Pyrimidines dihydro

Dondoni has elaborated this methodology to include C-glycosylated dihydro-pyrimidines/ The sugar residue can be a subunit in the aldehyde, 1,3-dicarbonyl, or urea consequently, substitution of the DHPM ring may occur in one of three places depending on which component originally contains the glycosidic residue. In the example... 

Bei der Reduktion von Purinen wird zumeist der Funfring aufgespalten. Die galvano-statische Elektrolyse (3—4 A/8 V fur mehrere Stdn.) von 2,8-Diamino-purin in 25,8 n Schwefelsaure an Blei-Kathoden liefert neben 2,8-Diamino-1,2,3,4,5,6-hexahydro-9H-purin 2-Amino-5-guanidino-6-oxo-3,4,5,6-tetrahydro- und 2-Amino-5-guanidino-3,4-dihydro-pyrimidin (nur das Tetrahydro-pyrimidin-Derivat ist abtrennbar (Totalausbeute -45% d.Th.)3. 

The 6-yl radicals produced by (the selective) [23, 24] addition of OH to C(5) of the C(5)/(6) double bond of naturally occurring pyrimidine bases, nucleosides and nucleotides or those formed by H-abstraction from C(6) of 5,6-dihydro-pyrimidines [25] react with para-substituted nitrobenzenes by addition (k 6xl0 to 2 X s ) to yield nitroxyl-type radicals which were... 

Bahrami K, Khodaei MM, Farrokhi A (2009) Highly efficient solvent-free synthesis of dihydropyrimidinones catalyzed by zinc oxide. Synth Commun 39 1801-1808 74. Gross GA, Wurziger H, Schober A (2006) Solid-phase synthesis of 4,6-diaryl-3,4-dihydro-pyrimidine-2(lH)-one-5-carboxylic acid amide derivatives a Biginelli three-component-condensation protocol based on immobilized beta-ketoamides. J Comb Chem 8 153-155 Desai B, Dallinger D, Kappe CO (2006) Microwave-assisted solution phase synthesis of dihydropyrimidine C5 amides and esters. Tetrahedron 62 4651 664 Kumar A, Maurya RA (2007) An efficient bakers yeast catalyzed synthesis of 3,4-dihydro-pyrimidin-2-(lH)-ones. Tetrahedron Lett 48 4569-4571 77. Zalavadiya P, Tala S, Akbari J, Joshi H (2009) Multi-component synthesis of dihydropyrimidines by iodine catalyst at ambient temperature and in-vitro anti mycobacterial activity. Arch Pharm 342 469-475... 

Schnell B, Strauss UT, Verdino P, Faber K, Kappe CO (2000) Synthesis of enantiomerically pure 4-aryl-3,4-dihydro-pyrimidin-2(lH)-ones via enzymatic resolution preparation of the antihypertensive agent (R)-SQ 32926. Tetrahedron Asymmetry 11 1449-1453... 

The cadmium complexes were also investigated potentiometrically. Using this method, the complexes of cadmium with asparagine [128], taurine [129], A -(6-ami-no-3-methyl-5-nitroso-4-oxo-3,4-dihydro-pyrimidin-2-yl)glycine [130], succinate and malate [131], acetate at different temperatures [132], pyridine oxime ligands [133], 2-hydroxypropene-l,3-diamine-Af,Af,Af, A -tetraacetic acid [134] were studied. The stoichiometry and stability constants of these complexes were determined. 

Acylamino-2,4-dioxo-l,2,3,4-tetrahydro- bzw. 5-Acylamino-4-oxo-3,4-dihydro-pyrimidine werden durch Umsetzung mit ethanolischem Natriumhydroxid in Ausbeuten von 34-84% zu 4-Aminocarbonyl-5-methyl-imidazolen umgelagert437. 

There are a series of communications about the formation of dihydroazines by direct reaction of urea-like compounds with synthetic precursors of unsaturated carbonyls—ketones, containing an activated methyl or methylene group. The reaction products formed in this case are usually identical to the heterocycles obtained in reactions of the same binuclephiles with a,(3-unsatu-rated ketones. For example, interaction of 2 equiv of acetophenone 103 with urea under acidic catalysis yielded 6-methyl-4,6-diphenyl-2-oxi- 1,6-dihydro-pyrimidine 106 and two products of the self-condensation of acetophenone— dipnone 104 and 1,3,5-triphenylbenzene 105 [100] (Scheme 3.32). When urea was absent from the reaction mixture or substituted with 1,3-dimethylurea, the only isolated product was dipnon 104. In addition, ketone 104 and urea in a multicomponent reaction form the same pyrimidine derivative 106. All these facts suggest mechanism for the heterocyclization shown in Scheme 3.32. 

The behavior of pyrimidine during polarographic reduction depends on the pH of the aqueous solution. In acidic solution two one-electron waves are observed, while in neutral solution two two-electron waves result. In alkaline solution four-electron reduction is effected via 1,6-dihydro pyrimidine to give tetrahydropyrimidine <1984AHC(36)235>. 

The free radical scavenging effects of compounds 57 derived from dihydro-pyrimidines 56 (Scheme 12) was also examined by the DPPH method and by measuring hydroxyl radical scavenging activity (RSA) [33]. It was found that compounds derived from the thioureas had the best antioxidant activities. Compounds 58 and 59 were the most potent and had comparable activity to quercetol (Table 4). 

Reaction between DNA/RNA and Mn04 or 0s04 , where the formal metal oxidation states are Mn + and Os +, results in base-specific modification of thymidine/uridine residues. These anionic metal species can oxidize the pyrimidine C5-C6 double bond, which results in formation of m-5,6-dihydroxy-5,6-dihydro-pyrimidine. This reaction is followed by opening of the pyrimidine ring and its subsequent removal from the polynucleotide chain. Permanganate can also oxidize and remove guanine residues (but not adenine) while osmium tetroxide acts much more specifically on pyrimidine residues with the following kinetic preferences (relative rates shown in parenthesis) T (45) U(4.5) > dU(2.8) >... 

In aprotic medium, on the other hand, pyrimidine gives a reversible diffusion-controlled 1 e wave at a very negative potential, with formation of a radical anion which is deactivated via two pathways rapid formation of the anionic, probably 4,4 -, dimer, with a rate constant of 8 x 10 L mol sec , and proton abstraction from residual water in the medium at a much lower rate constant, 7 L mol sec This is rapidly followed by a further le reduction to produce, ultimately, 3,4-dihydro-pyrimidine In the presence of acid there is also a le reduction wave corresponding to formation of a free radical which, as in aqueous medium, dimerizes, most likely to 4,4 -(>w-(3,4-dihydropyrimidine). Examination of the mechanism of reduction in acetonitrile in the presence of acids supported the conclusion that reduction of pyrimidine in aqueous medium is preceded by its protonation... 

Yadav, J. S., Reddy, B. V. S., Reddy, E. J., Ramalingam, T. Microwave-assisted efficient synthesis of dihydro pyrimidines improved high yielding protocol for the Biginelli reaction. J. Chem. Res., Synop. 2000, 354-355. 

A method for extraction and spectrophotometric determination of traces of Te(IV) from hydrochloric acid media with l-(4-bromophenyl)-4,6,6-trimethyl-l,4-dihydro-pyrimidine-2-thiol (4-bromoPTPT) in CHCI3 has been described [1]. Tellurium in alloys and in synthetic mixtures with Se(lV) was determined. 

In the present review the primary chemical literature up to the end of 1981 has been surveyed. Chemical Abstracts Subject and Chemical Substance Indexes up to and including Volume 94 have been searched. Throughout this chapter the name and numbering style favored by Chemical Abstracts is used, i.e., pyrido[l,2-a]pyrimidine for ring system (1). Earlier names to designate the pyrido[l,2-a]pyrimidine derivatives include 1,2-divinylene-pyrimidine (for numbering cf. 2), l,2-(dihydropyrido-r,2 )-5,6-dihydro-pyrimidine, malonyl-a-aminopyridine, 4,10-dihydro-l,10-diazanaphthalene... 

Similarly, introduction of electron-donating substituents such as NR2, SR, or OR in the a or y position of usually unstable cyclic imines E, F, and G enhances chemical stability and enables these compounds to be easily isolated in each DHA family, for instance, 3,4-dihydropyridines (18a), 2,5-dihydro-pyrimidines (18b), 4,5-dihydropyrimidines (18c), and 4,5-dihydropyridazines (18d). 

The authors postulated a di-re-methane mechanism for the photochemical isomerization, with the formation of 2,4-diazabicyclo[3.1.0]hex-2(3)-ene (123) as an intermediate. Subsequent opening of the three-membered ring with a concomitant [1,5]-hydrogen shift from nitrogen to C-2 gave 2,5-dihydro-pyrimidine 124 [Eq. (57)]. 

Dureh Umsetzung von 3,5-Diphenyl-l, 2,4-dithiazolium-perchlorat mit Acceptor-substituierten Acetonitrilen ist in mittleren Ausbeuten 5-Cyan-2,4-diphenyl-l,3-thiazol (Schmp. 132°) erhalt-lich.906 Diese Reaktion lafit sich nicht ohne weiteres auf andere Carbonsaure-nitrile ausweiten, da in diesen Fallen 2-Thiono-l,2-dihydro-pyrimidine entstehen. 

Mit (2-Chlor-6-phenyl-3,4-dihydro-pyrimidin-4-yliden)-malonsaure-dinitril ist die direkte Umsetzung mit Hydrazin ebenfalls moglich, wobei gleichzeitig Halogen-Substitution erfolgt443 und man erhalt 3,5-Diami-no-4- (2-hydrazino-6-phenyl-4-pyrimidyl)-1 H-pyrazol (44%). 

Unter N,N-Spaltung iiber eine 1,2-Dihydro-pyrimidin-Zwischenstufe verlauft die Ringoffnung von 1-Aryl-2-ethenyl-pyrazolium-tetrafluoroboraten in waBriger Kaliumcyanid-Losung2544. 

Methyl-, 1-Ethyl- und 1-Benzyl-lH-pyrazol bilden beim Erhitzen auf 550° in Gegenwart von Tetrachlormethan 2-Chlor-pyrimidin2120a. 1,2-Dihydro-pyrimidine werden bei der Einwir-kung von Natriumamid auf 1-Benzyl- bzw. 3,5-Dimethyl-l-diphcnylmethyl-lH-pyrazol (150 155°) erhalten2548... 

In neutralem oder basischem Milieu werden mit Palladium/Kohle oder Raney-Nickel Dihydro-pyrimidine erhalten6. 

Aluminum isopropoxide has been described in a 1958 US patent (39) as an MPV reductant to selectively convert the 7-ethylenedioxy derivative of a substituted dodecahydrophenanthrene to its 4b-methyl-7-ethylenedioxy-l,2,3,4,4a.4b,5,6,7,8,10,10a-dodecahydrophenanthrene-4-ol-l-one. The MPV reduction of pyrimidin-2(lH)-ones to the corresponding 3,4-dihydro- pyrimidin-2(lH)-ones has been accomplished with zirconium tetraalkoxide and with AIP, although the Zr-alkoxide was more effective (40). Aluminum isopropoxide has proven useful in the reduction of 5P-hydroxy-8-oxo-l,4,4aa,5,8,8aa-hexahydronapthalene-lp-carboxylic acid to a preciusor used in the synthesis of reserpine and related comnpoimds (41,42). 

Heating diphenylcyclopropenone (DPP) with aryl amidoximes ArC(NH2)NOH gives pyrimidin-4-ones (225) this usefully supplements the previously reported reactions of DPP with amidines, which give dihydro-pyrimidin-4-ones. The previously mentioned /3-lactone (119) (see p. 240), which is an internally protected 1,3-dicarbonyl compound, reacts with acetamidine to give the pyrimidin-4-one (226). ... 

Pyrimidines and their oxo-derivatives have attracted immense interest due to their structural resemblance with the nucleotide bases, which is perhaps the reason behind their extensive biological activities, dos Anjos and coworkers have reported a new eco-fiiendly multicomponent methodology for the synthesis of 6-oxo-2,4-diaryl-l,6-dihydro-pyrimidine-5-carbonitriles 43 and 4-amino-2,6-diaryl-pyrimidine-5-caibonitriles 45 using microwave irradiation (2013TL(54)3462). These compounds were found to possess significant analgesic activity. In this protocol, aromatic aldehydes 40 were reacted with ethyl cyanoacetate 42 and benzamidine... 

For example, mesoionic 2-[2-(isopropenylcarbonyloxy)ethylthio]-l-methyl-6-oxo-3-phenyl-5-propyl-l,6-dihydro-pyrimidin-3-ium-4-olate (11) (34) was stirred in equimolar amoimt with a solution of RAMEB for 5 days at ambient temperature. The 2 1 hosfc-guest complex 11/RAMEB was isolated in 71% srield relative to the guest monomer. The water solubility of complex was about 800 mg in 1-ml water at ambient temperature. The radical polymerization of RAMEB-complexed monomer was carried out with 3.3 mol% of redox initiator potassiiun peroxodisul-fate and sodium hydrogensulfite. According to the results of the gel-permeation chromatography (GPC) obtained for the polymer prepared from the imcomplexed monomer, 85% of 11 was unreacted after 1 h. Additionally, the molecular weight distribution of the polymer synthesized without RAMEB is bimodal with = 11,000 g/mol and polydispersity of 4.5 (35). 

For selected examples, see (a) J. C. Legeay, J. J. V. Eynde, L. Toupet, J. P. Bazureau, Arkivoc 2007, (iii), 13-28. A three-component condensation protocol based on ionic liquid phase bound acetoacetate for the synthesis of BigineUi 3,4-dihydro-pyrimidine-2(17/)-ones. (b) J. C. Legeay, J. J. V. Eyndeb, J. P. Bazureau, Tetrahedron Lett. 2007, 48, 1063-1068. A new approach to N-3 functionalized 3,4-dihydropyrimidine-2(l//)-ones with 1,2,4-oxadiazole group as amide isostere via ionic Uquid-phase technology. 

R. S. Bhosale, S. V. Bhosale, S. V. Bhosale, T. Wang, P. K. Zubaidha, Tetrahedron Lett. 2004, 45, 9111-9113. An efficient, high yield protocol for the one-pot synthesis of dihydro-pyrimidin-2(l//)-ones catalyzed by iodine. 

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