Borylation of Propargylic Substrates by Bimetallic Catalysis. Synthesis of Allenyl, Propargylic, and Butadienyl Bpin Derivatives
摘要:
Bimetallic Pd/Cu and Pd/Ag catalytic systems were used for borylation of propargylic alcohol derivatives. The substrate scope includes even terminal alkynes. The reactions proceed stererospecifically with formal S(N)2' pathways to give allenyl boronates. Opening of propargyl epoxides leads to 1,2-diborylated butadienes probably via en allenylboronate intermediate.
Efficientborylation of sp3 C–O bonds by supported Au catalysts is described. Au nanoparticles supported on TiO2 showed high activity under mild conditions employing low catalyst loading conditions without the aid of any additives, such as phosphine and bases. A variety of allyl, propargyl, and benzyl substrates participated in the heterogeneously catalyzed reactions to furnish the corresponding allyl
描述了负载型Au催化剂对sp 3 C–O键的有效硼化作用。负载在TiO 2上的Au纳米颗粒在温和条件下采用低催化剂负载条件显示出高活性,而无需任何添加剂,例如膦和碱。各种烯丙基,炔丙基和苄基底物参与了非均相催化反应,以高产率提供了相应的烯丙基,烯丙基和苄基硼酸酯。此外,Au / TiO 2对烯丙基和苄基醇的直接硼化也有效。基于Hammett研究和控制实验的机理研究表明,负载型Au催化剂上的sp 3 C–O键硼化通过S N进行1'型机制涉及碳阳离子中间体的形成。负载的金催化剂的高活性,可重复使用性和环境相容性以及反应体系的可扩展性使有价值的有机硼化合物的实际合成成为可能。
Synthesis of Benzyl-, Allyl-, and Allenyl-boronates via Copper-Catalyzed Borylation of Alcohols
作者:Lujia Mao、Kálmán J. Szabó、Todd B. Marder
DOI:10.1021/acs.orglett.7b00256
日期:2017.3.3
Alcohols are among the most abundant and readily available organic feedstocks in industrial processes. The direct catalytic functionalization of sp3 C–O bonds of alcohols remains the main challenge in this field. Here, we report a copper-catalyzed synthesis of benzyl-, allyl-, and allenyl-boronates from benzylic, allylic, and propargylic alcohols, respectively. This protocol exhibits a broad reaction
of the intrinsic high strain energy and anti-aromaticity, the preparation of butafulvene compounds has been a fundamental issue for the development of butafulvene chemistry. Here an efficient palladium-catalysed coupling protocol involving propargylic compounds has been developed, providing a solid and versatile strategy for the rapid assembly of symmetric butafulvene derivatives. Based on mechanistic
We describe a 1,3-boron shift-type reaction of homoallenylboronates at the center (sp) carbon in allenes to afford 2-boryl-1,3-dienes with a variety of substituents.
Copper(I)-Catalyzed Substitution of Propargylic Carbonates with Diboron: Selective Synthesis of Multisubstituted Allenylboronates
作者:Hajime Ito、Yusuke Sasaki、Masaya Sawamura
DOI:10.1021/ja806602h
日期:2008.11.26
A versatile synthetic method for the preparation of the allenylboronates, Cu(I)-catalyzed reaction of propargylic carbonates with a diboron, is described. A Cu(O-t-Bu)-Xantphos catalyst system was effective for the preparation of various allenylboron compounds, allenylboronates with different substitution patterns, those with functional groups, and an axially chiral one. The Lewis acid promoted stereoselective addition to aldehydes leading to homopropargylic alcohols showed the usefulness of the new allenylboronates.