尽管末端烯烃取得了巨大进展,但内部烯烃的不对称自由基引发的双官能化(产生两个邻位立体中心)一直是一项重大的合成挑战。这归因于通常的逐步机理,该机理涉及以非立体选择性方式将初始自由基加成至烯烃。在铜(I)-金鸡纳生物碱基磺酰胺催化剂存在下,我们在这里报告了β,γ-不饱和酮肟中末端和内部芳基烯烃的第一个不对称自由基1,2-氧磺酰化。实验和计算机制研究共同支持Cu II -Cu I这种机制的特点是将磺酰基快速,可逆地加成到烯烃上,并随后由速率和立体决定C-O键的形成,即在Curtin-Hammett动力学控制下的情况。该方法为各种有价值的手性含磺酰基的结构单元的各种阵列的集体合成提供了鲁棒的平台。
尽管末端烯烃取得了巨大进展,但内部烯烃的不对称自由基引发的双官能化(产生两个邻位立体中心)一直是一项重大的合成挑战。这归因于通常的逐步机理,该机理涉及以非立体选择性方式将初始自由基加成至烯烃。在铜(I)-金鸡纳生物碱基磺酰胺催化剂存在下,我们在这里报告了β,γ-不饱和酮肟中末端和内部芳基烯烃的第一个不对称自由基1,2-氧磺酰化。实验和计算机制研究共同支持Cu II -Cu I这种机制的特点是将磺酰基快速,可逆地加成到烯烃上,并随后由速率和立体决定C-O键的形成,即在Curtin-Hammett动力学控制下的情况。该方法为各种有价值的手性含磺酰基的结构单元的各种阵列的集体合成提供了鲁棒的平台。
In the presence of a mesoporous aluminosilicate Al-MCM-41, aldolreaction of various silyl enol ethers with both aromatic and aliphatic aldehydes proceeded under mild reaction conditions to afford the corresponding O-silylated aldol adducts in high yields. The solid acid catalyst was easily recovered and reusable three times.
A mesoporous aluminosilicate (Al-MCM-41) was found to be an effective heterogeneous catalyst for the reaction of both aldehydes and acetals with silylenolethers or ketene silylacetals to give the corresponding aldol adducts in moderate to high yields. The remarkable high catalytic activity of Al-MCM-41 over amorphous silica-alumina and aluminum-free mesoporous silicate was observed in the reaction
Crucial role of the ligand of silyl Lewis acid in the Mukaiyama aldol reactionElectronic supplementary information (ESI) available: experimental section. See http://www.rsc.org/suppdata/cc/b2/b203838b/
The Me3SiX-induced Mukaiyamaaldolreaction proceeds through each catalytic cycle under the influence of X-: the silyl group of Me3SiNTf2 does not release from -NTf2 and that of silyl enol ether intermolecularly transfers to the product, while the silyl group of Me3SiOTf remains in the product and that of the silyl enol ether becomes the catalyst for the next catalytic cycle.
In the silylLewis acid-promoted Mukaiyamaaldolreaction, the steric and electronic properties of the silyl group on the silylLewisacid influence the reaction mechanism and product distribution. When super silyl triflates such as (TMS)3SiOTf and (TES)3SiOTf are used as Lewisacids, the silyl group of the silyl enol ether chemoselectively transfers to the product. The mechanistic details have been