Search results for "Trie"

Riverine impacts on benthic biodiversity and functional traits: A comparison of two sub-Arctic fjords

2020

Abstract Climate change is leading to increases in freshwater discharge to coastal environments with implications for benthic community structure and functioning. Freshwater inputs create strong environmental gradients, which potentially affect the community structure of benthic infauna. In turn, changes in functional trait composition have the potential to affect the processing of terrestrially-derived nutrients and organic matter along the freshwater to marine continuum. We investigated the effects of riverine inputs on benthic community structure, functional traits, taxonomic and functional diversity, and utilization of terrestrial organic matter in two contrasting northern Norwegian fjo…

ChemInform Abstract: Highly Enantioselective Copper(I)-Catalyzed Conjugate Addition of 1,3-Diynes to α,β-Unsaturated Trifluoromethyl Ketones.

2015

The conjugate diynylation of α,β-saturated trifluoromethyl ketones is carried out at low catalytic loading (2.5 mol% for aryl substituents) of a copper(I)—MeO-BIPHEP complex, triethylamine and a terminal 1,3-diyne.

Die herstellung molekulareinheitlicher leiteroligomerer und einer molekulareinheitlichen hexaacrylsäure. IV. Mitt.: Modelle für matrizenreaktionen

1968

Die phenolischen Hydroxylgruppen molekulareinheitlicher Mehrkernverbindungen mit vier und funf pKresolbausteinen je Molekul konnten vollstandig mit Acrylsaurechlorid in Gegenwart von Triathylamin verestert werden. Lies man auf die in siedendem Benzol stark verdunnten mehrafachen Acrylsaureester einen Uberschus an Radikalen aus α.α′-Azoisobutyrodinitril einwirken, so bildeten sich mit guter Ausbeute molekulareinheitliche, dunnschichtchromatographisch reine Leiteroligomere. Die alkalische Verseifung des Leiteroilgomeren mit vier p-Kresolbausteinen gab eine molekulareinheitliche Hexaacrylsaure, die als Hexamethylester durch Elementaranalyse und Molekulargewicht charakterisiert wurde; die gefun…

1983

Water soluble polyamides with iminoethylene and oxyethylene units in the main chain were obtained by condensation polymerization of diethylenetriamine and triethylenetetramine with suitable dimethylesters containing two or three oxyethylene units. The molecular weights were in the range of Mn = 5000–7000. By potentiometric and conductometric titration only 80–85% of the expected amount of basic groups was found which was probably caused by branching. Durch Polykondensation von Diethylentriamin und Triethylentetramin mit Dimethylestern von Sauren, die zwei oder drei Oxyethyleneinheiten enthalten, wurden wasserlosliche Polyamide mit Iminoethylen- und Oxyethyleneinheiten in der Hauptkette erha…

ChemInform Abstract: The Chemistry of Unsaturated Nitrogen-Heterocyclic Compounds Containing Carbonyl Groups

2010

Publisher Summary Most hydroxy-substituted azaheteroaromatic compounds exist predominately in the NH/carbonyl tautomeric form, and these compounds have been widely discussed. This chapter provides an overview of azaheteroaromatic compounds and I-azetin-4-ones—these are those azaheterocycles that contain in the ring at least one carbonyl group and one or two nitrogen atoms in the form of C=N or N=N bonds. Many of these compounds are unstable but their importance as reactive intermediates is established, and many of them could be used as synthons in the preparation of pharmacologically active compounds. The chapter describes the free existence of I-azetin-4-one and the nucleophilic substituti…

The Chemistry of Unsaturated Nitrogen–Heterocyclic Compounds Containing Carbonyl Groups

1993

Publisher Summary Most hydroxy-substituted azaheteroaromatic compounds exist predominately in the NH/carbonyl tautomeric form, and these compounds have been widely discussed. This chapter provides an overview of azaheteroaromatic compounds and I-azetin-4-ones—these are those azaheterocycles that contain in the ring at least one carbonyl group and one or two nitrogen atoms in the form of C=N or N=N bonds. Many of these compounds are unstable but their importance as reactive intermediates is established, and many of them could be used as synthons in the preparation of pharmacologically active compounds. The chapter describes the free existence of I-azetin-4-one and the nucleophilic substituti…

1977

The reaction of ethylene glycol, 1,4-butanediol, 1,6-hexanediol, 3,6-dioxaoctane-1,8-diol (triethylene glycol), poly(ethylene oxide)s with Mn = 300,1000 and 3000, or with poly(propylene oxide)s with Mn = 425 and 2000 in excess with AIBN leads to the corresponding bis(hydroxyalkyl) 2,2′-azodiisobutyrates (1a–i). These initiators are suited to synthesize telechelics. With equimolar amounts of AIBN and 3-oxapentane-1,5-diol (diethylene glycol), poly(ethylene oxide)s with Mn = 300, 1000 and 12000, poly(propylene oxide) with Mn = 425, or with poly(tetrahydrofuran) with Mn = 1000 and 2000 polymeric azoinitiators of structure 2 are formed. Blockcopolymers may be synthesized by means of these polym…

Synthesis of Chiral Catalyst Modifiers by Hydrosilylation of Cinchonidine and Their Application in the Hydrogenation of 1-Phenylpropane-1,2-dione and…

2005

Four new chiral modifiers were synthesized in order to investigate the effect of distal modifier substitution in the hydrogenation of ethyl pyruvate and 1-phenylpropane-1,2-dione on a supported Pt/Al2O3 catalyst. The chiral modifiers were prepared in good to moderate overall yields by Pt-catalyzed hydrosilylation of 9-O-TMS-protected cinchonidine with triethylsilane, triphenylsilane, bis(dimethylsilyl)ethane and (+)-(R)-methyl(1-naphthyl)phenylsilane followed by cleavage of the silyl ether protective group. Comparison of the synthesized modifiers in enantioselective hydrogenation using cinchonidine as reference modifier is reported, as well as details on their synthesis and characterization…

Competing Ring-Photoisomerization Pathways in the 1,2,4-Oxadiazole Series. An Unprecedented Ring-Degenerate Photoisomerization

2002

The irradiation of some 5-alkyl-3-amino-1,2,4-oxadiazoles at lambda = 254 nm in methanol in the presence of triethylamine (TEA) gave ring-photoisomerization both into 2-alkyl-5-amino-1,3,4-oxadiazoles and, unprecedently, into the ring-degenerate 3-alkyl-5-amino-1,2,4-oxadiazoles. The competing ring contraction-ring expansion route and the internal cyclization-isomerization mechanism explain the results.

Soil‐plant relationships, micronutrient contents, and cardenolide production in natural populations of Digitalis obscura

2004

The production of secondary metabolites by plants growing in natural populations is conditioned by environmental factors. In the present study, we have investigated the relationships among soil properties, micronutrients in soils and plants, and cardenolide production from wild Digitalis obscura (Scrophulariaceae) populations. Young and mature leaves and soil samples were collected in ten different populations, corresponding to three Mediterranean bioclimatic belts (Thermo-, Meso-, and Supramediterranean belts). Soil (total and EDTA-extractable) and leaf micronutrients (Fe, Mn, Zn, and Cu), and leaf cardenolide accumulation have been determined. Significant negative correlations were observ…