The Scope and Limitations of Intramolecular Radical Cyclizations of Acylsilanes with Alkyl, Aryl, and Vinyl Radicals
摘要:
5-Exo cyclizations of primary and secondary radicals with acylsilanes successfully give cyclopentyl silyl ethers. The corresponding 6-exo cyclizations are sensitive to changes of the size of silyl groups. Secondary radicals undergo 6-exo cyclizations with acylsilanes more slowly. Reaction of aryl radical with acylsilane proceeds well for 5-exo cyclization but not for 6-exo cyclization. Vinyl radicals give best results in 5-exo cyclizations with acylsilanes but give low yields (similar to 30%) in 6-exo cyclizations. Intramolecular cyclizations of vinyl radicals with acylsilanes give enol silyl ethers regiospecifically.
ω-Haloacylsilanes 1a–d were transformed by H2S/HCl into the corresponding silylthiones 2 which underwent enethiolization on base treatment. Enethiols 3 cyclizedintramolecularly to afford the title compounds 4a–d in high yields.
ω-卤代硅烷1a-d通过H 2 S / HCl转化为相应的甲硅烷基硫酮2,在碱处理中进行了烯硫化。烯硫醇3分子内环化,以高收率得到标题化合物4a-d。
Radical cyclizations of bromo acylsilanes and intramolecular trapping of the rearranged α-silyloxy radicals
作者:Yeun-Min Tsai、Kuo-Hsiang Tang、Weir-Torn Jiaang
DOI:10.1016/s0040-4039(00)91780-5
日期:1993.2
Radical 1,5-exo cyclizations of acylsilanes involving secondary radicals are quite effective. In contrast, 1,6-exo cyclizations are more sensitive toward steric effect. Tandem radical cyclization process can be designed.