Search results for "Functional group"

Synthesis of all-syn Functionalized Triphenylene Ketals

2011

The stereoselective synthesis of triphenylene ketals offers access to unique scaffolds. For a good performance in supramolecular applications an all-syn orientation of the functional groups is essential. The oxidative trimerization of catechol ketals by molybdenum pentachloride or mixtures with titanium tetrachloride leads to a template-directed formation. Several heterocyclic moieties are suitable for this transformation. A template-directed isomerization of anti,anti,syn isomers to the desired C 3 -symmetric derivative was demonstrated in two cases.

A road less traveled to functional polymers: epoxide termination in living carbanionic polymer synthesis.

2010

Functional polymers possess tremendous potential both in academia and in industry. In particular, oxiranes offer manifold possibilities for the introduction of single hydroxyl or multiple orthogonal functionalities in carbanionic polymerization. Here, we present a brief overview of the fascinating possibilities arising from the employment of common as well as individually designed epoxide derivatives for the synthesis of end-functional polymers. Continuous flow techniques can be utilized for the rapid generation and screening of precisely defined hydroxyl-modified polymers. The utilization of functionalized polymers as precursors for the formation of complex macromolecular architectures (e.…

Mesoporous Materials Incorporating Metal Triflates

2016

Metal triflates attracted a large interest as catalysts in the past three decades especially due to the Lewis acid properties exhibited by these compounds and the variety of the functional group transformations. This chapter proposes an overview presenting the catalytic performances of triflates both as molecular compounds and as triflates dispersed in different solid matrices. In the first part the performances of molecular triflates in organic reactions carried out in the presence of water or water as solvent considering both water-sensitive and -insensitive metals are discussed. Then, the importance of materials incorporating triflates is demonstrated for catalysts obtained via immobiliz…

Fluorinated Pyrazoles and Indazoles

2014

The synthesis of fluorine containing pyrazoles has been boosted in the past decades due to the interesting properties that confer these building blocks in pharmaceutical and agricultural active ingredients. There are two main methods for the synthesis of fluorine-containing organic compounds, namely, the direct replacement of an atom or functional group such as diazo, hydroxyl, halogen or hydrogen by fluorine, and the modification of fluorine-containing building blocks. In the case of fluorinated pyrazoles the latter approach is the most commonly applied. This chapter deals primarily with the pivotal procedures that allow the preparation of fluoro- and fluoroalkyl- pyrazoles. Their benzocon…

Book Review: Organoselenium Chemistry I. Functional Group Transformations. By A. Krief and L. Hevesi

1989

ChemInform Abstract: Thioetherification of Chloroheteroarenes: A Binuclear Catalyst Promotes Wide Scope and High Functional-Group Tolerance.

2015

The nucleophilic substitution of a variety of chloro- and bromohetarenes with arylthiols is optimized to use [PdCl(allyl)]2 in combination with a ferrocenyltetraphosphane as ligand.

ChemInform Abstract: Amphiphilic Dyes for Nonlinear Optics: Dependence of Second Harmonic Generation on Functional Group Substitution.

2010

Organoselenum chemistry I. Functional Group Transformations. Von A. Krief und L. Hevesi. Springer, Berlin 1988. XI, 221 S., geb. DM 186.00. – ISBN 3-…

1988

Sūnu daudzveidība uz atmirušās koksnes egļu mežos saistībā ar koksnes vecumu un substrāta īpašībām

2015

Atmirusī koksne ir specifisks un dinamisks substrāts. Tā kalpo kā dzīves vide daudzām retām un tieši šim substrātam specifiskām sūnu sugām, kas norāda uz nepieciešamību veikt detalizētus pētījumus par atmirušo koksni kā sūnām nozīmīgu substrātu. Pētījumā salīdzināts sūnu sugu un funkcionālo grupu sastāvs uz dažādiem atmirušās koksnes veidiem (kritalām, stumbeņiem, sausokņiem), analizēta sūnu sugu un funkcionālo grupu bagātība saistībā ar atmirušās koksnes vecumu un substrāta parametriem (izmēri, sadalīšanās pakāpe). Kopumā uz visiem atmirušās koksnes veidiem konstatētas 53 sūnu sugas (40 lapu un 13 aknu sūnas). Novērotas atšķirības sūnu sugu sastāvā starp kritalām un stāvošu atmirušo koksni…

Study of the role of sulfur functionalities in humic acids for uranium(VI) complexation

2009

Humic substances influence the speciation and migration behavior of toxic and radiotoxic metal ions, such as actinides, in the environment. Depending on their origin, humic substances contain different amounts of sulfur ranging from 0.1 to 3.6% and 0.5 to 1.43% in soil and aquatic humic substances, respectively [1]. Reduced, intermediately oxidized and highly oxidized sulfur functionalities occur in humic substances [1]. Although sulfur functionalities occur in small concentrations, they can play an important role in the complexation of selected metal ions. Knowledge about the impact of sulfur functionalities on the metal ion complexation by humic substances and their significance compared …