Syntheses, characterizations, and olefin polymerizations of methylene-bridged 1,3-dimethylcyclopentadienyl/indenyl and 1,3-dimethylcyclopentadienyl/tetrahydroindenyl zirconium complexes

A cyclopentadiene compound having methyl substituents on 1,3-positions, 1,3-Me₂-2-CH₂(OTHP)-C₅H₃ (3) is prepared from 2-bromo-3-methyl-2-cyclopenten-1-one ethylene ketal (1) in 48% overall yield. Addition of 2.5 equivalents of indenyllithium to 3 affords a methylene bridged 1,3-dimethylcyclopentadienyl indenyl compound, CH₂(1,3-Me₂C₅H₃)(C₉H₇) (5) in 72% yield. Reaction of dilithium salt of 5 with ZrCl₂(NMe₂)₂ (DME) furnishes an ansa-zirconocene complex [CH₂(1,3-Me₂C₅H₂)(C₉H₆)]Zr(NMe₂)₂ (6), which is transformed cleanly to the dichloride complex, [CH₂(1,3-Me₂C₅H₂)(C₉H₆)]ZrCl₂ (7), by treatment of Me₃SiCl. Hydrogenation of 7 over PtO₂ gives a tetrahydroindenyl complex [CH₂(1,3-Me₂C₅H₂)(C₉H₁₀)]ZrCl₂ (8). Reaction of the dilithium salt of 5 with Ti(NMe₂)₂Cl₂ does not provide the desired ansa-titanocene complex, but a dinuclear complex [(1,3-Me₂C₅H₂)Ti(NMe₂)₂Cl]-CH₂-[(C₉H₆)Ti(NMe₂)Cl] (9) is obtained. The solid structures of 6 and 9 were determined by X-ray crystallography. The ethylene and ethylene/norbornene (co)polymerizations were studied with 7/MAO and 8/MAO.     

1,3-Bis(α-aminoisopropyl)benzene, meta-C6H4(CMe2NH2)2: An N,N-bridging and N,C,N-cyclometalating ligand

Saponification of the bis(carbamic acid ester) 1,3-C₆H₄(CMe₂NHCO₂Me)₂ (1), made by the addition of methanol to commercial 1,3-C₆H₄(CMe₂NCO)₂, yielded the meta-phenylene-based bis(tertiary carbinamine) 1,3-C₆H₄(CMe₂NH₂)₂ (2). Dinuclear [{(η⁴-1,5-C₈H₁₂)RhCl}₂{μ-1,3-C₆H₄(CMe₂NH₂)₂}] (3) resulted from the action of 2 on [{(η⁴-1,5-C₈H₁₂)Rh(μ-Cl)}₂] in toluene. Combination of 2 with PdCl₂ or K₂[PdCl₄] gave the dipalladium macrocycle trans,trans-[{μ-1,3-C₆H₄(CMe₂NH₂)₂}₂(PdCl₂)₂] (4) along with cyclometalated [{2,6-C₆H₃(CMe₂NH₂)₂-κN,κC¹,κN′}PdCl] (5). Substitution of PEt₃ for the labile chlorido ligand of 5 afforded [{2,6-C₆H₃(CMe₂NH₂)₂-κN,κC¹, κN′}Pd(PEt₃)]Cl (6). The crystal structures of the following compounds were determined: bis(carbamic acid ester) 1, ligand 2 as its bis(trifluoroacetate) salt [1,3-C₆H₄(CMe₂NH₃)₂](O₂CCF₃)₂, 2 · (HAc_f)₂, complexes 3 and 6, as well as 1,3-C₆H₄(CMe₂OH)₂ (the diol analogue of 2).     

Synthesis and characterization of a N-salicylaldimine ligand and its vanadium(V) complex

The reduction of 2-nitro-1,3-di(pyridin-2-yl)-1,3-di(tert -butyldimethylsilyloxy)propane 1 with sodium borohydride affords 2-amino-1,3-di(pyridin-2-yl)-1,3-di(tert-butyldimethylsilyloxy)propane 2 which was subsequently reacted with salicyl aldehyde yielding rac-((2,2,3,3,9,9,10,10-octamethyl-5,7-di(pyridin-2-yl)-4,8-dioxa-3,9-disilaundecan-6-ylimino)methyl)phenol (Proligand 3 = HL(SiMe₂tBu)₂), with excellent yield. Reaction of 3 with vanadyl acetylacetonate followed by aerial oxidation diastereoselectively led to the octahedral coordinated vanadium(V) complex 4([VO(OMe)L(SiMe₂t Bu)]). Compound 3 together with vanadyl acetylacetonate as well as with molybdenyl acetylacetonate shows catalytic activity in the sulfoxidation of (methylsulfanyl)benzene I, which was followed by NMR spectroscopy. The vanadium complex 4 was also able to catalyze the sulfoxidation but was considerably slower. All three tested catalytic systems lead to almost quantitative formation of the sulfoxide with only minor formation of the respective sulfone.     

Metal-ion-catalyzed hydrolysis of monomethyl and dimethyl esters of 3-(2-imidazoleazo)phthalic acid: Bifunctional catalysis by carboxyl group and the metal ion in the hydrolysis of an alkyl ester

The Cu(II) or Ni(II) ion-catalyzed hydrolysis of methyl 2-carboxy-6-(2-imidazoleazo)benzoate (1) and the corresponding dimethyl ester (2) was studied kinetically at various pH values. For 2, the ester group located at the o position to the azo substiuent was hydrolyzed. From the rate data obtained at various metal concentrations, the values of k_cat and K_f were estimated at each pH value. For the Ni(II)-catalyzed hydrolysis of 1 at pH < 4, k_cat increases as pH is lowered, indicating bifunctional catalysis by the carboxyl group and the metal ion. For most of the reactions investigated under other conditions, the ester hydrolysis was subjected to sole catalysis by the metal ions. Detailed analysis of kinetic data obtained for these reactions indicated that the metal-ion catalysis involves the rate-determining breakdown of the tetrahedral intermediates formed by the addition of a water molecule or hydroxide ion. The bifunctional catalysis by the carboxyl group and Ni(II) ion can be considered as a model for carboxypeptidase A. The kinetic data indicate that the bifunctional catalysis proceeds through the nucleophilic attack of the carboxylate ion at the Ni(II)-coordinated carbonyl group.     

Cis-diastereoselectivity in pictet-spengler reactions of L-tryptophan and electronic circular dichroism studies

The diastereoselective synthesis of optically active 1,3‐disubstituted tetrahydro‐β‐carbolines using polar protic Pictet–Spengler cyclization of (S)‐tryptophan methyl ester with five aldehydes RCHO (R═CH₃, C₂H₅, C₃H₇, C₄H₉, and C₆H₅) was studied. As an alternate route, the cyclization of (S)‐tryptophan with the same aldehydes and subsequent methylation of the resulting tetrahydro‐β‐carboline carboxylic acids were also performed for comparison. ¹³C NMR and electronic circular dichroism (ECD) studies and time‐dependent density functional theory ECD calculations data established the relative 1,3 cis/trans and the absolute configuration (1S,3S/ 1R,3S) of the synthesized compounds. The solid‐state and solution ECD study of the prepared compounds, supported by ECD calculation and X‐ray data, afforded a reliable ECD method for the configurational assignment of 1,3‐disubstituted tetrahydro‐β‐carbolines and revealed the stereochemical factors that determine the characteristic ECD data. Chirality 24:789–795, 2012. © 2012 Wiley Periodicals, Inc.     

Synthesis,characterization, and biological assessment of the four stereoisomers of the H3 receptor antagonist 5-fluoro-2-methyl-N-[2-methyl-4-(2-methyl[1,3′]bipyrrolidinyl-1′-yl)phenyl]benzamide

This Letter describes the asymmetric synthesis of the four stereoisomers (8a–8d) of a potent and highly selective histamine H₃ receptor (H₃R) antagonist, 5-fluoro-2-methyl-N-[2-methyl-4-(2-methyl[1,3′]bipyrrolidinyl-1′-yl) phenyl]benzamide (1). The physico-chemical properties, in vitro H₃R affinities and ADME of 8a–8d were determined. Stereoisomer 8c (2S,3′S) displayed superior in vitro H₃R affinity over other three stereoisomers and was selected for further profiling in in vivo PK and drug safety. Compound 8c exhibited excellent PK properties with high exposure, desired brain to plasma ratio and reasonable brain half life. However, all stereoisomers showed similar unwanted hERG affinities.     

Synthesis of deuterium-labelled analogues of NLRP3 inflammasome inhibitor MCC950

This study describes the syntheses of di, tetra and hexa deuterated analogues of the NOD-like receptor pyrin domain-containing protein 3 (NLRP3) inflammasome inhibitor MCC950. In di and tetra deuterated analogues, deuteriums were incorporated into the 1,2,3,5,6,7-hexahydro-s-indacene moiety, whereas in the hexa deuterated MCC950 deuteriums were incorporated into the 2-(furan-3-yl)propan-2-ol moiety. The di deuterated MCC950 analogue was synthesised from 4-amino-3,5,6,7-tetrahydro-s-indacen-1(2H)-one 5. Tetra deuterated analogues were synthesised in 10 chemical steps starting with 5-bromo-2,3-dihydro-1H-inden-1-one 9, whereas the hexa deuterated analogue was synthesised in four chemical steps starting with ethyl-3-furoate 24. All of the compounds exhibited similar activity to MCC950 (IC₅₀?=?8?nM). These deuterated analogues are useful as internal standards in LC-MS analyses of biological samples from in vivo studies.     

Synthesis and characterization of copper and manganese complexes of monodentate functionalized isocyanide: trimethylsilylmethylisocyanide and p-tolylsulfonylmethylisocyanide

Reaction of excess CNCH₂SiMe₃(L) with CuX₂·nH₂O (X=NO₃⁻, n=3; ClO₄⁻, n=6) in THF gives the Cu^I complexes [CuL₄]NO₃ (1) and [CuL₄]ClO₄ (2). When CuCN is used as starting material, complex 3, Cu(L₃)CN, C₄H₁₀O·3H₂O, is obtained. Immediate reduction occurs with AgNO₃ precipitating metallic Ag. Reactions with MnCl₂·6H₂O and Mn(NO₃)₂·6H₂O in THF produce two new compounds which analyze as MnL₄Cl₂·4H₂O (6) and MnL₂(NO₃)₂·H₂O (7). When excess p-tolylsulfonylmethylisocyanide (L′) is reacted with Cu(NO₃)₂, the mixed-valence Cu^I---Cu^II complex Cu₂L′₆(NO₃)₃ (5) is precipitated, while using CuCN gives the Cu^I dimer Cu₂L′₄(CN)₂ (4). In analogous conditions the manganese complex MnL′₂(NO₃)₂·C₃H₆O·3H₂O (8) is precipitated. All these complexes have been isolated, characterized by IR, NMR for diamagnetic species, magnetic susceptibilities, EPR measurements and electrochemical analyses. Influence of the two substituents is discussed.     

Rhodium aryloxide complexes containing terdentate nitrogen ligands, C-O bond formation, hydrogen bonding with phenol and oxidative addition reactions. Molecular structure of an Rh(III)-acetyl complex

The new rhodium(I) phenoxide complexes [Rh(OPh) (2,6-(CH=R²)₂C₅H₃N)] (R² = i-Pr(3), t-Bu(4)) containing strongly electrondonating N-N′-N ligands, have been prepared by a metathesis reaction of [RhCl(2,6-(CH=R²)₂C₅H₃N)] (R² = i-Pr (1), t-Bu (2)) with NaOPh. These rhodium(I) phenoxide complexes 3 and 4, which are very sensitive to O₂ but stable towards H₂O, give with phenol the adducts [Rh(OPh) (2,6-(CH=NR²)₂C₅H₃N)] · HOPh (R2 = i-Pr (5), t-Bu (6)), which contain strong O-HO hydrogen bonds. The hydrogen bonded phenol could not be extracted with diethyl ether, while no exchange of the hydrogen bonded phenol and the phenoxide ligand in 4 is observed on the NMR time scale. However, a small excess of phenol results in exchange of the hydrogen bonded phenol, the coordinated phenoxide ligand and free phenol on the NMR time scale. Reaction of 3 and 4 with p-nitrophenol afforded [Rh(OC₆H₄-(NO₂-4))(2,6-(CH=R²)₂C₅H₃N)] · HOPh (R² = i-Pr (7), t-Bu (8)) in which the formed phenol is hydrogen bonded to the Rh(I)-OC₆H₄-(NO₂-4) moiety. The O-HO bond is less strong than in 5 and 6, as the hydrogen bonded phenol could be removed by diethyl ether.Treatment of 3 with acetyl chloride and benzoyl chloride in benzene at room temperature gave phenylacetate and RhCl₂(C(O)C₆H₃) (2,6(C(H)=N-i-Pr)₂C₅H₃N)] (15), and phenylbenzoate and [RhCl₂(C(O)Ph) (2,6-(C(H)=N-i-Pr)₂C₅H₃N)] (19), respectively. Complex 15 and the analogous complex [RhCl₂(C(O)CH₃) (2,6-(C(H)=N-t-Bu)₂C₅H₃N)] (16) could also be prepared directly from acetyl chloride and 1 or 2, respectively. The single crystal X-ray determination of complex 16, monoclinic, space group P2₁/_c, a = 10.0477(5), b= 11.7268(6), c= 19.2336(9) Å, β = 92.041(4)°, Z = 4, R₁ = 0.0281, shows that the acetyl group occupies an axial position, while the N-N′-N ligand is positioned equatorially. In solution this geometry remains unchanged as was shown by variable temperature ¹H NMR measurements. When the oxidative addition of acetyl chloride to 3 was carried out at −78°C in toluene the intermediate complex [RhCl(OPh) (C(O)Me) (2,6-(C(H)=N-i-Pr)₂C₅H₃N)] (11) could be isolated, which at room temperature reductively eliminates phenylacetate with formation of 1. Oxidative addition of acetyl chlori de to 4 at room temperature gives [RhCl(OPh) (C(O)Me) (2,6-(C(H)=Nt-Bu)₂C₅H₃N)] (12) which yields phenylacetate and 2 at 70°C in benzene by inductive elimination. Treatment of 3 with two equivalents of benzyl chloride afforded a mixture of [RhCl(OPh) (CH₂Ph) (2,6-(C(H)=N-i-Pr)₂C₅H₃N)] (13) and [RhCl₂(CH₂Ph) (2,6-(C(H)=N-i-Pr)₂C₅H₃N)] (17) and some non-characterizable organic products, while 4 only yielded [RhCl(OPh) (CH₂Ph) (2,6-(C(H)=N-tBu)₂C₅H₃N)] (14).     

Dinuclear and mononuclear copper(II) carboxylate complexes with cis-chelating diacids

The synthesis and crystal structures of two new copper complexes with chelating dicarboxylic acids are described. Reaction of copper(II) acetate with diacid H₂L2 (HO₂CC(Me)₂OArOC(Me)₂CO₂H, Ar=1,3-substituted phenyl) gave a bischelate complex (L2)₂Cu₂ · 2MeOH with the normal paddlewheel structure and tilted, trans-oriented chelate rings with skewed conformations. The overall structure was reasonably well reproduced by density functional calculations on (L2)₂Cu₂. Treatment of the product from reaction of Cu₂(OAc)₄ and diacid H₂L3 (Ar=1,3-substituted 2,4-dibromophenyl) with pyridine gave a six-coordinate mononuclear chelate (L3)Py₂Cu · H₂O in which one chelate carboxylate is monodentate, the other is unsymmetrically bidentate, and the pyridines are cis-coordinated.     

Synthesis,structures and characterization of the dinuclear nickel(II) complexes containing N,N,N′,N′-tetrakis[(1-ethyl-2-benzimidazolyl)methyl]-2-hydroxy-1,3-diaminopropane and an azide ion

Two dinuclear nickel(II) complexes, [Ni₂(L-Et)(N₃)(H₂O)₃](NO₃)₂ · 2H₂O (1) and [Ni₂(L-Et)(μ-1,3-N₃)(H₂O)₂](NO₃)₂ · 4H₂O (2) containing (HL-Et = N,N,N′,N′-tetrakis[(1-ethyl-2-benzimidazolyl)methyl]-2-hydroxy-1,3-diaminopropane), have been synthesized and characterized by their IR and UV–Vis spectra and magnetic susceptibilities. The crystal structures of [Ni₂(L-Et)(N₃)(H₂O)₃](NO₃)₂ · CH₃OH (1′) and [Ni₂(L-Et)(μ-1,3-N₃)(H₂O)₂](NO₃)₂ · 2C₂H₅OH (2′) similar to 1 and 2 were determined by X-ray crystallography. In 1′, the two nickel(II) ions are bridged by only an alkoxo group of L-Et⁻, while an azido and an alkoxo connect two nickel(II) ions in 2′. Magnetic susceptibility measurements (2–300 K) showed a weak ferromagnetic exchange coupling between the two nickel(II) ions (2J = 10.1 cm⁻¹) for 1. On the other hand, antiferromagnetic interactions were observed for 2 (2J = −15.8 cm⁻¹).     

Synthesis of 5,6-dihydro-4H-1,3-oxazines from neutral and cationic platinum(II) nitrile complexes. X-ray structure of trans-[Pt(CF3){ H2CH2}(PPh3)2]BF4

The 1,3-oxazine complexes cis- and trans-[PtCl₂{ C(R)OCH₂CH₂C}H₂₂] (cis: R=CH₃ (1a), CH₂CH₃ (2a), (CH3)₃C (3a), C₆H₅ (4a); trans:R =CH₃ (1b), C₆H₅ (4b)) were obtained in 51-71% yield by reaction in THF at 0 °C of the corresponding nitrile complexes cis- and trans-[PtCl2(NCR)₂] with 2 equiv. of ⁻OCH₂CH₂CH₂Cl, generated by deprotonation of 3-chloro-1-propanol with n-BuLi. The cationic nitrile complexes trans-[Pt(CF₃)(NCR)(PPh₃)₂]BF₄ (R=CH3, C₆H₅) react with 1 equiv, of ⁻ OCH2CH2CH2Cl to give a mixture of products, including the corresponding oxazine derivatives trans-[Pt(CF₃){ CH₂}(PPh₃)₂]BF₄ (5 and 6), the chloro complex _trans- [Pt(CF₃)Cl(PPh₃)₂] and free oxazine H2. For short reaction times (c. 5–15 min) the oxazine complexes 5 and 6 could be isolated in modest yield (37–49%) from the reaction mixtures and they could be separated from the corresponding chloro complex (yield 40%) by taking advantage of the higher solubility of the latter derivative in benzene. For longer reaction times (> 2 h), trans-[Pt(CF₃)Cl(PPh₃)₂] was the only isolated product. Complex 6 was crystallographically characterized and it was found to contain also crystals of trans- [PtCl{ H₂}(PPh₃)₂]BF₄, which prevented a more detailed analysis of the bond lengths and angles within the metal coordination sphere. The 1,3-oxazine ring, which shows an overall planar arrangement, is characterized by high thermal values of the carbon atoms of the methylene groups indicative of disordering in this part of the molecule in agreement with fast dynamic ring processes suggested on the basis of ¹H NMR spectra. It crystallizes in the trigonal space group P , with a=22.590(4), b=15.970(3) Å, γ=120°, V=7058(1) ų and Z=6. The structure was refined to R=0.059 for 3903 unique observed (I3σ(I)) reflections. A mechanism is proposed for the conversion of nitrile ligands to oxazines in Pt(II) complexes.     

Self-assembly of 2D zinc metal-organic frameworks based on mixed organic ligands

Self-assembly of Zn(NO₃)₂·6H₂O, 5-amino-2,4,6-triiodoisophthalic acid (H₂atiip) and 4,4′-bipyridine (bpy) or 1,3-di(4-pyridyl)propane (dpp) gave rise to three unusual zinc metal-organic frameworks, Zn₂(bpy)₂(atiip)₂·3H₂O·2dmf (1), Zn₈(dpp)₈(atiip)₈·4H₂O (2), Zn(dpp)(atiip)·(dmf)·(H₂O) (3). All complexes possess 2D layer frameworks constructed from 1D Zn-carboxylate tubular unit for 1, 1D Zn-carboxylate helical chain for 2 and 3. In 1 and 2, the bpy or dpp act as both bridging and blocking ligands and the blocking ligands play an important role in the formation of the 2D layer frameworks. Both 2 and 3 contain two different large metallomacrocycles. Photoluminescence measurements of 1-3 in the solid state at room temperature show that all complexes exhibit luminescence, which can be assigned to an intraligand π → π^∗ transition or ligand-to-metal charge transfer (LMCT).     

Synthesis and anti-proliferative activity of aromatic substituted 5-((1-benzyl-1H-indol-3-yl)methylene)-1,3-dimethylpyrimidine-2,4,6(1H,3H,5H)-trione analogs against human tumor cell lines

Based on previous SAR studies on N-benzylindole and barbituric acid hybrid molecules, we have synthesized a series of aromatic substituted 5-((1-benzyl-1H-indol-3-yl)methylene)-1,3-dimethylpyrimidine-2,4,6(1H,3H,5H)-trione analogs (3a–i) and evaluated them for their in vitro growth inhibition and cytotoxicity against a panel of 60 human tumor cell lines. Compounds 3c, 3d, 3f and 3g were identified as highly potent anti-proliferative compounds against ovarian, renal and breast cancer cell lines with GI₅₀ values in low the nanomolar range. The 4-methoxy-N-benzyl analog (3d) was the most active compound with GI₅₀ values of 20 nM and 40 nM against OVCAR-5 ovarian cancer cells and MDA-MB-468 breast cancer cells, respectively. Two other analogs, 3c (the 4-methyl-N-benzyl analog) and 3g (the 4-fluoro-N-benzyl analog) exhibited equimolar potency against MDA-MB-468 cells GI₅₀ = 30 nM). Analog 3f (the 4-chloro-N-benzyl analog) exhibited a GI₅₀ value of 40 nM against renal cancer cell line A498. These results suggest that aromatic substituted N-benzylindole dimethylbarbituric acid hybrids may have potential for development as clinical candidates to treat a variety of solid tumors.     

Synthesis of 2- (and 6-) -dithian-2-yluracil nucleosides and their conversion into nucleoside derivatives

Addition of 2,2′-anhydro-[1-(3-O-acetyl-5-O-trityl-β-D-arabinofuranosyl)uracil] (1) to excess 2-litho-1,3-dithiane (2)in oxolane at ?78° gave 2-(1,3-dithian-2-yl)-1-(5-O-trityl-β-D-arabinofuranosyl)-4(1H)pyrimidinone (3), O²,2′-anhydro-5,6-di-hydro-6-(S)-(1,3-dithian-2-yl)-5′-O-trityluridine (4), and 2-(1,4-dihydroxybutyl)-1,3-dithiane (5) in yields of 15, 30, and 10% respectively. The structure of 3 was proved by its hydrolysis in acid to give 2-(1,3-dithian-2-yl)-4-pyrimidinone (6) and arabinose, and by desulfurization with Raney nickel to yield the known 2-methyl-1-(5-O-trityl-β-D-arabinofuranosyl)-4(1H)-pyrimidinone (7). Detritylation of 3 without glycosidic cleavage could only be effected by prior acetylation to 1-(2,3-di-O-acetyl-5-O-trityl-β-D-arabinofuranosyl)-2-(1,3-dithian-2-yl)-4(1H)-pyrimidinone (8) which, after treatment with acetic acid at room temperature for 65 h followed by the action of sodium methoxide gave 2-(1,3-dithian-2-yl)-1-β-D-arabinofuranosyl-4(1H)-pyrimidinone (10) in 45% yield. Detritylation of 4 in boiling acetic acid gave 5,6-dihydro-6-(S)-(1,3-dithian-2-yl)-1-β-D-arabinofuranosyluracil (12) and 3-[(S)-1-(1,3-dithian-2-yl)]propionamido-(1,2-dideoxy-β-D-arabinofurano)-[1,2-d]-2-oxazolidinone (13) in 10 and 90% yields, respectively. When 12 was kept in water or methanol for 7 days, quantitative conversion into 13 occurred. Acid hydrolysis of 12 afforded arabinose and 5,6-di-hydro-6-(1,3-dithian-2-yl)uracil (14), which was desulfurized with Raney nickel to the known 5,6-dihydro-6-methyluracil (15). Treatment of 13 with trifluoroacetic anhydride-pyridine yielded 77% of the cyano derivative 17. Similar dehydration of 3-(R)-1-methylpropionamido-(1,2-dideoxy-β-D-arabinofurano)-[1,2-d]-2-oxalidinone (18), obtained by desulfurization of 13, gave 60% of the nitrile 19. Hydrogenation of 19 over platinum oxide in acetic anhydride gave the acetamide derivative 20 in 95% yield. Nitrobenzoylation of 13 gave 3-[(S)-1-(1,3-dithian-2-yl)]cyanomethyl-3,5-di-O-p-nitrobenzoyl-(1,2-dideoxy-β-D-arabinofurano)-[1,2-d]-2-oxazolidinone (22), which was converted in 37% yield by treatment with methyl iodide in dimethyl sulfoxide into the aldehyde 24, characterized as the semicarbazone 25. The purification of 5 and its characterization as 2-(1,4-di-O-p-nitrobenzoylbutyl)-1,3-dithiane (27) is described.     

Dinuclear alkoxo-bridged copper(II) coordination polymers: Syntheses, structural and magnetic properties

The alkoxo-bridged dinuclear copper(II) complexes [Cu₂(ap)₂(NO₂)₂] (1), [Cu₂(ap)₂(C₆H₅COO)₂] (2) and [Cu₂(ap)₂μ-1,3-C₆H₄(COO)₂(dmso)₂]·dmso (3) (ap = 3-aminopropanolato and dmso = dimethyl sulfoxide) have been synthesized via self-assembly from copper(II) perchlorate, 3-aminopropanol as main chelating ligand and nitrite and isophthalate anions as spacers and benzoate anion as auxiliary ligand. Complexes 1 and 3 crystallize as 2D and 1D coordination polymers, respectively, and their structures consist of dinuclear [Cu₂(ap)₂]²⁺ units connected with nitrite and isophthalate ligands. The adjacent dinuclear units of 2 and 1D polymers of 3 are further connected by hydrogen bonds resulting in the formation of 2D layers. The variable temperature crystallographic measurements of 1 at 100, 173 and 293 K indicate the static Jahn-Teller distortion with librational disorder in the nitrite group. Experimental magnetic studies showed that complexes 1-3 exhibit strong antiferromagnetic couplings. The values of the magnetic exchange coupling constant for 1-3 are well reproduced by the theoretical calculations.     

Ketone H2-hydrogenation catalysts: Ruthenium complexes with the headphone-like ligand bis(phosphaadamantyl)propane

Treatment of 1,3-diphosphinopropane with acetylacetone in the presence of HCl gives the new chiral bis(phosphaadamantyl)propane ligand (bpap) (1) as a mixture of diastereoisomers. Recrystallization from ethanol gives a mixture enriched in rac diastereoisomer (90% rac/10% meso). The enriched mixture reacts with [RuHCl(PPh₃)₃] in refluxing THF to give [RuHCl(bpap)(PPh₃)] (2) in 73% yield. Compound 2 reacts readily with chiral diamines giving octahedral trans-[RuHCl(bpap)(diamine)] complexes 3 (diamine = (1R,2R)-1,2-diaminocyclohexane) and 4 (diamine = (1R,2R)-1,2-diphenylethylenediamine). Compounds 3 and 4 are very active catalysts for H₂-hydrogenation of neat acetophenone in the presence of KO^tBu as a strong base under mild conditions (room temperature, 3 atm of H₂). The low ee values for 1-phenethanol can be attributed to the similar shapes of two terminal adamantoid cages and the flexible backbone of the bpap ligand. The structures of complexes 2 and 3 have been determined by single-crystal X-ray diffraction.     

Acidic 1,3-propanediaminetetraacetate zinc complexes as a probe of water soluble coordination polymers

In a very acidic solution, potassium 1,3-propanediaminetetraacetate zinc chloride K_2n[ZnCl₂(1,3-H₂pdta)ZnCl₂]_n (1) and its substituted iodide [ZnI₂(H₂O)(1,3-H₄pdta)]_n (2) (H₄pdta = 1,3-propanediaminetetraacetatic acid, C₁₁H₁₈N₂O₈) were isolated. The former was obtained from the reaction of zinc chloride and H₄pdta in pH ∼1.5. Further substitution of 1 results in the formation of iodide 2 with the addition of potassium iodide in acidic solution of pH 0.5. Complex 1 consists of a dimeric anionic unit [ZnCl₂(1,3-H₂pdta)ZnCl₂]²⁻ with strong intra-molecular hydrogen bonds [N1?O2 2.648(4); N1?O4 2.710(4) Å]. In neutral complex 2, an 1,3-pdta ligand links each monomeric unit [Zn(H₂O)I₂] to generate an infinite 1D chain, which extents into a 3D supramolecular structure by very strong inter-molecular hydrogen bonds the [O4?O2b 2.50 (1) Å, bx, y, z + 1]. 1 is soluble in water at room temperature, which is traced by ¹³C NMR experiment.     

Synthesis and characterization of new ruthenium(II) complexes containing coupled di(2-pyridyl) and 1,3-dithiole units

Two new ruthenium (II) complexes containing coupled di(2-pyridyl) and 1,3-dithiole units, cis-[Ru(Medpydt)₂(NCS)₂] (2, Medpydt = dimethyl 2-(di(2-pyridyl)methylene)-1,3-dithiole-4,5-dicarboxylate) and cis-[Ru(H₂dpydt)₂(NCS)₂] (3, H₂dpydt = 2-(di(2-pyridyl)methylene)-1,3-dithiole-4,5-dicarboxylate), have been synthesized and characterized. The structure of complex 2 has been determined by X-ray crystallography. There exist intermolecular H-bonding interactions between carbomethoxy groups on neighboring pyridine rings giving rise to 2D H-bonded arrays. The metal-to-ligand charge-transfer (MLCT) absorptions were observed around 480 nm. Redox properties of ruthenium complexes have been investigated by cyclic voltammetry. Solar cells involving thin films of anatase TiO₂ impregnated with cis-[Ru(H₂dpydt)₂(NCS)₂] were prepared, and the photovoltaic performance was preliminarily investigated.