Pyrimidines

The possibility of the direct passage from 2-hydroxypyrimidines to pyrimidines by lithium aluminum hydride reduction has been established. Thus, starting from the corresponding 2-hydroxy derivatives we have obtained 4-phenylpyrimidine, 4, 6-diphenylpyrimidine, and 4-phenylbenzo[h]quinazoline. With 2-hydroxy-4, 6-diphenylpyrimidine as an example, it has been shown that when an excess of the reducing agent is used there is more far-reaching reduction to the corresponding dihydropyrimidine.For part XII, see [1].     

Synthesis of 2-Amino- and 2-Hydrazino-substituted 5-Nitro-4,6-diphenylpyrimidines

Nitrogen-containing derivatives of 5-nitro-4,6-diphenylpyrimidine have been synthesized by the reaction of 2-chloro-5-nitro-4,6-diphenylpyrimidine with amines or of 2-hydrazino-5-nitro-4,6-diphenylpyrimidine with carbonyl or -dicarbonyl compounds. Their structures were confirmed by data of IR spectroscopy and mass spectrometry.     

Pyrimidines. 72. Synthesis and some properties of 5-amino-2-r-4,6-diphenylpyrimidines and the products of their transformations

The corresponding 5-aminopyrimidines were obtained by reduction of 2-substituted 5-nitro-4,6-diphenylpyrimidines, and reactions involving the amino group were studied. A Schiff base was obtained, and acetylation and diazotization reactions were carried out. The corresponding diazonium salts were converted to 2-dimethylamino-5-hydroxy-4,6-diphenylpyrimidine and 5-azido-2-methoxy-4,6-diphenylpyrimidine. 2-Methoxy-4-phenyl-5H-pyrimido[5,4-b]indole was obtained by photocyclization of the latter.See [1] for Communication 71.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1278–1282, September, 1980.     

An efficient synthesis of 3,4-dihydropyrimidin-2(1<Emphasis Type="Italic">H</Emphasis>)-one and 5,6-diphenylpyrimidine derivatives under solvent-free and base conditions

An efficient and convenient Biginelli-like reaction one-pot synthesis of a series of 4-aryl-5,6-diphenyl-3,4-dihydropyrimidin-2(1H)-one and 4-aryl-5,6-diphenylpyrimidine derivatives under solvent-free conditions from the reaction of aromatic aldehydes, 1,2-diphenylethanone, urea, guanidine carbonate or acetamidine hydrochloride has been reported. This methodology has the advantages of short reaction time, mild reaction conditions, easy work-up and environmental friendliness. Moreover, 4-aryl-5,6-diphenylpyrimidine derivatives were first reported in this process. The structures of the title compounds were further determined by X-ray diffraction. More importantly, different from general Biginelli reaction, this reported method was carried out under base conditions.     

Chemical Transformations of 4-(4-Aminophenyl)-2,6-diphenylpyrimidine

Russian Journal of Organic Chemistry - 4-(4-Aminophenyl)-2,6-diphenylpyrimidine was synthesized by reaction of (E)-1-(4-aminophenyl)-3-phenylprop-2-en-1-one with benzamidine and was involved in a...     

Ring transformation of 5-acylpyrimidines into 4-acylpyrazoles with hydrazine and phenylhydrazine in acidic medium

5-Benzoyl-4-methylpyrimidines 4a,b and 5-acetyl-4-phenylpyrimidines 5a,b reacted with hydrazines in alcoholic acidic medium to give respectively 4-acetyl-3-phenylpyrazoles 7, 9 and 10 and 4-benzoyl-3-methylpyrazoles 6, 8 and 11 . In the reaction with phenylhydrazine, 5-benzoyl-4-methyl-2-methylthiopyrimidine ( 4a ) led exclusively to 4-acetyl-1,3-diphenylpyrazole ( 10 ) as 5-acetyl4-phenyl-2-methylthiopyrimidine ( 5a ) led to 4-benzoyl-3-methyl-1-phenylpyrazole ( 11 ) via the initial formation of phenylhydrazones of pyrimidines 4a and 5a . However, 5-benzoyl-4-methyl-2-phenylpyrimidine ( 4b ) and 5-acetyl-2,4-diphenylpyrimidine ( 5b ) reacted with phenylhydrazine to afford, each of them, a mixture of two isomeric pyrazoles. The mechanism of these ring contraction reactions is discussed.     

Reaction of fullerene C60 with 2-azido-4,6-diphenylpyrimidine

The first representative of the pyrimidine-substituted [60]fullereno[1,2-b]aziridines was synthesized by the reaction of fullerene C₆₀ with 2-azido-4,6-diphenylpyrimidine. 2-(Azahomo[60]fullereno)-4,6-diphenylpyrimidine was found to be formed as a by-product. The electrochemical properties of the adducts were studied.     

Heterocyclic polyfluoro-Compounds. Part XXVII[1]. Nucleophilic substitution in perfluoro-(4-phenylpyrimidine)

Treatment of tetrafluoropyrimidine with pentafluoro-phenylmagnesium bromide provides perfluoro-(4-phenylpyrimidine) (1) and perfluoro- (4,6-diphenylpyrimidine) (2). Attack on the former product by appropriate nucleophiles yields compounds (3)–(5) and thence (6)–(10). ¹⁹F N.m.r. data for all these new pyrimidine derivatives are discussed.

     

Synthesis of pyrimidine derivatives by reaction of pyrylium salts with guanidine and compounds of the guanidine series

2,4,6-Triphenylpyrylium perchlorate reacts with methylguanidine to give 1-methyl-2-amino-4,6-diphenylpyrimidinium perchlorate, which undergoes the Dimroth rearrangement to give 2-methylamino-4,6-diphenylpyrimidine. 2,4,6-Triarylpyrylium perchlorates react with guanidine to give N-pyrimidinylpyridinium salts. Pyrylium salts react with aminoguanidine, sulfanilylguanidine, and symmetrical diphenylguanidine at one amino group to give the corresponding pyridinium salts. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 748–752, June, 1980.     

Pyrimidines

The condensation of -substituted acetophenones with benzylidenebisurea in an acid medium has given 5-R-2-oxo-4,6-diphenyl-1,2,3,4-tetrahydropyrimidones. The analogous condensation of propiophenone forms 5-methyl-2-hydroxy-4,6-diphenylpyrimidine. The tetrahydro derivatives obtained are readily dehydrogenated to 5-R-2-hydroxy-4,6-diphenylpyrimidines.For part XX, see [1].     

Cyclopalladated ethylenediamine complexes on the basis of 4-phenylpyrimidine and 4,6-diphenylpyrimidine

Mono-and binuclear cyclopalladated complexes [Pd(ppm)En]ClO₄, [Pd(Hdphpm)En]ClO₄, and [(PdEn)₂(μ-dphpm)]ClO₄ (ppm^? is the deprotonated form of 4-phenylpyridine, Hdphpm^? and dphpm^2? are the mono-and bisdeprotonated forms of 4,6-diphenylpyrimidine, En is 1,2-diaminoethane) were prepared and characterized by means of ¹H NMR and electronic absorption and emission spectroscopy, and cyclic voltammetry. It was shown that cyclopalladation leads to a bathochromic shift of intraligand absorption and phosphorescence bands, appearance of new absorption band associated with metal-to-ligand charge transfer, and an anodic potential shift of the ligand-centered electroreduction Hppm ≈ H₂dphpm < [Pd(ppm)En]⁺ ≈ [Pd(Hdphpm)En]⁺ < [(PdEn)₂(μ-dphpm)]²⁺.     

Pyrimidine-pyrimidylidene tautomerism of some 4-pyrimidylmalonic acid derivatives

2,6-Diphenyl-4-pyrimidylmalonic esters (I, II) 2,6-diphenyl-4-cyanoacetic ester (III), and 2,6-diphenyl-4-pyrimidylmalononitrile (IV) were obtained for the study of pyrimidine-pyrimidylidene tautomerism by condensation of 4-chloro-2,6-diphenylpyrimidine with the appropriate malonic acid derivatives. The structures of the tautomeric forms and the positions of the equilibria were studied by PMR, IR, and UV spectroscopic methods.Communication LVI from the series Pyrimidines.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 395–397, March, 1977.     

New manganese-scaffolded organic triple-deckers based on quinoxaline, pyrazine and pyrimidine cores

The thermolytic coupling of Ph(2)CN(2) and (t-Bu)(Ph)CN(2) with doubly cyclomanganated 2,5-diphenylpyrazine and 4,6-diphenylpyrimidine afforded substantial amounts of new triple decker compounds of either C(i) and C(2) symmetry respectively containing, in both series, two eta(3)-bonded Mn(CO)(3) fragments which intervene as scaffolds sustaining the helical non-conjugated triaryl backbone. The molecular structures of two pyrazine derivatives show a typical non-parallel stacking of the aromatic rings and the encapsulation of the central pyrazyl fragment with interplanar centroid-to-centroid distances of ca. 3.5 A. The stacking of the aromatics in the triple-decker pyrimidine derivatives has been assessed by (1)H NMR experiments at low temperature. All the triple-decker-type compounds are electroactive. Pyrimidine triple-deckers can reversibly be electrochemically reduced to the corresponding anions.     

Ethylenediamine and 1,10-phenanthroline biscyclometallated complexes of Pd(II) and Pt(II) based on 4,6-diphenylpyrimidine

Biscyclometallated [(M(N∧N))₂(μ-dphpm)](ClO₄)₂ and [(N∧N)Pd(μ-dphpm)Pt(N∧N)]Cl₂ complexes [M = Pd(II), Pt(II); (N∧N) ethylenediamine (En), 1,10-phenanthroline (phen); dphpm² — bisdeprotonated form of 4,6-diphenylpyrimidine)] have been characterized by the ¹H NMR, electronic absorption and emission spectroscopy, and also cyclic voltammetry methods. The lowest unoccupied molecular orbital (LUMO) of biscyclometallated complexes with ethylenediamine, responsible for low-energy photo- and electro-stimulated processes irrespective of the metal nature, is assigned to the π* orbital mainly localized on the pyrimidine part of the bridging ligand. In the case of complexes with phenanthroline chelating ligands, the replacement of one or two palladium metal centers [{Pd(phen)}₂(μ-dphpm)]²⁺ by platinum centers changes the LUMO nature of the complexes for the π* orbital mainly localized on the peripheral metal-complex fragment {Pt(phen)}.     

Cu(II) and Cu(I) complexes with 2-(3,5-diphenyl-1H-pyrazole-1-yl)-4,6-diphenylpyrimidine: Synthesis and structure. Catalytic activity of Cu(II) compounds in reaction of ethylene polymerization

The Cu(II) and Cu(I) complexes with 2-(3,5-diphenyl-1H-pyrazole-1-yl)-4,6-diphenylpyrimidine (L) of the composition CuLX₂ (X = Cl, Br) and CuL(MeCN)Br are synthesized. According to X-ray diffraction data, the complexes have molecular structures. The molecules L are coordinated to the copper atom in bidentate-cyclic mode, i.e., through the N² atom of pyrazole and N¹ atom of pyrimidine rings. The coordination polyhedron of the Cu²⁺ ion in CuLX₂ compounds is completed to a distorted tetrahedron with halide ions, that of the Cu⁺ ion in CuL(MeCN)Br compounds, with the bromide ion and the nitrogen atom of acetonitrile molecule. The CuLX₂ complexes (X = Cl, Br) in combination with cocatalysts (methylaluminoxane and triisobutylaluminium) exhibit catalytic activity in ethylene polymerization.     

New pyrimidine- and fluorene-containing oligo(arylene)s: synthesis, crystal structures, optoelectronic properties and a theoretical study

New pyrimidine containing oligo(arylene)s, notably the pyrimidine-fluorene hybrid systems 13-16, have been synthesised by Suzuki cross-coupling methodology. An efficient synthesis of the key reagent 9,9-dihexylfluorene-2,7-diboronic acid 10 from 2,7-dibromo-9,9-dihexylfluorene 9 is reported. Cross-coupling of 10 with two equivalents of 2-bromopyrimidine, 5-bromopyrimidine and 2,5-dibromopyrimidine gave 2,7-bis(2-pyrimidyl)-9,9-dihexylfluorene 13. 2,7-bis(5-pyrimidyl)-9,9-dihexylfluorene 14 and 2,7-bis(5-bromo-2-pyrimidyl)-9,9-dihexylfluorene 15 in 23-34% yields. A further two-fold Suzuki reaction of benzeneboronic acid with compound 15 gave 2,7-bis(5-phenyl-2-pyrimidyl)-9,9-dihexylfluorene 16 (35% yield). Ab initio calculations of the geometries and electronic structures at the Hartree Fock (HF) and density functional theory (DFT) levels of theory are reported for compounds 13, 14 and 16 (with ethyl substituents replacing hexyl) and for their dipyrazinyl and bistetraazenyl analogues, 17, 18, 20 and 21. The heterocyclic nitrogen atoms of 13 and 16 facilitate planarisation of the system, compared to 14, which is in agreement with X-ray structural data obtained for 5-bromo-2-phenylpyrimidine 6, 2,5-diphenylpyrimidine 7 and compound 15. Bistetrazenyl derivative 21 is calculated to be a fully planar system. The cyclic voltammogram (CV) of compound 16 in dichloromethane solution shows a quasi-reversible oxidation wave at E(1/2)0 = +1.36 V (vs. Ag/Ag+). Compound 13 is a poorer donor with an oxidation observed at Epa = +1.50 V which is in good agreement with the difference in the energies of their HOMO orbitals calculated at both HF and DFT levels of theory (0.11-0.12 eV). For compound 14 we were not able to measure an Eox potential which should lie at much more positive potentials. Compounds 15 and 16 are blue emitters in solution, with photoluminescence quantum yields (PLQY) of 25% and 85%, respectively. For thin films of 16 the PLQY is reduced to 21%. An OLED using compound 16 as the emissive layer has been fabricated in the configuration ITO/PEDOT/16/Ca/Al: blue-green light (lambda max 500 nm) most likely emanating primarily from excimer states is emitted at a high turn-on voltage.     

催化裂化干气与苯烷基化催化蒸馏制乙苯反应网络热力学研究

 高温气相反应条件下的催化裂化干气制乙苯过程中，容易生成甲苯和二甲苯等副产物；在该过程中采用催化蒸馏技术，使苯与乙烯在低温条件下进行反应，可大幅度降低产品中二甲苯的含量．通过对催化裂化干气与苯烷基化催化精馏过程中的各反应步骤进行分析与热力学计算，结合反应的实际产物组成，提出了苯与乙烯烷基化的反应网络，探讨了苯与乙烯烷基化反应过程中甲苯和二甲苯的形成机理及影响因素．结果表明，增大苯／乙烯比对提高乙烯平衡转化率及乙苯收率有利；在较低温度下进行烷基化反应，可大大减缓C－C键裂解速度，抑制甲苯和二甲苯生成，提高乙苯产品质量．     

Homobinuclear cyanide-bridged linkage isomers containing the redox-active unit [(micro-XY)Ru(CO)2L(o-O2C6Cl4)] (XY=CN or NC)

The salts [NEt4][Ru(CN)(CO)2L(o-O2C6Cl4)] {L=PPh3 or P(OPh)3}, which undergo one-electron oxidation at the catecholate ligand to give neutral semiquinone complexes [Ru(CN)(CO)2L(o-O2C6Cl4)], react with the dimers [{Ru(CO)2L(micro-o-O2C6Cl4)}2] {L=PPh3 or P(OPh)3} to give [NEt4][(o-O2C6Cl4)L(OC)2Ru(micro-CN)Ru(CO)2L'(o-O2C6Cl4)] {L or L'=PPh3 or P(OPh)3}. The cyanide-bridged binuclear anions are, in turn, reversibly oxidised to isolable neutral and cationic complexes [(o-O2C6Cl4)L(OC)2Ru(micro-CN)Ru(CO)2L'(o-O2C6Cl4)] and [(o-O2C6Cl4)L(OC)2Ru(micro-CN)Ru(CO)2L'(o-O2C6Cl4)]+ which contain one and two semiquinone ligands respectively. Structural studies on the redox pair [(o-O2C6Cl4)(Ph3P)(OC)2Ru(micro-CN)Ru(CO)2(PPh3)(o-O2C6Cl4)]- and [(o-O2C6Cl4)(Ph3P)(OC)2Ru(micro-CN)Ru(CO)2(PPh3)(o-O2C6Cl4)] confirm that the C-bound Ru(CO)2(o-O2C6Cl4) fragment is oxidised first. Uniquely, [(o-O2C6Cl4){(PhO)3P}(OC)2Ru(micro-CN)Ru(CO)2(PPh3)(o-O2C6Cl4)]- is oxidised first at the N-bound fragment, indicating that it is possible to control the site of electron transfer by tuning the co-ligands. Crystallisation of [(o-O2C6Cl4)(Ph3P)(OC)2Ru(micro-CN)Ru(CO)2{P(OPh)3}(o-O2C6Cl4)] resulted in the formation of an isomer in which the P(OPh)3 ligand is cis to the cyanide bridge, contrasting with the trans arrangement of the X-Ru-L fragment in all other complexes of the type RuX(CO)2L(o-O2C6Cl4).     

Epoxidation of propyl- and isobutyl-β-alkylvinylketones

A study is made of the epoxidation of hepten-2-one-4, octen-3-one-5, nonen-4-one-6, 2-methylhepten-5-one-4, 2-methylocten-5-one-4, and 2-methylnonen-5-one-4 with alkaline methanolic hydrogen peroxide. 46–71% yield of the corresponding epoxy ketones are obtained. It is shown that treatment of the 2, 3-epoxyheptanone-4, 3, 4-epoxyoctanone-5, 4, 5-epoxynonanone-6, 2-methyl-5, 6-epoxyheptanone-4, 2-methyl-5, 6-epoxyoctanone-4 and 2-methyl-5, 6-epoxynonanone-4 with zinc chloride isomerizes them to, respectively, heptandione-3, 4, octandione-4, 5, nonandione-4, 5, 2-methylheptandione-4, 5, 2-methyloctandione-4, 5, and 2-methylnonandione-4, 5 in upto 78% yield.     

When arsine makes the difference: chelating phosphino and bridging arsinoarylthiolato gallium complexes

The (organo)gallium compounds GaCl{(SC6H4-2-PPh2)-kappa2S,P}2 (1), Ga{(SC6H4-2-PPh2)-kappa2S,P}{(SC6H4-2-PPh2)-kappaS}2 (2), GaMe2{(SC6H4-2-PPh2)-kappa2S,P} (3), GatBu2{(SC6H4-2-PPh2)-kappa2S,P} (4), GatBu{(SC6H4-2-PPh2)-kappa2S,P}{(SC6H4-2-PPh2)-kappaS} (5), [GaMe2{(mu2-SC6H4-2-AsPh2)-kappaS}]2 (6), and GatBu{(SC6H4-2-AsPh2)-kappa2S,As}{(SC6H4-2-AsPh2)-kappaS} (7) were obtained from the reaction of 2-EPh2C6H4SH (E = P (PSH), As (AsSH)) with GaCl3 (1, 2) or GaR3 (R = Me, tBu; 3-7) in different molar ratios and under different reaction conditions. Compound 2 was also obtained from Li(PS) and GaCl3 (3.5:1). While a monomeric structure with a chelating phosphinoarylthiolato ligand is observed in GaMe2{(SC6H4-2-PPh2)-kappa2S,P} (3), a dimeric arsinoarylthiolato-bridged complex [GaMe2{(mu2-SC6H4-2-AsPh2)-kappaS}]2 (6) is obtained with the corresponding AsS- ligand. B3LYP/6-31G(d) calculations show that although the dimer is thermodynamically favored for both ligands, the formation of 3 is due to the combination of higher stability of the chelate compared with the monodentate phosphorus ligand and a higher barrier for the ring opening of the PS- than of the AsS- chelate.