Rhodium(III)-Catalyzed Dehydrogenative Heck Reaction of Salicylaldehydes
作者:Zhuangzhi Shi、Nils Schröder、Frank Glorius
DOI:10.1002/anie.201203224
日期:2012.8.6
RhIII‐catalyzed dehydrogenativeHeckreaction (DHR) of salicylaldehydes with different classes of olefins extends the oxidative Heckreaction to aldehyde CH bonds. Several structural motifs similar to natural products and bioactive molecules such as aurones, flavones, 2′‐hydroxychalcones, and flavanones could be efficiently produced. Initial mechanistic studies give insight into the reaction mechanism.
A 2‐alkenoylpyridine‐bound N,N′‐dioxide–TbIII complex has been found to absorb visible light to reach the excited state, leading to the direct visible‐light‐excited catalytic enantioselective [2+2] cycloaddition of 2‐alkenoylpyridines to various alkenes in the absence of an additional photosensitizer. Diverse enantioenriched cyclobutanes were successfully obtained (yields up to 70 %, >19:1 d.r., 92 %
Enantioselective biomimetic cyclization of 2′-hydroxychalcones to flavanones
作者:Yan-Lei Zhang、Yong-Qiang Wang
DOI:10.1016/j.tetlet.2014.04.032
日期:2014.5
developed and shown to catalyze the direct and highly enantioselective cyclization of 2′-hydroxychalcones in imitation of the natural process of chalcone cyclization. The straightforward synthetic process occurs under mild reaction conditions, tolerates moisture and air, and gives an enantiomeric excess up to 99%. This approach provides a facile and efficient access to chiral flavanones.
Ionic liquid mediated Cu-catalyzed cascade oxa-Michael-oxidation: efficient synthesis of flavones under mild reaction conditions
作者:Zhiyun Du、Huifen Ng、Kun Zhang、Huaqiang Zeng、Jian Wang
DOI:10.1039/c1ob06209c
日期:——
Flavonoids are a class of natural products, found in a wide range of vascular plants and dietary components. Their low toxicity and extensive biological activities, including anti-cancer and anti-bacterial, have made them attractive candidates to serve as therapeutic agents for many diseases. Herein, we disclose a highly efficient synthetic method of CuI-catalyzed cascade oxa-Michael-oxidation, using chalcones as substrates, mediated by the ionic liquid [bmim][NTf2] at a low temperature. This efficient synthetic method has demonstrated high synthetic utility and can afford flavones in good to high yields (up to 98%).
Enantioselective photochemistry through Lewis acid–catalyzed triplet energy transfer
作者:Travis R. Blum、Zachary D. Miller、Desiree M. Bates、Ilia A. Guzei、Tehshik P. Yoon
DOI:10.1126/science.aai8228
日期:2016.12.16
spectroscopic data rule out substrate activation by means of photoinduced electron transfer and instead support a mechanism in which Lewisacid coordination dramatically lowers the triplet energy of the chalcone substrate. We expect that this approach will enable chemists to more broadly apply their detailed understanding of chiral Lewisacid catalysis to stereocontrol in reactions involving electronically excited