Achiral Ligands Research Articles

ChemInform Abstract: Sequential Rhodium/Palladium Catalysis: Enantioselective Formation of Dihydroquinolinones in the Presence of Achiral and Chiral Ligands.

ChemInformVolume 46, Issue 19 Heterocyclic Compounds ChemInform Abstract: Sequential Rhodium/Palladium Catalysis: Enantioselective Formation of Dihydroquinolinones in the Presence of Achiral and Chiral Ligands. Lei Zhang, Lei Zhang Dep. Chem., Univ. Toronto, Toronto, Ont. M5S 3H6, Can.Search for more papers by this authorZafar Qureshi, Zafar Qureshi Dep. Chem., Univ. Toronto, Toronto, Ont. M5S 3H6, Can.Search for more papers by this authorLorenzo Sonaglia, Lorenzo Sonaglia Dep. Chem., Univ. Toronto, Toronto, Ont. M5S 3H6, Can.Search for more papers by this authorMark Lautens, Mark Lautens Dep. Chem., Univ. Toronto, Toronto, Ont. M5S 3H6, Can.Search for more papers by this author Lei Zhang, Lei Zhang Dep. Chem., Univ. Toronto, Toronto, Ont. M5S 3H6, Can.Search for more papers by this authorZafar Qureshi, Zafar Qureshi Dep. Chem., Univ. Toronto, Toronto, Ont. M5S 3H6, Can.Search for more papers by this authorLorenzo Sonaglia, Lorenzo Sonaglia Dep. Chem., Univ. Toronto, Toronto, Ont. M5S 3H6, Can.Search for more papers by this authorMark Lautens, Mark Lautens Dep. Chem., Univ. Toronto, Toronto, Ont. M5S 3H6, Can.Search for more papers by this author First published: 23 April 2015 https://doi.org/10.1002/chin.201519200Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume46, Issue19May, 2015 RelatedInformation

Spontaneous Resolution Induced by a Chiral Ni(II) Complex with an Achiral Tripodal Ligand#

A chiral nickel(II) complex, [Ni(II)H3L](ClO4)2 (1), with an achiral ligand H3L (=tris{2‐(4‐imidazolyl)methyliminoethyl}amine) was synthesized by in situ reaction between nickel(II) perchlorate hexahydrate and a condensation mixture of 4‐imidazolecarboxaldehyde and tris(2‐aminoethyl)amine. Single crystal X‐ray analysis revealed that the H3L ligand hexadentately binds to Ni(II) ion through three Schiff‐base imine N atoms and three imidazole N atoms with distorted octahedral geometry. Both single‐crystal X‐ray diffraction and circular dichroism investigations found that the crystal of complex 1 was an enantiopure conglomerate. The hydrogen‐bond network of NimidazoleH⋯OClO4⋯HNimidazole induced spontaneous resolution to form the conglomerate. The capped tripod‐shaped [Ni(II)H3L]2+ complex ions are hydrogen‐bonded in a tail‐to‐tail mode and array in an up‐and‐down manner repeatedly to honeycomb an extended two‐dimensional homochiral network with trigonal voids.

A thermally stable and homochiral jsm-type metal–organic framework: Syntheses, structure and properties

A novel 3D homochiral framework, [Co(L)(BYBP)0.5] (1), has been synthesized by the solvothermal reaction of a much longer ligand, 4,4′-di(4-pyridyl)-biphenyl (BYBP, 15.7Å) which is more than twice the length of 4,4′-bipy, and an achiral flexible V-shaped ligand, 4,4′-dicarboxydiphenylamine (H2L) (Scheme 1). The resultant complex was characterized by IR spectroscopy, thermal analysis, single crystal X-ray diffraction, in situ variable-temperature power X-ray diffraction and circular dichroism (CD). The results indicated that complex 1 is a rare homochiral 3-fold jsm net. Its thermal stability was investigated and 1 keeps its crystal structure up to 375°C. Magnetic susceptibility measurements indicate that 1 exhibits antiferromagnetic behavior.

Atropselective syntheses of (-) and (+) rugulotrosin A utilizing point-to-axial chirality transfer.

Chiral, dimeric natural products containing complex structures and interesting biological properties have inspired chemists and biologists for decades. A seven step total synthesis of the axially chiral, dimeric tetrahydroxanthone natural product rugulotrosin A is described. The synthesis employs a one-pot Suzuki coupling/dimerization to generate the requisite 2,2'-linked biaryl linkage. Highly selective point-to-axial chirality transfer was achieved using palladium catalysis with achiral phosphine ligands. Single X-ray crystal diffraction data was obtained to confirm both the atropisomeric configuration and absolute stereochemistry of rugulotrosin A. Computational studies are described to rationalize the atropselectivity observed in the key dimerization step. Comparison of the crude fungal extract with synthetic rugulotros in A and its atropisomer verified that nature generates a single atropisomer of the natural product.

Syntheses, structures, photoluminescence and photocatalysis of chiral 3D Cd(II) frameworks from achiral mixed flexible ligands by spontaneous resolution.

Unprecedented two homochiral Cd(ii) enantiomers [Cd(dtba)(bpp)]n (1: 1P and 1M) (H2dtba = 2,2'-dithiodibenzoic acid, bpp = 1,3-bis(4-pyridyl)propane), were obtained by self-assembly with mixed achiral flexible ligands. Single-crystal X-ray diffraction analysis reveals that complexes 1P and 1M crystallize in trigonal space groups P3121 and P3221, respectively. The compounds are optically active, and their UV spectra in the solid state showed Cotton effects in the opposite directions. Compounds 1P and 1M present the examples of three-interpenetrating chiral frameworks with triangular and quasi-heart-like threefold helical chiral channels, chair-like twofold helical chiral channels and one type of threefold double-helical chain. The 3D metal-organic framework can be regarded as a bcu-type topology with the symbol of 8(6). The photoluminescent properties of compound 1 have been studied. Remarkably, compound 1 exhibits good photocatalytic activity for degradation of dyes under the simulated sunlight irradiation in the pH = 3 aqueous solution.

Homochiral 3D coordination polymer with unprecedented three-directional helical topology from achiral precursor: synthesis, crystal structure, and luminescence properties of uranyl succinate metal-organic framework.

A luminescent homochiral uranyl succinate coordination polymer with unprecedented three-directional helices was synthesized hydrothermally via spontaneous symmetry breaking, and fully characterized. Its homochirality has been confirmed by singe crystal X-ray diffraction and solid state circular dichroism (CD) spectra. The polymer exhibited a Stokes shift greater than 180 nm.

A homochiral magnet based on D₃ symmetric [(NaO₃)Co₃] clusters: from spontaneous resolution to absolute chiral induction.

A pair of novel enantiomeric 3D magnetic complexes [NaCo3(IA)6](NO3)·H2O (1Δ and 1Λ) have been synthesized using an achiral ligand HIA via spontaneous resolution, which crystallize in the hexagonal crystal system with a chiral P63 space group, and diamagnetic sodium cations are located at the center of D3 symmetric clusters. This kind of spontaneous resolution is uncontrollable and dependent on batches. By utilizing cheap enantiopure mandelic acid as a chiral inducing agent, they are driven to controllable homochiral crystallization of the desired enantiomorph, confirmed by circular dichroism spectra.

Chiral four-fold interpenetrating 2D cadmium networks based on two achiral ligands

The new coordination polymer {[Cd(DPPA)(ecdbc)](H2O)2}n was prepared and characterized by X-ray diffraction analysis revealing chiral four-fold interpenetrating 2D networks, within which two kinds of helical chains can be distinguished.

Chirality detection of two enantiomorphic 3D lanthanide coordination polymers by vibrational circular dichroism spectra.

Two enantiomorphic 3D lanthanide coordination polymers of {[Dy5(L)4(H2O)10][Dy(H2O)7][Na(H2O)5]}·(ClO4)7·(H2O)15 (1a for R and 1b for S) with chiral helical chains were synthesized based on an achiral ligand N-(2-hydroxyethyl)ethylenediamine-N,N',N'-triacetic acid (H3L) and Dy(ClO4)3. Crystal analysis revealed that 1a and 1b were crystallized in chiral space groups P4132 and P4332, respectively. The absolute configurations of the two structures were evidenced by vibrational circular dichroism (VCD) spectra with one single crystal sample.

Tuning Supramolecular Chiral Architecture of Molecular Corners from Achiral Dipalladium(II) and Diplatinum(II) Complexes with Achiral Anthracyl Pyrazole Ligand

A novel kind of coordination molecular corners [M2L2]([1=(bpy)Pd]2L2, 2=[(dmbpy)Pd]2L2, 3=[(phen)Pd]2L2,4=[(ppy)Pt]2L2, where bpy=2,2′-bipyridine, dmbpy=4,4′-dimethyl-2,2′-bipyridine, phen=1,10-phenanthroline, ppy=2-phenylpyridine) was synthesized through synergistic metal-metal bonding interaction and spontaneous deprotonation from the pyrazole linkers 4-(4-(anthracen-9-yl)phenyl)-3,5-dimethyl-1H-pyrazole(L). Three complexes 1~3 were characterized by single crystal X-ray diffraction,1H and13 C NMR, ESI-MS and fluorescence spectroscopy. The neutral organometallic corner [(ppy)Pt]2L24 was also determined by1 H and13C NMR, MALDITOF-MS and fluorescence spectroscopy. These achiral molecular corners assemble from different achiral dimetallic centers with the achiral ligand HL in quite different crystal structures, in particular, 3 with a [(phen)Pd]2assembling center crystallizes into a supramolecular chiral architecture.

Optically active II-VI semiconductor nanocrystals via chiral phase transfer

ABSTRACTWe report optically active ensembles of II-VI semiconductor nanocrystals prepared via chiral phase transfer, which is initiated by exchange of the original achiral ligands capping the nanocrystals surfaces for chiral L- and D-cysteine. We used this method to obtain ensembles of CdSe, CdS, ZnS:Mn, and CdSe/ZnS quantum dots and CdSe/CdS quantum rods exhibited Circular Dichroism (CD) and Circularly Polarized Luminescence (CPL) signals. The optically active nanocrystals revealed the CD and CPL bands strongly correlated with absorption and luminescence bands with unique band “pattern” for each material and the nanocrystal shape.

Self-selecting homochiral quadruple-stranded helicates and control of supramolecular chirality.

Enantiomeric M4L4 helical cages have been prepared whose supramolecular chirality is induced by the chemical chirality of the self-sorting amino acid-derived ligands that are used. Using scrambled diastereomeric ligands or achiral glycine-derived ligands yields analogous complexes yet 'turns off' the supramolecular chirality by producing centrosymmetric cages.

Recent advances in the use of chiral metal complexes with achiral ligands for application in asymmetric catalysis

Recent progress in asymmetric catalysis using chiral only-at-metal complexes is reviewed, with emphasis on Ir(iii) and Rh(iii) systems.

Catalytic asymmetric construction of pyrroloindolines via an in situ generated magnesium catalyst.

An asymmetric formal [3 + 2]-cycloaddition between meso-aziridines and C3-alkylindoles mediated by an in situ generated magnesium catalyst was developed for asymmetric construction of pyrroloindolines. A variety of pyrroloindolines could be obtained by employing commercial available ligands with the assistance of an easily prepared achiral ligand.

Homochiral Layered Coordination Polymers from Chiral N-Carbamylglutamate and Achiral Flexible Bis(pyridine) Ligands: Syntheses, Crystal Structures, and Properties

Four new homochiral two-dimensional (2D) coordination polymers, namely, [Zn2L(NCG)2(H2O)2·4H2O]n (1), [Zn(bpe)(NCG)·3H2O]n (2), [Zn(bpe)(NCG)(NaNO3)0.5H2O]n (3), and [Zn(bpp)(NCG)·3.5H2O]n (4) (NCG = N-carbamylglutamate, L = 1,2-bis(4′-pyridylmethylamino)ethane, bpe = 1,2-bis(4-pyridyl)ethane, bpp = 1,3-bis(4-pyridyl)propane), have been prepared under mild conditions. The structures of CPs 1–4 were determined by single-crystal X-ray diffraction analysis. Complexes 1 and 2 display novel homochiral wavelike networks, with adjacent layers stacked in an AA type arrangement. Complex 3 shows an interesting 2D double-layered framework, which is further connected to form a 3D supermolecular structure through hydrogen bonding and aromatic π–π stacking interactions. The 2D structure of complex 4 contains two uncommon helical chains of bpp and NCG, with two flexures in each single strand. Different layers are stacked in an offset ABAB fashion. The mixed-ligand strategy, cooperation of a chiral and an achiral ligand,...

ChemInform Abstract: Ruthenium Complexes of the General Formula [RuCl2(PHOX)2] and Their Catalytic Activity in the Mukaiyama Aldol Reaction.

Abstract New ruthenium phosphinooxazoline (PHOX) complexes were synthesized and applied in the Mukaiyama aldol reaction. Four ruthenium complexes of the general formula [RuCl2(PHOX)2] were synthesized from [RuCl2(dmso)4] and the corresponding PHOX ligands through thermal ligand exchange. Two of the complexes were characterized structurally. Achiral PHOX ligands gave the ruthenium complexes as single isomers, whereas chiral PHOX ligands gave a mixture of isomers and also some incomplete substitution. After activation by chloride abstraction, one of the new ruthenium complexes was applied as catalyst in the Mukaiyama aldol reaction to give silyl-protected β-hydroxyl alcohols in 74–92% isolated yields (room temperature, 18–24 h reaction time, 1 mol % catalyst loading).

Two different porous coordination polymers regulated by the conformations of flexible ligands

Two porous coordination polymers, {[Cu(2,3-pydc)(bpp)·2.5H2O}n (1) and {[Cu(2,3-pydc)(bpp)·3.5H2O}n (2) (2,3-H2pydc=pyridine-2,3-dicarboxylic acid, bpp=1,3-bis(4-pyridyl)propane), have been synthesized with the same reactant ratio in different solvents. Two complexes have the same components, coordination environment of Cu(II), as well as the coordination mode of ligands, but represent two quite different porous architectures. 1 is a homochiral 2D→3D porous polymer with polycatenated layers of achiral ligands. 2 is a 2D centrosymmetric pillared-bilayer porous polymer with water-filled channels. They have been characterized by infrared spectroscopy, elemental analysis, thermogravimetric analysis and X-ray crystallography.

Sequential Rhodium/Palladium Catalysis: Enantioselective Formation of Dihydroquinolinones in the Presence of Achiral and Chiral Ligands

AbstractCompatible combinations of achiral and chiral ligands can be used in rhodium/palladium catalysis to achieve highly enantioselective domino reactions. The difference in rates of catalysis and minimal effects of ligand interference confer control in the domino sequence. The “all‐in‐one” 1,4‐conjugate arylation and CN cross‐coupling through sequential Rh/Pd catalysis provides access to enantioenriched dihydroquinolinone building blocks.

Sequential rhodium/palladium catalysis: enantioselective formation of dihydroquinolinones in the presence of achiral and chiral ligands.

Compatible combinations of achiral and chiral ligands can be used in rhodium/palladium catalysis to achieve highly enantioselective domino reactions. The difference in rates of catalysis and minimal effects of ligand interference confer control in the domino sequence. The "all-in-one" 1,4-conjugate arylation and C-N cross-coupling through sequential Rh/Pd catalysis provides access to enantioenriched dihydroquinolinone building blocks.

Microwave‐Enhanced Asymmetric Transfer Hydrogenation of N‐(tert‐Butylsulfinyl)imines

AbstractMicrowave irradiation has considerably enhanced the efficiency of the asymmetric transfer hydrogenation of N‐(tert‐butylsulfinyl)imines in isopropyl alcohol catalyzed by a ruthenium complex bearing the achiral ligand 2‐amino‐2‐methylpropan‐1‐ol. In addition to shortening reaction times for the transfer hydrogenation processes to only 30 min, the amounts of ruthenium catalyst and isopropyl alcohol can be considerably reduced in comparison with our previous procedure assisted by conventional heating, which diminishes the environmental impact of this new protocol. This methodology can be applied to aromatic, heteroaromatic and aliphatic N‐(tert‐butylsulfinyl)ketimines, leading, after desulfinylation, to the expected primary amines in excellent yields and with enantiomeric excesses of up to 96 %.