Condensed phosphoric acids synthesis

Tlie condensation of nitromalonic aldehyde (26) with 2,6-diaminopyridine (27) in the presence of phosphoric acid, affording 2-amino-6-nitro-l,8-naphthyridine (28,37%) (77TL2087), is another example of a successful application of a nitro aliphatic compound in the synthesis of nitronaphthy-ridines. 

The condensation reactions are preferentially carried out in pyridine. As reactive species for phosphorylation of the nucleoside R OH (synthesis of a phosphortriester), the phosphoric acid azolide has been assumed. The mixed phosphoric sulfonic anhydride and a pyrophosphate tetraester have been suggested as intermediates leading to the phosphoric acid azolide. 

Ordered mesoporous materials of compositions other than silica or silica-alumina are also accessible. Employing the micelle templating route, several oxidic mesostructures have been made. Unfortunately, the pores of many such materials collapse upon template removal by calcination. The oxides in the pore walls are often not very well condensed or suffer from reciystallization of the oxides. In some cases, even changes of the oxidation state of the metals may play a role. Stabilization of the pore walls in post-synthesis results in a material that is rather stable toward calcination. By post-synthetic treatment with phosphoric acid, stable alumina, titania, and zirconia mesophases were obtained (see [27] and references therein). The phosphoric acid results in further condensation of the pore walls and the materials can be calcined with preservation of the pore system. Not only mesoporous oxidic materials but also phosphates, sulfides, and selenides can be obtained by surfactant templating. These materials have pore systems similar to OMS materials. 

Weber [61,62] has developed in the context of prebiotic chemistry an original pathway for a-aminothioester synthesis [180], which can start from hydroxyaldehydes 30 intermediates in the formose reaction (a likely prebiotic pathway to carbohydrates). Obviously, thioesters themselves are not observed as products because of their fast hydrolysis in the medium, but they could be converted into peptide bonds in the presence of amino acids or peptide free amino groups, and into mixed anhydride with phosphoric acid in the presence of inorganic phosphate. The reaction involves two key-steps the condensation of ammonia and of the mercaptan on a-keto aldehyde 31... 

Production of alumina aquosols from alumina has been well researched in sol-gel science [19]. Yoldas [20] was the first one to show that monolithic alumina gels could be formed by hydrolysis and condensation of aluminum alkoxide. As discussed in Chapter 5, formation of aquosols and their gel is an intermediate step in the formation of chemically bonded phosphate ceramics. Condensation of the hydrated alumina sols by reaction with phosphoric acid to form A1(H2P04)3-H20 gel is the first step toward synthesis of a berlinite-bonded alumina ceramic. When this gel is heated to 150°C, this gel reacts with additional alumina and releases water, and crystalline berlinite is produced. This Chapter... 

In addition to the orthophosphates, other rare earth phosphates could also be obtained through hydrothermal routes. Tang et al. reported the synthesis of so-called CeP (with a composition of Ce(FIP04)2" H2O) nanotubes (Tang et al., 2005c). Concentrated phosphoric acid solution of 6 M was heated to a temperature ranging from 50 to 110 °C to form a condensed lirrear polyphosphate (P 03 +i) +2 Then, the (NH4)2Ce(N03)e solution is... 

Using the Birth modification (57) of the Cranwell-Saxton (55) methodology, Narasimhan and Dhavale (97) have described a synthesis of 6-methyl-11-de-methylellipticine (171) (Scheme 29). Carbazole aldehyde 167 underwent the usual condensation to give imine 168. Direct cyclization of 168 with phosphoric acid gave a mixture of 171 and 172, although only the former could be obtained in pure form (by repeated crystallization). However, reduction of 168 to 169, followed by tosylation and cyclization, gave 171 exclusively. 

While many phenanthrolines are available from commercial suppliers, the synthesis of this ligand from its various precursors is often necessary in the preparation of more elaborate structures. The earliest syntheses of (1) proceeded by dual Skraup condensation about o-phenylenediamine, in a single-pot reaction.1 2 The low reported yields of this reaction, along with failed subsequent attempts to improve upon it,17 led to the use of sequential Skraup or Dobner-Miller condensations, with isolation of the intermediate 8-aminoquinoline (2). Reaction of (2) with glycerol (3) or acrolein (4) in the presence of sulfuric or phosphoric acid and arsenic pentoxide produces (1) directly, Scheme 1.4,8-10,17,18... 

The continuous increase of isoprene demand has determined the enhancement of researches focused on the elaboraticxi of new and efficient routes for the industrial synthesis of this valuable diene. The acid-catalyzed cc ensation of formaldehyde and isobutene, known as Prins reacticxi, is already a recognized industrial route for the isoprene synthesis, being applied as two-stages process, condensation to form 4,4-dimethyl-l,3-dioxane in the presence of an aqueous sulphuric acid and its decomposition to isoprene using solid phosphoric acid catalysts. 

SYNTHESIS Condensation polymerization of 3,3, 4,4 -tetraaminobiphenyl (TAB) and diphenyl isophthalate (DPIP) in poly(phosphoric) acid, or in a hot molten nonsolvent such as sulfolane or diphenyl sulfone. ... 

---