KTH Royal Institute of Technology, School of Chemical Science and Engineering, Department of Chemistry, Organic Chemistry, SE 100 44 Stockholm, Sweden.
J Am Chem Soc. 2012 Sep 26;134(38):15992-9. doi: 10.1021/ja3070717. Epub 2012 Sep 18.
1,3-Dienyl-2-silanols with a wide range of substitution patterns are readily obtained by palladium-catalyzed silaboration of 1,3-enynes followed by Suzuki-Miyaura cross coupling with aryl bromides. Subsequent Hiyama-Denmark cross coupling with aryl iodides provides either 1,3- or 1,2-dienes in high yields. The site selectivity can be fully controlled by the choice of activator used in the coupling reaction. In the presence of strong bases such as NaOt-Bu, KOt-Bu, and NaH, clean formation of 1,2-dienes takes place via allylic rearrangement. In contrast, stereo- and site-selective formation of tetra- and trisubstituted 1,3-dienes results from use of Ag(2)O and Bu(4)NF·3H(2)O, respectively, as activators. Under microwave heating at 100 °C the base-mediated cross couplings are largely accelerated and are completed within one hour or less. The ratio of diastereomeric allenes varies depending on the substitution pattern of the silanol and ranges from >99:1 to 52:48.
1,3-二烯基-2-硅醇具有广泛的取代模式，可通过钯催化的 1,3-烯炔的硅化反应得到，然后与芳基溴进行铃木-宫浦交叉偶联。随后与芳基碘的 Hiyama-Denmark 交叉偶联以高收率提供 1,3-或 1,2-二烯。通过在偶联反应中选择使用的活化剂，可以完全控制位置选择性。在强碱如 NaOt-Bu、KOt-Bu 和 NaH 的存在下，通过烯丙基重排可清洁地形成 1,2-二烯。相比之下，通过使用 Ag(2)O 和 Bu(4)NF·3H(2)O 分别作为活化剂，可立体和位置选择性地形成四取代和三取代的 1,3-二烯。在 100°C 的微波加热下，碱介导的交叉偶联大大加速，在一小时或更短的时间内完成。非对映异构体的比例取决于硅醇的取代模式，范围从>99:1 到 52:48。
