Partial Oxidation of Alkenylsilanes with Ozone: A Novel Stereoselective Approach to the Diol and Triol Derivatives

Abstract

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.

Key words

alkenes - oxidations - ozonolysis - peroxides - silicon

References

• For leading reviews on ozonolysis and other ozone oxidations, see:
• 1a Bailey PS. Ozonation in Organic Chemistry, Olefinic Compounds   Vol. 1:  Academic Press; London: 1978. 
• 1b Bailey PS. 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: Anglada MJ. Crehuet R. Bofill JM. Chem. Eur. J.  1999,  5:  1809 
• 3 Murakami M. Sakita K. Igawa K. Tomooka K. 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: Büchi G. Wüest H. J. Am. Chem. Soc.  1978,  100:  294 
• 6a Castrantas HM. Banerjee DK. Noller DC. Fire and Explosion Hazards of Peroxy Compounds, ASTM STP 394   American Society for Testing and Materials; Philadelphia PA: 1965. 
• 6b Castrantas HM. Banerjee DK. Laboratory Handling and Storage of Peroxy Compounds, ASTM STP 471   American Society for Testing and Materials; Philadelphia PA: 1970. 
• 8a Denmark SE. Jones TK. J. Org. Chem.  1982,  47:  4595 
• 8b Igawa K. Tomooka K. Angew. Chem. Int. Ed.  2006,  45:  232 
• 9 A related reduction of silyl peroxide in a norcamphor derivative has been reported, see: Jefford CW. Rimbault CG. J. Am. Chem. Soc.  1978,  100:  6437 
• 10 Cyclic peroxide has been utilized as a synthetic equivalent of ketone, see: Singh C. Malik H. Org. Lett.  2005,  7:  5673 

5

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.