Selectivity in Lewis acid-mediated fragmentations of peroxides and ozonides: Application to the synthesis of alkenes, homoallyl ethers, and 1,2-dioxolanes

Fragmentation of dialkyl peroxides and ozonides is strongly influenced by the choice of Lewis acid. TiCl₄ promotes C-O ionization (S_N1 reaction) of tertiary peroxides while SnCl₄ and BF₃·OEt₂ promote O-O heterolysis (Hock reaction). The cationic intermediates are trapped with allyltrimethylsilane to afford allylated alkanes and homoallyl ethers. In the absence of a nucleophile, ozonides (1,2,4-trioxolanes) invariably undergo O-O heterolysis. However, the combination of allyltrimethylsilane and SnCl₄ results in formation of 1,2-dioxolanes via trapping of intermediates derived from S_N1 ionization.