Pyrolysis of 1,1,1-trimethylamine-2-arylcarbamoylimides

Pyrolysis of 1,1,1-trimethylamine-2-phenylcarbamoylimide gave sym-diphenylurea, phenylurea, 1,1-dimethyl-4-phenylsemicarbazide, 1,1,2-trimethyl-4-phenylsemicarbazide, aniline, 1,1-dimethylhydrazine, trimethylamine, nitrogen and carbon monoxide as products. Azoformanilide, a possible intermediate, decomposed at lower temperatures and gave diphenylurea, formanilide. and phenyl isocyanate. 1,1,1-Trimethylamine-2-[1-naphthylcarbamoyl]imide behaved s in addition a small amount of naphthalene. Carbarmoylimides involving two substituents in the 2-position behaved differently and gave indazolones.     

Synthesis of 2H-1,5-benzodioxepin and 2,5-dihydro-1,6-benzodioxocin derivatives via ring-closing metathesis reaction

The synthesis of various 2H-1,5-benzodioxepin and 2,5-dihydro-1,6-benzodioxocin derivatives is described. The key step involves the construction of seven- and eight-membered rings via ring-closing metathesis reaction.     

Synthesis and application of phosphinoferrocenylaminophosphine ligands for asymmetric catalysis

A new class of bidentate ligands utilizing a phosphine-aminophosphine structure has been prepared on a ferrocenylethyl backbone in a straightforward and scalable fashion from acetylferrocene. The unique property of the alpha-ferrocenyl carbonium ion that allows the replacement of a variety of "leaving groups" with retention of configuration greatly facilitates the synthesis, and a number of ligands have been prepared by varying the nitrogen and phosphorus substituents on the aminophosphine. These readily prepared phosphinoferrocenylaminophosphines, known as BoPhoz ligands, show surprising hydrolytic and air stability, with no degradation after 3 years open to the air. The rhodium complexes of these ligands show exceedingly high enantioselectivities (generally >95% ee) and activities often in excess of 50,000 catalyst turnovers per hour for the asymmetric hydrogenation of a wide variety of dehydro-alpha-amino acid and itaconic acid derivatives. They also show high activity and good to excellent enantioselectivity for the hydrogenation of a number of alpha-ketoesters.     

Enol-enamine tautomerism in crystals of 1,3-bis(pyridin-2-yl) propan-2-one: a combined crystallographic and quantum-chemical investigation of the effect of packing on tautomerization processes

The enolpyridine, OH-ketoenamime, NH equilibrium in crystals of 1,3-bis(pyridin-2-yl)propan-2-one was studied using temperature-dependent single-crystal X-ray diffraction. The relative population of the different tautomers was found to be sensitive to the temperature in the range of 100-300 K, illustrating the small thermodynamic difference between these two tautomers. This energy resemblance is partially attributed to the molecular packing in the crystal, where the molecules are arranged in the form of dimers. Ab initio electronic energy calculations (HF/6-31G** and MP2/6-31G**) reveal the effect of dimerization in the crystal on the electronic energy levels. Several tautomeric states were identified in the dimer of 1,3-bis(pyridin-2-yl)propan-2-one. A model is proposed in which four of these dimer states are populated in the crystal at ambient temperatures. The crystallographic data were treated according to this four-state dimer model, suggesting that the free energy of the OH-NH dimers is higher than that of the OH-OH dimers by 120 +/- 10 cal mol(-1) and that the NH-NH dimers are yet higher in free energy by 50 +/- 10 cal mol(-1).     

Light‐triggered stabilization of microgel aggregates

Supramolecular assembly holds great potential in many technological applications. Such structures, however, tend to destabilize in dynamic environments due to weak interactions between their constituent entities. We report on a highly modular and biofriendly chemistry for the stabilization of supramolecular microgel aggregates. Upon irradiation, these structures undergo intermolecular cross‐linking, providing an efficient mechanism for stabilization.     

The structure of vincarodine

The structure of vincarodine has been determined to be 1 by an investigation of its IR.-, UV.-, ¹H- and ¹³C-NMR.- and mass spectra. A ¹³C-NMR. analysis has been performed on the bases vincamine ( 2 ), epivincine ( 9 ), 14, 15-dehydrovincine ( 7 ) and its 16-epimer ( 8 ).     

A theoretical study of three and four proton donors on linear HX···BeH2···HX and bifurcate BeH2···2HX trimolecular dihydrogen-bonded complexes with X?=?CN and NC

The interaction phenomenon H^−δ···H^+δ between two hydrogen atoms binding each other is well-known in dihydrogen-bonded complexes. Either by experimental or theoretical viewpoint, dihydrogen bonds are often known as directional or bifurcate interactions. Regarding the beryllium hydride BeH₂, its capacity to form bimolecular complexes with proton donors has been demonstrated, but in some cases, trimolecular complexes are also characterized in a minimum of the potential energy surface. As such, in this work is presented a theoretical study about the formation of trimolecular dihydrogen complexes with three hydrogen centers. By taking into account the beryllium hydride BeH₂ as proton acceptor, two classical proton donors were chosen, HCN and HNC. The great goal of this work is the analysis of two dihydrogen complexes types: bifurcate BeH₂···2HX and linear HX···BeH₂···HX. In these systems, it is discussed the capacity of one hydride H^−δ (H–Be–H^−δ) to interact simultaneously with two proton donors, as well as when two hydrides H^−δ (^−δH–Be–H^−δ) form linear dihydrogen bonds. In this context, the analysis of the vibrational harmonic spectrum at B3LYP/6-311 ++G(3d,3p) level of theory and the interpretation of the topological parameters derived from Quantum Theory of Atoms in Molecules (QTAIM) aided us to determine which is the most stable trimolecular complex, either bifurcate or linear. Moreover, quantification of charge transfer measured by the QTAIM formalism as well as by ChelpG calculations also were used with the purpose to justify infrared effects, such as red-shift and blue-shift stretch modes on donors (HCN and HNC) and acceptors (BeH₂) of protons.     

The gauge theory of dislocations: A nonuniformly moving screw dislocation

We investigate the nonuniform motion of a straight screw dislocation in infinite media in the framework of the translational gauge theory of dislocations. The equations of motion are derived for an arbitrarily moving screw dislocation. The fields of the elastic velocity, elastic distortion, dislocation density and dislocation current surrounding the arbitrarily moving screw dislocation are derived explicitly in the form of integral representations. We calculate the radiation fields and the fields depending on the dislocation velocities.     

Thermal behaviour of new biological active cadmium mixed ligands complexes

This paper reports the investigation on the thermal stability of new complexes with mixed ligands of the type [Cd(NN)(C₃H₃O₂)₂(H₂O)_m]·nH₂O [(1) NN: 1,10-phenantroline, m = 1, n = 0; (2) NN: 2,2′-bipyridine, m = 0, n = 1.5 and (C₃H₃O₂): acrylate anion]. The IR data indicate a bidentate coordination mode for both heterocyclic amine and acrylate. The in vitro qualitative and quantitative antimicrobial activity assays showed that the complexes exhibited variable antimicrobial activity against planktonic as well as biofilm embedded Gram-negative (Escherichia coli, Klebsiella sp., Proteus sp., Salmonella sp., Shigella sp., Acinetobacter boumani, Pseudomonas aeruginosa), Gram-positive (Bacillus subtilis, Staphylococcus aureus) and fungal (Candida albicans) strains, reference and isolated ones from the hospital environment. The thermal behaviour steps were investigated in synthetic air flow. The thermal transformations are complex processes according to TG and DTA curves including dehydration, amine as well as acrylate thermolysis. The final products of decomposition are the most stable metal oxides.