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Self-assembled monolayers (SAMs) provide a simple route to functionalize electrode surfaces with organic molecules. Herein we use cavity-containing derivatives of calix[4]arenes in SAMs. Bound to noble metal surface, the assembled molecules are candidates to serve as molecular sieves for H 2 molecules and H (+) ions, which could have relevance for fuel cell applications. Tetra- O-alkylated calix[4]arenes with thiolacetate and thiolamide wide-rim anchoring groups in cone and partial-cone conformations were designed, synthesized and self-assembled onto Au, Pt, and Pd surfaces. The resulting SAMs were systematically examined. Single crystal X-ray diffraction of 5,11,17,23-tetrakis(thioacetyl)-25,26,27,28-tetra- i-propoxycalix[4]arene confirmed the cone conformation and revealed the cavity dimensions of the SAMs that were formed by immersing noble metal substrates (Au, Pt and Pd deposited on Si-wafers) in solutions of calix[4]arenes. Surface characterization techniques including ellipsometry, cyclic voltammetry (CV) and X-ray photoelectron spectroscopy (XPS) were used, indicating that the metal surface is terminated with a monomolecular layer. Experimental thicknesses obtained from the ellipsometry are consistent with the calculated values. CV results showed 50 to 80% physical passivation against the Fe(CN) 6 (3-/4-) couple, implying an overall relatively low concentration of defects and pinholes in the films. The binding energies of the S2p core level in the XPS were consistent with the literature values and revealed that up to 3.2 out of four anchoring groups were bonded to the noble metal surface.

Dimethyl 3-oxopentane-1,5-dioate (dimethyl acetone-1,3-dicarboxylate) (1) was transformed first with (hetero)arenediazonium salts 3a – j into dimethyl 2-[(hetero)arylhydrazono]pentane-1,5-dioates 4a – j followed by reaction with N,N-dimethylformamide dimethylacetal (DMFDMA) to afford, without isolation of intermediates 5a – j, dimethyl 1-(hetero)aryl-4-oxo-1,4-dihydropyridazine-3,5dicarboxylates 6a – j. An alternative method represents transformation of 1 with DMFDMA into dimethyl 2-[(dimethylamino)methylidene]-3-oxopentane-1,5-dioate (7) followed by treatment with (hetero)arenediazonium salts 3a – c, j to give pyridazine derivatives 6a – c, j.

Two variations of enaminone-based parallel solution-phase synthesis of 1-substituted 4-(2-aminoethyl)-1 H-pyrazol-5-ols 8 and their NH-tautomers 8' were developed. The synthetic strategy comprises a two step preparation of the N-protected alpha-enamino lactams 3a and 3b from 2-pyrrolidinone (1), "ring switching" transformation of 3a, b with monosubstituted hydrazines 4a-u, and acidolytic removal of the N-protecting group. In order to ensure a clean and fast conversion, reactions of Cbz-enaminone 3a with hydrazines 4a-k were carried out under microwave irradiation to afford the "ring-switched" intermediates 7a-k. Deprotection of 7a-k with HBr-AcOH at 50 degrees C gave a library of 11 analytically pure 4-(2-aminoethyl)-1 H-pyrazol-5-ols (di)hydrobromides 8/ 8'a-k in 16-75% yields over two steps. The other reagent, Boc-enaminone 3b, was more reactive and ring switching transformations with hydrazines 4b, d, k proceeded smoothly and cleanly under conventional heating. Finally, a parallel one-pot transformation of the Boc-enaminone 3b with hydrazines 4a-u followed by subsequent deprotection of the intermediates 9a-u with HCl-EtOAc furnished a library of 21 analytically pure 4-(2-aminoethyl)-1 H-pyrazol-5-ols (di)hydrochlorides 8/ 8'a-u in 40-100% yields.

Thermal transformations of 3-azido-4H-quinolizin-4-ones 4a,b and 3-azido-4H-azino[1,2–x]pyrimidin-4-ones 4c,d, available from the corresponding heteroarylamines 2a–d, were studied. The reaction products were mostly dependent on the solvent. Thus, heating of 3-azido-1-cyano-4H-quinolizin-4-one (4a) in toluene afforded 2-(pyridin-2-yl)fumaronitrile 5a, whereas 3-amino-1-cyano-4H-quinolizin-4-one (8) was obtained on treatment of 4a in a mixture of toluene and trifluoroacetic anhydride. However, heating of 4a in acetic anhydride and in acetic acid resulted in a ring contraction to produce 3-(diacetylamino)indolizine-1-carbonitrile 6a and 3-(acetylamino)indolizine-1-carbonitrile 7a, respectively. Similarly, ring contractions took place on heating ethyl 3-azido-4-oxo-4H-quinolizin-1-carboxylate 4b and 3-azido-4H-azino[1,2–x]pyrimidin-4-ones 4c,d in acetic anhydride or acetic acid to produce the N-acetylated 3-aminoindolizine derivatives 6b, 7b and 3-aminoimidazo[1,2–x]azine derivatives 6c,d in 30–89% yields. The structures of compounds 5–8 were determined by NMR spectroscopy and X-ray diffraction.

1,3-Dipolar cycloadditions of azomethine imines 3a and 3b, available by acid-catalyzed treatment of 3-pyrazolidinone 1 with acetone (2a) and butyraldehyde (2b), respectively, were studied. Reactions of 3a with DMAD (4) afforded a mixture of products 9 and 10a, whilst treatment of 3b with DMAD (4) gave a mixture of compound 9 and epimeric cycloadducts 10/10′b. On the other hand, cycloadducts 13a,b-16a,b were isolated as single diastereomers in 9–37% yields upon reactions of 3a,b with olefinic dipolarophiles 5–8. The structures of cycloadducts 9, 10a, 10/10′b, and 13a,b-16a,b were determined by 1H nmr and NOESY spectroscopy. The structure of compound 13a was confirmed by X-ray diffraction.

A simple four-step synthesis of 4-(2-aminoethyl)-5-hydroxy-1H-pyrazoles 8 (or their 1H-pyrazol-3(2H)-one tautomers 8′) as the pyrazole analogues of histamine was developed. First, enamino lactam 3 was prepared as the key intermediate in two steps from 2-pyrrolidinone (1). Next, acid-catalysed ‘ring switching’ transformations of 3 with monosubstituted hydrazines 4 gave N-[(1-substituted 5-hydroxy-1H-pyrazol-4-yl)ethyl]benzamides 7a–k and N-[2-(2-heteroaryl-3-oxo-2,3-dihydro-1H-pyrazol-4-yl)ethyl]benzamides 7′l–o. Benzamides 7a–k and 7′l–o were finally hydrolysed by heating in 6 M hydrochloric acid to furnish 1-substituted 4-(2-aminoethyl)-5-hydroxy-1H-pyrazoles 8a–k and 4-(2-aminoethyl)-2-heteroaryl-1H-pyrazol-3(2H)-ones 8′l–o in good overall yields.

A simple and efficient synthesis of four new substituted pyrimidines, compounds 9a–d, from the title compound 3 is described. Conversion of 3 to methyl (E)-3-(dimethylamino)-2-(6-methoxy-2-phenylpyrimidin-4-yl)prop-2-enoate (4), followed by condensation with various dinucleophiles according to the ‘enaminone methodology’, afforded the target compounds 9 in medium-to-good yields.

Solution-phase combinatorial synthesis of (2S,4S)-4-acylamino-5-oxopyrrolidine-2-carboxamides was studied. First, di-tert-butyl (2S,4S)-4-amino-5-oxopyrrolidine-1,2-dicarboxylate hydrochloride was prepared as the key intermediate in five steps from (S)-pyroglutamic acid. Acylation of the amino group followed by acidolytic deprotection gave (2S,4S)-4-acylamino-5-oxopyrrolidine-2-carboxylic acids, which were then coupled with amines to furnish a library of (2S,4S)-4-acylamino-5-oxopyrrolidine-2-carboxamides. Four coupling reagents, BPC, EEDQ, TBTU, and PFTU, were tested for the amidation reactions in the final step. Amidations with EEDQ and TBTU led to the desired carboxamides. On the other hand, BPC and PFTU were not suited, since diketopiperazines were sometimes obtained instead of the desired carboxamides.

Substituted 2,3,5,6,7,8-hexahydropyrazolo[4,3-d][1,2]diazepine-8-carboxylates were prepared in good to excellent yields from ethyl (2E)-3-(dimethylamino)-2-{(4Z)-4-[(dimethylamino)methylidene]-5-oxo-1-phenyl-4,5-dihydro-1H-pyrazol-3-yl}propenoate with 1,2-disubstituted hydrazines by heating in an alcohol.

Stable triethylammonium triazenide salts were obtained on treatment of the appropriate triazenes with triethylamine. Those salts are described and fully characterized for the first time and are used for the preparation of alkoxycarbonylvinyltriethylammonium triazenides, which are prone to transesterification.

(S)-3-(Dimethylamino)methylidene-5-benzyltetramic acid derivatives 4a and 4b were prepared in three steps from N-protected (S)-3-phenylalanines la and 1b, respectively. Similarly, N-[N-(benzyloxycarbonyl)glycyl]glycine (1c) was transformed into the enaminone 4c. Acid-catalysed coupling of enaminones 4a-c with aliphatic, aromatic, and heteroaromatic primary amines 5-34 afforded the corresponding N(3')-substituted 3-aminomethylidenetetramic acid derivatives 35-64 in 29-96% yields.

Various (1R,5S)-4-[(E)-alkylidene]-1,8,8-trimethyl-2-oxabicyclo[3.2. 1]octan-3-ones were prepared, stereoselectively, via coupling of (1R,5S)-4-[(E)-(dimethylamino)methylidene]-1,8,8-tri-methyl-2-oxabicyclo[3.2.1]octan-3-one with Grignard reagents, potassium cyanide, and 2-methyl-lH-indole.

By a selective exchange of ligand Br by Cl, a series of nonstoichiometric bromo-chloro-pyridine- molybdenum(III) octahedral compounds of the type (cat)[MoBraCl(4-a)py2] (cat = pyH, a = 3–1 (1, 4, 7)); cat = [(C2H5)3NH], a = 2.744 (2); cat = Rb, a = 2.278 (5); cat =[(C6H5)4)As], a = 1.258 (8) and [MoBraCl(3–a)py3] (a = 2–1 (3, 6)) have been prepared and characterized. Owing to great similarity of the powder diffraction patterns and IR spectra of compounds mer- [MoBraCl(3-a)py3] (a = 3–0) with the known monoclinic modification in the space group P21/c and compounds [MoBraCl(3-a)py3] (a = 2-1 (3, 6)), the same type of crystal lattice was confirmed. Isostructurality was observed also for the orthorhombic trans-(pyH)[MoBr4py2]](Pnma) and compounds 1 and 4, while compound 7 is isostructural to trans-(pyH)[MoCl4py2]. X-ray crystallographic analyses of 2, 5 and 8, obtained by recrystallization of (pyH)[MoBraCl(4-a)py2] (a = 3–1) with different cations, were performed. In these compounds, MoIII is octahedrally coordinated with four halogenido ions at distances 2.4953(6)–2.5920(10) Å and two pyridine molecules at distances 2.195(4)-2.220(4) Å. Trans oriented pyridine rings in compounds 5 and 8 are co-planar, while deviation from co-planarity was noticed for compound 2 (8.9(3)°). The stoichiometry of four coordinated Br and Cl atoms in these compounds is not ideal, since the structure analysis results for 2, 5 and 8 show a mixed occupancy of crystallographic sites; thus, refined population parameters for both atoms (Br and Cl) were calculated., Selektivnom zamjenom bromovoga liganda klorovim dobijena je i karakterizirana serija nestehiometrijskih bromo-kloro-piridin-MoIII kompleksa tipa (cat)[MoBraCl(4–a)py2] (cat = pyH, a = 3–1 (1, 4, 7); cat = [(C2H5)3NH], a = 2.744 (2); cat = Rb, a = 2.278 (5); cat = [(C6H5)4As], a = 1.258 (8)) i [MoBraCl(3–a)py3] (a = 2–1 (3, 6)). Uslijed velike sličnosti difraktograma praha i IR spektara spojeva mer-[MoBraCl(3–a)py3] (a = 3–0) poznate monoklinske modifikacije u prostornoj grupi P21/c i spojeva [MoBraCl(3–a)py3] (a = 2–1 (3, 6)), potvr|en je isti tip kristalne re{etke. Opa`ena je izostrukturnost rompskoga trans-(pyH)[MoBr4py2] (Pnma) i spojeva 1 i 4, dok je spoj 7 izostrukturiran s trans-(pyH)[MoCl4py2]. Načinjena je rentgenska strukturna analiza spojeva 2, 5 i 8 dobijenih prekristalizacijom (pyH)[MoBraCl(4–a)py2] (a = 3–1) s različitim kationima. U tim je spojevima MoIII oktaedarski koordiniran s četiri halogenidna iona na udaljenostima 2.4953(6)–2.5920(10) Å i dvije molekule piridina na udaljenostima 2.195(4)–2.220(4) Å. Trans orijentirani piridinski prstenovi u spojevima 5 i 8 su koplanarni dok je kod spoja 2 ustanovljena devijacija od koplanarnosti (8.9(3)°). Strukturnom analizom utočnjeni su faktori zauzetosti četiri koordinirana atoma (Br, Cl) u spojevima 2, 5 i 8. Na|eno je da su navedeni kristalografski položaji zauzeti atomima Cl i Br u nestehiometrijskome omjeru.

Methods for the crystal structure determination from powder diffraction data are reviewed with special emphasis on the application to technical ceramics. Experimental techniques using other than laboratory X-ray, such as synchrotron radiation, neutron and electron beams, are also described. As an illustrative example, the crystal structure determinations of compounds LaNbTiO6, La0.462Nb0.614Ti0.386O3 and La0.37Nb0.889Ti0.111O3 in the ternary system of La2O3–Nb2O5–TiO2 are reported.

To compare the structural properties of oxalamide and thiooxalamide groups in the formation of hydrogen bonds suitable for supramolecular assemblies a series of retropeptides was studied. Some of them, having oxalamide bridges, are gelators of organic solvents and water. However, retropeptides with oxygen replaced by the sp 2 sulfur have not exhibited such properties. The crystal structures of the two title compounds are homostructural, i.e. they have similar packing arrangements. The monothio compound crystallizes in the orthorhombic space group P212121 with two molecules in the asymmetric unit arranged in a hydrogen-bond network with an approximate 41 axis along the crystallographic b axis. However, the dithio and dioxo analogues crystallize in the tetragonal space group P41 with similar packing patterns and hydrogen-bonding systems arranged in agreement with a crystallographic 41 axis. Thus, these two analogues are isostructural having closely related hydrogen-bonding patterns in spite of the different size and polarity of oxygen and sulfur which serve as the proton acceptors.

The title compound, C 14 H 26 N 8 O 2 , belongs to a class of retropeptides with an oxalamide unit (-NH-CO-CO-NH-), and is a precursor for the synthesis of an amine-terminal gelator. The compound is a good synthon for one-dimensional hydrogen bonding. The crystal structure reveals a hydrogen-bonded cyclic dimer with unusual twofold rotation symmetry.

Over the last 20 years, the effects of using limestone in Portland cement (PC) have been well studied. The benefits of limestone as a partial replacement for PC are well established. Its economic and environmental advantages of reducing CO2 emissions are well known. For a long time, the limestone has been considered as an inert filler. Recently it has been concluded that limestone serves both as an inert filler and also reacts to a limited extend. The reactivity depends on its fineness (specific surface)[1] and content [2,3]. The question arose, whether a) it is the availability of excess carbonate ion in the hydration system, which determines the degree of influence on the hydration process or b) does the system have its internal capacity to include carbonate ions and the increased availability (more carbonate ions in the solution, embedding the hydrating particles) would not have a significant effect. So the question was if the more soluble carbonates would have more pronounced effect on the hydration of the Portland cement than the limestone, which is only slightly soluble. The influence of slightly soluble (CaCO3, MgCO3, dolomite), medium soluble (Li2CO3) and highly soluble (K2CO3 and KHCO3) carbonates on the hydration of Portland cement was studied using Rietveld analysis. The results indicated that the amount of reacted carbonate in cement hydration at a 15% addition of slightly or medium soluble carbonates does not exceed 5% and is not affected by their solubility; at a 15% addition of the highly soluble carbonate K2CO3 the amount of reacted carbonate is around 6% leading to the conclusion that the system behaves according to the option b). The fugure presents the quantitative analysis of cement hydration at 3, 7, 28 and 90 days of hydration and temperatures of 25 and 400C.

The triclinic form of AlPO4-34, a microporous aluminophosphate with the chabazite (CHA) topology, adopts a rhombohedral symmetry upon calcination. The framework structure of this phase remains intact under ambient conditions, but it distorts dramatically, though reversibly, in the presence of water. Following these structural changes in situ by X-ray diffraction revealed that there are actually two stable rehydrated phases, which differ from each other by one water molecule in the channel. Both of these phases have triclinic unit cells that are closely related to that of the calcined rhombohedral phase. The structure of the low-temperature (10 °C), fully rehydrated phase (phase B) was elucidated by combining high-resolution synchrotron powder diffraction with solid-state NMR techniques. Coordination of three of the six Al atoms to water molecules causes the deformation of the framework and the reduction of the symmetry. Rietveld refinement of the structure of phase B in the triclinic space group P1 (a = 9.026, b = 9.338, c = 9.508 Å, α = 95.1°, β = 104.1°, and γ = 96.6°) converged with RF = 0.079 and RWP = 0.176 (Rexp = 0.087). Framework connectivities derived from the structure were used to assign 31P NMR lines as well as part of the 27Al NMR signal.

An overview of contemporary methods of crystal structure solution from powder diffraction data is given. Methods are compared with respect to their advantages and disadvantages. A choice of an appropriate method is discussed in the light of understanding the structural problem to be solved. The need of the variety of methods for the variety of problems is illustrated by examples. Some directions of possible future development are discussed.

The tris(1,2-diaminoethane)nickel(II) complex was found to be a novel structure-directing agent for the preparation of the chabazite-like AlPO 4 -34 molecular sieve. During crystallization the complex undergoes a ligand exchange, thus helping stabilization of the AlPO 4 's chabazite structure by hydroxyls that have exchanged one 1,2-diaminoethane (en) molecule from the Ni(II) coordination sphere. The exchanged complex, [Ni(en) 2 (OH) 2 ], remains in the chabazite host causing a triclinic deformation of the rhombohedral chabazite framework. Upon calcination the triclinic phase completely transforms into the rhombohedral chabazite-like AlPO 4 -34 as evidenced from the in situ XRD pattern.

Zinc, manganese and cobalt containing aluminophosphates with the chabazite (CHA) structure type (MeAPO-34, MeZn, Mn and Co) have been synthesized hydrothermally in the presence of tetraethylammonium hydroxide. All samples showed a very high crystallinity without impurity phases, as evidenced by X-ray diffraction and scanning electron microscopy. The results of EXAFS spectroscopy on as-synthesized samples show that the metals possess 4 oxygen atoms in the first coordination shell which is an indication for a tetrahedral coordination in the lattice. The decrease of the EXAFS amplitude for some samples upon calcination is in agreement with the presence of Lewis acid sites, as previously reported. 31P NMR confirmed the incorporation of metals in the AlPO4-34 structure. For Zn and Mn, the 31P NMR spectra show various lines attributed to different P(nAl, 4-nMe) units and the calculation of the fraction of metal in the samples after deconvolution of the spectra is in very good agreement with elemental analysis. Comparison of the relative intensities of the lines with those obtained by a binomial theorem showed that metals randomly substitute Al in the AlPO4-34 framework. Incorporation of Co in the samples was suggested by a strong decrease in both T1 and T2 relaxation times with respect to SAPO-34 or ZnAPO-34, thus confirming EXAFS data.

ZnAPO-34 and MnZnAPO-34 materials were synthesised hydrothermally in the presence of tetraethylammonium hydroxide as a template. Rietveld refinement and EXAFS studies indicate the incorporation of zinc cation into tetrahedral framework sites of AlPO 4 -34 and imply the presence of extra-framework manganese atoms located in cavities.

The title compound, C10H9NS2, represents the first structurally studied derivative of di­thio­phthal­imide. The C=S bond lengths are 1.629 (3) and 1.637 (3) A; other geometric parameters are very close to the analogous values observed in the phthal­imide structures. The least-square planes of the di­thio­phthal­imide parts of the mol­ecules in the crystal are parallel; these parts do not form any short contacts, leaving space for the ethyl groups pointing out of the plane [the `out-of-plane torsion angles' C—N—C—C being equal to 90.7 (4) and −91.6 (4)°].

The alkali diaqua complexes of hydrogen chloranilic acid of [KHCA(H2O)2], [RbHCA(H2O)2] and [CsHCA(H2O)2], and the salt of NH4HCA·2H2O were prepared and their crystal structures determined. The homologues of lithium and sodium are not stable, but their analogues [LiHCAEtOH] and [Na5HCA(CA)2(H2O)10] were obtained. All crystal structures studied, with exception of [LiHCAEtOH], reveal 3D-hydrogen bond networks with pronounced π⋯π interactions between anions supported by attractive polar interactions ; the shortest separation distance between the centroids [3.229(2) Å] of the hydrogen chloranilate rings in a face-to-face stack is observed in the structure of [KHCA(H2O)2]. The analysis presented is focused on noncovalent interactions, in particular, the influence of cations and hydrogen bonds on the π-stacking of quinoid rings.

The possible mechanism of lithium exchange from Li 2 FeTiO 4 is discussed on the basis of three different in situ structural characterization methods. The in situ X-ray diffraction (XRD) showed that the mechanism of lithium exchange was through a solid solution formation whereby the change in volume during the oxidation was 1.4%. The reversibility in terms of charge recuperation was complete; however, after the first reduction, the change in volume was still 0.4%. In situ Mossbauer spectroscopy experiment showed complete Fe(II) oxidization to Fe(III), while the reduction was not reversible. After the complete first cycle, the number of local environments in the Mossbauer spectra needed for a successful fit increased by at least two. Several local environments can be explained on the basis of extended X-ray absorption fine structure results. In the as-prepared sample, Fe cations are coordinated to three oxygen atoms at 2.03 A and another three at 2.13 A. With the oxidation of Fe, the splitting of two oxygen atoms gradually increases to 0.18 A, and the octahedra deformation gradually changes from 3 + 3 to 4 + 2. This deformation is not reversible and it can explain changes in the long-range order as observed from in situ XRD.

Two new imidazo[1,2-a]pyridines, 8-hydroxyimidazo[1,2-a]pyridine-2-carboxylic acid (4) and ethyl 8-hydroxyimidazo[1,2-a]pyridine-2-carboxylate (6) were prepared via cyclization of 2-aminopyridin-3-ol (1) with bromopyruvic acid (2) and ethyl bromopyruvate (3), respectively. 8-Hydroxyimidazo[l,2-a]-pyridine-2-carboxylic acid (4) was successfully coupled with various amino acid derivatives via its active ester intermediate into the corresponding amides 22-27. O-protected ethyl 8-hydroxyimidazo[l,2-a]pyridine-2-carboxylate 11 was transformed into its hydrazide 13, acyl azide 14, and amide 15 derivatives.

Thermal transformations of 3-azido-4H-quinolizin-4-ones 4a,b and 3-azido-4H-azino[1,2–x]pyrimidin-4-ones 4c,d, available from the corresponding heteroarylamines 2a–d, were studied. The reaction products were mostly dependent on the solvent. Thus, heating of 3-azido-1-cyano-4H-quinolizin-4-one (4a) in toluene afforded 2-(pyridin-2-yl)fumaronitrile 5a, whereas 3-amino-1-cyano-4H-quinolizin-4-one (8) was obtained on treatment of 4a in a mixture of toluene and trifluoroacetic anhydride. However, heating of 4a in acetic anhydride and in acetic acid resulted in a ring contraction to produce 3-(diacetylamino)indolizine-1-carbonitrile 6a and 3-(acetylamino)indolizine-1-carbonitrile 7a, respectively. Similarly, ring contractions took place on heating ethyl 3-azido-4-oxo-4H-quinolizin-1-carboxylate 4b and 3-azido-4H-azino[1,2–x]pyrimidin-4-ones 4c,d in acetic anhydride or acetic acid to produce the N-acetylated 3-aminoindolizine derivatives 6b, 7b and 3-aminoimidazo[1,2–x]azine derivatives 6c,d in 30–89% yields. The structures of compounds 5–8 were determined by NMR spectroscopy and X-ray diffraction.

Indolyl glycinates (3, 7, and 11) were transformed with t-butoxybis(dimethylamino)methane (Bredereck's reagent) into 3-[(dimethylamino)methylidene]-2,3-dihydropyrazino[1,2-a]indole-1,4-dione (4), 3-(dimethylamino)-2-[(1H-indol-3-ylcarbonyl)amino]propenoate (8), and 2-(1-methyl-1H-indol-2-yl)-1,3-oxazol-5(4H)-one derivative (12). Dipeptides (16a-c) were transformed with Bredereck's reagent into the hydantoin (imidazolidine-2,4-dione) derivatives (17a-c).

Methyl (E)-2-[(benzyloxycarbonyl)amino]-3-cyanopropenoate (4) was, as a versatile multifunctional reagent, transformed with hydrazine and monosubstituted aromatic and heteroaromatic hydrazines under various conditions into derivatives of pyridazine (6), pyrrole (7), imidazole-2,4-dione (9), and pyrazole (13).

Ethyl (2E)-3-dimethylamino-2-[(4Z)-4-dimethylaminomethylidene-5-oxo-1-phenyl-4,5-dihydro-1H-pyrazol-3-yl]propenoate (3) was transformed with N-nucleophiles into ethyl 3-oxo-2-phenyl-3,5-dihydro-2H-pyrazolo[4,3-c]pyridine-7-carboxylates (6, 7, 9, 12, and 14).

Methyl 2-benzoylamino-2-oxobutanoate (1) was transformed with aromatic amines (2a-d) into methyl 2-arylamino-2-(benzoylamino)but-2-enoates (3a-d) Cyclization of compounds (3a-c) in polyphosphoric acid affords a mixture ofoxazolo[4,5-c]quinoline derivatives (4a-c) and 1 -aryl-2-phenyl-5-methyl- 1H-imidazole-4-carboxylates (5a-c), while compound 3d gives a mixture of 9-bromo- (4d) and 7-bromooxazolo[4,5-c]quinoline derivative (4d').