Pyridines functionalized

The coordination chemistry of ancillary amidinate ligands with a pyridine functionality has been described. Magnesium, aluminum, zirconium, and lanthanum complexes have been prepared in which the amidinate anions act as tridentate, six-electron-donor ligands Amidinate ligands containing quinolyl substituents were constructed in the coordination sphere of lanthanide... 

Fig. 19. A pyridine-functionalized porphyrin that can be photoswitched between a trivial open polymer and a cooperative closed dimer.

Fig. 30. A trivial open polymer assembled from pyridine-functionalized porphyrins.

Kinetic Studies. The pioneering work of Hierl et al. (8) and Delaney et al. (9) had established that hydrolysis of jr-nitro-phenylcarboxylates was an excellent means of observing the nucleophilic catalysis by 4-(dialkylamino) pyridine functionalized polymers. Hydrolysis of p-nitrophenylacetate in a buffer at pH 8.5 showed that the polymer was a slightly better catalyst than the monomeric analog PPY (Table II). However, preliminary results indicate that the polymer bound 4-(dialkylamino) pyridine is more effective as a catalyst than the monomeric analog in the hydrolysis of longer carbon chain p-nitrophenylcarboxylates, such as p-nitrophenylcaproate. 

A tripodal ligand (tpmetame) based on l,l,l-tris(aminomethyl)-ethane substituted by three pyridine functions has recently been prepared [26] (21). 

Other examples of pyridine functionalization reactions have been published, which are mediated by polynuclear metallic species (Equations (79) and (80)).75,75a... 

This alkylation reaction can be applied to intramolecular alkylation affording cyclic products, as shown in Equations (19)-(21). The reaction of 2-vinylpyridines with 1,5- or 1,6-dienes results in the formation of five- or six-membered carbocycles with good efficiency.20,20a,20b In addition to pyridine functionality, oxozole and imidazole rings can be applied to this intramolecular cyclization. When the reaction is conducted in the presence of a monodentate chiral ferrocenylphosphine and [RhCl(coe)2]2, enantiomerically enriched carbocycles are obtained. A similar type of intramolecular cyclization is applied to TV-heterocycles. The microwave irradiation strongly... 

One of the first examples of this type of blend was composed of SPEEK or SPES as the acidic component and diaminated PES, poly(4-vinylpyridine) (P4VP), poly(benzimidazole) (PBl), or poly(ethyleneimine) (PEI) as the basic component. " For blend lEC values of 1.0 meq/g, conductivity values were reported to be good, as was H2/O2 EC performance. Thermal stabilities for these blends was also demonstrated to be high (>270°C). Other examples of acid-base PEMs include blends of SPPO and PBI, sulfonated poly(phthalazinone ether ketone) and aminated SPES, SPIs and aminated Pls, and SPEEK with PES bearing benzimidazole side groups, ° as well as an unusual example in which the blend is composed of sulfonated, hyper-branched polyether and pyridine-functionalized polysulfone. ... 

Ion-exchange reactions were used for the accumulation of europium(III) [158] and iron(III) [159] ions on the surface of GCE coated with Nafion , and chromium(VI) ions on the surface of GCE covered by a pyridine-functionalized sol-gel film [160], which were combined with the stripping SWV Furthermore, a cathodic stripping SWV was used for the determination of sulfide [161,162], thiols [163-166], selenium(lV) [167-170], halides [171-173] and arsenic [174] accumulated on the snrface of mercury electrode. 

Pyridine-functionalized N-heterocyclic carbene Rh and Ir complexes have also been described as active precatalysts for C=0 bond TH. For example, Peris and coworkers observed the formation of metal hydrides by C—H oxidative addition of a pyridine-N-substituted imidazolium salt such as N-"Bu-N -(2-pyridylmethyl-imidazolium) hexafluorophosphate in the reaction leading to M-pyNHC complexes, that is [lr(cod)H(pyNHC)Cl] (58) [54]. Transmetallation from silver carbene... 

Triethylamine in THF can be used as the external base to deprotonate triazolium salts. The resulting NHCs were complexed in situ, e.g., to [(/7 -cymene)RuCl2]2, [(/ -cod)RhCl]2, and [(/ -C5Me5)RhCl2]2. Sodium carbonate in water/ DMSO deprotonates imidazolium iodides in the presence of mercury(II) dichloride to give [Hg(NHC)2][Hgl3Cl]. " A pyridine-functionalized imidazolium salt was deprotonated by lithium diisopropylamide (LDA) in THF and attached in situ to [(p -cod)Pd(Me)Br] [Eq.(17)]. After abstraction of the bromide anion with silver(I) a tetranuclear ring is formed. 

Additional types of k C-k E chelating ylide complexes merit mentioning here, in addition to the species already presented, and some of them are shown in Scheme 24. The first is formed by ylides containing a pyridine functionality as substituent of the ylidic carbon. This type of ligand has allowed the S3mthesis of many loose clusters (82) of Cu, Ag, and Au which show weak metal( / °)-metal( / °) interactions. These facts have prompted the definition of a new phenomenon numismophilicity) to account for these weak interactions, uniquely shared by the three coinage metals [164]. Nitrogen and sulfur keto-stabilized ylides have been reacted with Pt and... 

B-80MI20501 Pyridine Functionality in Polymer Form , Reilly Tar and Chemical Corp.,... 

When furan was substituted at C-2 by a pyridine function [e.g., 4 -(2, 6 -dimethyl)pyridyl] high yields (>90%) of the 5-bromo derivatives were... 

The intramolecular C-H insertion reaction of phenyldiazoacetates on cyclohexadiene, utilizing the catalyst Rh2(S-DOSP)4, leads to the asymmetric synthesis of diarylacetates (Scheme 8). Utilizing the phenyl di azoacetate 38 and cyclohexadiene, the C-H insertion product 39 was produced in 59% yield and 99% ee. Oxidative aromatization of 39 with DDQ followed by catalytic hydrogenation gave the diarylester 40 in 96% ee. Ester hydrolysis followed by intramolecular Friedel-Crafts gave the tetralone 31 (96% ee) and represents a formal synthesis of sertraline (5). Later studies utilized the catalyst on a pyridine functionalized highly cross-linked polystyrene resin. ... 

A quantitative assessment of the effects of head group bulk on Sn2 and E2 reactions in cationic micelles has been made.148 The kinetics of the acid-catalysed hydrolysis of methyl acetate in the presence of cationic, anionic, and non-ionic surfactants has been reported on.149 The alkaline hydrolysis of -butyl acetate with cetyltrimethylammonium bromide has also been investigated.150 The alkaline hydrolysis of aromatic and aliphatic ethyl esters in anionic and non-ionic surfactants has been studied.151 Specific salting-in effects that lead to striking substrate selectivity were observed for the hydrolysis of />-nitrophenyl alkanoates (185 n = 2-16) catalysed by the 4-(dialkylamino)pyridine-functionalized polymer (186) in aqueous Tris buffer solution at pH 8 and 30 °C. The formation of a reactive catalyst-substrate complex, (185)-(186), seems to be promoted by the presence of tris(hydroxymethyl)methylammonium ion.152... 

In Table 1, the diimine ligands were either 2,2/-bipyridine or 1,10-phenanthroline, or one of their derivatives, although 2,2,-bipyrazinc and derivatives of 2,2 -bipyrimidine are also listed. Some monodentate chelating ligands contained one or more pyridine functionality and could bind an... 

Atazanavir 87, a 2-arylsubstituted pyridine derivative, is used as an antiviral AIDS drug <1998USP5849911>. Nelfinavir mesilate 88 has found use as an antiviral agent <1994DDR1043>. Potential drugs for HIV inhibition that contain pyridine functionalities are Sch-C 89 and Sch-D 90 <2003MI30>. 

Exploiting the same concept, Reinhoudt and Shinkai were able to obtain another example of enantioenriched chiral double-rosette made of achiral components. In this case achiral calix[4]arene bearing dimelamine moieties with pyridine functionalities were assembled with achiral cyanurate leading to racemic chiral double rosettes. The latter are perfect counterparts for chiral D-dibenzoyl tartaric acid via two-point hydrogen-bonding interactions thus... 

Better catalytic behavior was observed in the copolymerization of CO and norbornadiene with palladium complexes containing a hemilabile pyridyl-carbene ligand [23]. The choice of a pyridine-functionalized carbene can be explained by the fact that the hemilabile arm in such a ligand is capable of reversible dissociation from the metal center, leading to vacant coordination sites for the complexation of the substrates while the strong donor moiety remains bound to the metal. 

The pyridine functionality can also be part of a more structurally complex molecule. Oftentimes, pyridines serve as the starting materials for the preparation of fused or annulated target molecules <02TL1093, 02SL155,02H21>. Other transformations such as the Diels-Alder... 

In this area, recent unrelated efforts of the groups of Bhattacharya and Fife toward the development of new aggregate and polymer-based DAAP catalysts deserve mention. Bhattacharya and Snehalatha [22] report the micellar catalysis in mixtures of cetyl trimethyl ammonium bromide (CTAB) with synthetic anionic, cationic, nonionic, and zwitterionic 4,4 -(dialkylamino)pyridine functional surfactant systems, lb-c and 2a-b. Mixed micelles of these functional surfactants in CTAB effectively catalyze cleavage of various alkanoate and phosphotriester substrates. Interestingly these catalysts also conform to the Michaelis-Menten model often used to characterize the efficiency of natural enzymes. These systems also demonstrate superior catalytic activity as compared to the ones previously developed by Katritzky and co-workers (3 and 4). 

Introduction of a bulky pyridyl ligand again results in a reduced ligating ability of the pyridine functionality [41], which this time could be visualised using the rhodium(I) cod complexes instead of the palladium allyl ones (see Figure 3.5). 

The solid-state structure of (12) reveals that it consists of a planar, rhomboidal molecule with N-Pd-N angle of 84° and a C-l-C comer angle of 99°. Bis-pyridine ligands can be varied in numerous ways to yield a variety of diverse stractures these include macrocycles containing bis-pyridine functionalized Ceo molecules (13) and the bis-pyridine incorporated porphyrin compound (14). ... 

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