without normal fission of the C=C bond. The obtained α-formyl silyl peroxides serve as good precursors for the stereochemically defined diol or triol derivatives via nucleophilic addition to the formyl group and reduction of the peroxide moiety.
alkenes - oxidations - ozonolysis - peroxides - silicon
- For leading reviews on ozonolysis and other ozone oxidations, see:
BaileyPS. Ozonation in Organic Chemistry, Olefinic Compounds Vol. 1: Academic Press; London: 1978.
BaileyPS. Ozonation in Organic Chemistry, Nonolefinic Compounds Vol. 2: Academic Press; London: 1982.
- 2 Theoretical studies suggest that the formation of primary ozonide is a rate-determining step for the ozonolysis of alkenes. For a representative example, see:
AngladaMJ. CrehuetR. BofillJM. Chem. Eur. J. 1999, 5: 1809
MurakamiM. SakitaK. IgawaK. TomookaK. Org. Lett. 2006, 8: 4023
- 4 Büchi and Wüest reported the ozonization of trimethylsilyl-substituted alkenes in the 1970s, in which they proposed a similar silyl peroxide as an intermediate, see:
BüchiG. WüestH. J. Am. Chem. Soc. 1978, 100: 294
CastrantasHM. BanerjeeDK. NollerDC. Fire and Explosion Hazards of Peroxy Compounds, ASTM STP 394 American Society for Testing and Materials; Philadelphia PA: 1965.
CastrantasHM. BanerjeeDK. Laboratory Handling and Storage of Peroxy Compounds, ASTM STP 471 American Society for Testing and Materials; Philadelphia PA: 1970.
DenmarkSE. JonesTK. J. Org. Chem. 1982, 47: 4595
IgawaK. TomookaK. Angew. Chem. Int. Ed. 2006, 45: 232
- 9 A related reduction of silyl peroxide in a norcamphor derivative has been reported, see:
JeffordCW. RimbaultCG. J. Am. Chem. Soc. 1978, 100: 6437
- 10 Cyclic peroxide has been utilized as a synthetic equivalent of ketone, see:
SinghC. MalikH. Org. Lett. 2005, 7: 5673
Normal oxidative cleavage products were obtained in the ozonation of alkenylsilanes 1 in MeOH, CH2Cl2 or hexane in 10-30% yields.7
Although Büchi’s trimethylsilyl peroxide is too reactive to be handled with ease (see ref. 4), our silyl peroxides are tolerant not only to the reductive workup process using NaBH4 but also to purification on silica gel, most probably due to the bulky silyl group on the peroxide moiety. Furthermore, slow thermal degradation was observed at >80 °C in thermogravimetric analysis (TGA) of 2c and 4q; see ref. 3.