Pyridines with phosphonate substituents

Pyridines with phosphonate substituents are valuable for medicinal chemistry or iV,P-bisdentate ligands (Scheme 46) (13JA9322).Thus, a C-H phosphorylation process was developed where the heterocycle directs ortho-palladation. This intermediate can be intercepted by H-phosphonates and diaryl phosphine oxides to provide phosphonate-substituted pyridines. 

A new one-pot method has been developed by Kraszewski for the synthesis of aryl nucleoside phosphate (3a-p) and phosphorothioate (4a-p) diesters. This method, based on H-phosphonate chemistry, employed diphenyl phosphoroch-loridate and a series of phenols. Depending on the substituents present on the phenols, oxidation conditions were optimized to avoid competing hydrolysis. A versatile procedure that permits easy access to H-phosphonoselenoate monoesters (5) has been developed by Stawinski. These monoesters, obtained by selenisation of a phosphinate using triphenylphosphine selenide in combination with trimethylsilyl chloride, reacted with a suitable nucleoside in pyridine/acetonitrile in the presence of diphenyl phosphorochloridate to yield... 

Kinetic studies of the reaction between dialkyl H-phosphonates and hydrochlorides of diethylamine and pyridine indicate that this reaction is a second-order bimolecular nucle-ophihc substitution [308], The reaction rate depends on the type of alkyl substituents of the H-phosphonate diester as well as on the basicity of the amine. The low reaction rate observed for dibutyl H-phosphonate and the absence of reaction with diisopropyl H-phosphonate is not solely associated with the inductive effect of the alkyl substituents on the a-carbon atom but is also due to steric effects, which is especially apparent in the case of diisopropyl H-phosphonate. 

Pyridine derivatives having phosphonate group substituents in para or ortho positions with respect to the nitrogen atom are used as corrosion inhibitors [134,135], These compounds effectively protect metal surfaces against the action of air humidity, soil humidity, and water, water steam, hot water, weak inorganic acids, organic acids, COj, H2S, and others. 

Phosphonate ester or phosphonic acid substituents have been additionally evaluated in an attempt to increase the interacting sites with the phosphoric acid doping agent along the polyelectrolyte macromolecular chains. These were strategically located as side groups in a diol monomer which was prepared by a phosphoms-carbon coupling reaction of tetrahydropyranyloxy diprotected 2,5-dibromo-1,4-dihydroxy benzene with diethylphosphite. Either in the phosphonate ester or in the phosphonic acid form the diol was used in polymerizations with the bis (4-fluorophenyl) sulfone or bis(4-fluorophenyl) phenylphosphinoxide as well as with the 2,5-diphenyl-pyridine diol and the tetramethyl-... 

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