Methyl Picolinate Research Articles

Quaternization of Methyl Picolinate with Some Phenacyl Bromides. Synthesis of DL-Baikiain Alkaloid

By fusing methyl picolinate with phenacyl bromides, the corresponding phenacyl salts were obtained, cyclization of which in acetic anhydride led to previously undescribed 3-aryl-1H-pyrido[2,1-c][1,4]oxazinium bromides. Reduction of the quaternary salts of methyl picolinate followed by acid hydrolysis leads to the alkaloid DL-baikiain.

Mechanical tough and multicolor aggregation-induced emissive polymeric hydrogels for fluorescent patterning.

Aggregation-induced emissive fluorogens (AIEgens) are promising building blocks for fluorescent polymeric hydrogels (FPHs) because intense fluorescence intensities are usually guaranteed by spontaneous aggregates of hydrophobic AIEgens in a hydrophilic polymer network. However, most AIE-active FPHs are single-color fluorescent and cannot display tunable emission colors. Additionally, efforts to produce mechanically strong AIE-active hydrogels have been largely ignored, restricting their potential uses. Herein, we present the synthesis of an AIE-active methyl picolinate-substituted 1,8-naphthalimide monomer (MP-NI) for fabricating mechanical tough and multicolor FPHs. Owing to the introduction of bulky and coordinative methyl picolinate group, these specially designed MP-NI molecules were forced to adopt propeller-shaped conformation that renders them with intense aggregation-induced blue emission. Moreover, the MP-NI moieties grafted in a hydrogel matrix can sensitize red and green fluorescence of Eu3+and Tb3+ via antenna effect. Consequently, multicolor fluorescent hydrogels that sustain a high stress of 1 MPa were obtained by chemically introducing MP-NI moieties into dually cross-linked alginate polymer networks with high-density metal (Ca2+/Tb3+/Eu3+) coordination and hydrogen bonding crosslinks. Their capacity to enable the writing of arbitrary multicolor fluorescent patterns using Eu3+/Tb3+ as inks were finally demonstrated, suggesting their potential uses for smart display and information encryption.

McLafferty-type rearrangement of protonated N-[nicotinoyl]phenylethyl amines and consequent elimination of styrene.

McLafferty rearrangements occur in radical cations of molecules containing a carbonyl group and a γ hydrogen atom but are not common in the [M+H](+) ions of carbonyl compounds. We propose to investigate the collision-induced dissociation (CID) of the [M+H](+) ions of nicotinoyl and picolinoyl amides of 1- and 2-phenylethylamines to explore the possibility of McLafferty-type rearrangement. The compounds for study were synthesized by the reaction of methyl nicotinate or methyl picolinate with 1- and 2-phenylethylamines. The CID mass spectra of electrospray ionization (ESI)-generated protonated molecules were obtained using a QSTAR XL quadrupole time-of-flight (QTOF) mass spectrometer, and density functional theory (DFT) calculations using the B3LYP method were employed to elucidate the fragmentation mechanisms. The total electronic and thermal energies of intermediate transition states (TSs) and product ions are reported relative to those of the [M+H](+) ions. CID of the [M+H](+) ions of N-[nicotinoyl]-2-phenylethylamine (1) yielded product ions of m/z 105 (1-phenylethyl cation) and 123 ([M+H-styrene](+) cation). The competitive formation of the ions of m/z 123 and 105 is proposed to involve a McLafferty-type rearrangement. Similarly, the [M+H](+) ions of the isomeric compound 2 and the N-[picolinoyl] phenylethyl amines (3 and 4) dissociate to yield ions of m/z 123 and 105. A molecule of styrene was eliminated from the ESI-generated [M+H](+) ions of N-[nicotinoyl]phenylethylamines and the isomeric N-[picolinoyl]phenylethylamines, through a mechanism involving a McLafferty-type 1,5-H shift. The transition state energy for the 1,5-H shift is less for the amides of 1-phenylethylamine than for the amides of 2-phenylethylamine. The process occurs as a charge remote process and the presence of the pyridine ring is essential for the process.

Is Macrocycle a Synonym for Kinetic Inertness in Gd(III) Complexes? Effect of Coordinating and Noncoordinating Substituents on Inertness and Relaxivity of Gd(III) Chelates with DO3A-like Ligands

Gadolinium chelates with octadentate ligands are widely used as contrast agents for magnetic resonance imaging (MRI), with macrocyclic ligands based on DO3A being preferred for the high kinetic inertness of their Gd chelates. A major challenge in the design of new bifunctional MRI probes is the need to control the rotational motion of the chelate, which greatly affects its relaxivity. In this work we explored facile alkylation of a secondary amine in macrocyclic DO3A-like ligands to create a short, achiral linkage to limit the undesired internal motion of chelates within larger molecular constructs. The acetate moiety on the trans nitrogen was also replaced with either a bidentate (ethoxyacetate, L1 or methyl picolinate, L2) or bulky monodentate (methyl phosphonate, L3) donor arm to give octa- or heptadentate ligands, respectively. The resultant Gd(III) complexes were all monohydrated (q = 1) and exhibited water residency times that spanned 2 orders of magnitude (τM = 2190 ± 170, 3500 ± 90, and 12.7 ± 3.8 ns at 37 °C for GdL1, GdL2, and GdL3, respectively). Alkylation of the secondary amine with a noncoordinating biphenyl moiety resulted in coordinatively saturated q = 0 complexes of octadentate ligands L1 and L2. Relaxivities were limited by slow water exchange and/or lack of water coligand. All complexes showed decreased inertness compared to [Gd(DO3A)] despite higher ligand denticity, and inertness was further decreased upon N-alkylation. These results demonstrate that high kinetic inertness and in vivo safety of Gd chelates with macrocyclic ligands should not be generalized.

Dicarbonyliridium(I) complexes of pyridine ester ligands and their reactivity towards various electrophiles

Abstract The reaction of dimeric precursor [Ir(CO)2Cl]2 with two molar equivalent of the pyridine-ester ligands (L) like methyl picolinate (a), ethyl picolinate (b), methyl nicotinate (c), ethyl nicotinate (d), methyl isonicotinate (e) and ethyl isonicotinate (f) affords the tetra coordinated neutral complexes of the type [Ir(CO)2ClL] (1a–f). The single crystal X-ray structure of 1d reveals that the Ir atom occupies the centre of an approximately square planar geometry with two CO groups cis- to each other. Intermolecular C–H⋯O and Ir⋯C interactions greatly stabilize the supramolecular structure of 1d in the solid state. The oxidative addition (OA) reactions of 1a–f with different electrophiles such as CH3I, C2H5I and I2 undergo decarbonylation of one CO group to generate the oxidized products of the type [Ir(CO)RClIL] where R = –CH3 (2a–f); –C2H5 (3a–f) and [Ir(CO)ClI2L] (4a–f). Kinetic study of the reaction of 1c–f with CH3I indicates a first order reaction which follow the order 1d > 1c > 1f > 1e. All the synthesized complexes were characterized by elemental analyses, IR, and multinuclear NMR spectroscopy.

First asymmetric synthesis of CJ-14877 and its enantiomer and their interleukin-1β inhibitory activities

A potent antiinflammatory methyl picolinate alkaloid CJ-14877 [(+)- 1] and its enantiomer (−)- 1 were synthesized in two steps starting from commercially available methyl 5-bromopicolinate. The synthesis includes microwave-assisted Suzuki coupling reaction and Sharpless asymmetric dihydroxylation.

Dicarbonylrhodium(I) complexes of functionalized pyridine ligands and their catalytic activities

Reactions of dimeric complex [Rh(CO)2Cl]2 (1) with pyridine ester ligands methyl picolinate (a), methyl nicotinate (b), methyl isonicotinate (c), ethyl picolinate (d), ethyl nicotinate (e) and ethyl isonicotinate (f) in the 1:2 molar ratio afford the complexes of the type [Rh(CO)2ClL] (1a–f). The complexes 1a–f exhibit two equally intense ν(CO) bands in the range 1990–2091cm−1 indicating cis-disposition of the two terminal carbonyl groups. The complexes 1a and 1d undergo partial decarbonylation reaction in solution to give the corresponding chelated monocarbonyl complexes [Rh(CO)Cl(methyl picolinate)] (1a′) and [Rh(CO)Cl(ethyl picolinate)] (1d′), respectively. The complexes 1a–f undergo oxidative addition reaction with different types of electrophiles like CH3I, C2H5I, C6H5CH2Cl and I2 to yield [Rh(CO)(COCH3)ClIL] (2a–f), [Rh(CO)(COC2H5)ClIL] (3a–f), [Rh(CO)(COCH2C6H5)Cl2L] (4a–f) and [Rh(CO)ClI2L] (5a–f) complexes, respectively. The complexes have been characterized by elemental analysis, IR and 1H NMR spectroscopy. The time taken by the different complexes 1a–f for the completion of oxidative addition reactions of CH3I are different and the complex 1f took the shortest time while the complex 1b required the longest time. The catalytic activity of the complexes [Rh(CO)2ClL] (1) in carbonylation of methanol is higher (TON=844–1251) than the well known [Rh(CO)2I2]− species (TON=653).

Multinuclear NMR spectroscopic and theoretical study on the interactions between diperoxovanadate complex and picoline-like ligands

To understand the substituting effects of organic ligands on the reaction equilibrium, the interactions between diperoxovanadate complex [OV(O2)2(H2O)]− and a series of picoline-like ligands in solution were explored using 1D multinuclear (1H, 13C, and 51V) magnetic resonance, 2D diffusion ordered spectroscopy (DOSY), and variable temperature NMR in 0.15mol/l NaCl ionic medium for mimicking the physiological conditions. The order of reactive capability of the picoline-like ligands with [OV(O2)2(H2O)]− is found to be picolinamide>N-methylpicolinamide>methyl picolinate>ethyl picolinate≈propyl picoliniate>isopropyl picolinate. The substituting group influences the reactivity by either steric effect or electron-donating effect. Competitive coordination interactions result in a series of new seven-coordinated peroxovanadate species [OV(O2)2L]− (L=picoline-like ligands). Their coordination ways were confirmed by density functional calculations.

Conformational studies by [formula omitted] in a nematic solvent: methyl isonicotinate. methyl nicotinate and methyl picolinate

The structures of methyl isonicotinate (MI), methyl nicotinate (MN) and methyl picolinate (MP), i.e., 4-, 3-, and 2-pyridinecarboxylic acid methyl esters, were studied by 1 H−NMR at 296 K using nematic liquid–crystal solvent ZLI 1167. Conformational analysis was performed according to the model of Emsley, Luckhurst and Stockley to take account of the correlation between rotation and internal rotation. Only the conformer with a planar skeleton was detected for MI but s- trans and s- cis conformers were found for MN and MP. The relative abundance of the s- trans form was determined to be 64(2) and 68(2)% for MN and MP, respectively, which are in agreement with those determined by gas-phase electron diffraction. The positions of the ring protons of MI in ZLI 1167 agree with those in the gas phase within experimental errors. In the case of MN and MP, however, observed direct coupling constants between the ring protons are in poor agreement with those calculated from the gas-phase structures due to the deformation of the pyridine rings in ZLI 1167.

Structure Determination of Methyl Nicotinate and Methyl Picolinate by Gas Electron Diffraction Combined with ab Initio Calculations

The molecular structures of isomers, methyl nicotinate and methyl picolinate, have been studied by gas electron diffraction. The samples were heated to 341−343 K by using a high-temperature nozzle to get enough vapor pressure. HF/6-31G* ab initio calculations were carried out, and structural constraints were taken from their results. Vibrational amplitudes and shrinkage corrections were calculated from the harmonic force constants given by normal coordinate analyses. The principal structural parameters of the s-trans conformer of methyl nicotinate are as follows (angle brackets mean averaged values): 〈rg(N−C)〉 = 1.337(7) Å; 〈rg(C−C)ring〉 = 1.402(3) Å; rg(Cring−C(O)) = 1.480(12) Å; rg(CO) = 1.199(7) Å; 〈rg(C−O)〉 = 1.380(11) Å; ∠αCNC = 119.0(14)°; 〈∠αNCC〉 = 122.8(11)°; ∠α(N)C−Cring−C(O) = 118.3(12)°; ∠αCring−CO = 121.5(12)°; ∠αCring−C−O = 115.6(10)°. Those of the s-trans conformer of methyl picolinate are as follows: 〈rg(N−C)〉 = 1.344(7) Å; 〈rg(C−C)ring〉 = 1.398(4) Å; rg(Cring−C(O)) = 1.497(11) Å; rg(CO) = 1.209(7) Å; 〈rg(C−O)〉 = 1.380(11) Å; ∠αCNC = 117.2(12)°; 〈∠αNCC〉 = 123.9(12)°; ∠αN−C−C(O) = 115.1(10)°; ∠αCring−CO = 121.0(12)°; ∠αCring−C−O = 115.1(12)°. The structural parameters of the two isomers and methyl isonicotinate have been compared and their similarity and differences have been discussed.

Catalysis of picolinate ester hydrolysis at the oxide/water interface: inhibition by adsorbed natural organic matter

Natural organic matter (NOM) has been found to inhibit TiO 2 -catalyzed hydrolysis of methyl picolinate (MEP), which is used to represent a broader class of hydrolyzable pollutants. NOM must adsorb at the oxide/water interface in order for inhibition to take place. At equal NOM surface coverage (in mg C/m 2 ), a nearly 60% variation is observed among NOM samples from five different sources. As NOM-laden water poses through soils and sediments, surface-active NOM molecules are removed by adsorption. This fractionation process has been simulated in the laboratory by pretreating a NOM sample with TiO 2 , FeOOH, and Al 2 O 3 - FeOOH is extremely efficient at removing the NOM subfraction responsible for the inhibitory effect, while Al 2 O 3 is the least efficient of the three oxides

Catalysis of picolinate ester hydrolysis at the oxide/water interface: inhibition by coadsorbed species

This work is part of a series which evaluates whether the catalysis of organic pollutant hydrolysis by oxide-bound metal atoms is an important and widespread phenomenon in the environment. Inorganic ions (calcium and phosphate) and low molecular weight organic acids (benzoate, picolinate, and salicylate) have been found to inhibit FeOOH- and TiO 2 -catalyzed hudrolysis of Phenyl Picolinate (PHP) and methyl picolinate (MEP). Added chemicals must adsorb in order for inhibition to occur. Most loss in catalytic activity arises from the occupation of surface sites by coadsorbate. When present at the same surface concentration, the loss of catalytic activity decremes in the order: picolinate>salicylate>phosphate

Complexes of esters of pyridine carboxylic acids. Part I. complexes with Ni(II) and Co(II) thiocyanates

The syntheses of Nickel(II) and Cobalt(II) thio- cyanate complexes of type ML n(NCS) 2 where M = Co or Ni and n = 2 for L = methyl picolinate (MP), ethyl picolinate (EP), isopropyl picolinate (IP) and n = 4 for L = ethyl nicotinate (EN) and ethyl isonicotinate (EIN), are described. The complexes have been characterised by elemental analyses, molar conductance, magnetic susceptibility, thermogravimetric, electronic and infrared spectral data. The complexes are non-electrolytes in nitrobenzene and have high spin distorted octahedral structure with N-bonded thiocyanate groups in trans-position. MP, EP and IP act as bidentate ligands coordinating through pyridine ring nitrogen and carbonyl oxygen while EN and EIN act as unidentate ligands and coordinate through ring nitrogen only. The values of splitting energy (10 Dq), Racah parameter (B) and nephelauxetic ratio (β) have been evaluated for the nickel complexes.