Correlation between Solution and the Solid State: The pH Dependent Composition in the Ternary System [Co(H2O)6]2+ or [Ni(H2O)6]2+/Piperazine/Phosphate

The protolytic equilibria of piperazine (C₄H₁₀N₂) and phosphate have been investigated in the presence of cobalt or nickel chloride or nitrate by potentiometric titrations between pH 2 and 8. Potentiometric titrations suggest the presence of [M²⁺(H₂O)₅(C₄H₁₁N₂⁺)]³⁺ and [M²⁺(H₂O)₅(C₄H₁₀N₂)]²⁺ in solution with stability constants logK of 3.1 and 3.8 for M = Co and 3.1 and 3.6 for M = Ni, respectively. Crystallization experiments were then conducted at selected pH values to isolate desired species from the known solution composition. Crystallization afforded [M(H₂O)₆]²⁺(C₄H₁₂N₂²⁺)(HPO₄^2—)₂ at pH 3.5 and 6.2 (M = Co, Ni), and Co₃(PO₄)₂·8H₂O at pH 10.5. No crystals with the dihydrogenphosphate anion or a metal‐bound piperazine ligand could be isolated under the reaction conditions. The solid‐state assembly in the isomorphous structures of [M(H₂O)₆](C₄H₁₂N₂)(HPO₄)₂ with M = Co and Ni is based on an extended hydrogen bonded network between the three ionic building blocks.     

Spectroscopic characterization and preparation of low molecular,water‐soluble chitosan with free‐amine group by novel method

Low molecular, water‐soluble chitosan (LMWSC) with a free amine group was prepared by the novel salts‐removal method described in this study. A weight‐average molecular weight and degree of deacetylation (DDA) of LMWSC were determined by viscometry and Kina titration, resulting in 18,579 Da and 93% DDA, respectively. In the Fourier transform infrared spectroscopic, ¹H NMR, and ¹³C NMR spectra the absorption band by the carboxyl group derived from lactic acid and the impurities formed in the enzymatic process disappeared or were significantly lower than that of the control chitosan. Also, from the ¹H NMR and ¹³C NMR spectra the empirical value for the area ratio of the proton and carbon corresponds nearly to its theoretical values. The matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrum identified the difference in the two adjacent peaks as 161. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3796–3803, 2002     

Novel Sesquiterpenes from the Fungus Lactarius piperatus

Four novel sesquiterpenes, namely 7α,8β,13‐trihydroxy‐5,13‐marasmanolide ( 2 ), isoplorantinone ( 5 ), 4,8,14‐trihydroxyilludala‐2,6,8‐triene ( 6 ), and 8‐hydroxy‐8,9‐secolactara‐1,6‐dien‐5,13‐olide ( 10 ), together with six known ones, 7α,8β‐dihydroxy‐5,13‐marasmanolide ( 1) , 7α,8α‐dihydroxy‐5,13‐marasmanolide ( 3 ), isolactarorufin ( 4 ), blennin A ( 7 ), blennin D ( 8 ), and lactarorufin ( 9 ), were isolated from the ethanolic extract of Lactarius piperatus. The structures of these sesquiterpenes, representing diversified structural types, were determined mainly by spectroscopic methods, especially 2D‐NMR techniques. The structure of 6 was further confirmed by a single‐crystal X‐ray‐diffraction determination.     

用硼酸作催化剂一锅法合成双（二氢化嘧啶酮-4-基）苯

A simple effective synthesis of bis(dihydropyrimidinone-4-yl)benzene derivatives, using boric acid as catalyst,from isophthalic aldehyde or terephthalic aldehyde, 1,3-dicarbonyl compounds and urea or thiourea in glacial acetic acid was described. As the expansion of the classical Biginelli reaction, this method has the advantage of excellent yields 83%-94% and short reaction time 0.5-1.5 h.     

Synthesis,Spectroscopic Studies,and Crystal Structures of Phenylorganotin Derivatives with [Bis(2,6‐dimethylphenyl)amino]benzoic Acid: Novel Antituberculosis Agents

The novel triphenyl adduct of 2‐[(2,6‐dimethylphenyl)amino]benzoic acid (HDMPA; 1 ), i.e., [SnPh₃(DMPA)] ( 2 ), the dimeric tetraorganostannoxane [Ph₂(DMPA)SnOSn(DMPA)Ph₂]₂ ( 3 ), and the monomeric adduct [SnPh₂(DMPA)₂] ( 4 ), where DMPA is monodeprotonated HDMPA, have been prepared and structurally characterized by means of IR, ¹H‐NMR, and ¹³C‐NMR spectroscopy. The structures of 1 and 2 have been determined by X‐ray crystallography. Single‐crystal X‐ray‐diffraction analysis of 1 revealed that there are two molecules in the asymmetric unit, HD1 and HD2 , differing in conformation, both forming centrosymmetric dimers linked by H‐bonds between the carboxylic O‐atoms. X‐Ray analysis of 2 revealed a pentacoordinate structure containing Ph₃Sn coordinated to the carboxylato group. Significant C? H/π interactions and intramolecular H‐bonds stabilize the structures of 1 and 2 , which self‐assembled via C? H/π and π/π‐stacking interactions. The Ph₃Sn adduct 2 was found to be a promising antimycobacterial lead compound, displaying activity against Mycobacterium tuberculosis H37Rv. The cytotoxiciy in the Vero cell line is also reported.     

Novel Hydrogen‐bond Three Dimensional Networks Generated from the Reaction of Metal Nitrate Hydrate (M = Co,Ni) with Ammonium Thiocynate and Bidentate Ligand Piperazine

The reaction of Co(NO₃)₂·6H₂O with two equivalents of PPz (PPz = piperazine hexahydrate) and two equivalents of NH₄SCN in CH₃OH afforded the complex [Co(NCS)₂(PPz)₂(CH₃OH)₂]. The reaction of Ni(NO₃)₂·6H₂O with two equivalents of PPz and four equivalents of NH₄SCN in CH₃OH afforded the complex [Ni(NCS)₄(PPz)₂]. Their IR spectra have been recorded and the structures have been determined. Crystal data for 1 : space group P&1bar;, a = 6.7208(6) Å, b = 8.4310(8) Å, c = 8.5923(8) Å, a = 77.881(2)°, β = 76.342(2)°, γ = 83.936(2)°, V = 461.75(1) ų, Z = 1 with final residuals R1 = 0.0650 and wR2 = 0.1725. Crystal data for 2 : space group P2(1)/n, a = 7.4209(6) Å, b = 11.0231(9) Å, c = 12.317(1) Å, β = 96.642(9)°, V = 1000.9(2) ų, Z = 2 with final residuals R1 = 0.0378 and wR2 = 0.0809. Important NCS—H‐N and O‐H—N(PPz) hydrogen‐bonding interactions in compound 1 and NCS···H‐N hydrogen‐bonding interactions and NCS—SCN interactions in compound 2 play a significant role in aligning the polymer strands in crystalline solids.     

Self－assembly of Novel Hetero[3]rotaxane, [2]Rotaxanes and [2]Catenane

One linear template 13 and one cyclophane template 15, both incorporating two electron rich 1,4‐dialkoxybenzene units and one diamide unit, have been synthesized. By utilizing donor‐acceptor interaction and/or intermolecular hydrogen bonding assembling principles, one novel hetero[3]rotazane 22·4Cl, possessing one neutral and one tetracationic ring components, has been synthesized from 13, through neutral [2]rotaxane 21 as intermediate. With 15 as template, tetracationic [2]catenane 23·4PF₆ was assembled by using donor‐acceptor interaction, but no neutral [2]rotaxane could be obtained under the typical conditions of hydrogen bonding assembling principle. The interlocked supramolecular compounds have been characterized and their spectral properties are investigated.     

Cleavage of the Fe—Fe Bond of （Me2SiSiMe2） [η^5－C5H4Fe（CO）2]2 with Na／Hg and Molecular Structure of the Ring－Opened Complex

The reaction of the rifle cyclic complex (1) with sodium amalgam in THF resulted in the expected cleavage of the Fe-Fe bond to afford his-sodium salt ( Me2SiSiMe2 ) [η^5-C5H4Fe(CO)2]2 (4). The latter was not isolated and was used directly to react with MeI, PhCH2Cl, CH3C(O)Cl, PhC(O)Cl,Cy3SnCl (Cy= cyclohexyl) or Ph3SnCl to afford corresponding ring-opened derivatives (Me2SiSiMe2) [η^5-C5H4Fe(CO)2]2 [5, R=Me; 6, R=PhCH2; 7, R=CH3C(O); 8, R=PhC(O); 9, R = Cy3Sn or 10, R = Ph3Sn ]. The crystal and molecular structures of 10 were determined by X-ray diffraction analysis. The molecule took the desired ant/ conformation around the Si-Si bond. The length of the Si--Si bond is 0.2343(3)nm, which is essentially identical to that in the cyclic structure of 1[0.2346(4) tun]. This result unambiguously demonstrates that the Si--Si bond in the cyclic structure of 1 is not subject to obvious strain.     

The Chemistry of Tetrafluoroallene： One－pot Synthesis of Trifluoromethylindolizines from 1,3－Diiodo－1,1,3,3－tetrafluoropropane by 1,3－Dipolar Cycloaddition

Heating a mixture of 1, 3-diiodo-1, 1, 3, 3-tetrafluoropropane (2), K2CO3, pyridinium bromides (3) in CH3CN at 65℃ for 10 h gives the corresponding trifluoromethylindolizines.     

The Methoxycarbonylation of Vinyl Acetate Catalyzed by Palladium Complexes of [1,2‐Phenylenebis(methylene)]bis[di(tert‐butyl)phosphine]

Palladium complexes of [1,2‐phenylenebis(methylene)]bis[di(tert‐butyl)phosphine] ( 1 ) catalyze the methoxycarbonylation of vinyl acetate (= ethenyl acetate) in the presence of methanesulfonic acid (Scheme 1). High selectivities to ester products can be obtained if free phosphine ligand is in excess over the amount of added acid (Table 1). Selectivities to methyl 2‐acetoxypropanoate, a precursor to lactate esters, can be as high as 3.6 : 1 at low temperature and pressure (Table 2). Replacing ^tBu by ⁱPr groups leads to less‐active catalysts and lower selectivities to the branched product. Replacing the phenylene moiety by a naphthalenediyl moiety also gives lower activity, but with similar selectivity to the phenylene‐based analogues. Linear hydrocarbon‐chain linkers as the backbone instead of the phenylenebis(methylene) linker leads to poor catalysis, except for a propane‐1,3‐diyl linker, which gives good rates but poor branched selectivity (Table 5). The effect of different reaction conditions on the catalysis is discussed. The syntheses of the new xylene‐based diphosphines 2 – 5 with one to four ⁱPr groups replacing the ^tBu groups at the P‐atoms of 1 and of the ligands 6 and 7 based on 1,2‐ and 2,3‐dimethylnaphthalene are also described (Schemes 2 and 3).