A diastereoselective cobalt-mediated synthesis of benzopyrans using a novel variation of an intramolecular Nicholas reaction in the key cyclisation step: optimisation and biological evaluation 1
of novel intramolecular cyclisation reactions between an organocobalt stabilised cation and a trisubstituted alkene have been accomplished that provide a concise route for the diastereoselective synthesis of a range of functionalised benzopyrans. In addition to the usual Lewis acids employed in the Nicholas reaction our studies have identified several other reagents for effecting the cyclisation reaction
Copper(I)-Catalyzed Hydroalkoxylation/Hydrogen-Bonding-Induced Asymmetric Hetero-Diels-Alder Cycloaddition Cascade: An Approach to Aromatic Spiroketals
作者:Xin Li、Jijun Xue、Chusheng Huang、Ying Li
DOI:10.1002/asia.201101056
日期:2012.5
One thing leads to another: Bis(benzannelated) 5,6‐spiroketal skeletons can be constructed by an efficient cascade process involving an unprecedented CuI‐catalyzed intramolecular alkyne hydroalkoxylation and an asymmetric hetero‐Diels–Alder cycloaddition. The method yields a series of diversely functionalized spiroketals from two readily available open‐chained starting materials in good yields and
A Novel Synthesis of 2-Functionalized Benzofurans by Palladium-Catalyzed Cycloisomerization of 2-(1-Hydroxyprop-2-ynyl)phenols Followed by Acid-Catalyzed Allylic Isomerization or Allylic Nucleophilic Substitution
furans 3 and 2-alkoxymethylbenzofurans 4-6, based on palladium-catalyzed cycloisomerization of 2-(1-hydroxyprop-2-ynyl)phenols 1 under basic conditions to give 2-methylene-2,3-dihydrobenzofuran-3-ols 2, followed by acid-catalyzed isomerization or allylic nucleophilic substitution with alcohols as nucleophiles, is reported. Cycloisomerization reactions leading to 2 (80-98% yields) were carried out at
synthetic coumarins 1-3 were also in vitro assayed on seedlings growth of the model species Arabidopsis thaliana to identify the possible physiological targets. All molecules strongly affected seed germination and root growth of both weeds. Interestingly, the effects of syntheticcoumarins on weed germination were higher than template natural coumarin, pointing out ED50 values ranging from 50-115 µM. Moreover
[GRAPHICS]A novel approach to coumarin derivatives has been developed starting from readily available 2-(1-hydroxyprop-2-ynyl)phenols, based on an unprecedented palladium-catalyzed dicarbonylation process. Reactions were carried out in the presence of catalytic amounts of PdI2 in conjunction with an excess of KI in MeOH as the solvent at room temperature and under 90 atm of CO to give 3-[(methoxycarbonyl)-methyl]coumarins in good to high isolated yields (62-87%).