2-Pyridylmethyl formate

Directed ruthenium-catalyzed hydroesterifications of alkenes, employing 2-pyridylmethyl formate, leads to esters (Equation (136)). With vinyl ethers a-adducts are obtained (Equation (137)). 

RuCNC heterobi metal lie ruthenium/cobalt nanoparticle immobilized on charcoal. 2-Pyridylmethyl formate is used. 

The presence of catalytic amounts of halide salts (e.g. BU4NI) was found to enhance dramatically the efficiency of hydroesterification of alkenes (e.g. cyclohexenone) and alkynes catalysed by [(CO)i2Ru3] in the presence of the chelating 2-pyridylmethyl formate (2-C5H4NCH2OCHO). On the basis of IR and NMR studies, the halide effect... 

The neat Ru-catalyzed hydroesterification of 3,3-dimethyl-l-propene with 2-pyridylmethyl formates afforded exclusively a linear ester in 89% isolated yield using only 0.2 mol%... 

Very recently, a new strategy for the hydroesterification and hydroamidation of olefins was reported by Chang and coworkers [83]. They used a chelation-assisted protocol for the hydroesterification of olefins. The reaction of 2-pyridylmethyl formate with 1-hexene in the presence of a Ru3(CO)12 catalyst gave the hydroesterification product in 98% yield as a mixture of linear and branched isomers (Eq. 54). The chain length of the methylene tether is important for a successful reaction. Thus, the reaction of 2-pyridyl formate (n=0) afforded 2-hydroxypyridine, a decarbonylation product, and the reaction of 2-pyridiylethyl formate (n=2) resulted in a low conversion (7% conversion) of the starting formate. From these results, the formation of a six-membered ruthenacycle intermediate is crucial for this chelation-assisted hydroesterification. 

Bonds. 2-Pyridylmethyl formate is coupled with aryl and vinyl halides using a bimetallic system, Ru3(CO)i2 andPdCo (eq 18). C-H bond cleavage in the formate by the Ru3(CO)i2 complex, followed by a Pd-catalyzed coupling reaction of organic... 

Ruthenium catalysts for hydroesterification are also known, but these catalysts typically operate by the addition of formates, rather than by the use of the combination of CO and alcohol. Nevertheless, some leading citations to this literature are provided here. In some cases, milder conditions have been developed with pyridylmethyl formates (Equation 17.36). These substrates were designed so that the pyridyl group would bind to the catalyst. -The synthesis of amides from olefins, CO, and amines is much less developed, and the most active catalyst for this process and for the addition of for-mamides to olefins is simply Ru3(C0)jj. Ruthenium-catalyzed hydroesterification with pyridylmethylformates has been used to prepare the lactone fragment of an HIV inte-grase inhibitor shown in Scheme 17.17. 

S-Diphenyl-4-pyridylmethyl Thioether RSC(C6H5)2 -pyridyl Formation... 

The ligand 4,5-bis(di(2-pyridylmethyl)aminomethyl)imidazole has been utilized in the formation of Cu-Zn dinuclear complex [CuZnL(CH3CN)2](C104)3. The resonance Raman spectra of hydroperoxo intermediates were studied.117... 

Kinetics of formation of the dinuclear iron(III) complex [(tpa)Fe (p-0)(p-urea)Fe(tpa)]s+ tpa = tris(2-pyridylmethyl)amine were investigated in relation to the suggestion that urease action in vivo involves an intermediate containing Ni (p - O H) (p -ur e a) Ni. The mechanism of formation of the di-iron species from [(tpa)(H20)Fe(p-0)Fe(0H)(tpa)]3+ is proposed to involve three reversible steps (350). Three kinetically distinct steps are also involved in the deposition of FeO(OH) in... 

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... 

Another interesting reaction of sulfonylpyridines is with f-BuOK in CH2CI2, in which even a bulky alkoxide such as f-BuOK substitutes the sulfonyl group to give 2-r-butoxypyridine in substantial yield together with (6 -chloro-2 -pyridylmethyl)-6-chloro-2-pyridyl sulfone. The formation of this sulfone is accounted for by the initial formation of the sulfonyl carbanion which reacts further with the starting sulfone to afford the product [reaction (27)] (82UP2). This reaction also demonstrates that even a... 

Zhang C. X. Kaderli S. Costas M. KimE. -I. Neuhold Y. -M. Karlin K. D. Zuberbuhler A. D. Copper(I)-dioxygen reactivity of [(L)Cu(I)]( +) (L = tris(2-pyridylmethyl)amine) kinetic/thermodynamic and spectroscopic studies concerning the formation of Cu-02 and Cu2 02 adducts as a function of solvent medium and 4-pyridyl ligand substituent variations. Inorg. Chem. 2003, 42, 1807-1824. 

Ethoxycarbonyl moieties may be introduced at the benzylic position by reaction of pyridylmethyl anions with diethyl carbonate <1997S949> or ethyl chloroformate <2004BML1795>. Fries rearrangement of 0-(2-methylpyr-idyl)carbamates has been used to introduce an acetamide group to the benzylic position of 2-methylpyridines <1997SL839>. Treatment of O-pyridylmethylcarbamate 40 with 2.2equiv of LDA at —78 °C leads to the formation of pyridylacetamide 41 in 70% yield (Equation 30). 

There are currently four racemic PPIs available on the market omeprazole, lansoprazole, pantoprazole, and rabeprazole. (More recently, enantiomerically pure versions have also been studied and developed, e.g., S-omeprazole, marketed by AstraZeneca as esomeprazole see Chapter II-2.) Proton pump inhibitors share the same core structure, the substituted pyridylmethyl-sulfmyl-benzimidazole, but differ in terms of substituents on this core structure. The absolute requirements of the core structure for the activity of PPIs was not understood until it became clear that the active PPIs are derived from inactive prodrugs the prodrugs are transformed, in the acid-secreting parietal cells, by a unique cascade of chemical structural transformations leading to the active principle, a cyclic sulfenamide species. Inhibition of acid secretion in turn is then achieved by formation of covalent disulfide bonds with key cysteines of the (H+/K+)-ATPase. 

Nucleic acid selection methods have also been exploited for the development of novel RNA enzymes or ribozymes (58). An m-vitro-selected RNA that contains the modified nucleotide 5-(4-pyridylmethyl)-uridine (Table 1) can catalyze carbon-carbon bond formation in a Diels-Alder cycloaddition, with an 800-fold rate acceleration compared with a random RNA (49). Modified RNAs that contain the same uridine modification have also been selected to mediate metal-metal bond formation in the synthesis of palladium nanoparticles (59). Modified RNAs are likely to have many other applications as novel ribozymes that catalyze important biological reactions or can be used to create novel materials. 

A further refinement of this strategy has recently been shown by the self-assembly of the cage complex (25) formed from the reaction of three palladium(II) ions with l,3,5-tris(4-pyridylmethyl)benzene (24) [34]. A key feature of this process is the critical role played by aromatic guests (such as 4-methoxyphenylacetic acid) in templating the formation of (25). In the absence of guest, only ill-defined, oligomeric metal complexes are formed. 

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