Search results for "Condensation"

ChemInform Abstract: Cross-Metathesis Reactions as an Efficient Tool in the Synthesis of Fluorinated Cyclic β-Amino Acids.

2009

The synthesis of enantiomerically pure, cyclic, gamma,gamma-difluorinated beta-amino acids with various ring sizes has been carried out with a cross-metathesis (CM) reaction being one of the key steps, followed by a Dieckmann-type condensation to bring about the cyclization. Subsequent catalytic hydrogenation under microwave irradiation with (-)-8-phenylmenthol as a chiral auxiliary led to the successful chemo- and diastereoselective chemical reduction of the resulting cyclic beta-enamino esters. The efficiency and scope of the CM reaction with different types of fluorinated imidoyl chlorides and unsaturated esters has also been studied in order to determine the optimal reaction conditions …

1990

The anionic polymerization of tert-butyl acylate (tBuA) initiated by tert-butyl α-lithioisobutyrate was investigated in THF at 25°C. The individual oligomers were isolated and characterized by UV, IR and NMR spectroscopy. The distribution of products was determined in the range of reaction times 0,02 s ≤ t ≤ 1800 s. The oligomerization is extremely fast. Even after 0,02 s at -30°C, no residual monomer could be detected. After short reaction times the reaction mixture almost exclusively consists of linear oligomers of tBuA. This indicates that there is no termination reaction by Claisen condensation during polymerization. Nevertheless, the molecular weight distribution is rather broad (Mw/Mn…

A DFT study of IRMOF-3 catalysed Knoevenagel condensation

2011

It has been recently reported that IRMOF-3 [Gascon et al., J. Catal, 2009, 261, 75] may behave as a basic catalyst, active in the Knoevenagel condensation. In particular, it has been shown that the basicity of aniline-like amino moieties is enhanced, along with the catalytic activity, when incorporated into MOF structures. The computational study here was aimed at finding possible atomistic explanations of the increased basicity and catalytic activity of the IRMOF-3 embedded aniline groups, experimentally claimed. It was, moreover, aimed at guessing a reaction mechanism for the IRMOF-3 catalysed Knoevenagel condensation of benzaldehyde and ethyl-cyanoacetate. Within the DFT framework we hav…

Analysis of Specific Protein-DNA Interactions

1998

The central issue in the regulation of genome functions is the mechanism of sequence-specific protein-nucleic acid interactions. Gene expression, replication, recombination and DNA condensation in chromatin are steered by binding of regulatory protein ligands to specific sites in DNA. Numerous methods have been developed to study protein-DNA interactions. In this chapter we discuss two widely used and straightforward approaches to address this problem.

ChemInform Abstract: Synthesis of Fluorinated and Non-Fluorinated Bicyclic Amidines Through Ring-Closing Metathesis.

2012

Condensation of unsaturated esters (I) and (VII) with 1,2-diamines proceeds in the presence of trimethylaluminum providing imidazolines (III) and (VIII) which are further allylated giving suitable dienes (V) and (IX).

In vitro istraživanje apikalnog mikropropuštanja pet tehnika punjenja kanala

2014

Aim A comparison was made between the root canal lateral condensation technique and other condensation techniques in which physical (temperature: Soft-Core®, Obtura II®) or chemical changes (condensation: Guttaflow®, Resilon®) may affect the dimensional stability of obturation and thus favor apical microleakage. Materials and methods A total of 212 single-root teeth removed for orthodontic or periodontal reasons were randomized to 5 groups of 40 teeth each. Six samples were used as positive controls, and another 6 as negative controls. The teeth were worked with the Hero 642 system, and each group was obturated using a different technique: lateral condensation, Obtura II®, Soft-Core®, Gutta…

A rare case of solution and solid state inter-conversion of two copper(II) dimers and a copper(II) chain

2011

Abstract Three Cu(II)-azido complexes of formula [Cu2L2(N3)2] (1), [Cu2L2(N3)2]·H2O (2) and [CuL(N3)]n (3) have been synthesized using the same tridentate Schiff base ligand HL (2-[(3-methylaminopropylimino)-methyl]-phenol), the condensation product of N-methyl-1,3-propanediamine and salicyldehyde). Compounds 1 and 2 are basal-apical μ-1,1 double azido bridged dimers. The dimeric structure of 1 is centrosymmetric but that of 2 is non-centrommetric. Compound 3 is a μ-1,1 single azido bridged 1D chain. The three complexes interconvert in solution and can be obtained in pure form by carefully controlling the synthetic conditions. Compound 2 undergoes an irreversible transformation to 1 upon de…

Homo- and heterometallic complexes constructed from hexafluoroacetylacetonato and Schiff-base complexes as building-blocks

2018

Three new homo- and heterotrimetallic complexes have been synthesized and crystallographically characterized: [Cu2(saldmpn)2(μ-OCH3)2Cu2(hfac)2] (1), [Ni2(valaepy)2(hfac)2] (2), [Cu(saldmpn)Co(hfac)2] (3) [H2saldmpn is the Schiff-base resulting from condensation of salicylaldehyde with 2,2-dimethyl-1,3-diaminopropane and Hvalaepy results from the reaction of o-vanillin with 2-(2-aminoethyl)pyridine)]. The structure of 1 consists of a neutral tetranuclear species that can be viewed as resulting from mutual coordination of one {(hfac)Cu(μ-OCH3)2(Cu(hfac)} and two {Cu(saldmpn)} building blocks. Compound 2 is a binuclear complex that results from two {Ni(hfac)(valaepy} fragments, the nickel(II)…

Quantitative estimation of the antiferromagnetic interaction between Cu(II) and Sm(III) in two dimensional heterometallic coordination polymer with i…

2013

Abstract The syntheses, structure and magnetic property of a novel two dimensional 3d–4f coordination polymer 2∞[CuSmL(NO3)2(IN)], 1 (L2−  = N, N′- propylenedi (3-ehoxysalicylideneiminato), the dianion of the Schiff base obtained from the 2:1 condensation of 3-ethoxysalicylaldehyde with 1,3-propanediamine, IN− = the isonicotinate ion) has been reported. The heterobinuclear units are connected through exo-bidentate ligands IN−, leading to an extended 2D structure. A fit of the magnetic susceptibility data yields gCu = 2.109, gSm = 0.476, JCuSm = − 0.893 cm− 1, θ = − 3.37 K, and TIP = 0.001257 emu K mol− 1 with a good discrepancy factor of Rχ = 4.4 × 10− 5. This is the first quantitative esti…

Multi Stage Flash Desalination with Direct Mixing Condensation

2011

Multi Stage Flash desalination technology has been a leading technology in the desalination market for the last four decades. However as a result of the continuous increase of costs for the special materials required for the tube bundles the share of MSF technology in the market is nowadays steadily shrinking. Aim of the present work is to present a novel configuration for the MSF process. In the proposed arrangement evaporation occurs in a multi stage vertical column filled with packing material to enhance the achievement of flashing equilibrium in each stage, while condensation occurs in a second column through direct mixing with a colder water stream. Thermal integration for the recovery…