Selectivity in Lewis acid-mediated fragmentations of peroxides and ozonides: application to the synthesis of alkenes, homoallyl ethers, and 1,2-dioxolanes †
作者:Patrick H. Dussault、Hyung-Jae Lee、Xuejun Liu
DOI:10.1039/b001391i
日期:——
Fragmentation of dialkyl peroxides and ozonides is strongly influenced by the choice of Lewis acid. TiCl4 promotes C–O ionization (SN1 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 SN1 ionization.
二烷基过氧化物和臭氧化物的断裂强烈受到路易斯酸选择的影响。TiCl4促进叔过氧化物的C-O离子化(SN1反应),而SnCl4和BF3·OEt2促进O-O异裂(Hock反应)。阳离子中间体被烯丙基三甲基硅烷捕获,得到烯丙基化的烷烃和同烯丙基醚。在缺少亲核试剂的情况下,臭氧化物(1,2,4-三氧杂环戊烷)不可避免地发生O-O异裂。然而,烯丙基三甲基硅烷和SnCl4的组合导致通过捕获SN1离子化产生的中等体形成1,2-二氧杂环戊烷。