Polyphosphate esters

Over the last several years research groups have also explored the use of microwaves to increase the reaction rate and efficiency of the Biginelli reaction. In one example, polyphosphate ester (PPE) was used as the promoter under microwave conditions to deliver a variety of DHPMs 38 in yields ranging from 65-95% yield with reaction times typically below 2 minutes. ... 

Cyclizations can also be carried out with an esterified oligomer of phosphoric acid called polyphosphate ester, which is chloroform soluble.55 Another reagent of this type is trimethylsilyl polyphosphate (Scheme 11.4, Entry 13).56 Neat methanesul-fonic acid is also an effective reagent for intramolecular Friedel-Crafts acylation (Scheme 11.4, Entry 14).57... 

In Entry 10, intramolecular acylation is followed by dehydrohalogenation. Entries 11 and 12 illustrate the use of polyphosphate ester. The cyclization in Entry 13 is done in neat methanesulfonic acid. 

As early as five years after the Miller-Urey experiments, Schramm and Wissmann from the Max Planck Institute for Virus Research in Tubingen reported a successful synthesis of polypeptides using polyphosphate esters. Thus, they were able to... 

Varma and Kappe have developed a method that enables the rapid and parallel synthesis of DHPM 58 (Scheme 8.22) but does not rely on polymer-supported building blocks and therefore does not require the development of solid-phase linkingcleaving chemistry. They showed that polyphosphate ester (PPE) serves as an excel-... 

Using a similar format, dihydropyrimidines were obtained in a microwave-expedited version of the classical Biginelli three-component condensation (Scheme 12.24) [73]. Neat mixtures of /i-kctocstcrs, aryl aldehydes and (thio)ureas with polyphosphate ester (PPE) as reaction mediator were irradiated in a domestic microwave oven for 1.5 min. The desired dihydropyrimidines were obtained in 61-95% yield after aqu-... 

A nucleoside consists of a purine or pyrimidine base linked to a pentose, either D-ribose to form a ribonucleo-side or 2-deoxy-D-ribose to form a deoxyribonucleoside. Three major purine bases and their corresponding ribo-nucleosides are adenine/adenosine, guanine/guanosine and hypoxanthine/inosine. The three major pyrimidines and their corresponding ribonucleosides are cytosine/ cytodine, uracil/uradine and thymine/thymidine. A nucleotide such as ATP (Fig. 17-1) is a phosphate or polyphosphate ester of a nucleoside. 

In the Codex Alimentarius a number of further sequestrants and antioxidant synergists are issued which also pertain to the group of antioxidants. The main representatives of sequestrants are acetates, citrates, tartrates, phosphates, orthophosphates, diphosphates, triphosphates, and polyphosphates, esters of glycerol, sorbitol and sorbitol syrup, gluconates, and 1,4-heptonolactone. Lactates and tartaric acid are considered as antioxidant synergists. The spectrum... 

Nakagome and co-workers effected the successful cyclization of N-ethyl-N-arylaminomethylenemalonates (749) in poly phosphoric acid, prepared from orthophosphoric acid and phosphorus pentoxide in polyphosphate ester (PPE), prepared from phosphorus pentoxide and anhydrous diethyl ether in chloroform in phosphoryl chloride on the action of boron trifluoride etherate on the action of acetic anhydride and concentrated sulfuric acid or on the action of phosphorus pentoxide in benzene [71GEP2033971, 71JHC357 76JAP(K) 18440]. Depending on the work-up process, l-ethyl-4-oxoquinoline-3-carboxylates (750, R1 = Et), l-ethyl-4-oxoquinoline-3-carboxylic acids (750, R2 = H) and 3-ethoxycarbonyl-4-chloroquinolinium iodides (751) were obtained. Only the cyclization of... 

Indolylthio)phenylacetic acid 168 in 50% polyphosphate ester in methylene chloride at room temperature affords 169 as a major product in 65% yield. In hot polyphosphoric acid (PPA) cyclized 169 and 170 were formed in 15 and 21% yields, respectively, due to the partial isomerization. Heating in PPA for a prolonged period gives a 90% yield of 170 as a sole product of... 

The two major types of nucleic acids are DNA and RNA. Nucleic acids are polyphosphate esters containing the phosphate, sugar, and base moieties. Nucleic acids contain one of five purine or pyrimidine bases that are coupled within double-stranded helices. DNA, which is an essential part of the cell s chromosome, contains the information for the synthesis of protein molecules. For double-stranded nucleic acids, as the two strands separate, they act as a template for the construction of a complementary chain. The reproduction or duplication of the DNA chains is called replication. The DNA undergoes semiconservative replication where each of the two new strands contains one of the original strands. 

Siloxanes Polyphosphazenes Polyphosphate esters Polysilanes Sol-gel networks... 

In a similar manner, aryl acid hydrazides 150 were condensed with benzaldehydes 151 <99SC3503>. Intermediates 152 underwent cyclodehydration in the presence of polyphosphate ester (PPE) to provide phthalazines 153 in good yields. 

The yield of the Fischer indole reaction was improved dramatically by employing 3-cyanopropanal diethylacetal as the aldehyde coupling partner (Scheme 10). Thus the hydrazone 33 was formed by reacting the hydrochloride salt of 31 with the diethylacetal in aqueous HCl. The hydrazone 33 was treated with polyphosphate ester in... 

Naratriptan was also prepared using the Fischer indole reaction (Scheme 15). Thus hydrazine 43 was condensed with Al-methyl-4-piperidineacetaldehyde in aqueous HCl to form hydrazone 44. Fischer indohzation was effected by treating 44 with polyphosphate ester in refluxing CHCI3 to provide naratriptan (3) in low yield. Higher yields may be attainable with the use of milder Fischer cyclization conditions (i.e. acetic acid or aqueous HCl). 

Trimethylsilyl polyphosphate (PPSE),1 The reagent is prepared from P205 and [(CHj),Si]20. It is a colorless, volatile liquid, soluble in the usual organic solvents. It is comparable to polyphosphate ester for the Beckmann rearrangement of oximes to amides (3, 230 231). but it is prepared more easily. 

In the preparation of amidine-containing substrates and inhibitors of trypsin, various nitriles have been synthesized as intermediates for these amidines. 15 In order to improve the yields of these nitriles and to preserve the optical activity of the amidines, many dehydrating agents such as POCl3, P2Os, TosCl/pyridine, and polyphosphate ester (PPE) and various dehydrating conditions have been evaluated. 101516 ... 

NMO NMP Nu PPA PCC PDC phen Phth PPE PPTS Red-Al SEM Sia2BH TAS TBAF TBDMS TBDMS-C1 TBHP TCE TCNE TES Tf TFA TFAA THF THP TIPBS-C1 TIPS-C1 TMEDA TMS TMS-C1 TMS-CN Tol TosMIC TPP Tr Ts TTFA TTN N-methylmorpholine N-oxide jV-methyl-2-pyrrolidone nucleophile polyphosphoric acid pyridinium chlorochromate pyridinium dichromate 1,10-phenanthroline phthaloyl polyphosphate ester pyridinium p-toluenesulfonate sodium bis(methoxyethoxy)aluminum dihydride (3-trimethylsilylethoxy methyl disiamylborane tris(diethylamino)sulfonium tetra-n-butylammonium fluoride f-butyldimethylsilyl f-butyldimethylsilyl chloride f-butyl hydroperoxide 2,2,2-trichloroethanol tetracyanoethylene triethylsilyl triflyl (trifluoromethanesulfonyl) trifluoroacetic acid trifluoroacetic anhydride tetrahydrofuran tetrahydropyranyl 2,4,6-triisopropylbenzenesulfonyl chloride 1,3-dichloro-1,1,3,3-tetraisopropyldisiloxane tetramethylethylenediamine [ 1,2-bis(dimethylamino)ethane] trimethylsilyl trimethylsilyl chloride trimethylsilyl cyanide tolyl tosylmethyl isocyanide meso-tetraphenylporphyrin trityl (triphenylmethyl) tosyl (p-toluenesulfonyl) thallium trifluoroacetate thallium(III) nitrate... 

Cyclodehydration. This reagent is superior to polyphosphate ester (PPE) for synthesis of benzimadazoles, indoles, and isoquinolines. 

CYCLODEHYDRATION Methanesulfonic acid. Phosphorus(V) oxide-Hexamethyl-disiloxane. Phosphorus(V) oxide-Methanesulfonic acid. Polyphosphate ester. 

THIOL ESTERS Chlorodiphenylphosphine. Diphenylphosphinyl azide. Polyphosphate ester. Sodium borohydride. 2,4,6-Trichlorobenzyl chloride. Triphenylphosphine-Diisopropyl azodicarboxylate-Thiolacetic acid. 

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