Search results for "Base"

Aminosäureester als chirale Hilfsgruppen in Lewis-Säure-katalysierten Umsetzungen elektronenreicher Siloxydiene mit Iminen

1990

ChemInform Abstract: Reversal of Asymmetric Induction in Stereoselective Strecker Synthesis on Galactosyl Amine as the Chiral Matrix.

1989

Abstract The reversal of the direction of asymmetric induction in Lewis acid catalyzed Strecker synthesis using the 2,3,4,6-tetra-O-pivaloyl-β-D-galactopyranosyl amine 1 is described. In isopropanol or tetrahydrofuran 1 had given ( R )-diastereomers of the corresponding α-amino nitriles preferably. However, in chloroform in the presence of heterogeneous zinc chloride the same auxiliary alternatively leads to an excess of the ( S )-diastereomers.

Nickel as a Lewis Base in a T‐Shaped Nickel(0) Germylene Complex Incorporating a Flexible Bis(NHC) Ligand

2018

Flexible, chelating bis(NHC) ligand 2, able to accommodate both cis- and trans-coordination modes, was used to synthesize (2)Ni(η 2 -cod), 3. In reaction with GeCl2, this produced (2)NiGeCl2, 4, featuring a T-shaped Ni(0) and a pyramidal Ge center. Complex 4 could also be prepared from [(2)GeCl]Cl, 5, and Ni(cod)2, in a reaction that formally involved Ni-Ge transmetalation, followed by coordination of the extruded GeCl2 moiety to Ni. A computational analysis showed that 4 possesses considerable multiconfigurational character and the Ni→Ge bond is formed through σ-donation from the Ni 4s, 4p, and 3d orbitals to Ge. (NHC)2Ni(cod) complexes 9 and 10, as well as (NHC)2GeCl2 derivative 11, incor…

Excited State N−H Tautomer Selectivity in the Singlet Energy Transfer of a Zinc(II)-Porphyrin-Truxene-Corrole Assembly

2017

International audience; An original corrole-containing polyad for S-1 energy transfer, in which one zinc(II)-porphyrin donor is linked to two free-base corrole acceptors by a truxene linker, is reported. This polyad exhibits a rapid zinc(II)-porphyrin*free-base corrole transfer (4.83x10(10)s(-1); 298K), even faster than the tautomerization in the excited state processes taking advantage of the good electronic communication provided by the truxene bridge. Importantly, the energy transfer process shows approximately 3-fold selectivity for one corrole N-H tautomer over the other even at low temperature (77K). This selectivity is due to the difference in the J-integral being effective in both t…

The Aluminyl Anion : A New Generation of Aluminium Nucleophile

2020

Trivalent aluminium compounds are well known for their reactivity as Lewis acids/electrophiles, a feature that is exploited in many pharmaceutical, industrial and laboratory-based reactions. Recently, a series of isolable aluminium(I) anions ('aluminyls') have been reported, which offer an alternative to this textbook description: these reagents behave as aluminium nucleophiles. This minireview covers the synthesis, structure and reactivity of aluminyl species reported to date, together with their associated metal complexes. The frontier orbitals of each of these species have been investigated using a common methodology to allow for a like-for-like comparison of their electronic structure a…

A New pH-Dependent Macrocyclic Rhodamine B-Based Fluorescent Probe for Copper Detection in White Wine

2019

For efficiently measuring copper (II) ions in the acidic media of white wine, a new chemosensor based on rhodamine B coupled to a tetraazamacrocyclic ring (13aneN4CH2NH2) was designed and synthesized by a one-pot reaction using ethanol as a green solvent. The obtained chemosensor was characterized via NMR, UV and fluorescent spectra. It was marked with no color emission under neutral pH conditions, with a pink color emission under acidic conditions, and a magenta color emission under acidic conditions where copper (II) ions were present. The sensitivity towards copper (II) ions was tested and verified over Ca2+, Ag+, Zn2+, Mg2+, Co2+, Ni2+, Fe2+, Pb2+, Cd2+, Fe3+, and Mn2+, with a detection…

From needs to competencies : a case study on the integration of a rights based approach into NGO practises

2010

The objective of this qualitative case study is to provide knowledge on the possibilities of incorporating a rights based approach (RBA) into practises of non-governmental organisations (NGOs) in the context of development and children. The study is confined to examine the possibilities of RBA in realising children’s rights within the child sponsorship programme (CSP) of a Finnish NGO, Fida International (Fida), and the conceptualisation of the child in regard to different approaches. The theoretical framework is built on contemporary development discourse concerning the approximation of human rights and development as well as the underlying reasons for the emergence of RBA as a contributio…

¿Quién decide qué y cómo? el conflicto en torno a la participación ciudadana en el contexto del desarrollo de la iniciativa urbana: Cuenca-San Antón …

2018

This article describes the main results of an ethnographic study on citizen participation carried out in the context of the development of the Urban Initiative (2007-2015): Cuenca-Barrio de San Antón. Managed by the City Council of Cuenca and financed by the European Regional Development Funds (FEDER) under the Ministry of Economy and Finance at the Government of Spain The results of the research show how in the context of the application of neoliberal policies, citizen participation becomes the trigger for new conflicts between institutions and citizens. In this sense, it is worth noting how, in practice, institutions in their capacity as experts and not willing to dis-empower themselves, …

Miradas urbanas del profesorado iberoamericano desde la cultura visual

2018

We are interested in knowing if there is a proper view of the teaching staff towards the urban reality. We start with verbal and visual descriptions, through images and texts. The research has been developed in Santiago de Chile, Valencia, Lima, Medellin, Montevideo and Buenos Aires, and combines direct participatory actions with personal interviews. The methodology follows a mixed method and is based on a case study that is complemented by research based on the arts. We concluded that there is a particular view of the teaching group towards their own city, which is full of critical reflection. This is a topic that has been little addressed and needs more attention.

Impact of the knowledge society in the university and in scientific communication

2014

Over the last two decades, as a result of the introduction and intensive use of technologies for information and general knowledge, especially from the internet, the university is living in a process of complete transformation that affects it´s academic and organizational structures as well as the conception of educational methodology. The ICTs have demonstrated a need to establish coherent institutional strategies in their use and application, along with the possibility to expand the sphere of institutional action, in regards to general access to higher education. All of this shows an existing change from a model of education based on the transmission of knowledge, that was rather limited …