Access to a new family of medium ring aromatic lactones
摘要:
We report a new method for preparation of hydroxyacids as precursors of benzolactones using a simple and an efficient electrochemical step. This gives in only four steps six- to eleven-membered lactones with high isolated yields from conveniently substituted aryl bromides. The lactonisation was performed according to the Yamamoto's process. (c) 2006 Elsevier Ltd. All rights reserved.
Substituent effects of cis-cinnamic acid analogues as plant growh inhibitors
摘要:
1-O-cis-Cinnamoyl-beta-D-glucopyranose is one of the most potent allelochemicals that has been isolated from Spiraea thunbergii Sieb by Hiradate et al. It derives its strong inhibitory activity from cis-cinnamic acid (cis-CA), which is crucial for phytotoxicity. By preparing and assaying a series of cis-CA analogues, it was previously found that the key features of cis-CA for lettuce root growth inhibition are a phenyl ring, cis-configuration of the alkene moiety, and carboxylic acid. On the basis of a structure-activity relationship study, the substituent effects on the aromatic ring of cis-CA were examined by systematic synthesis and the lettuce root growth inhibition assay of a series of cis-CA analogues having substituents on the aromatic ring. While ortho- and para-substituted analogues exhibited low potency in most cases, meta-substitution was not critical for potency, and analogues having a hydrophobic and sterically small substituent were more likely to be potent. Finally, several cis-CA analogues were found to be more potent root growth inhibitors than cis-CA. (C) 2013 Elsevier Ltd. All rights reserved.
Diazo Reagents in Copper(I)-Catalyzed Olefination of Aldehydes
作者:Hélène Lebel、Michaël Davi
DOI:10.1002/adsc.200800381
日期:2008.10.6
The olefination of aldehydes to synthesize unsaturated ketones, esters, amides and phosphonates using diazo reagents and triphenylphosphine in the presence of copper(I) iodide as catalyst, is described. Good to excellent E:Z selectivities as well as yields were obtained for a large variety of aliphatic, aromatic and heteroaromatic aldehydes. The reaction showed also an excellent functional group compatibility
Rh(III)-Catalyzed Enaminone-Directed C–H Coupling with α-Diazo-α-phosphonoacetate for Reactivity Discovery: Fluoride-Mediated Dephosphonation for C–C Coupling Reactions
Rh(III)-catalyzed enaminone-directed C–H coupling with α-diazo-α-phosphonoacetate has been used for the identification of fluoride-mediated dephosphonation C–C coupling reactivity for the synthesis of 4-hydroxy-1-naphthoates. Intermolecular C–C coupling of α-phosphonoacetate and benzaldehyde for (E)-selective α,β-unsaturated ester synthesis has also been achieved.
Palladium-Catalyzed Tandem Reactions To Form 1-Vinyl-1<i>H</i>-isochromene Derivatives<sup>1</sup>
作者:Roger Mutter、Ian B. Campbell、Eva M. Martin de la Nava、Andy T. Merritt、Martin Wills
DOI:10.1021/jo0011991
日期:2001.5.1
also an essential choice as it furnishes the appropriate reactivity to promote allylic substitution after the aryl coupling process. The use of more effective leaving groups, such as acetate, results in reaction of the allylic group, and no aryl coupling is observed. Through the appropriate selection of phosphine ligand and solvent, either the cyclized isochromene product or the noncyclized intermediate
Chromatography-Free Wittig Reactions Using a Bifunctional Polymeric Reagent
作者:Peter Shu-Wai Leung、Yan Teng、Patrick H. Toy
DOI:10.1021/ol1021614
日期:2010.11.5
The first example of a polystyrene bearing two distinct reagent groups has been prepared. This phosphine and amine functionalized material was used in one-pot Wittig reactions with an aldehyde and either an α-halo-ester, -ketone, or -amide. Due to the heterogeneous nature of the polymer, the desired alkene product of these reactions could be isolated in excellent yield in essentially pure form after
Highly Enantioselective, Base-Free Synthesis of α-Quaternary Succinimides through Catalytic Asymmetric Allylic Alkylation
作者:Tao Song、Stellios Arseniyadis、Janine Cossy
DOI:10.1002/chem.201800920
日期:2018.6.7
The synthesis of diversely substituted five‐membered ring succinimide derivatives is reported featuring a direct, base‐free, palladium‐catalyzed asymmetric allylicalkylation. The method allows a straightforward access to the desired heterocyclic scaffold bearing an all‐carbon α‐quaternary stereogenic center in high yields and good to excellent enantioselectivities. To further demonstrate the synthetic