2‐Amino‐4‐chloro‐6‐[N‐methyl‐N‐(4‐methylphenyl)amino]pyrimidine: formation versus fragmentation of hydrogen‐bonded chains of edge‐fused R22(8) rings in 4,6‐disubstituted 2‐aminopyrimidines

Molecules of the title compound, C₁₂H₁₃ClN₄, are linked by two independent N—H...N hydrogen bonds into a chain of edge‐fused R₂²(8) rings. The significance of this study lies in its attempt to rationalize the patterns of supramolecular aggregation in the title compound and in a range of analogous 4,6‐disubstituted 2‐aminopyrimidines.     

Hydrogen‐bonded sheets in benzylmethylammonium hydrogen maleate

In the title compound, C₈H₁₂N⁺·C₄H₃O₄⁻, there is a short and almost linear but asymmetric O—H...O hydrogen bond in the anion. The ions are linked into C₂²(6) chains by two short and nearly linear N—H...O hydrogen bonds and the chains are further weakly linked into sheets by a single C—H...O hydrogen bond.     

Synthesis of 6‐(2‐hydroxybenzoyl)pyrazolo[1,5‐a]pyrimidines by reaction of 5‐amino‐1h‐pyrazoles and 3‐formylchromone

Reaction of 3‐formylchromone ( 1 ) with 5‐amino‐1H‐pyrazoles ( 2 ) in ethanol, afforded 6‐(2‐hydroxy‐benzoyl)pyrazolo[1,5‐a]pyrimidines ( 3a‐g ) in good yields. The structures and the regiospecificity of the reaction were established by nmr measurements and X‐ray analysis, in which soft intermolecular hydrogen‐bonded networks were found.     

Thermal study of an aged dredged sludge

A dredged sludge was studied to investigate the influence of ageing and of pretreatment on its drying rate, water sorption/retention, thermal mass loss, XRD and microstructure (SEM).Ageing caused change in particle thickness and specific surface, a gradual aggregation to form units of the size 10–50 m, formation of macropores of similar size, unhomogeneity and fissures between aggregates and super-aggregates. Macropores were detectable by the initial drying rate especially at 45°C. They indicated a tendency of collapsing at a lower drying rate at 30°C. This is consistent with SEM observations. With ageing the aggregates were more compact and less sensitive to drying.The aggregated system indicated a higher initial drying rate (higher permeability), whereas stirring induced a lower drying rate, favouring the formation of compact laminar structure.XRD peak intensity was lowered with ageing due to decrease in crystallinity (stacking faults and/or decrease in crystallite size). The content of amorphous material was lowered as well, reducing water sorption/desorption, which indicated that the specific surface is lower.From the suitable microstructure induced by ageing some new phases may form (feldspar, zeolites), preferably in the coarser fraction of the sludge. This is disturbed by stirring which operation expels also carbonates from the particle edges and this may reduce the structural strength of the sludge. In aged bentonite suspension a similar tendency was observed of formation of specific microstructures capable of phase transformation, e.g. to feldspar.     

Enantiomerically pure alpha-amino aldehydes from silylated alpha-amino acids

The disilylation of alpha-amino acids 1 to provide 2 (72-87%) was achieved without racemization. An unprecedented borane-mediated semi-reduction strategy was devised to convert 2 to stable, isolable oxazaborolidines 3 (100%) which were hydrolyzed to provide 5 (49-60%) as pure, stable compounds. Analysis of the Mosher amides (8) of the gamma-amino esters 7 reveals that < or =2% racemization occurs in the 1 --> 8 conversions.     

[N‐(6‐Amino‐3,4‐di­hydro‐3‐methyl‐5‐nitroso‐4‐oxopyrimidin‐2‐yl)glycylglycinato]aquapotassium,a three‐dimensional coordination polymer

In the title compound, polymeric potassium N‐(6‐amino‐3,4‐di­hydro‐3‐methyl‐5‐nitro­so‐4‐oxopyrimidin‐2‐yl)­glycyl­gly­cinate hydrate, (K⁺·C₉H₁₁N₆O₅^?·H₂O)_n, the hexacoordinate K⁺ cation is linked to five different anions as well as to the water mol­ecule, with K—O distances in the range 2.617 (2)–2.850 (2) Å. Four of the O atoms in each anion coordinate to K centres, one of them acting as a bridging ligand, leading to the formation of nearly square centrosymmetric K₂O₂ rings. The structure is analysed in terms of (010) metal–ligand sheets linked by [010] chains of fused rings.     

4-(4-Chlorophenyl)-3,7,7-trimethyl-1-[2-(4-nitrobenzoyl)ethyl]-4,7,8,9-tetrahydro-1H-pyrazolo[3,4-b]quinolin-5(6H)-one–ethanol (1/1)

Molecules of the title compound, C₂₈H₂₇ClN₄O₄·C₂H₆O, form a C(6) chain via an N—H⋯O hydrogen bond along the c axis by the operation of a c-glide plane, with N⋯O = 2.761 (3) Å and N—H⋯O = 165°. The mol­ecules are further linked by a weak C—H⋯O interaction, with C⋯O = 3.344 (4) Å and C—H⋯O = 150°. Pendant hydrogen-bonded ethanol solvent mol­ecules are attached to the chains by O—H⋯N hydrogen bonds, with O⋯N = 2.904 (3) Å and O—H⋯N = 175°.     

Highly Dispersible and Stable Anionic Boron Cluster–Graphene Oxide Nanohybrids

An efficient process to produce boron cluster–graphene oxide nanohybrids that are highly dispersible in water and organic solvents is established for the first time. Dispersions of these nanohybrid materials in water were extraordinarily stable after one month. Characterization of hybrids after grafting of appropriate cobaltabisdicarbollide and closo‐dodecaborate derivatives onto the surface of graphene oxide (GO) was done by FT‐IR, XPS, and UV/Vis. Thermogravimetric analysis (TGA) clearly shows a higher thermal stability for the modified‐GO nanohybrids compared to the parent GO. Of particular note, elemental mapping by energy‐filtered transmission electron microscopy (EFTEM) reveals that a uniform decoration of the graphene oxide surface with the boron clusters is achieved under the reported conditions. Therefore, the resulting nanohybrid systems show exceptional physico‐chemical and thermal properties, paving the way for an enhanced processability and further expanding the range of application for graphene‐based materials.     

8‐tert‐Butyl‐7‐(4‐chlorophenyl)‐10‐phenyl‐5,6‐dihydro‐10H‐benzo[h]pyrazolo[3,4‐b]quinoline

The title compound, C₃₀H₂₆ClN₃, crystallizes with Z′ = 3 in the P space group. The three independent molecules have very similar, although not identical, conformations, with almost perfect screw‐boat forms adopted by the non‐aromatic carbocyclic rings. Four independent C—H...π(arene) hydrogen bonds link the molecules into centrosymmetric six‐component aggregates.     

Redetermination of 6‐amino‐5‐formyl‐1,3‐dimethyluracil monohydrate at 120 K: a polarized molecular structure and two interwoven hydrogen‐bonded frameworks

The title compound [systematic name: 6‐amino‐5‐formyl‐1,3‐dimethylpyrimidine‐2,4(1H,3H)‐dione monohydrate], C₇H₉N₃O₃·H₂O, has been reexamined at 120 K. The improved precision of the intramolecular dimensions provides evidence for a polarized molecular–electronic structure, and the molecular components are linked by one N—H...O and two O—H...O hydrogen bonds into two interwoven three‐dimensional frameworks, which are weakly linked by the longer component of a three‐centre N—H...(O)₂ hydrogen bond.