Overman Larry E, Velthuisen Emile J
Department of Chemistry, 516 Rowland Hall, University of California, Irvine, California 92697-2025, USA.
J Org Chem. 2006 Feb 17;71(4):1581-7. doi: 10.1021/jo0522862.
Using a B-alkyl Suzuki cross-coupling as a key step, a concise and stereocontrolled synthesis of five- to eight-membered triisopropylsiloxy ethers having (2Z)-(6,6-dimethoxyhexylidene) or (2Z)-(5,5-dimethoxypentylidene) side chains was developed. Prins-pinacol reactions of these precursors promoted by SnCl4 provide bicyclic products in which 5-, 6-, or 7-membered rings are joined by a C-C single bond. Synthetically challenging attached ring systems in which both rings are chiral can be prepared in this fashion with high stereo- and enantioselectivity. Stabilizing through-space electrostatic interactions between the alpha-alkoxycarbenium ion and an axially positioned oxygen substituent are believed to play a significant role in organizing the transition structure of the Prins cyclization.
以B-烷基铃木交叉偶联反应作为关键步骤，开发了一种简洁且立体可控的合成方法，用于制备带有(2Z)-(6,6-二甲氧基亚己基)或(2Z)-(5,5-二甲氧基亚戊基)侧链的五元至八元三异丙基硅氧基醚。由SnCl4促进的这些前体的普林斯-频哪醇反应提供了双环产物，其中五元、六元或七元环通过碳-碳单键相连。通过这种方式可以以高立体选择性和对映选择性制备两个环均为手性的合成挑战性连接环系统。据信，α-烷氧基碳鎓离子与轴向定位的氧取代基之间稳定的空间静电相互作用在组织普林斯环化反应的过渡结构中起着重要作用。
