Condensation of thiourea with uracyl derivatives containing ketone and ketoester fragments,alkylation and macrocyclization of the condensation products

By condensation of thiourea with 6-methyluracyl derivatives containing ketone and ketoester fragmenst in the alkyl chains attached to the nitrogen atoms of the pyrimidine ring the products containing 6-methyl- or 3,6-dimethyluracyl fragment and one or two 6-methyl-4-oxo-2-thio-1,2,3,4-tetrahydropyrimidin-5-yl fragments were synthesized. These compounds can be alkylated with alkyl bromides.     

Modular,Homochiral, Porous Coordination Polymers: Rational Design,Enantioselective Guest Exchange Sorption and Ab Initio Calculations of Host–Guest Interactions

Two new, homochiral, porous metal–organic coordination polymers [Zn₂(ndc){(R)‐man}(dmf)]?3DMF and [Zn₂(bpdc){(R)‐man}(dmf)]?2DMF (ndc=2,6‐naphthalenedicarboxylate; bpdc=4,4′‐biphenyldicarboxylate; man=mandelate; dmf=N,N′‐dimethylformamide) have been synthesized by heating Zn^II nitrate, H₂ndc or H₂bpdc and chiral (R)‐mandelic acid (H₂man) in DMF. The colorless crystals were obtained and their structures were established by single‐crystal X‐ray diffraction. These isoreticular structures share the same topological features as the previously reported zinc(II) terephthalate lactate [Zn₂(bdc){(S)‐lac}(dmf)]?DMF framework, but have larger pores and opposite absolute configuration of the chiral centers. The enhanced pores size results in differing stereoselective sorption properties: the new metal–organic frameworks effectively and stereoselectively (ee up to 62 %) accommodate bulkier guest molecules (alkyl aryl sulfoxides) than the parent [Zn₂(bdc){(S)‐lac}(dmf)]?DMF, while the latter demonstrates decent enantioselectivity toward precursor of chiral anticancer drug sulforaphane, CH₃SO(CH₂)₄OH. The new homochiral porous metal–organic coordination polymers are capable of catalyzing a highly selective oxidation of bulkier sulfides (2‐NaphSMe (2‐C₁₀H₇SMe) and PhSCH₂Ph) that could not be achieved by the smaller‐pore [Zn₂(bdc){(S)‐lac}(dmf)]?DMF. The sorption of different guest molecules (both R and S isomers) into the chiral pores of [Zn₂(bdc){(S)‐lac}(dmf)]?DMF was modeled by using ab initio calculations that provided a qualitative explanation for the observed sorption enantioselectivity. The high stereo‐preference is accounted for by the presence of coordinated inner‐pore DMF molecule that forms a weak C? H???O bond between the DMF methyl group and the (S)‐PhSOCH₃ sulfinyl group.     

Study of the protonation (methylation) position and tautomeric structure of thiopyrimidine derivatives by 2D <Superscript>1</Superscript>H—<Superscript>15</Superscript>H NMR HSQC/HMBC. Experimental approach and theoretical modeling

Two-dimensional ₁H—₁₅N NMR HSQC/HMBC experiments enable the unambiguous determination of the protonation (methylation) position and tautomeric structure of nitrogen-containing heterocycles. In investigated thiopyrimidines protonation (or methylation) occurs at the N(1) atom of the pyrimidine ring. The tautomeric structures of these compounds were established based on the analysis of ₁H—₁₅N NMR spectra. Ab initio calculations of chemical shifts (GIAO B3LYP/6-31G(d)//HF/6-31G) are in full agreement with experimental values. The stability of various protonated (methylated) and tautomeric species is explained in terms of a thermodynamic approach.     

Excited state properties and quadratic optical nonlinearities in charged organic chromophores: theoretical analysis

As it has been found experimentally [K. Clays and B. Coe, Chem. Mater. 15, 642 (2003); B. J. Coe et al., 126, 10418 (2004)], elongation of the conjugation path length and N-arylation in stilbazolium chromophores both lead to substantial enhancement of the molecular optical nonlinearities. In the present contribution the authors perform a quantum chemical analysis of the excited state properties and quadratic nonlinear optical responses of a series of this type of dyes. Nonlinear optical responses are estimated by both finite-field and two-state model approaches that demonstrate an excellent qualitative mutual agreement. Time-dependent density functional theory calculations on the isolated cations predict redshift in the energy of the intramolecular charge transfer transition that is overestimated for cations with the longer conjugation path length. At the same time, in comparison with the Stark spectroscopy measurements the differences between the excited and ground state dipole moments are grossly underestimated for all compounds. The inclusion of solvent effect by polarizable continuum model affords a better agreement with experiment for these quantities. The authors' calculations demonstrate the crucial dependence of the electronic excitation properties on the way of the investigated compound geometry optimization. The origin of such dependence is discussed.     

Numerical Studies of the Influence of the Porosity on Macroscopic Elastic Properties of Carbon/Carbon Composites

Material parameter identification of the carbon/carbon composites was provided using numerical implementation of semi-analytical methods and FE-calculations. The distribution of the fibers and pores obtained from microstructural studies is used as input for homogenization schemes for the determination of the effective elastic constants. The predictions are compared to experimental results. (© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Regulation of the rate of hydrolysis of phosphorus acid esters in organized systems based on amphiphilic pyrimidinophanes

The aggregation and catalytic activity of supramolecular systems based on new macrocyclic dimeric surfactants (pyrimidinophanes) was studied both in the absence and in the presence of polyethyleneimine (PEI). It was found that the critical micelle concentrations measured by tensiometry were independent of the structure of surfactants. The morphology of aggregates was responsible for various characters of the catalytic effects of pyrimidinophanes in the hydrolysis of phosphonic acid esters. A less hydrophobic pyrimidinophane exhibited a typical effect of cationic surfactants to accelerate the reaction both in the absence and in the presence of PEI. Unlike cationic micelles, a heminal-type pyrimidinophane exhibited an anomalous behavior: it had no effect on the rates of hydrolysis of the substrates and did not inhibit the hydrolysis. Upon the addition of lanthanum ions, the catalytic activity of dimeric surfactants increased. The overall catalytic effect due to the action of supramolecular systems based on pyrimidinophanes, PEI, and lanthanum ions can increase the rates of hydrolysis of the substrates by three orders of magnitude, as compared with that of alkaline hydrolysis.     

Heterocyclophanes with 6-methyluracyl and hydantoin fragments. Ring contraction in 1,3-bis(5-bromopentyl)-5-nitrouracyl

Russian Journal of Organic Chemistry -