Mechanistic Study of the Ring-Enlargement Reaction of (3-Oxa-2-silacyclopentyl)methyl Radicals into 4-Oxa-3-silacyclohexyl Radicals. Evidence for a Pentavalent Silicon-Bridging Radical Transition State in 1,2-Rearrangement Reactions of β-Silyl Radicals
作者:Satoshi Shuto、Isamu Sugimoto、Hiroshi Abe、Akira Matsuda
DOI:10.1021/ja993239s
日期:2000.2.1
novel radical ring-enlargement reaction of (3-oxa-2-silacyclopentyl)methyl radicals into 4-oxa-3-silacyclohexyl radicals. Two pathways, one via a pentavalent silicon-bridging radical transition state (or intermediate), the other via β-elimination to give a ring-opened silyl radical, can be postulated. The radical reactions of 1 and 2, which are precursors for a (3-oxa-2-silacyclopentyl)methyl radical
对 (3-oxa-2-silacyclopentyl) 甲基自由基向 4-oxa-3-silacyclohexyl 自由基的新型自由基扩环反应进行了机理研究。可以假设有两种途径,一种通过五价硅桥接自由基过渡态(或中间体),另一种通过β-消除产生开环甲硅烷基自由基。1 和 2 分别是(3-氧杂-2-硅杂环戊基)甲基自由基 C' 和 4-氧杂-3-硅杂环己基自由基 D' 的前体的自由基反应,表明 C 的扩环重排'变成D'是不可逆的。8a 和 8b 的自由基反应的 1H NMR 分析表明,在扩环反应期间,硅原子的构型通过五价硅桥基自由基过渡态(或中间体)保持不变。