Picolinamide Groups Research Articles

Iridium(III)-Catalyzed Intermolecular Mild N-Arylation of Aliphatic Amides Using Quinoid Carbene: A Migratory Insertion-Based Approach

An efficient Ir(III)-catalyzed straightforward intermolecular N-arylation of acyclic aliphatic amides has been achieved using quinone diazide as a coupling partner. The reaction has been developed under simple and mild reaction conditions with a broad substrate scope. The bidentate picolinamide group is essential for successful transformation. Mechanistic studies and DFT calculations highlighted the migratory insertion-based pathway. The developed method exhibits different reactivities compared to the reactions of acyclic aliphatic amides using related diazo/azide congeners under Rh(III)/Ir(III) catalysis.

Picolinamide Assisted Oxidation of CH2 Groups Bound to Organic and Organometallic Compounds Using Ferrocene as a Catalyst

Picolinamide group assisted sp3 C–H bond oxidation of methylene groups to the corresponding carbonyl compounds has been achieved by using simple bottle ferrocene as catalyst and Cu(OAc)2 or tert-butyl peroxybenzoate (TBPB) as oxidant under mild conditions. This method is applicable for picolinamide bound organic as well as organometallic compounds with yields in the range of 46–82%. Control experiments and mechanistic studies indicate that a radical mechanism is responsible for these oxidative transformations in which ferrocene acts as a catalyst.

Palladium(ii)-catalyzed ortho-C–H olefination of phenylalanine and phenylethylamine derivatives directed by removable picolinamide group

Palladium-catalyzed ortho-C–H olefination of phenylalanine and phenylethylamine derivatives assisted by a removable picolinamide group has been achieved.

Lanthanide Complexes of a Calix[4]arene Ligand with Dangling Phosphonate and Picolinamide Arms: Synthesis, Crystal Structures, and Extraction Properties

The coordination behavior of the neutral calix[4]arene‐based ligand L exhibiting dangling phosphonate ester and picolinamide groups in 1,3‐ and 2,4‐distal positions towards a series of lanthanide ions was examined. Reaction of L with Ln(NO3)3 in MeOH afforded mononuclear [LnL(µ1,3‐NO3)2]NO3 complexes [Ln = La (6), Pr (7), Eu (8), Gd (9)]. X‐ray crystallography for 6 and 7 revealed tenfold coordination by phosphoryl O, amide O, and pyridine N atoms from L and four O atoms from two chelating nitrato coligands. Treatment of the [LnL(µ1,3‐NO3)2]NO3 salts with NaBPh4 leads to metathesis of the counterion and, in the case of Pr, Eu, and Gd, to substitution of one nitrato coligand by a methanol molecule yielding [LnL(µ1,3‐NO3)2–n(MeOH)n](BPh4)n+1 for n = 0, Ln = La (10) and n = 1, Ln = Pr (11), Eu (12), Gd (13). X‐ray crystallography of complexes 11–13 revealed an isostructural series of ninefold‐coordinated lanthanide complexes in which one nitrato coligand is exchanged by a methanol molecule. UV/Vis batch titration experiments showed the formation of 1:1 complexes of L with trivalent lanthanides (La3+, Pr3+, Eu3+, Gd3+, Yb3+). The stability constants of the complexes determined by UV/Vis spectroscopic titrations are log K11 = 6.44 ± 0.02 (La), 5.96 ± 0.01 (Pr), 6.37 ± 0.01 (Eu), 7.38 ± 0.3 (Gd), and 9.6 ± 0.2 (Yb). Solvent‐extraction experiments with lanthanide picrates revealed that L is able to extract both La3+ and Eu3+ in 1:1 stoichiometry from aqueous media into chloroform.

1,10-Phenanthroline and non-symmetrical 1,3,5-triazine dipicolinamide-based ligands for group actinide extraction.

The synthesis and evaluation of new extractants for spent nuclear fuel reprocessing are described. New bitopic ligands constituted of phenanthroline and 1,3,5-triazine cores functionalized by picolinamide groups were designed. Synthetic routes were investigated and optimized to obtain twelve new polyaza-heterocyclic ligands. In particular, an efficient and versatile methodology was developed to access non-symmetric 2-substituted-4,6-di(6-picolin-2-yl)-1,3,5-triazines from the 1,3,5-triazapentadiene precursor in the presence of anhydride reagents. Extraction studies showed the ability of both ligand series to extract and separate actinides selectively at different oxidation states (U(VI), Np(V,VI), Am(III), Cm(III), and Pu(IV)) from an acidic solution (3 M HNO3). Phenanthroline-based ligands show the most promising efficiency for use in the group actinide extraction (GANEX) process due to a higher number of donor nitrogen atoms and a suitable pre-organization of the dipicolinamide-1,10-phenanthroline architecture.

Synthesis of phenanthridines via palladium-catalyzed picolinamide-directed sequential C-H functionalization.

We report a new synthesis of phenanthridines based on palladium-catalyzed picolinamide-directed sequential C–H functionalization reactions starting from readily available benzylamine and aryl iodide precursors. Under the catalysis of Pd(OAc)2, the ortho-C–H bond of benzylpicolinamides is first arylated with an aryl iodide. The resulting biaryl compound is then subjected to palladium-catalyzed picolinamide-directed intramolecular dehydrogenative C–H amination with PhI(OAc)2 oxidant to form the corresponding cyclized dihydrophenanthridines. The benzylic position of these dihydrophenanthridines could be further oxidized with Cu(OAc)2, removing the picolinamide group and providing phenathridine products. The cyclization and oxidation could be carried out in a single step and afford phenathridines in moderate to good yields.

Enantioselective fluoride ring opening of aziridines enabled by cooperative Lewis acid catalysis

The enantioselective ring opening of aziridines using a latent source of HF is described. A combination of two Lewis acids, (salen)Co and an achiral Ti(IV) cocatalyst, provided optimal reactivity and enantioselectivity for the trans β-fluoroamine product. The use of a chelating aziridine protecting group was crucial. Acyclic and cyclic meso N-picolinamide aziridines underwent fluoride ring opening in up to 84% ee, and the kinetic resolution of a piperidine-derived aziridine was performed with krel=6.6. The picolinamide group may be readily removed without epimerization of the fluoroamine. Preliminary studies revealed a bimetallic mechanism wherein the chiral (salen)Co catalyst delivers the nucleophile and the Ti(IV) cocatalyst activates the aziridine.

Copper(II) ion-sensing mechanism of oligo-phenylene vinylene derivatives: syntheses and theoretical calculations

Oligo-phenylene vinylene (oligo-PV) with two picolinamide side-groups and six methoxy end-groups was synthesized in order to be a fluorescent sensing molecule. Various metal ion solutions (1.5×10−4 M) were added to the 1.5×10−6 M acetonitrile solution of the fluorescent molecule. The fluorescent emission spectra showed that, at about the same concentration (1.5×10−4 M), only Cu(II) ion can quench the fluorescent emission of the picolinamide-PV solution. Possible metal ion-sensing mechanisms could be either the binding at picolinamide side-groups or methoxy end-groups, or interchain-stacking driven by the metal ions. Hence, oligo-PVs with six methoxy end-groups but without substituted side-groups, and another oligo-PV with six methoxy end-groups and two ethoxy side-groups were synthesized for comparison. These molecules turned out to be inactive to any metal ion solutions. Moreover, quantum calculation was used to confirm the result. Binding energy and conformation were calculated and simulated. It could be concluded that nitrogen and oxygen atoms of the picolinamide group and one oxygen atom from the methoxy group are involved in the metal ion-binding process.

Palladium-Catalyzed Alkylation of ortho-C(sp2)–H Bonds of Benzylamide Substrates with Alkyl Halides

A highly efficient and generally applicable method has been developed to functionalize the ortho-C(sp(2))-H bonds of picolinamide (PA)-protected benzylamine substrates with a broad range of β-H-containing alkyl halides. Sodium triflate has been identified as a critical promoter for this reaction system. The PA group can be easily installed and removed under mild conditions. This method provides a new strategy to prepare highly functionalized benzylamines for the synthesis of complex molecules.

Tetra-CMPO-derivatives of calix[4]arenes fixed in the 1,3-alternate conformation

Calix[4]arene derivatives fixed in the 1,3-alternate conformation and substituted at one side by four carbamoylmethylphosphine oxide (CMPO) residues were synthesised. Two CMPO groups are directly attached to the wide rim, while the second pair is bound to the narrow rim via a tri- or tetramethylene spacer. Similar compounds, in which two CMPO groups at the wide rim are combined with two picolinamide groups or two ionisable carboxylic groups at the narrow rim, were also prepared. Some of these calixarene derivatives were studied as extractants for lanthanides (La3+, Eu3+, Yb3+) and thorium (Th4+) from acidic solution into methylene chloride. For selected samples, stability constants in methanol were determined by spectrophotometric titrations. Three compounds (1b′, 13, 17) in the 1,3-alternate conformation and one intermediate in the cone conformation (18) were confirmed by a crystal structure.

Polyisophthalamides with heteroaromatic pendent rings: Synthesis, physical properties, and water uptake

AbstractA set of novel aromatic polyamides containing pyridine pendent groups was prepared from aromatic diamines and new monomers that are 5‐substituted derivatives of isophthalic acid bearing nicotinamide, isonicotinamide, or picolinamide groups. The polymers were obtained in high yield and high molecular weight by the phosphorylation method of polycondensation. They were characterized by spectroscopic and chromatographic methods and several of their properties were investigated. All of the polymers were soluble in polar aprotic solvents and gave films of good mechanical properties. Glass transition temperatures were higher than that of the reference polymer, poly(m‐phenyleneisophthalamide) (IP‐MPD), while the thermal resistance, defined by the initial decomposition temperature observed by thermogravimetry, was in the range 370–420 °C, lower by 30–70 °C than that of IP‐MPD. The presence of a pendent pyridine group and an additional amide side group per repeat unit made the polymers essentially amorphous and greatly improved their abilities to absorb water in comparison with nonsubstituted polyamides. Water uptake values up to 15% were observed at 65% relative humidity. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5300–5311, 2005

Designed Ligands as Probes for the Catalytic Binding Mode in Mo-Catalyzed Asymmetric Allylic Alkylation We thank the National Science Foundation and the National Institutes of Health for their generous support of the work carried out at Stanford. I.H. thanks the Japan Society for the Promotion of Science for a postdoctoral fellowship. Mass spectra were provided by the Mass Spectrometry Facility

Unusual coordination in the asymmetric allylic alkylation catalyzed by molybdenum (see scheme) was revealed by a study on several ligands, for example, 1. Unexpectedly, only the nitrogen atom of one picolinamide group coordinates to Mo, while the other amide group rigidifies the system. Based on the effectiveness of the bisdeprotonated ligand, the observed reaction can be rationalized and new ligands can be designed for asymmetric induction in allylic alkylations.

PH dependence of binding site in complexation of CuII with picolinamide groups: crystallographic studies of mono- and binuclear complexes with N,N'-dipicolinoyl-1,3-propanediamine

pH dependence of binding site in complexation of Cu^II with picolinamide groups: crystallographic studies of mono- and binuclear complexes with <i>N</i>,<i>N</i>'-dipicolinoyl-1,3-propanediamine

Studies on the metal-amide bond. XVI. The coordination chemistry of the di-tertiary amide ligand N,N′-dimethyl-N,N′-bis(2′-pyridinecarboxamide)-1,2-ethane, [bpenMe 2], including the crystal structure of trans-[Pd(bpenMe 2)Cl 2

The isolation and characterization of a number of transition metal complexes of the di-tertiary-amide ligand N,N′-dimethyl-N,N′-bis(2′-pyridinecarboxamide)-1,2-ethane, bpenMe 2, is described. Six-coordinate polymeric complexes involving coordination as a [NO] 2-bis-bidentate through pyridyl-N and amide-O atoms were obtained with bivalent copper, nickel, cobalt and zinc. N 2-Bidentate function through pyridlyl-N atoms alone is concluded for complexes of Ag(I), Pt(II) and Pd(II). The crystal structure of [Pd(bpenMe 2)Cl 2] was determined by X-ray diffraction methods. C 16H 18N 4O 2Cl 2Pd is orthorhombic, space group P2 12 1 2, with a = 12.229(10), b = 17.053(13), c = 8.757(9) Å and Z = 4. These structure was refined to R 0.072 by least-squares techniques for 1360 photographic reflexions. The coordination geometry about Pd is square planar and the molecule possesses an approximate two-fold rotation axis. The ligand functions as a rare N 2- trans-bidentate, coordinating through two pyridyl-N atoms alone [average Pd-N 2.00(1) Å]. The two Cl atoms complete the coordination sphere [average Pd-Cl 2.311(7) Å]. The two picolinamide groups are non-planar, the dihedral angles between the amide groups planes and their corresponding pyridine ring planes being 69.7 and 86.1°. The central ethane link has a staggered conformation, the NCCN torsion angle being 58.8°. This rigid structure, with a two-fold rotation axis, is retained in solution. The complex 200 MHz proton n.m.r. spectrum in CDCl 3 may be simulated assuming such a structure and HCCH torsion angles calculated from the observed vicinal coupling constants confirm the gauche conformation of the central ethane bond in solution. The separate chemical shifts of these methylene protons are explained in terms of the non-planar structure of the ligand in the chelate molecule.