1,3-dialkyl- and 1,3-diaryl-3,4,5,6-tetrahydropyrimidin-2-ylidene rhodium(i) and palladium(II) complexes: synthesis, structure, and reactivity

The synthesis of novel 1,3-diaryl- and 1,3-dialkylpyrimidin-2-ylidene-based N-heterocyclic carbenes (NHCs) and their rhodium(i) and palladium(II) complexes is described. The rhodium compounds bromo(cod)[1,3-bis(2-propyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene]rhodium (7), bromo(cod)(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene)rhodium (8) (cod=eta(4)-1,5-cyclooctadiene, mesityl=2,4,6-trimethylphenyl), chloro(cod)(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene)rhodium (9), and chloro(cod)[1,3-bis(2-propyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene]rhodium (10) were prepared by reaction of [[Rh(cod)Cl](2)] with lithium tert-butoxide followed by addition of 1,3-dimesityl-3,4,5,6-tetrahydropyrimidinium bromide (3), 1,3-dimesityl-3,4,5,6-tetrahydropyrimidinium tetrafluoroborate (4), 1,3-di-2-propyl-3,4,5,6-tetrahydropyrimidinium bromide (6), and 1,3-di-2-propyl-3,4,5,6-tetrahydropyrimidinium tetrafluoroborate, respectively. Complex 7 crystallizes in the monoclinic space group P2(1)/n, and 8 in the monoclinic space group P2(1). Complexes 9 and 10 were used for the synthesis of the corresponding dicarbonyl complexes dicarbonylchloro(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene)rhodium (11), and dicarbonylchloro[1,3-bis(2-propyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene]rhodium (12). The wavenumbers nu(CO I)/nu(CO II) for 11 and 12 were used as a quantitative measure for the basicity of the NHC ligand. The values of 2062/1976 and 2063/1982 cm(-1), respectively, indicate that the new NHCs are among the most basic cyclic ligands reported so far. Compounds 3 and 6 were additionally converted to the corresponding cationic silver(i) bis-NHC complexes [Ag(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene)(2)]AgBr(2) (13) and [Ag[1,3-bis(2-propyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene](2)]AgBr(2) (14), which were subsequently used in transmetalation reactions for the synthesis of the corresponding palladium(II) complexes Pd(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene)(2) (2+)(Ag(2)Br(2)Cl(4) (4-))(1/2) (15) and Pd[1,3-bis(2-propyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene)(2)]Cl(2) (16). Complex 15 crystallizes in the monoclinic space group P2(1)/c, and 16 in the monoclinic space group C(2)/c. The catalytic activity of 15 and 16 in Heck-type reactions was studied in detail. Both compounds are highly active in the coupling of aliphatic and aromatic vinyl compounds with aryl bromides and chlorides with turnover numbers (TONs) up to 2000000. Stabilities of 15 and 16 under Heck-couplings conditions were correlated with their molecular structure. Finally, selected kinetic data for these couplings are presented.     

碳碳相关谱测定泽泻萜醇F的结构

从泽泻中分离出新化合物泽泻萜醇F，采用二维核磁共振碳相关技术研究了该化合物的骨架结构。结合碳碳相关谱及远程碳氢相关谱等其它二维核磁共振技术，分析了该化合物的常规氢谱和碳谱，并准确归属了质子和碳核的化学位移。     

Biomimetic Asymmetric Reduction of Quinazolinones with Chiral and Regenerable NAD(P)H Models

A facile approach to chiral dihydroquinazolinone derivatives has been described via biomimetic asymmetric reduction of quinazolinones with chiral and regenerable NAD(P)H models. The utility of this method was demonstrated by a concise synthesis of the bromodomain protein divalent inhibitor.     

Reactivation pathway of the hydrogenase H‐cluster: Density functional theory study

This work puts forth a reaction pathway for the reactivation of exogenous ligand inhibited H‐cluster, the active site of Fe‐only hydrogenases. The H‐cluster is a dimetal complex, Fe–Fe, with the metal centers bridged by di(thiomethyl)amine. Exogenous ligands, H₂O, and OH^?, are bound to the distal iron (Fe_d). Density functional theory (DFT) calculations on the native and ruthenium‐modified H‐cluster have been performed using the B3LYP functional with 6‐31+G** and 6‐311+G** basis sets. We have ascertained that there is a thermodynamically favorable pathway for the reactivation of the OH^? inhibited H‐cluster, which proceeds by an initial protonation of the Fe_d–OH^? complex. The proposed reaction pathway has all its intermediate reactions ensue exothermically. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007     

Deoxypegan-1-one derivatives. synthesis and borohydride reduction of 3-[(E)-arylmethylidene]-3,9-dihydropyrrolo[2,1-b]quinazolin-1(2H)-ones

3-[(E)-Arylmethylidene]-3,9-dihydropyrrolo[2,1-b]quinazolin-1(2H)-ones were prepared by reaction of quinazolyl-2-propionic acid hydrochloride with aromatic aldehydes in acetic anhydride in the presence of Et₃N. 3-[(E)-Arylmethylidene]-1,2,3,9-tetrahydropyrrolo[2,1-b]quinazolin-1-ols were formed by reduction of the 3-arylidene derivatives with sodium borohydride in methanol, readily lost water when heated with acids, and were converted into 3-[(E)-arylmethylidene]-3,9-dihydropyrrolo[2,1-b]quinazolines. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 463–467, September–October, 2006.     

Thermotropic Liquid Crystals Formed by Intermolecular Hydrogen Bonding Interactions

The role of hydrogen bonding in the formation or stabilization of liquid crystalline phases has only recently been appreciated. Following the first, wellestablished examples of liquid crystal formation from the dimerization of aromatic carboxylic acids, through hydrogen bonding, several classes of compounds have recently been synthesized, the liquid crystalline behavior of which is also dependent on intermolecular hydrogen bonds between similar or dissimilar molecules. In this review the main classes of compounds exhibiting liquid crystallinity due to hydrogen bonding are presented to show the diversity of organic compounds that can be used as building elements in liquid crystals. The molecules are either of the rigid-rod anisotropic or amphiphilic types such as molecules appropriately functionalized with pyridyl and carboxyl groups, whose interaction leads to the formation of liquid crystals; amphiphilic carbohydrates and amphiphilic and bolaamphiphilic compounds with multiple hydroxyl groups whose dimerization or association is indispensable for the formation of liquid crystals; and certain amphiphilic carboxylic acids with monomeric or polymeric mesogens and amphiphilic-type compounds bearing different moieties, whose interaction may lead to the formation of mesomorphic compounds. Associated with the macroscopic display of liquid crystalline phases is the supramolecular structure, and therefore rather extended discussion of these structures are included in this review.     

F and C spectra of fluorinated and partially fluorinated vinyl alkyl ethers

Fluorine, hydrogen, and ¹³C NMR spectral data have been obtained for vinyl alkyl ethers containing fluorines. Some of the molecules are perfluorinated and others include hydrogen, bromine, and chlorine substituents. New generalizations regarding FF spin-spin coupling are developed and used, along with previously recognized correlations, in the confirmation of structures and the assignments of resonances. ¹³C spectroscopy, especially the analysis of ¹³C¹⁹F coupling, is critical in several of the structure determinations. Chlorine isotope effects on fluorine chemical shifts are observed when the chlorine and fluorine are attached to the same carbon, and are also used in the structure analyses. Long-range couplings between fluorines in the vinyl group and fluorines in the alkyl group are interpreted in terms of molecular geometry which allows certain of the alkyl fluorines to “touch” the fluorines cis and gem to the ether oxygen but not the fluorine trans to the oxygen. Two bond ¹³C¹⁹F coupling across the vinyl double bond is found to vary dramatically with the electronegativity of the vinyl substituents in the ethers, in accordance with previous observations for olefins.     

PEMFC催化剂的研究：自制抗CO中毒Pt-Ru/C电催化剂的性质

用胶体法制备了抗CO中毒PEMFC阳极Pt-Ru/C电催化剂（标记为THYT－2）,对 比研究了THYT－2与Johnson Matthey (JM)公司同类品牌Pt-Ru/C催化剂的电化学及 其它物理化学性能。结果表明,THYT－2电催化剂在甲醇燃料电池和CO／H_2（Φ_ (CO) = 1 * 10~(-4)）的氢氧燃料电池中的电催化行为与JM催化剂相当,但THYT－ 2在低浓度CO氢气燃料中的电池性能更好。两种催化剂的其它物理化学性质具有类 似性：XPS分析结果表明THYT－2和JM催化剂 中都有三种不同价态的Pt存在：即金 属态Pt(0)、氧化态Pt(II)和Pt(IV)。HRTEM测试结果表明两种催化剂的粒径处在2 ～3 mn左右,这可能是它们拥有良好电化学性能的主要原因之一。本文还对催化剂 中Pt与Ru组分的分布和相互作用进行了讨论,提出了改进Pt-Ru/C电催化剂的思路 。     

Synthesis of the anionic fluororeceptors based on thiourea and amide groups and recognition property for α,ω-dicarboxylate

Three new neutral receptors (1, 2 and 3) containing thiourea and amide groups were synthesized by simple steps in good yields. The binding properties for anions of 1, 2 and 3 were examined by UV-vis, fluorescence, and ¹H NMR spectroscopy. Receptors 1, 2 and 3 all had a better adipate anion selectivity by comparison with other dicarboxylate anions. The association constants of 1, 2 and 3 with adipate were higher as compared to other anions (malonate, succinate, glutarate). In particular, a distinct color change was observed from light yellow to orange-red upon addition of adipate to the solution of 1 in DMSO. The UV-vis and fluorescence data indicate that a 1:1 stoichiometry complex is formed between compound 1, 2 or 3 and dicarboxylate anions through hydrogen bonding interactions.     

Synthesis, Crystal Structure, and IR Spectroscopic Characterization of 1,6-Hexanediammonium Dihydrogendecavanadate

Summary.  Anhydrous 1,6-hexanediammonium dihydrogendecavanadate ((HdaH₂)₂H₂V₁₀O₂₈, 1) was prepared by reaction of V₂O₅ with 1,6-hexanediamine in aqueous solution. The crystal structure of 1 was determined, and the proton positions in the H₂V₁₀O₂₈ ⁴⁻ anion were calculated by the bond length/bond number method. The protons are bound to the centrosymmetrically oriented μ–OV₃ groups of the decavanadate anion. Based on the analysis of IR spectra of 1 prepared from H₂O and D₂O, the absorption band at 871 cm⁻¹ can be attributed to δ(V–O_b–H) vibrations. Received August 3, 2001. Accepted (revised) October 8, 2001