Phosphonates dimeric

Diethyl diazomethanephosphonate added slowly via syringe pump to a well-stirred soln. of cyclopentene (in excess to prevent formation of phosphonate dimer) and Cu(I)-trifluoromethanesulfonate in methylene chloride at 4-8° - product. Y 62%. The procedure is incompatible with acetal, aldehydic and siloxy functionality as well as alkyl chloride. F.e. and conversion to alkylidenecyclopropanes s. R.T. Lewis, W.B. Motherwell, Tetrahedron Letters 29, 5033-6 (1988). 

Dinucleoside H-phosphonate dimers have been used as intermediates for the synthesis of phosphorothioates (10), phosphoramidates (10), phosphate triesters (10), and methyl phosphonates (15) (Fig. 3). This method has been extended to the synthesis of polynucleoside phosphorothioates (7,12,13) and phosphoramidates (7,10,11,16). Much of this chapter is devoted to the coupling and the oxidation reactions. The coupling step is very sensitive to overactivation by acyl chlorides, and thus, precautions must be taken to avoid the consequent side reactions. The oxidation reaction is important because of the fact that all linkages are oxidized at once, and care must be taken at this step to ensure complete oxidation, yet prevent the alkaline hydrolysis of the backbone. Often, poor quality of synthetic oligodeoxynucleotide is the result of hydrolysis of the backbone or incomplete oxidation, not inadequate chain elongation. 

Jager, A., Charubala, R, and Pfieiderer, W (1987) Synthesis and characterization of deoxy- and ribo H-phosphonate dimers Nucleic Acid Symp. Ser. 18,197-200. 

Acryhc esters dimerize to give the 2-methylene glutaric acid esters catalyzed by tertiary organic phosphines (37) or organic phosphorous triamides, phosphonous diamides, or phosphinous amides (38). Yields of 75—80% dimer, together with 15—20% trimer, are obtained. Reaction conditions can be varied to obtain high yields of trimer, tetramer, and other polymers. 

The dimer of phosphonic acid, diphosphonic acid [36465-90-4] (pyrophosphoms acid), H4P2O3, is formed by the reaction of phosphoms trichloride and phosphonic acid in the ratio of 1 5. It is also formed by the thermal decomposition of phosphonic acid. Unlike the chemistry of phosphoric acid, thermal dehydration does not lead to polymers beyond the dimer extended dehydration leads to a disproportionation to condensed forms of phosphoric acid, such as [2466-09-3] and phosphine. 

Trimethylsilyl esters of tris(thio)phosphonic acids 2070 are readily oxidized by DMSO in toluene at -30 °C to give the dimeric tetra(thia)diaphosphorinanes 2071 and HMDSO 7 [208] (cf. also the oxidation of silylated thiophenol via 2055 to diphenyl disulfide). The polymeric Se02 is depolymerized and activated by reaction with trimethylsilyl polyphosphate 195 to give the corresponding modified polymer... 

The acid strengths of a series of phosphonic acid derivatives in a variety of solvents have also been used to estimate Hammett constants. In contrast to carboxylic acids, the phosphonic acids are stronger in ketonic solvents than in hydroxylic solvents, which may be attributed to the dissociation of phosphonic acids without the necessity to disrupt the dimeric nature of the acid (see Scheme 3). 

Gonzales, L., Mo, O., Yafiez, M., Elguerdo, J., 1998b, Very Strong Hydrogen Bonds in Neutral Molecules The Phosphonic Acid Dimers , J. Chem. Phys., 109, 2685. 

Incorporation of a flavin electron donor and a thymine dimer acceptor into DNA double strands was achieved as depicted in Scheme 5 using a complex phosphoramidite/H-phosphonate/phosphoramidite DNA synthesis protocol. For the preparation of a flavin-base, which fits well into a DNA double strand structure, riboflavin was reacted with benzaldehyde-dimethylacetale to rigidify the ribityl-chain as a part of a 1,3-dioxane substructure [49]. The benzacetal-protected flavin was finally converted into the 5 -dimethoxytri-tyl-protected-3 -H-phosphonate ready for the incorporation into DNA using machine assisted DNA synthesis (Scheme 5a). For the cyclobutane pyrimidine dimer acceptor, a formacetal-linked thymine dimer phosphoramidite was prepared, which was found to be accessible in large quantities [50]. Both the flavin base and the formacetal-linked thymidine dimer, were finally incorporated into DNA strands like 7-12 (Scheme 5c). As depicted in... 

Scheme 5 a Flavin-H-phosphonate and formacetal-linked thymine dimer phospho-ramidite used for the synthesis of the flavin and dimer containing DNA-strands 7-12. b Representation of a reduced flavin- and formacetal-linked cyclobutane pyrimidine dimer containing DNA strand, which upon irradiation (hv) and electron transfer (ET) performs a cycloreversion (CR) of the dimer unit, c Depiction of the investigated oligonucleotides... 

The perylene chromophotes were modified by covalently attaching different side groups. Two bulky groups (tertiary-butyl), indicated by a prime, prevented dimerization of neighbouring perylene chromophores when attached to the surface. Linkage to the semiconductor was achieved by different anchor-cum-spacer groups carbonic acid (-COOH) [4], propionic acid (-CH2-CH2-COOH) [2], phosphonic acid (-P(0)(OH)2) [4], methyl-phosphonic acid (-CH2-PO(OH)2) [2] and a -Tripod (see inset in Fig.2) [5], The preparation and sensitization of the nano-structured TiC>2 film and further experimental details have been described before [2]. 

The first account on the carbonylation of heterocyclic compounds with metallo-dendrimers was recently reported by Lu and Alper using Rh-complexed dendrimers on a resin [207]. The building-block techniques of solid-phase chemistry were used to synthesize dendrimers, followed by phosphonation of the dendrimers with diphenylphosphinomethanol. The resulting phosphonated dendrimers were then reacted with chloro(dicarbonyl)rhodium(I) dimer to give dendritic catalysts A and B (31P NMR, 8 - 25 ppm loading of rhodium A, 0.74 mmol g-1 B, 0.83 mmol g ). As a model study, the reaction of l-ferf-butyl-2-phenylaziridine with carbon monoxide in catalytic presence of A afforded the desired [3-lactam... 

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