Asymmetric cyanosilylation of ketones catalyzed by novel chiral N,N′-dioxide titanium complexes

A novel C₂-symmetric chiral N,N′-dioxide titanium complex was described, which could efficiently catalyze the asymmetric cyanosilylation of ketones in high yields with up to 92% ee under mild conditions. In addition, the catalyst system was simple and the ligands could be easily prepared from commercially available chiral amino acid.     

Synthesis, characterization and crystal structures of cyclometallated palladium (II) compounds containing difunctional ligands with [P,P], [As,As], [N,N], [P,As], [P,N] and [P,O] donor atoms

Treatment of the chloro-bridged dinuclear complex [Pd{3,4-(MeO)₂C₆H₂C(H)N(Cy)-C6,N}(μ-Cl)]₂ (1) with homobidentate [P,P], [As,As], [N,N], and heterobidentate [P,As], [P,N] ligands in a 1:1 molar ratio gave the dinuclear complexes [{Pd[3,4-(MeO)₂C₆H₂C(H)N(Cy)-C6,N](Cl)}₂{μ-L}] (L = Ph₂PC₄H₆(NH)CH₂PPh₂ (2); Ph₂As(CH₂)₂AsPh₂ (3); 1,3-(NH₂CH₂)₂C₆H₄ (4); Ph₂P(CH₂)₂AsPh₂ (5); Ph₂P(CH₂)₂NH₂ (6)), with the bidentate ligands bridging the two cyclometallated fragments.The reaction with the homobidentate ligands in a 1:2 molar ratio in the presence of NaClO₄ afforded the mononuclear compounds [[Pd{3,4-(MeO)₂C₆H₂C(H)N(Cy)-C6,N}{L-P,P}][ClO₄] (L = Ph₂PC₄H₆(NH)CH₂PPh₂ (7); (o-Tol)₂P(CH₂)₂P(o-Tol)₂ (8)), [Pd{3,4-(MeO)₂C₆H₂C(H)N(Cy)-C6,N}{Ph₂As(CH₂)₂AsPh₂-As,As}][ClO₄] (9) and [Pd{3,4-(MeO)₂C₆H₂C(H)N(Cy)-C6,N}{L-N,N}][ClO₄] (L = NH₂(CH₂)₃NH₂ (10); NH₂(C₆H₈)CH₂(C₆H₈)NH₂ (11); 1,3-(NH₂CH₂)₂C₆H₄ (12); 1,3-(NH₂)₂C₅H₃N (13); NH₂(C₆H₄)O(C₆H₄)NH₂ (14); NMe₂(CH₂)₂NMe₂ (15)), in which the chloro ligands are absent and the bidentate ligands are chelated to the palladium atom.Reaction of 1 with Ph₂P(CH₂)₂AsPh₂ in 1:2 molar ratio in acetone in the presence of NH₄PF₆ afforded the analogous mononuclear compound [Pd{3,4-(MeO)₂C₆H₂C(H)N(Cy)-C6,N}{Ph₂P(CH₂)₂AsPh₂-P,As}][PF₆] (16); whereas reaction with Ph₂P(CH₂)₃NH₂ gave [Pd{3,4-(MeO)₂C₆H₂C(H)N(Cy)-C6,N}{Ph₂P(CH₂)₃N(CMe₂)-P,N}][PF₆] (17), derived from intermolecular condensation between the aminophosphine and acetone. Condensation of the NH₂ group was precluded by change of solvent, using dichloromethane.Iminophoshines also reacted with 1 in 1:2 molar ratio in acetone to give a new series of mononuclear cyclometallated complexes: [Pd{3,4-(MeO)₂C₆H₂C(H)N(Cy)-C6,N}{L-P,N}][ClO₄] (L = Ph₂PC₆H₄C(H)NCy (20); Ph₂PC₆H₄C(H)NC(CH₃)₃ (21); Ph₂PC₆H₄C(H)NNMe₂ (22); Ph₂PC₆H₄C(H)NNHMe (23); Ph₂PC₆H₄C(H)NNHPh (24)). Analogous complexes with a stable P,O-chelate were obtained using bidentate [P,O] donor ligands: [Pd{3,4-(MeO)₂C₆H₂C(H)N(Cy)-C6,N}{L-P,O}][Cl] (L = 2-(Ph₂P)C₆H₄CHO (25); Ph₂PN(Me)C(O)Me (26)).The crystal structures of compounds 1, 5, 15, 16, 18, 20 have been determined by X-ray crystallography.     

Uranyl(VI) complexes of [O,N,O,N′]-type diaminobis(phenolate) ligands: Syntheses,structures and extraction studies

The syntheses and crystal structures of four new uranyl complexes with [O,N,O,N′]-type ligands are described. The reaction between uranyl nitrate hexahydrate and the phenolic ligand [(N,N-bis(2-hydroxy-3,5-dimethylbenzyl)-N′,N′-dimethylethylenediamine)], H₂L1 in a 1:2 molar ratio (M to L), yields a uranyl complex with the formula [UO₂(HL1)(NO₃)] · CH₃CN (1). In the presence of a base (triethylamine, one mole per ligand mole) with the same molar ratio, the uranyl complex [UO₂(HL1)₂] (2) is formed. The reaction between uranyl nitrate hexahydrate and the ligand [(N,N-bis(2-hydroxy-3,5-di-t-butylbenzyl)-N′,N′-dimethylethylenediamine)], H₂L2, yields a uranyl complex with the formula [UO₂(HL2)(NO₃)] · 2CH₃CN (3) and the ligand [N-(2-pyridylmethyl)-N,N-bis(2-hydroxy-3,5-dimethylbenzyl)amine], H₂L3, in the presence of a base yields a uranyl complex with the formula [UO₂(HL3)₂] · 2CH₃CN (4). The molecular structures of 1–4 were verified by X-ray crystallography. The complexes 1–4 are zwitter ions with a neutral net charge. Compounds 1 and 3 are rare neutral mononuclear [UO₂(HLn)(NO₃)] complexes with the nitrate bonded in η²-fashion to the uranyl ion. Furthermore, the ability of the ligands H₂L1–H₂L4 to extract the uranyl ion from water to dichloromethane, and the selectivity of extraction with ligands H₂L1, H₃L5 (N,N-bis(2-hydroxy-3,5-dimethylbenzyl)-3-amino-1-propanol), H₂L6 · HCl (N,N-bis(2-hydroxy-5-tert-butyl-3-methylbenzyl)-1-aminobutane · HCl) and H₃L7 · HCl (N,N-bis(2-hydroxy-5-tert-butyl-3-methylbenzyl)-6-amino-1-hexanol · HCl) under varied chemical conditions were studied. As a result, the most efficient and selective ligand for uranyl ion extraction proved to be H₃L7 · HCl.     

Regioselective synthesis of optically active (pyrazolyl)pyridines with adjacent quaternary carbon stereocenter: chiral N,N-donating ligands

Novel optically active 2-(pyrazol-1-yl)pyridines have been prepared using resolved the O-methyl ether of atrolactic acid as a source of the adjacent quaternary carbon stereocenter. Different regioisomers were formed selectively in the reaction of 2-hydrazinopyridines with the chiral 1,3-diketone and in the nucleophilic substitution of 2-chloropyridines with the potassium salt of the chiral pyrazole. The second route gave 2-(pyrazol-1-yl)pyridines with the stereogenic center neighboring the coordinating nitrogen in the pyrazole ring. Also, new C₂-symmetric chiral ligands based on 2,6-bis(pyrazolyl)pyridine and 6,6′-bis(pirazolyl)-2,2′-bipyridine structures were obtained.     

Novel chiral dibenzo[a,c]cycloheptadiene bis(oxazoline) and catalytic enantioselective cyclopropanation of styrene

A series of chiral C₂-symmetric bis(oxazoline) ligands containing dibenzo[a,c]cycloheptadiene units were synthesized. The copper complexes, prepared in situ from copper (I)-triflate and the new enantiopure oxazoline ligands, were assessed as chiral catalysts in the enantioselective cyclopropanation of styrene with diazoacetate. Enantioselectivities up to 82 and 62%, respectively, for trans- and cis-2-phenylcyclopropanecarboxylate were observed.     

Enantioselective synthesis of (2S,3′R,7′Z)-N-(3′-hydroxy-7′-tetradecenoyl)-homoserine lactone

A concise enantioselective total synthesis of (2S,3′R,7′Z)-N-(3′-hydroxy-7′-tetradecenoyl)-homoserine lactone is described. Key feature of this protocol is a catalytic asymmetric hydrogenation and a prophenol-zinc-catalyzed diazo addition to imine reaction as genesis of chirality. Moreover, flexibility is built in the synthesis to generate enantioenriched analogs using catalytic amount of enantioenriched C₂-symmetric ligands.     

New heterogenized C2-symmetric bis(sulfonamide)-cyclohexane-1,2-diamine-RhCp∗ complexes and their application in the asymmetric transfer hydrogenation (ATH) of ketones in water

C₂-symmetric bis(sulfonamide) ligands derived from chiral trans-(1R,2R)-cyclohexane-1,2-diamine were immobilized on silica gel and on polystyrene resin, and complexed to Rh^IIICp∗. The resulting complexes were used as catalysts in the asymmetric transfer hydrogenation (ATH) of acetophenone. The chiral secondary alcohol was obtained in high yields (>99%) and enantioselectivities (92%) with aqueous sodium formate as the hydride source. The immobilized catalysts were recycled with no loss in activity.     

Synthesis of chiral vicinal C2 symmetric and unsymmetric bis(sulfonamide) ligands based on trans-1,2-cyclohexanediamine by aminolysis of N-tosylaziridines

The ring opening of N-tosylaziridines with aliphatic amines can be efficiently catalyzed by lithium perchlorate to provide derivatives of the trans-1,2-diamine in high yields. The reaction was used in desymmetrization of several cyclic N-tosylaziridines using chiral amines. Using this strategy, an efficient synthesis of chiral vicinal C₂ symmetric bis(sulfonamide) and unsymmetrical bis(sulfonamide) ligands based on trans-1,2-cyclohexanediamine was developed.     

Copper(I) catalysis: Synthesis of N,N′-diarylated and N-aryl,N′-formylated chiral C2-symmetric diamines

Chiral N,N′-diaryl C₂-symmetric diamines and N-aryl,N′-formyl-trans-(1R,2R)-diaminocyclohexane are readily accessed by copper catalyzed N,N′-diarylation and N-aryl,N′-formylation of trans-(1R,2R)-diaminocyclohexane with aryl bromides. N,N′-diarylation using (R)-1,1′-binaphthyl-2,2′-diamine and iodobenzene gave the corresponding (R)-N,N′-diphenyl-1,1′-binaphthyl-2,2′-diamine derivative in 83% yield.     

3,3-Bis(3,5-dimethylpyrazol-1-yl)propionic acid: A tripodal N,N,O ligand for manganese and rhenium complexes - Syntheses and structures

The tripodal N,N,O ligands 3,3-bis(3,5-dimethylpyrazol-1-yl)propionic acid (Hbdmpzp) (1) and 3,3-bis(pyrazol-1-yl)propionic acid (Hbpzp) (2) form the “missing link” between the well-known bis(pyrazol-1-yl)acetic acids and related ligands with a longer “carboxylate arm”. To illustrate the reactivity of this ligand, manganese and rhenium complexes bearing the ligand bdmpzp are reported. The complexes are compared to related compounds bearing other tripod ligands such as bis(3,5-dimethylpyrazol-1-yl)acetate (bdmpza) and 3,3-bis(1-methylimidazol-2-yl)propionate (bmip). Spectroscopic and structural data are used as a basis for comparison, as well as DFT calculations. Both ligands 1 and 2 and the complexes fac-[Mn(bdmpzp)(CO)₃] (3) and fac-[Re(bdmpzp)(CO)₃] (4) were characterised by X-ray crystallography.     

(N,N-dimethylbenzylamine-2C,N)palladium(II) and -platinium(II) β-diketonates and thio-β-diketonates

(N,N-dimethylbenzylamine-2C,N)palladium(II) and -platinum(II) β-diketonates, DmbaML, have been synthesized by reaction of [DmbaMCl]₂ with the free ligand and KOH, or with the thallium(I) salt of the ligand. The various isomers formed have been investigated by ¹H and ¹⁹F NMR spectroscopy. Infrared and mass spectroscopic studies have also been made on the compounds.     

Bis(dialkylmetal)-N,N′-dimethyloxamides of aluminium,gallium and indium,preparation, physical and spectroscopic properties

The reaction of N,N′-dimethyloxamide with trialkyl derivatives of aluminium, gallium, and indium yields bis(dialkylmetal) compounds of structural formula (R₂M)₂[O₂C₂(NCH₃)₂] (M = Al, Ga, In; and R = CH₃, C₂H₅). The M₂O₂C₂N₂ skeleton of these monomeric products forms an almost planar system of two fused five-membered rings, with S₂ symmetry. For the dimethylgallium and dimethylindium derivatives, ¹H and ¹³C NMR spectra show the presence of two conformational isomers which differ in the orientation of the N-methyl relative to the two metal-bound CH₃ groups.     

The synthesis and application of novel C2-symmetric chiral N,N,O,O bisoxazoline ligands with a ferrocene backbone

Novel C₂-symmetric bisoxazoline ligands 5 with a ferrocene backbone and a hydroxyl group at the substituent of the oxazoline ring were designed and prepared. With these ligands, up to 94% ee was obtained for the alkylation of arylaldehyde with diethylzinc.     

New C2-symmetric bis(sulfonamide)-cyclohexane-1,2-diamine-RhCp complex and its application in the asymmetric transfer hydrogenation (ATH) of ketones in water

C₂-symmetric bis(sulfonamide) ligands derived from trans-(1R,2R)-cyclohexane-1,2-diamine were synthesized and complexed with [Cp^∗RhCl₂]₂ in situ and used in the ATH of aromatic ketones with aqueous sodium formate as the hydrogen source. The chiral secondary alcohols were obtained with 90-99% enantioselectivity and in 50-100% yield. Reductions in water were faster than those in isopropanol/KOH.     

Hydrogen bonding and halogen bonding co-existing in the reaction of heptafluorobenzyl iodide with N,N,N,N-tetramethylethylene diamine

Two novel assembling systems 3 and 4, with the structures of C₆F₅CF₂⁻?H⁺N(Me)₂CH₂CH₂(Me₂)N⁺H?⁻CF₂C₆F₅ and C₆F₅CF₂I?N(Me)₂CH₂CH₂(Me)₂N?ICF₂C₆F₅, respectively, have been generated from the solution of heptafluorobenzyl iodide 1 and N,N,N^′,N^′-tetramethylethylenediamine 2 in dichloromethane. Their structures have been characterized by X-ray diffraction analysis, NMR and IR spectroscopy. Intermolecular N?I halogen bond and F?H hydrogen bond are revealed to be the driving forces for their formation.     

Novel chiral C2-symmetric multidentate aminophosphine ligands for use in catalytic asymmetric reduction of ketones

A series of novel chiral C₂-symmetric multidentate aminophosphine ligands have been successfully synthesized by Schiff-base condensation of bis（o-formylphenyl）phenylphosphane and easily available monoprotected（1R,2R）-diaminocyclohexane.The catalytic properties of these ligands were investigated in Ir-catalyzed asymmetric transfer hydrogenation of various aromatic ketones,giving the corresponding optical active alcohols with up to 98%conversion and good ee under mild reaction conditions.     

Spectroscopic and structural characterization of cationic N-(2-aminoethyl)aziridine-N,N′ chelate complexes of the d-metals Rh(III) and Ir(III)

The syntheses of the compounds [M(Cp^∗)(aeaz)(az)](OTf)₂ (4, 5) (M = Rh(III), Ir(III); aeaz = C₂H₄NC₂H₄NH₂, az = C₂H₄NH (3)) containing cationic N-(2-aminoethyl)aziridine-N,N′ chelate complexes are described. The bis-aziridine complexes [MCl(Cp^∗)(az)₂]Cl (M = Rh (1), M = Ir (2)) react with an excess of the aziridine (az) in the presence of AgO₃SCF₃ (=AgOTf) via AgCl precipitation and az addition followed by a metal-mediated coupling reaction, to give the compounds [M(Cp^∗)(aeaz)(az)](OTf)₂ (4, 5). The new aeaz ligand is formally the dimerisation product of az. Using the same reaction conditions with the analogous, but weaker Lewis acidic ruthenium(II) complex [RuCl(C₆Me₆)(az)₂]Cl (6) an anion exchange reaction yielding [RuCl(C₆Me₆)(az)₂]OTf (8) is observed. After purification, all compounds are fully characterized using IR, FAB-MS, ¹H and ¹³C NMR spectroscopy. The single crystal X-ray structure analysis reveals a distorted octahedral geometry for all complexes.     

Fluorogenic N,O-chelates built on a C2-symmetric aryleneethynylene platform: Spectroscopic and structural consequences of conformational preorganization and ligand denticity

Using π-extended aryleneethynylene as a rigid structural skeleton, a C₂-symmetric bis(picolinate) ligand was prepared. Binding of zinc(II) or cadmium(II) ion to this formally tetradentate N₂O₂-chelate resulted in significant red-shifts and enhancement in emission. The metal-ligand interaction responsible for such structural change was investigated by isolation and characterization of a tetrazinc(II) complex, in which the picolinate group functions not only as terminal bidentate but also as bridging with its μ-1,3 carboxylate unit.     

The first bis(orotato–N,O) complex: Synthesis,crystal structure,spectroscopic and thermal characterization of (chaH)2[Cu(HOr–N,O)2(cha)] · 2H2O (cha = cyclohexylamine and HOr = orotate(2−))

The novel bis(cyclohexylaminium) cyclohexylaminebis(orotate–N,O)cuprate(II) dihydrate, (C₆H₁₅N)₂[Cu(C₅H₂N₂O₄)₂(C₆H₁₄N)] · 2H₂O, has been prepared and characterized by elemental analysis, magnetic measurements, FT-IR and UV–Vis spectroscopy, thermal analysis and X-ray diffraction. The Cu(II) complex crystallizes in the monoclinic space group P2₁/c. The copper atom in the five-coordinated (chaH)₂[Cu(HOr–N,O)₂(cha)] · 2H₂O is chelated by a deprotonated pyrimidine nitrogen atom and carboxylate oxygen atom as a bis(bidentate) ligand and the cyclohexylamine ligand completes the square-pyramidal coordination. The thermal decomposition of the complex has been predicted by the help of thermal analysis (TG, DTG and DTA).     

Tri- and diorganostannates containing 2-(N,N-dimethylaminomethyl)phenyl ligand

The C,N-chelated tri and diorganotin(IV) chlorides react with both protic mineral acids and carboxylic acids. The nitrogen atom of the L^CN ligand (where L^CN is 2-(dimethylaminomethyl)phenyl) is thus quarternized - protonated and new Sn-X bond (X = Cl, Br, I or the remainder of the starting acid used) is simultaneously formed. The set of zwitterionic tri and diorganostannates containing protonated 2-(dimethylaminomethyl)phenyl-moiety was prepared and structurally characterized by multinuclear NMR spectroscopy and XRD techniques. In all these cases, the intramolecular N-H?X bond is present in the molecule. Despite the central tin atom remains five-coordinated (except for the [HL^CNH]⁺[(n-Bu)₂SnCl(NO₃)₂]⁻) and reveals a distorted trigonal bipyramidal geometry, the ¹¹⁹Sn NMR chemical shift values of these zwitterionic stannates are somewhat shifted to the higher field than corresponding starting C,N-chelated tri and diorganotin(IV) halides. Reactions of C,N-chelated organotin(IV) halides with various Lewis acids are also discussed.