RIGBY, JAMES H.;SENANAYAKE, CHRISANTHA, J. ORG. CHEM., 53,(1988) N 2, 440-443
作者:RIGBY, JAMES H.、SENANAYAKE, CHRISANTHA
DOI:——
日期:——
Sn(OTf)2 as an Effective Lewis Acid in Reactions of Cyclopropyl Ketones with Acetic Anhydride: Application in the Synthesis of a 19-Nor-B-homo Steroid
作者:Darius Paul Kranz、Aike Meier zu Greffen、Sherif El Sheikh、Jörg Martin Neudörfl、Hans-Günther Schmalz
DOI:10.1002/ejoc.201100020
日期:2011.5
Attempts to convert 3β-acetoxy-5,19-cyclo-pregna-6,20-di-one (8) into a cyclocitrinol-related steroid with a bicyclo[4.4.1]-undecane AB-ring substructure through a Lewis acid-assisted fragmentation failed. Instead, treating 8 with an excess of Ac 2 O and BF 3 ·Et 2 O afforded B-homo steroid 9 in 90 % yield. This unexpected rearrangement is assumed to proceed via an intermediate bicyclobutonium cation
尝试通过路易斯酸将 3β-乙酰氧基-5,19-cyclo-pregna-6,20-di-one (8) 转化为具有双环 [4.4.1]-十一烷 AB 环亚结构的环柠檬醇相关类固醇-辅助分片失败。相反,用过量的 Ac 2 O 和 BF 3 ·Et 2 O 处理 8 以 90% 的产率提供了 B-同型类固醇 9。这种意想不到的重排被认为是通过中间双环丁鎓阳离子进行的。值得注意的是,作为模型底物制备的三环 [4.4.1.0] undecane-1-one (rac-13) 在相同条件下没有反应。然而,通过筛选各种路易斯酸,三氟甲磺酸亚锡被确定为一种特别有效的试剂,用于在 Ac 2 O 和催化量的 Sn(OTf) 2 存在下进行环丙基酮的这种和相关的路易斯酸辅助开环反应(5 mol-%) 证明是有效的。
An efficient electrophile-initiated homoconjugate addition of acetate to cyclopropyl ketones