Recyclable alkylated Ru(bpy)32+ complex as a visible-light photoredox catalyst for perfluoroalkylation

A recyclable Ruthenium tris [4,4′-bis (dinonylmethyl)-2,2′-bipyridine] (Ru[(DNM)₂bpy]₃²⁺) photocatalyst (PC) was synthesized. Hexane-phase-selective solubility allowed its simple and efficient separation from reaction products via solvent extraction. The excellent catalytic activity and recoverability were demonstrated in batch and flow perfluoroalkylation reactions of coumarin under visible-light irradiation. High reaction rates and easy reusability of the catalyst make this approach attractive for large-scale applications.     

Coumarins with an unprecedented tetracyclic skeleton and coumarin dimers from chemically engineered extracts of a marine-derived fungus

The unprecedented tetracyclic coumarin derivatives 1 and 2 and the coumarin dimers 3–5 were isolated from chemically engineered extracts (coumarin dimerization of natural extract) of the marine-derived fungus Eurotium rubrum. The structures of these compounds were established using NMR, MS and IR methods. The absolute configuration of 1 was determined by ECD calculations. The unprecedented tetracyclic coumarin skeleton was generated by domino-Knoevenagel-Diels-Alder reactions. Compounds 1–5 showed tyrosinase inhibitory activity (IC₅₀?=?1.7, 1.2, 4.9, 1.8 and 2.9?μM, respectively). The isolated coumarin derivatives 1–5 were not observed by HPLC analysis in crude extracts of E. rubrum, suggesting that chemically engineered extract generated these new coumarin derivatives with tyrosinase inhibitory activity.     

Synthesis of 3-sulfonyl coumarins through radical sulfonylation with disulfides under catalyst-free conditions

An efficient and convenient aryl sulfonyl introducing strategy for the synthesis of 3-sulfonyl coumarins via ipso-cyclization/1,2-ester migration from substituted phenyl 3-phenylpropiolates with disulfides and potassium persulfate as sulfonylating reagents was developed, halogen and many other electron-withdrawing or -donating functional groups are tolerated. When naphthalen-1-yl 3-phenylpropiolate was used as a starting material, a spiro compound was obtained via ipso-cyclization.     

One-pot synthesis of 3-(furan-2-yl)-4-hydroxy-2H-chromen-2-ones using K10 montmorillonite clay as heterogeneous catalyst

A facile and efficient one-pot synthesis of 3-(furan-2-yl)-4-hydroxy-2H-chromen-2-ones was developed. The reaction of ethyl 3-(2-hydroxyphenyl)-3-oxopropanoates and 2,5-dimethoxy-2,5-dihydrofuran were performed in presence of K10 Montmorillonite Clay heterogeneous catalyst under the solvent-free condition at 80?°C for 1?h, and followed by further converted to 3-(furan-2-yl)-4-hydroxy-2H-chromen-2-ones via refluxing in the alkaline EtOH solution for 0.5?h. The demonstrate method not only avoided the usage of any expensive transition-metals, but also eliminated the tedious intermediate purification. Moreover, due to the wide functional group tolerance, it could be applied to various substrates and gave product in good to excellent yields.     

一种香豆素化合物的结构鉴定

一种香豆素化合物的结构鉴定陈望忠焦克芳（北京军事医学科学院毒物药物研究所，北京１００８５０）关键词２，１５－十六烷二酮３－乙酰基－６－乙氧羰基－５－羟基－４，７－二甲基香豆素ＮＭＲ中图分类号Ｏ６５６．２２麝香酮是麝香中的主要成分之一，Ｓｔｏｌ［１］采...     

Ba(OH)2 as catalyst in organic reactions,IV. Reaction between coumarin and diethyl malonate

The reaction of diethyl malonate and coumarin catalyzed by an activated barium hydroxide catalyst (C-200) in a solid-liquid-system is described. NoMichael addition takes place. An unusual nucleophilic addition-elimination process to the C=O bond of coumarin is observed and the new compound is described the first time. The process is explained by the microcrystalline structure of the solid, the nature of the active sites of the catalyst and the chelating action of coumarin on Ba^II of the lattice.

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Ba(OH)₂ als Katalysator organischer Reaktionen, 4. Mitt.: Die Reaktion zwischen Cumarin und Diethylmalonat

Zusammenfassung Es wird die Reaktion von Diethylmalonat mit Cumarin unter der katalytischen Wirkung von aktiviertem Bariumhydroxid (C-200) in einem Fest-flüssig-System beschrieben. Es ist keineMichael-Addition zu beobachten. Es tritt eine ungewöhnliche Addition-Eliminierung an der C=O-Bindung des Cumarin ein und die dabei entstehende Verbindung wird erstmals beschrieben. Der Prozeß wird auf der Basis der mikrokristallinen Struktur des Festkörpers, der Natur der aktiven Stellen am Katalysator und der chelierenden Wirkung von Cumarin auf die Gitter-Ba^II-Ionen erklärt.

     

Synthesis of coumarin-nucleoside conjugates via Huisgen 1,3-dipolar cycloaddition

An efficient synthesis of fluorescent coumarin-nucleoside conjugates via Cu(I) catalysed Huisgen 1,3-dipolar cycloaddition is described. Starting from azidonucleosides and coumarin derivatives, products are obtained in good yields. The fluorescent properties of the newly prepared coumarin-nucleoside conjugates are determined.     

Analysis of Cnidium monnieri fruits in different regions of China

Application of multivariate data analysis has become a popular method in the last decades, mainly because it can provide information not otherwise accessible. The information includes classification, searching similarities, finding relationships, finding physical significance to principal components, etc. Fifty three Chinese medicinal herbs of eleven kinds of coumarins were collected and determined by HPLC. The results were studied by principal component analysis (PCA) and cluster analysis. It was showed that the samples could be clustered reasonably into different groups, which correspond with variation of regularity and distribution of coumarin of Cnidium monnieri fruits in different regions of China.     

An efficient synthesis of the intrinsic fluorescent peptide labels, (S)- and (R)-(6,7-dimethoxy-4-coumaryl)alanines via asymmetric hydrogenations

The title compounds 1a,b are efficiently synthesized in high yields and with high enantioselectivity (>95% ee) by using a sequence in which the key step involves asymmetric hydrogenation of dehydroamino methyl ester 4 with Burk’s DuPHOS-based Rh(I) catalysts.     

Unexpected transformations of 3-(bromoacetyl)coumarin provides new evidence for the mechanism of thiol mediated dehalogenation of α-halocarbonyls

The mechanism for the thiol mediated dehalogenation of α-halogenated carbonyls has remained an unresolved problem, despite its ongoing application in synthetic organic chemistry. Nakamura and co-workers first proposed that net dehalogenation occurs via sequential nucleophilic substitutions, while Israel and co-workers concluded that the rate at which dehalogenation occurred suggested that dehalogenation proceeds in a single concerted step. In this study, we investigated the debromination and nucleophilic substitution of 3-(bromoacetyl)coumarin with a variety of thiophenols, whose electron donating or withdrawing natures resulted in large variations in the degree of nucleophilic substitution and dehalogenation products, respectively. Results from these experiments, in addition to an unexpected formation of thioether containing dibenzo[b,d]pyran-6-ones from a Robinson annulation, has provided new evidence for this disputed mechanism.