Exploring the Original Proposed Biosynthesis of (+)-Symbioimine: Remote Exocyclic Stereocontrol in a Type I IMDA Reaction
摘要:
The originally proposed biosynthesis of (+)-symbioimine was explored, resulting in the successful intramolecular Diels-Alder (IMDA) cyclization of an appropriate (E,E,E)-1,7,9-decatrien-3-one. In contrast to the originally proposed biosynthesis, the IMDA reaction appears to proceed via an endo transition state. Remarkably, a single exocyclic stereogenic center effectively controls the pi-facial selectivity affording a highly diastereoselective cycloaddition.
Stereoselective [4 + 1] Annulation Reactions with Silyl Vinylketenes Derived from Fischer Carbene Complexes
作者:William H. Moser、Laura A. Feltes、Liangdong Sun、Matthew W. Giese、Ryan W. Farrell
DOI:10.1021/jo060994x
日期:2006.8.1
Stable silyl vinylketenes were prepared via the thermal reaction of Fischercarbenecomplexes with triisopropylsilyl- or tert-butyldimethylsilyl-substituted alkynes. The ability of these silyl vinylketenes to participate with carbenoid reagents in [4 + 1] annulation reactions was investigated. The best results were obtained with diazomethane and substituted diazomethane reagents, which provided cyclopentenone
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。
Molecular Solar Thermal Batteries through Combination of Magnetic Nanoparticle Catalysts and Tailored Norbornadiene Photoswitches
作者:Patrick Lorenz、Tobias Luchs、Andreas Hirsch
DOI:10.1002/chem.202005427
日期:2021.3.12
Cobaltcatalysts are immobilized on the surface of iron oxide nanoparticles for the preparation of highly active quasi‐homogeneous catalysts toward an efficient release of photochemically stored energy in norbornadiene‐based photoswitches. The facile separation of the iron oxide nanoparticles through exploitation of the intrinsic magnetic properties of this material enables efficient cyclization of
将钴催化剂固定在氧化铁纳米颗粒的表面,用于制备高活性的准均相催化剂,以有效释放降冰片二烯基光开关中光化学储存的能量。通过利用这种材料的固有磁性,可以轻松分离氧化铁纳米粒子,从而实现能量存储和释放的有效环化。通过从钴(II)salphen到钴卟啉的转变,QC-NBD反向转换的催化效率提高了22.6倍,初始TOF高达3.64 s -1 ,并且出色的TON超过3305此外,还制备了一系列新型“推拉”功能化降冰片二烯衍生物,具有优异的吸收性能,最大波长可达366 nm,量子产率约为70%,储能容量高达98.0 kJ mol -1 。出色的热稳定性, t 1/2 (25 °C) 超过 100 天。最后,在放热实验中利用了这些分子太阳能热 (MOST) 系统的储能潜力。这证明了基于降冰片二烯的光开关与高效磁性催化剂相结合,产生环境友好的工艺热量的潜力。
Copper(I)-catalyzed stereoselective hydrogenation of 1,3-diynes and enynes
作者:Niklas O. Thiel、Sebastian Kemper、Johannes F. Teichert
DOI:10.1016/j.tet.2017.05.029
日期:2017.8
A stereoselective hydrogenation of 1,3-diynes with an air-stable copper(I)/N-heterocyclic carbene complex, [IPrCuOH], has been developed. The corresponding products, 1,3-dienes, are obtained in a stereoselective manner depending on their substitution pattern: Diaryl-diynes yield E,E-1,3-dienes, whereas dialkyl-diynes are converted to the corresponding Z,Z-1,3-dienes. Hydrogenation and deuteration experiments
An approach to the synthesis of dimeric resveratrol natural products via a palladium-catalyzed domino reaction
作者:Jenna L. Jeffrey、Richmond Sarpong
DOI:10.1016/j.tetlet.2009.02.067
日期:2009.4
A route for the rapid assembly of the carbon framework of several resveratrol naturalproducts is presented. A palladium-catalyzed dominoreaction of bromostilbene derivative 6 and tolane 7, involving two sequential Heck coupling reactions, provides access to the benzofulvene-based core of various resveratrol-derived naturalproducts. The carbon skeleton of pallidol and its congeners is achieved by