Pyridine template

A chlorine atom could also coordinate to the nitrogen of the pyridine template in compound 95, directing chlorination to C-9 in a radical relay process [168]. Spectro-... 

Scheme 6-7 Radical relay functionalization with a triply tethered template and with a tethered pyridine template.

In the presence of a homogeneous high-molecular-weight poly(2-vinyl-pyridine) template, the free-radical copolymerization of styrene and... 

Other indications of the template effect have been offered as well. Fenton, Cook and Nowell reported that the condensation of pyridine-2,6-dicarbaldehyde with 1,11-diamino-3,6,9-trioxaundecane in 1 1 molar ratio in butanol leads only to resinous gums . In the presence of equimolar amounts of Pb(SCN)2, the macrocycle illustrated in Eq. (2.5) was obtained in good yield . 

The incorporation of an ionizable center, such as an amine or similar function, into a template can bring a number of benefits, including water solubility. A key step in the discovery of the protease inhibitor, indinavir was the incorporation of a basic amine (and a pyridine) into the backbone of hydroxyethylene transition state mimic compounds L-685,434 to enhance solubility (and potency) (Fig. 1.2) [17]. 

The Mn" complex of the potentially quinquedentate Schiff-base ligand (12) derived from two molecules of pyridine-2-carboxaldehyde and one molecule of l,l,l-tris(aminoethyl)ethane has been isolated by means of a template... 

Mixed donor ligands. The complex [FeL3]Cl3 (L = acetylhydrazine) contains the ligand in its bidentate form, bonded via the carbonyl and primary amino-groups.Pyridine-2-carboxaldehyde and l,l,l-tris(aminoethyl)ethane react with Fe" via a template reaction to form [Fejlpyljltame) ], in which three molecules of carboxaldehyde have condensed with one molecule of triamine to produce (pyljltame). MeC(CH2N=CH-oc-py)3 the complex cation is octahedral. The complexes [FeL ] (L = l,10-phenanthroline-2-carboxamide, n = 1 or 2) have been isolated they are both six-co-ordinate. Very weak d-d bands have been identified in the spectra of complexes of ot-picolinic acid and quinaldic acid with Fe". ... 

Reactions of carbonyl compounds such as pyridine 2-carboxaldehyde, glyoxal, biacetyl, or benzil with 2-aminothiophenol on an Fe + template give benzothiazolinate (198) complexes. The complex from pyridine 2-carboxaldehyde, for example, was formulated, on the basis of NMR and Mossbauer spectroscopy and of analysis (C, H, N, and Fe) as the bis-(A,iS)-ligand-bis-aqua complexes of (199), an isomeric form in equilibrium with (198). However as they are diamagnetic it seems more likely that they are [Fe(199)2] 2H20, containing terdentate (N,N,S) (199), than the proposed [Fe(199)2(H20)2]. 

Attaching cyclic, bidentate 1-hydroxy-177-pyridin-2-thione, 1-hydroxy-177-pyridin-2-one (1,2-HOPO) and 2-hydroxy-277-isoquinolin-l-one (1,2-HOIQO) ligating units via their C-6 carbon to TREN template produced 19 , 20 and 21 , respectively. 

Because template polycondensation is not very well studied at present/ general mechanism is difficult to present. Two main types of polycondensation are well known in the case of conventional polycondensation. They are heteropolycondensation and homopolycondensation. In the heteropolycondensation two different monomers take part in the reaction (e.g., dicarboxylic acid and diamine). In the case of homopolycondensation, one type of monomer molecule is present in the reacting system (e.g., aminoacid). The results published on the template heteropolycondensation indicate that monomer (dicarboxylic acid) is incorporated into a structure of the matrix (prepared from N-phosphonium salt of poly-4-vinyl pyridine) and then the second monomer (diamine) can react with so activated molecules of the first monomer. The mechanism can be represented as in Figure 2.2. 

Spontaneous polymerization of 4-vinyl pyridine in the presence of polyacids was one of the earliest cases of template polymerization studied. Vinyl pyridine polymerizes without an additional initiator in the presence of both low molecular weight acids and polyacids such as poly(acrylic acid), poly(methacrylic acid), polyCvinyl phosphonic acid), or poly(styrene sulfonic acid). The polyacids, in comparison with low molecular weight acids, support much higher initial rates of polymerization and lead to different kinetic equations. The authors suggested that the reaction was initiated by zwitterions. The chain reaction mechanism includes anion addition to activated double bonds of quaternary salt molecules of 4-vinylpyridine, then propagation in the activated center, and termination of the growing center by protonization. The proposed structure of the product, obtained in the case of poly(acrylic acid), used as a template is ... 

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