Synthesis and structural features of cyclobutane-containing chiral bicyclic ureas

Efficient and stereoselective synthetic routes have been developed for the preparation of chiral N-monoprotected cyclobutane bicyclic ureas in which one of the NH groups is protected as a benzyl or tert-butyl carbamate. Ureas in both enantiomeric forms were obtained from a common chiral precursor via the selective manipulation of functional groups. These compounds have been subjected to a structural study in solution and in the solid state. NMR, IR and TEM techniques evidence a strong tendency to aggregation in solution giving regular assemblies, which is a result of intermolecular urea N–H?OC hydrogen bonding. In the solid state, X-ray analysis shows that two urea molecules interact through only one hydrogen bond yielding infinite chains. This fact and the almost complete coplanarity of both the urea and the carbamate carbonyl groups determine the crystal packing to be formed by a parallel molecular arrangement. All these structural features are well supported by theoretical calculations that allow us to conclude that the formation of a network based on hydrogen bonding is energetically favourable.     

Synthesis and structural studies of NCN diimine palladium pincer complexes bearing m-terphenyl scaffolds

The reaction of 2,6-[2-{RN=C(H)}C(6)H(4)](2)C(6)H(3)I [R = Ph (4), Cy (5), 2,6-Me(2)C(6)H(3) (6), 2,4,6-Me(3)C(6)H(2) (7), (S)-alpha-methylbenzyl (8)] with Pd(2)(dba)(3) afforded the NCN diimine pincer palladium complexes [2,6-[2-{RN=C(H)}C(6)H(4)](2)C(6)H(3)PdI] (9-13) by oxidative addition of the C-I bonds of the ligand precursors. Single-crystal X-ray diffraction analyses of complexes 9-13 reveal formal C(2)-symmetric environments. Variable-temperature NMR studies of complexes 11 and 12 show hindered rotation about the N-Ar bonds and also suggest that atropisomers of complexes 9-13 do not interconvert on the NMR time scale. Consistent with this proposal, isolation of the two possible isomers of 13 (13a and 13b) was possible, and their structures and NMR properties have been examined in detail.     

A new platform for NCN dimethylamino pincer complexes: Synthesis and structural studies

The reaction of 2,6-(2-{Me₂NCH₂}C₆H₄)₂C₆H₃I (2) with Pd₂(dba)₃ produced the NCN diamine pincer complex [2,6-(2-Me₂{NCH₂}C₆H₄)₂C₆H₃PdI] (3) by an oxidative addition route. The structural analysis of ligand precursor 2 revealed a syn-conformation in the solid state. Single crystal X-ray analysis of complex 3 revealed a conventional square planar geometry about the palladium center and a global C₂ symmetric structure. Variable temperature and concentration NMR spectroscopic studies of complex 3 suggest an equilibrium between 3 and the dinuclear species [{2,6-(2-{Me₂NCH₂}C₆H₄)₂C₆H₃Pd}₂μ²-I]I in CDCl₃ solution. An unusual carbonate complex [{2,6-(2-{Me₂NCH₂}C₆H₄)₂C₆H₃Pd}₃μ³-CO₃]I₃ (4) was also structurally characterized as a minor product during synthesis of 3.     

Synthesis and characterization of fluorophenylpalladium pincer complexes: electronic properties of some pincer ligands evaluated by multinuclear NMR spectroscopy and electrochemical studies

Palladium fluorophenyl complexes with different pincer ligands Pd(Ar)[2,6-(tBu(2)PCH(2))(2)C(6)H(3)] (13), Pd(Ar)[2,6-(tBu(2)PO)(2)C(6)H(3)] (14), Pd(Ar)[{2,5-(tBu(2)PCH(2))(2)C(5)H(2)}Fe(C(5)H(5))] (15), and Pd(Ar)[{2,5-(tBu(2)PCH(2))(2)C(5)H(2)}Ru(C(5)H(5))] (16) were synthesized by the reaction of LiAr (Ar = C(6)H(4)F-4) with the respective trifluoroacetate palladium pincer complexes 9-12. The molecular structures of 14 and 16 were determined by an X-ray crystallographic method. Complexes 13-16 and {Pd(Ar)[{2,5-(tBu(2)PCH(2))(2)C(5)H(2)}Fe(C(5)H(5))]}PF(6) (17) were studied by multinuclear NMR spectroscopy and cyclic voltammetry. On the basis of (19)F NMR chemical shifts and (1)J((13)C-(19)F) coupling constants, as well as Pd(II)/Pd(IV) oxidation potentials, electronic characteristics of the corresponding pincer ligands were elucidated.     

Synthesis and characterization of palladium amido complexes containing pincer CNO ligands through nitrene insertion

Catellani reactions of aryl iodides allow the double functionalization at the ortho and ipso positions in one pot. Catellani reactions involving a nitrene intermediate are not yet known. In this paper, a few palladium amino complexes were prepared from PdCl₂, anthranil and iodoarenes, and their structures were determined by X‐ray single‐crystal diffraction. These complexes are supported by a pincer C,N,O tridentate ligand forming fused six‐membered palladacycles. The high stability of the palladium complexes inhibits their reductive elimination.     

氯化磷酸二苯酯的合成和结构表征

以苯酚、三氯氧磷为原料,以无水三氯化铝为催化剂合成了氯化磷酸二苯酯;采用正交试验研究了反应温度、反应时间、催化剂用量和原料配比对反应收率的影响,确定了最佳工艺条件;并利用红外光谱和核磁共振谱表征了产物的结构.结果表明,影响反应收率的几种因素的排序为:反应温度>原料配比>催化剂用量>反应时间;最佳反应条件为:温度70℃、反应时间15h、原料配比(n苯酚∶n三氯氧磷)2∶1、催化剂用量0.8g(相对于苯酚的质量分数为4.25%).与此同时,采用加水后处理方法可以提高产品收率和可操作性.     

Synthesis and structural characterization of the isomuscarines

Four diastereomers of 2-[(trimethylammonium)-methyl]-5-methyltetrahydrofuran-3-ol, trivially named isomuscarine, allo-isomuscarine, epi-isomuscarine, and epiallo-isomuscarine, were prepared as bromide salts from 2,4-like and 2,4-unlike diastereomers of 3-(4-hydroxyhex-5-en-2-oxy)-4-methylthiazole-2(3H)-thione. The strategy for constructing the tetrahydrofuran nucleus of the isomuscarines uses alkenoxyl radical 5-exo-bromocyclization, occurring 2,3-cis-selectively for the 2,4-like-4-hydroxyhex-5-en-2-oxyl radical, and 2,3-trans-selectively for the 2,4-unlike diastereomer. A fraction of 4-hydroxyhex-5-en-2-oxyl radicals cyclizes 6-endo-selectively providing 5-bromo-2-methyltetrahydropyran-4-ols in yields between 3 and 15%. Substituting trimethylamine for bromide in 5-exo-bromocyclized products furnishes isomuscarine bromides, which were structurally characterized by X-ray diffraction and NMR-spectroscopy.     

Synthesis and structural characterization of amino-functionalized polysaccharides

A variety of carbohydrates, in particular polysaccharides can be subjected to chemical modification to obtain derivatives with amphiphilic properties, which enable biochemical or biological reactions at the polymer surface. In the present work, a polydisperse maltodextrin mixture of average molecular weight 3000 was coupled with 1,6-hexamethylenediamine (HMD) via reductive amination reaction. Resulting products were characterized by thermal analysis and positive nanoelectrospray quadrupole time-of-flight (Q-TOF) mass spectrometry (MS) and tandem mass spectrometry (MS/MS). Both thermal analysis and MS screening confirmed the formation of the HMD-polysaccharide coupling products. Moreover, HMD-linked polysaccharide chains containing 2 to 26 glucose building blocks were identified by nanoESI Q-TOF MS. MS/MS fragmentation using collision-induced dissociation (CID) at low ion acceleration energies provided strong evidence for HMD-maltodextrin linkage formation and the set of sequence ions diagnostic for the composition and structure of a HMD-linked chain containing 18 glucose residues.      

CCC-N-heterocyclic carbene pincer complexes: Synthesis, characterization and hydroamination activity of a hafnium complex

Our methodology for the stoichiometric preparation of CCC-NHC pincer complexes of Zr has been extended to Hf. The CCC^Bu-NHC pincer Hf complex has been characterized by X-ray crystal structure analysis. Catalytic activity in the intramolecular hydroamination/cyclization of unactivated alkenes is reported and compared to the recently reported Zr analog. An improved, scaled-up CuO-catalyzed aryl amination of 1,3-dibromobenzene and an improved salt formation methodology for preparation of bis(butyl-imidazolium)benzene are reported also.     

Synthesis of bicyclic gamma-ylidenetetronates

The bicyclic gamma-ylidenetetronate motif found in several Stemona alkaloids was prepared in a stereoselective manner by addition of lithium methyl tetronate to an alkoxy oxonium ion formed from a lactone. The corresponding mixed alkyl ketal obtained was subjected to a Lewis acid-base-promoted dealkoxylation reaction to deliver the desired products.     

Novel metal complexes containing a chiral trinitrogen isoindoline-based pincer ligand: in situ synthesis and structural characterization

The first synthesis and characterization of metal coordinated complexes containing in situ prepared chiral trinitrogen 1,3-bis(4,5-dihydrooxazol-2-ylimino)isoindoline-based pincer ligands are reported. Two zinc complexes, isolated as Zn(L)(2), where L = 1,3-bis(4,5-dihydro-4-(R)-phenyloxazol-2-ylimino)isoindoline ((R,R)-5) or 1,3-bis(4,5-dihydro-4-(S)-iso-propyloxazol-2-ylimino)isoindoline ((S,S)-6), respectively, are reported. Complexes Zn((R,R)-5)(2) and Zn((S,S)-6)(2) were prepared in situ through the condensation of phthalonitrile with enantiopure 2-amino-4-(R)-phenyloxazoline ((R)-3) or 2-amino-4-(S)-iso-propyloxazoline ((S)-4) in the presence of ZnCl(2) at 80 °C in dry toluene over 3-4 days. The characterizations of Zn((R,R)-5)(2) and Zn((S,S)-6)(2) in both the solid (X-ray crystallography) and solution (multinuclear NMR spectroscopy) states are reported.     

Synthesis and structural characterization of triphenyltin halide-lactam complexes

Reactions of triphenyltin chloride or isothiocyanate with lactum yield complexes of the type Ph₃SnX · L (X = Cl or NCS, L = lactam). The coordination of the carbonyl group of lactams to the tin atom has been suggested by IR data and confirmed by X-ray diffraction analysis.The crystal and molecular structure of triphenyltin chloride-ϵ-caprolactam complex, C₂₄H₂₆ClNOSn, has been determined by X-ray diffraction analysis. The crystals are orthorhombic, space group Pbca, a 18.839(1), b 14.392(2), c 29.059(6) Å, Z = 8; R = 0.047, R_w = 0.058 for 3579 unique reflections. The geometry around the tin atom is trigonal bipyramidal with the three phenyl groups defining the equatorial plane and a chlorine ion and a carbonyl oxygen of the caprolactam ligand occupying the axial positions.     

Synthesis and structural characterization of chiral dicationic imidazolophanes

Various chiral dicationic benzimidazolophanes were obtained from optically pure (S)-BINOL, benzimidazole and a suitable aryl alkyl dibromide.     

树枝状十二酯的合成与结构表征

根据聚酰胺-胺的合成工艺,以乙二胺和丙烯酸十二酯为原料,采用“发散合成法”合成一类新的树枝状化合物;同时采用元素分析、IR和NMR分析手段对合成产品的结构进行表征,结果表明,合成产物的分子结构与理论结构相符.     

Synthesis and structural characterization of novel pyranoluteolinidin dyes

The synthesis and structural characterization by LC–MS and NMR of novel pyranoluteolinidin derivatives are reported. The compounds result from the reactions between luteolinidin and three different carboxylic acids in wine model-like solutions. The three pigments possess different substituents attached to the D ring (methyl, catechol and dimethylaminophenyl groups) and the same catechol group in the B ring, yielding a wide spectrum of colors from yellow to pink-purple.