不对称氢化是制备单一对映体化合物的最有效方法之一。然而,在具有多个不饱和键的底物中相对惰性的不饱和基团的化学和对映选择性氢化仍然是一个挑战。我们在此报告了共轭烯炔的高度化学和对映选择性氢化同时保持炔键完整的协议。机理研究表明,Co II 配合物的锌还原产生的伴随的 Zn 2+在启动合理的 Co I /Co III催化循环中起着关键作用。这种方法可以高效生成手性炔丙胺(高达 99.9 % ee 和 2000 S/C)和进一步有用的化学转化。
Radical C(sp<sup>3</sup>)–H alkenylation, alkynylation and allylation of ethers and amides enabled by photocatalysis
作者:Subhasis Paul、Joyram Guin
DOI:10.1039/c7gc00840f
日期:——
enables selective incorporation of alkenyl, alkynyl and allyl functional groups into the C(sp3)–H bond under green reaction conditions is developed. The process is based on the catalytic formation of α-alkoxyl/α-amidyl radicals via the homolytic activation of the C(sp3)–H bond of ethers/amides with a catalytic amount of diarylketone in the presence of a household fluorescent light bulb. This simple reaction
Cobalt-catalyzed asymmetric sequential hydrogenations of conjugated enynes have been developed. The precise synthesis of chiral Z-allylamides has been realized in high activity (up to 1000 S/C) and with excellent enantioselectivity (up to >99 % ee). Mechanism experiment and theoretical calculation supported a reasonable cationic CoI/CoIII redox catalytic cycle, and explained the difference in reactivity
已经开发了钴催化的共轭烯炔的不对称顺序氢化。手性Z-烯丙基酰胺的精确合成已实现高活性(高达 1000 S/C)和出色的对映选择性(高达 >99% ee)。机理实验和理论计算支持合理的阳离子 Co I /Co III氧化还原催化循环,并解释了 Ph-BPE-Co 和 QuinoxP*-Co 之间反应性的差异。
Cobalt(II)-Catalyzed Conversion of Allylic Alcohols/Acetates to Allylic Amides in the Presence of Nitriles
作者:Manoj Mukhopadhyay、M. Madhava Reddy、G. C. Maikap、Javed Iqbal
DOI:10.1021/jo00114a013
日期:1995.5
Various secondary allylic alcohols or their acetates and tertiary allylic alcohols can be converted to the corresponding transposed allylic amides in the presence of a catalytic quantity of cobalt(II) chloride and acetic anhydride in acetonitrile. Tertiary alcohols undergo complete rearrangement whereas secondary ones afford a mixture of regioisomers. Moderate yields of amides are also obtained by reacting acrylonitrile with secondary alcohols in 1,2-dichloroethane. The presence of acetic anhydride or acetic acid is crucial to the formation of amides as the absence of the former affords no amides and the allylic alcohols are mainly recovered as regioisomeric mixtures. The regioselectivity during amide formation can be enhanced by using cobalt complexes 14-16 in acetic acid medium. Some preliminary studies indicate that these reactions are proceeding via an pi-allyl complex or tight ion pair rather than a [3,3] sigmatropic rearrangement of acetamidate obtained in a Pinner reaction.
Cobalt‐Catalyzed Chemo‐ and Enantioselective Hydrogenation of Conjugated Enynes
Asymmetric hydrogenation is one of the most powerful methods for the preparation of single enantiomer compounds. However, the chemo- and enantioselective hydrogenation of the relatively inert unsaturated group in substrates possessing multiple unsaturated bonds remains a challenge. We herein report a protocol for the highly chemo- and enantioselective hydrogenation of conjugated enynes while keeping
不对称氢化是制备单一对映体化合物的最有效方法之一。然而,在具有多个不饱和键的底物中相对惰性的不饱和基团的化学和对映选择性氢化仍然是一个挑战。我们在此报告了共轭烯炔的高度化学和对映选择性氢化同时保持炔键完整的协议。机理研究表明,Co II 配合物的锌还原产生的伴随的 Zn 2+在启动合理的 Co I /Co III催化循环中起着关键作用。这种方法可以高效生成手性炔丙胺(高达 99.9 % ee 和 2000 S/C)和进一步有用的化学转化。