Control of stepwise radial complexation in dendritic polyphenylazomethines

The fourth generation of a dendritic polyphenylazomethine (DPA G4) has 2, 4, 8, and 16 imine groups in the first, second, third, and fourth shells, respectively (total, 30 imine groups). DPA G4 can trap 30 equiv of SnCl(2) molecules, because the imine group is complexed with SnCl(2) at a ratio of 1:1. During addition of 30 equiv of SnCl(2) to DPA G4, four shifts in the isosbestic point were observed in the UV-vis spectra, and the amount of SnCl(2) added in each step is in agreement with the number of imine groups in each shell of DPA G4. This result shows that the complexation of the imine groups in DPA G4 with SnCl(2) occurs stepwise in the order of the first, second, third, and fourth shells. The unique stepwise complexation was also observed in DPA G2 and G3 as two and three shifts of the isosbestic point, respectively. The stepwise complexation was supported by TEM, NMR, and a novel shell-selective reduction (SSR) method for imines. An expansion in the molecular size of DPA G4 by the complexation was revealed by molecular modeling and TEM measurements. The stepwise complexation is caused by the different basicity of the imine groups between the shells, which was supported by the chemical shifts of the peaks attributed to the imine carbons in the (13)C NMR spectra. The gradients in the basicity were controlled by the introduction of electron-withdrawing or -releasing groups to the core of the dendrimers; the core imines were complexed last in DPAs having a 2,3,5,6-tetrafluoro or 2,5-dichlorophenyl core due to the low basicity of the core imines. The different complexation pattern was also clearly confirmed by the SSR method.     

A novel diacetylenic bilirubin

An etiobilirubin‐IIβ analog with the central C(10) CH₂ group replaced by a diacetylene unit ( 1 ) was synthesized by base‐catalyzed condensation of bis‐[3‐methyl‐4‐ethyl‐5‐formylpyrrol‐2‐yl]‐diacetylene ( 3 ) with 3‐methyl‐4‐ethyl‐5‐p‐toluenesulfonyl‐2‐pyrrolinone ( 10 ). Diacetylenic rubin 1 is a dark red solid, giving orange solutions with uv‐visible absorption maxima near 460 nm.     

Synthesis of (-)-quinocarcin by directed condensation of alpha-amino aldehydes

An enantioselective synthesis of the natural antiproliferative agent quinocarcin was achieved by the directed condensation of optically active alpha-amino aldehyde intermediates. Condensation of the N-protected alpha-amino aldehyde 1, prepared in eight steps (19% yield) from (R,R)-pseudoephedrine glycinamide, with the C-protected alpha-amino aldehyde derivative 2, prepared in seven steps (34% yield) from (R,R)-pseudoephedrine glycinamide, afforded the corresponding imine in quantitative yield. Without isolation, direct treatment of this imine intermediate with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and hydrogen cyanide led to cleavage of the fluorenylmethoxycarbonyl (Fmoc) protective group followed by addition of cyanide (Strecker reaction) to form the bis-amino nitriles 3 as a mixture of diastereomers, in 91% yield. Treatment of the diastereomers 3 with trimethylsilyl cyanide and zinc chloride in 2,2,2-trifluoroethanol at 60 degrees C led to stepwise cyclization to form the tetracyclic product 4 (42% yield from 1 and 2). The latter intermediate was transformed into (-)-quinocarcin (1) in five steps (45% yield). The yield of quinocarcin was 19% from 1 and 2 (7 steps), and 4% from pseudoephedrine glycinamide (15 steps).     

Synthesis of ferrocene-substituted 2-azetidinones.

The photochemical reaction of alkoxychromium(0)carbene complexes and ferrocene mono- and disubstituted imines formed 2-azetidinones having one or two ferrocene moieties in good yields. Yields decrease when the carbene moiety bears an aminoferrocene moiety attached to the carbene carbon, while complex 9 having the ferrocene directly bonded to the carbene carbon was totally inert in these reactions. Access to beta-lactams with the ferrocene tethered to the C3 position through a methylene group was gained using the lithium enolate derived from ethyl 3-ferrocenylpropanoate. The reaction of this enolate produced two unexpected processes. Thus, 2-azetidinone 15 having an hydroxyl group at the C3 position was obtained together with the expected beta-lactam 14, by reaction of the lithium enolate of ethyl 3-ferrocenylpropenoate and imine 1. Additionally, unsaturated amide 17 was obtained by base-promoted Hoffmann-like breakage of the beta-lactam ring formed in the reaction of the same enolate and imine 2. Oxidation of the anion at the C3 of the 2-azetidinone ring on compound 14, as well as the sterically driven ring-breakage of the C3 anion derived from the nonisolated 2-azetidinone 18, should be responsible for this behavior.     

Recyclization of enaminocarbonyl and enaminothiocarbonyl imidazolidine and pyrroline derivatives

It was shown that recyclization of enaminocarbonyl compounds in acid media affords pyrrolinone derivatives. 2-Methylthio-4-oxopyrroline-1-oxide reacts with NaBH₄ exclusively at the carbonyl group- and with methylmagnesium iodide, at the nitrone group- with substitution of the methylthiol group for a methyl group.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 437–443, February, 1991.     

The biosynthesis of the thiazole phosphate moiety of thiamin (vitamin B1): the early steps catalyzed by thiazole synthase

Thiazole synthase (ThiG) catalyzes an Amadori-type rearrangement of 1-deoxy-d-xylulose-5-phosphate (DXP) via an imine intermediate. In support of this, we have demonstrated enzyme-catalyzed exchange of the C2 carbonyl of DXP. Borohydride reduction of the enzyme DXP imine followed by top-down mass spectrometric analysis localized the imine to lysine 96. On the basis of these observations, a new mechanism for the biosynthesis of the thiazole phosphate moiety of thiamin pyrophosphate in Bacillus subtilis is proposed. This mechanism involves the generation of a ketone at C3 of DXP by an Amadori-type rearrangement of the imine followed by nucleophillic addition of the sulfur carrier protein (ThiS-thiocarboxylate) to this carbonyl group.     

First example of the solid-state thermal cyclometalation of ligated benzophenone imine giving novel luminescent platinum(II) species

The (benzophenone imine)platinum(II) compounds trans-[PtCl2(Ph2C=NH)(RR'SO)] [R, R'=Me, Me (2); n-Pr, n-Pr (3); (CH2)4 (4); Me, Ph (5); Me, p-MeC6H4 (6)] were prepared by the reaction of Ph2C=NH with K[PtCl3(RR'SO)], obtained in situ from K2[PtCl4] and the corresponding sulfoxide, giving 2-6 as well as cis-[PtCl2(Ph2C=NH)2] (1) as a minor product. The complexes were characterized by 1H, 13C, and 195Pt NMR and IR spectroscopy, electrospray ionization mass spectrometry, and C, H, and N elemental analysis. The X-ray crystallography of 1 enables confirmation of the cis configuration of the complex, while in 2 and 4.1/2CHCl3, the imine and sulfoxide ligands are mutually trans. The solid-state structure of 4.1/2CHCl3 consists of two dimeric Pt moieties representing a rather weak Pt...Pt interaction. The dimeric architecture of 4.1/2CHCl3 is enhanced by the hydrogen bonding between imine H atoms and O atoms. The orthometalation of 1 and 2-6 proceeds both in the solid phase and in a toluene suspension, leading to the formation of [PtCl{Ph(C6H4)C=NH}(Ph2C=NH)] (7) and [PtCl{Ph(C6H4)C=NH}(RR'SO)] (8-12), respectively, isolated in nearly quantitative yields. Complexes 8-12 are emissive at room temperature both in solution (lambdaemmax approximately 535 nm) and in the solid state (lambdaemmax 560-610 nm), with excited-state lifetimes of ca. 300-600 ns, representing a new family of PtII-based luminescent complexes. Compounds 8 and 10 have been characterized by X-ray analysis, confirming the square-planar coordination geometry of the metal center with the almost planar platinacycles. In 8, the asymmetric unit contains two independent Pt molecules, while in 10, it includes four Pt molecules linked by the intermolecular hydrogen-bonding network between the NH group and Cl atoms.     

The mutual influence of the imine substituents of terephthal-bis-imines concerning their reactivity towards Fe2(CO)9

The reaction of terephthal-bis-imines with Fe₂(CO)₉ proceeds via a C---H activation reaction in the ortho position with respect to one of the imine functions. The corresponding hydrogen atom is shifted towards the former imine carbon atom producing a methylene group instead. The dinuclear iron complexes formed by this reaction sequence and showing no coordination of the second imine group were isolated from reactions of bis-imines with both phenyl and cyclohexyl substituents at the imine nitrogen atoms. In addition, we observed three different reaction pathways of the second imine substituent of the starting material which is obviously thus influenced by the fact that the first one is coordinating an Fe₂(CO)₆ moiety. If the organic substituent at the imine nitrogen atoms is a phenyl group the formation of a trinuclear complex is achieved in which an additional Fe(CO)₃ group is coordinating the CN double bond and one of the carbon---carbon bonds of the central phenyl ring in an η⁴-fashion. The same reaction leads to the isolation of a tetranuclear iron---carbonyl compound in which both imine substituents were transformed via the pathway described above, each building up dinuclear subunits. In contrast to this the reaction of a bis-imine with cyclohexyl groups at the imine nitrogen and thus an enhanced nucleophilicity leads to the formation of a tetranuclear complex in which only one imine group reacts under C---H activation with subsequent hydrogen migration towards the former imine carbon atom. The second imine substituent also shows a C---H activation reaction in the ortho position with respect to the imine group but the corresponding hydrogen atom is transferred to one of the aromatic carbon atom of the central phenyl ring of the ligand. The C=N double bond remains unreacted and only coordinates the second Fe₂(CO)₆ moiety via the nitrogen lone pair.     

Oxidative coupling of arylboronic acids with arenes via Rh-catalyzed direct C-H arylation

Oxidative coupling of three different arenes and a thiophene derivative with various arylboronic acids was achieved with a [RhCl(C2H4)2]2/P[p-(CF3)C6H4]3 catalyst system. Commercially available 2,2,6,6-tetramethylpiperidine-N-oxyl radical (TEMPO) was used as a stoichiometric oxidant. A 2-pyridyl group and an imine functional group served as ortho-directing groups to mediate the direct C-H arylation by a Rh complex. Moderate to excellent yields were obtained for the coupling reactions.     

两种季铵盐型离子液体钯配合物的合成

以苯甲酰肼和4-醛基吡啶为原料,经过缩合反应制备亚胺型化合物1,分别与苄氯和对二苄氯结合制备了两个新型的离子液体型亚胺配体2和3,配体2和3分别与醋酸钯反应得到新型离子液体型钯配合物4和离子液体型自组装钯配合物5,其结构经¹H NMR,¹³C NMR,IR和MS确证。      

Diastereoselective synthesis of substituted 2,3,4,5‐tetrahydro‐1H‐1‐benzazepine‐5‐carboxylic esters by a tandem reduction‐reductive animation reaction

An efficient, diastereoselective synthesis of substituted and unsubstituted 2,3,4,5‐tetrahydro‐1H‐1‐benzazepine‐5‐carboxylic esters has been developed based on the tandem reduction‐reductive amination reac tion. Catalytic hydrogenation of a series of 2‐(2‐nitrophenyl)‐5‐oxoalkanoic esters initiates a reaction sequence involving (1) reduction of the aromatic nitro group, (2) condensation of the N‐hydroxylamino (or amino) nitrogen with the side chain carbonyl, and (3) reduction of the seven‐membered cyclic imine. Cyclizations that produce 2‐alkyl‐2,3,4,5‐tetrahydro‐1H‐1‐benzazepine‐5‐carboxylic esters are diastereose lective for the product having the C2 alkyl and the C5 ester groups cis. In these reactions, the transannular ester group exerts a strong stereodirecting effect on the reduction of the cyclic imine intermediate, though not as strong as that observed in previous closures of 2‐alkyl‐1,2,3,4‐tetrahydroquinoline‐4‐carboxylic esters. This decrease in diastereoselectivity is attributed to (1) the greater distance between the ester and the imine double bond and (2) the increased conformational mobility of the larger ring, both of which diminish the stereodirecting effect of the ester. Finally, formation of the seven‐membered ring is sufficiently slow that reaction with the side chain ester group competes with heterocycle formation in several of the reactions.     

Living polymerization of ethylene catalyzed by titanium complexes having fluorine-containing phenoxy-imine chelate ligands

Seven titanium complexes bearing fluorine-containing phenoxy-imine chelate ligands, TiCl(2)[eta(2)-1-[C(H)=NR]-2-O-3-(t)Bu-C(6)H(3)](2) [R = 2,3,4,5,6-pentafluorophenyl (1), R = 2,4,6-trifluorophenyl (2), R = 2,6-difluorophenyl (3), R = 2-fluorophenyl (4), R = 3,4,5-trifluorophenyl (5), R = 3,5-difluorophenyl (6), R = 4-fluorophenyl (7)], were synthesized from the lithium salt of the requisite ligand and TiCl(4) in good yields (22%-76%). X-ray analysis revealed that the complexes 1 and 3 adopt a distorted octahedral structure in which the two phenoxy oxygens are situated in the trans-position while the two imine nitrogens and the two chlorine atoms are located cis to one another, the same spatial disposition as that for the corresponding nonfluorinated complex. Although the Ti-O, Ti-N, and Ti-Cl bond distances for complexes 1 and 3 are very similar to those for the nonfluorinated complex, the bond angles between the ligands (e.g., O-Ti-O, N-Ti-N, and Cl-Ti-Cl) and the Ti-N-C-C torsion angles involving the phenyl on the imine nitrogen are different from those for the nonfluorinated complex, as a result of the introduction of fluorine atoms. Complex 1/methylalumoxane (MAO) catalyst system promoted living ethylene polymerization to produce high molecular weight polyethylenes (M(n) > 400 000) with extremely narrow polydispersities (M(w)/M(n) < 1.20). Very high activities (TOF > 20 000 min(-1) atm(-1)) were observed that are comparable to those of Cp(2)ZrCl(2)/MAO at high polymerization temperatures (25, 50 degrees C). Complexes 2-4, which have a fluorine atom adjacent to the imine nitrogen, behaved as living ethylene polymerization catalysts at 50 degrees C, whereas complexes 5-7, possessing no fluorine adjacent to the imine nitrogen, produced polyethylenes having M(w)/M(n) values of ca. 2 with beta-hydrogen transfer as the main termination pathway. These results together with DFT calculations suggested that the presence of a fluorine atom adjacent to the imine nitrogen is a requirement for the high-temperature living polymerization, and the fluorine of the active species for ethylene polymerization interacts with a beta-hydrogen of a polymer chain, resulting in the prevention of beta-hydrogen transfer. This catalyst system was used for the synthesis of a number of unique block copolymers such as polyethylene-b-poly(ethylene-co-propylene) diblock copolymer and polyethylene-b-poly(ethylene-co-propylene)-b-syndiotactic polypropylene triblock copolymer from ethylene and propylene.     

Characterization of a 1:1 Cu-O2 adduct supported by an anilido imine ligand

Copper(I) complexes of sterically hindered anilido imine ligands o-C6H4{N(C6H3(i)Pr2)}{C(R)=NC6H3(i)Pr2}- (L(1), R = H; L(2), R = CH3) have been prepared and characterized by spectroscopic and X-ray crystallographic methods. These complexes are highly reactive with O2, and in the case of L2 the product of low-temperature oxygenation was fully characterized by spectroscopic, X-ray crystallographic, and computational methods. The resonance Raman spectrum features an isotope-sensitive vibration at 974 cm(-1) (Delta(18O) = 66 cm(-1)), consistent with assignment as an O-O stretch. Despite the asymmetric coordination environment provided by the supporting anilido imine ligand, the X-ray crystal structure confirms rather symmetric side-on binding of the O2 moiety to the copper center, and the O-O bond length of 1.392(2) Angstroms indicates that this intermediate has significant Cu(III)-peroxo character. Theoretical calculations support this interpretation and predict that while a fully optimized end-on singlet geometry can be obtained, it is higher in energy than the side-on isomer by 3.5 kcal mol(-1) at the CASPT2/TZP level.     

Novel syntheses of pyrrolone and pyrrolopyridine derivatives

4-Arylmethylene-2-phenyl-2-oxazolin-5-ones 1a , b reacted with some active methylene reagents to afford pyrrolidine-3,5-dione, pyrrolo[2,3-b]pyridine and pyrrolinone derivatives. The cinnamate ester, obtained from 1a and sodium ethoxide, could be converted into a pyrrolidinone derivative having an active methylene group. This compound coupled with diazonium salts to afford the corresponding azo coupling products.     

1,3-Dipolar cycloaddition of diarylnitrones to 1-(4-nitrophenyl)-5H-pyrrolin-2-one

The reaction of diarylnitrones with 1-(4-nitrophenyl)-5H-pyrrolin-2-one to give 2-oxa-6-oxo-3-phenyl-4-(R-phenyl)-7-(4-nitrophenyl)-3,7-diazabicyclo(3,3,0)octanes has been examined. The structures of the products were established by NMR and IR spectroscopy, and x-ray diffraction studies. The stereoselectivity of the reaction is due to exo-approach of the reactants with cis-stereospecific addition of the trans-forms of the C,N-diarylnitrones to the pyrrolinone double bond.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1675–1678, December, 1990.     

Analysis of plasma polymerization of allylamine by FTIR

The plasma polymerization of allylamine in an inductively coupled rf plasma reactor is analyzed by Fourier transform infrared spectroscopy. Comparison of the infrared spectra of the as-received monomer and the plasma polymerized film reveals a conversion of the primary amine in the monomer (? CH₂? NH₂) to an imine (? CH?NH) and a nitrile (C?N). Plasma polymerization of ethylenediamine yields the same results, suggesting that this polymerization scheme may be typical of primary amines. Increasing the plasma power seems to increase the proportion of nitrile groups in relation to the imine groups. The infrared spectra of the vapor phase polymerized monomer was similar to that of the substrate-grafted allylamine film implying a similar structure. Aging of this vapor phase polymer at 120°C for 1 h in vacuum and at 295°C for 15 min in an oxygen free environment reveals nitrile group reaction similar to that observed in polyacrylonitrile. Thermogravimetric analyses of the vapor phase polymers in a nitrogen atmosphere at 20°C/min demonstrated the thermal stability, with the polymer produced at a plasma power level of 50 W retaining 20% of its weight at 1000°C. This was better than the stability shown by the polymer produced at 150 W and is attributed to the ease of nitrile group polymerization in the former.     

Mechanistic investigations of imine hydrogenation catalyzed by cationic iridium complexes

Complexes [IrH2(eta6-C6H6)(PiPr3)]BF4 (1) and [IrH2(NCMe)3(PiPr3)]BF4 (2) are catalyst precursors for homogeneous hydrogenation of N-benzylideneaniline under mild conditions. Precursor 1 generates the resting state [IrH2{eta5-(C6H5)NHCH2Ph}(PiPr3)]BF4 (3), while 2 gives rise to a mixture of [IrH{PhN=CH(C6H4)-kappaN,C}(NCMe)2(PiPr3)]BF4 (4) and [IrH{PhN=CH(C6H4)-kappaN,C}(NCMe)(NH2Ph)(PiPr3)]BF4 (5), in which the aniline ligand is derived from hydrolysis of the imine. The less hindered benzophenone imine forms the catalytically inactive, doubly cyclometalated compound [Ir{HN=CPh(C6H4)-kappaN,C}2(NH2CHPh2)(PiPr3)]BF4 (6). Hydrogenations with precursor 1 are fast and their reaction profiles are strongly dependent on solvent, concentrations, and temperature. Significant induction periods, minimized by addition of the amine hydrogenation product, are commonly observed. The catalytic rate law (THF) is rate = k[1][PhN=CHPh]p(H2). The results of selected stoichiometric reactions of potential catalytic intermediates exclude participation of the cyclometalated compounds [IrH{PhN=CH(C6H4)-kappaN,C}(S)2(PiPr3)]BF4 [S = acetonitrile (4), [D6]acetone (7), [D4]methanol (8)] in catalysis. Reactions between resting state 3 and D2 reveal a selective sequence of deuterium incorporation into the complex which is accelerated by the amine product. Hydrogen bonding among the components of the catalytic reaction was examined by MP2 calculations on model compounds. The calculations allow formulation of an ionic, outer-sphere, bifunctional hydrogenation mechanism comprising 1) amine-assisted oxidative addition of H2 to 3, the result of which is equivalent to heterolytic splitting of dihydrogen, 2) replacement of a hydrogen-bonded amine by imine, and 3) simultaneous H delta+/H delta- transfer to the imine substrate from the NH moiety of an arene-coordinated amine ligand and the metal, respectively.     

Synthesis and Crystal Structure of Cu(II) Complex with 2,9-Bis(n-2'''',5''''-diazaheptanyl)-1,10-phenanthroline

1 INTRODUCTION The polypyridine ligands, such as 2,2-bipyri- dine and 1,10-phenanthroline, continue to attract much research interest, mainly because of their rich redox chemistry and photochemistry[1, 2]. Most work on phenanthroline derivatives has bee…     

Alkyne-functionalized ruthenium nanoparticles: ruthenium-vinylidene bonds at the metal-ligand interface

Stable ruthenium nanoparticles were prepared by the self-assembly of 1-dodecyne onto the "bare" Ru colloid surface. The formation of a Ru-vinylidene (Ru═C═CH-R) interfacial bonding linkage was confirmed by the specific reactivity of the nanoparticles with imine derivatives to form a heterocyclic complex at the metal-ligand interface, as manifested in (1)H and (13)C NMR, photoluminescence, and electrochemical measurements in which a ferrocenyl imine was used as the labeling probe. Notably, the resulting nanoparticles could also undergo olefin metathesis reactions with vinyl-terminated molecules, as exemplified by the functionalization of the nanoparticles with 1-vinylpyrene. In sharp contrast, no reactvity was observed with 1-dodecynide-stabilized ruthenium nanoparticles with either imine or vinyl derivatives, indicating that these (deprotonated) nanoparticles were stabilized instead by the formation of a Ru-C≡ dπ bond at the metal-ligand interface.     

[Ni(C_5H_5N)_2(C_7·H_6O_2N)_2]H_2O三元配合物的合成及晶体结构

合成了标题化合物。该化合物的分子式[Ni(C5H5N)2(C7H6O2N)2]H2O(C24H24N4NiO3),分子量475.18,采用单色的MoKα (λ = 0.71073 )射线测定,共收集7408个数据,其中独立衍射点2567个(Rint = 0.0272),I > 2s(I)可观测点数1926个,结果表明该化合物属单斜晶系, 空间群C2/c其晶胞参数为: a = 14.466(2),b = 12.193(2),c = 14.072(2) ;β = 116.229(2)°,V = 2226.6(5) 3,Z = 4,Dc = 1.418 g/cm3 ,μ = 0.905 mm-1,F(000) = 992. 2个水杨醛亚胺各提供2个配位原子参与配位,2个吡啶各提供1个配位原子参与配位,该配合物是六配位的八面体构型,同时讨论了该体系中不同配位原子的配位能力的差异。