Regio- and stereoselective cyclopropanation of functionalised dienes. Novel methodology for the synthesis of vinyl- and divinyl-cyclopropanes
摘要:
Dienes, bearing an electron-withdrawing substituent at C-1, are cyclopropanated regio- and stereo selectively at the C-C double bond proximal to this electron-withdrawing group. The highest selectivity is observed in the case of dienylboronates. The cyclopropanation of these substrates affords almost exclusively the synthetically useful 1-boronato-2-vinyl-cyclopropanes. (C) 2002 Elsevier Science Ltd. All rights reserved.
Regio- and stereoselective cyclopropanation of functionalised dienes. Novel methodology for the synthesis of vinyl- and divinyl-cyclopropanes
摘要:
Dienes, bearing an electron-withdrawing substituent at C-1, are cyclopropanated regio- and stereo selectively at the C-C double bond proximal to this electron-withdrawing group. The highest selectivity is observed in the case of dienylboronates. The cyclopropanation of these substrates affords almost exclusively the synthetically useful 1-boronato-2-vinyl-cyclopropanes. (C) 2002 Elsevier Science Ltd. All rights reserved.
Synthesis of <i>Z</i>-(Pinacolato)allylboron and <i>Z</i>-(Pinacolato)alkenylboron Compounds through Stereoselective Catalytic Cross-Metathesis
作者:Elizabeth T. Kiesewetter、Robert V. O’Brien、Elsie C. Yu、Simon J. Meek、Richard R. Schrock、Amir H. Hoveyda
DOI:10.1021/ja403188t
日期:2013.4.24
first examples of catalytic cross-metathesis (CM) reactions that furnish Z-(pinacolato)allylboron and Z-(pinacolato)alkenylboron compounds are disclosed. Products are generated with high Z selectivity by the use of a W-based monoaryloxide pyrrolide (MAP) complex (up to 91% yield and >98:2 Z:E). The more sterically demanding Z-alkenylboron species are obtained in the presence of Mo-based MAP complexes
公开了提供Z-(频哪醇)烯基硼和Z-(频哪醇)烯基硼化合物的催化交叉复分解(CM)反应的第一实例。通过使用 W 基单芳氧基吡咯 (MAP) 络合物,生成具有高 Z 选择性的产品(产率高达 91%,Z:E >98:2)。在 Mo 基 MAP 配合物存在下,可以获得空间要求更高的 Z-烯基硼物质,产率高达 93%,Z 选择性高达 97%。首次报道了 1,3-二烯和芳基烯烃的 Z 选择性 CM。该方法与催化交叉偶联相结合的实用性通过抗癌剂考布他汀 A-4 的简洁和立体选择性合成得到了证明。
Site-Selective and Stereoselective <i>trans</i>-Hydroboration of 1,3-Enynes Catalyzed by 1,4-Azaborine-Based Phosphine–Pd Complex
作者:Senmiao Xu、Yuanzhe Zhang、Bo Li、Shih-Yuan Liu
DOI:10.1021/jacs.6b09759
日期:2016.11.9
A concise synthesis of monobenzofused 1,4-azaborine phosphine ligands (Senphos) is described. These Senphos ligands uniquely support Pd-catalyzed trans-selective hydroboration of terminal and internal 1,3-enynes to furnish corresponding dienylboronates in high efficiency and diastereoselectivity. X-ray structural analysis of the Senphos-Pd(0) complex reveals a κ2-P-η2-BC coordinationmode, and this
Substituted diazoalkanes react smoothly, in the presence of catalytic amounts of Pd(OAc)(2), with a range of vinyl- and dienylboronates, affording in good to excellent yields, the corresponding trisubstituted cyclopropanes. The reaction is remarkably regio-, chemo-, and diastereoselective. The synthetic utility of this novel protocol is illustrated by the efficient assembly of the middle fragment of ambruticin.