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Other Feedstocks—Coal, Oil Shale, and Biomass
Published in James G. Speight, Handbook of Petrochemical Processes, 2019
Other uses are in the preparation of 2-β-methoxyethyl pyridine (known as Promintic, an anthelmintic for cattle) and in the synthesis of a 2-picoline quaternary compound (Amprolium) which is used against coccidiosis in young poultry. Beta-picoline (3-picoline; 3-methylpryridine) can be oxidized to nicotinic acid, which with the amide form (nicotinamide), belongs to the vitamin B complex; both products are widely used to fortify human and animal diets. γ-Picoline (4-picoline, 4-methylpyridine) is an intermediate in the manufacture of isonicotinic acid hydrazide (Isoniazide) which is a tuberculostatic drug. The 2,6-Lutidine (2,6-dimethylpyridine) can be converted to dipicolinic acid, which is used as a stabilizer for hydrogen peroxide and peracetic acid.
Metal-Containing Conjugated Polymers
Published in John R. Reynolds, Barry C. Thompson, Terje A. Skotheim, Conjugated Polymers, 2019
Christopher M. Brown, Michael O. Wolf
The degree of aggregation was monitored via the photophysical effects of the zinc-containing metallopolymer 50a and 51a. On the addition of pyridine to 50a in CH2Cl2, a small effect was seen in the UV-vis spectrum, with a small decrease in the intensity of the transition at ~400 nm coupled with a small increase in the intensity at ~500 nm consistent with the deaggregation process. The emission properties were much more pronounced with a four-fold increase in the fluorescence upon addition of two equivalents of pyridine combined with a blue-shift in the emission from λmax = 590 nm to λmax = 546 nm. No change was seen on the addition of 2,6-lutidine. In an aggregated state, metallopolymer 50a is held together by Zn···O inter-strand contacts leading to excimer-like interactions, which can quench the luminescence. On breaking these interactions through addition of a Lewis base the excimer-like species is disrupted, causing an increase in luminescence intensity and a hypsochromic shift of the profile. Polymer 51a is much more soluble in organic solvents suggesting fewer cross links and thus the photophysical changes are much less pronounced.
Polypeptides
Published in Stanislaw Penczek, H. R. Kricheldorf, A. Le Borgne, N. Spassky, T. Uryu, P. Klosinski, Models of Biopolymers by Ring-Opening Polymerization, 2018
The relatively high nuc/bas ratio of pyridine compared to trialkylamines is documented by rapid reactions with alkyl-halogenides (quaternization) and by the finding of Gold and Jefferson143 that pyridine catalyzes the hydrolysis of carboxylic acid anhydrides by intermediate formation of N-acyl-pyridinium ions (Equation 82). These results suggest that pyridine, in contrast to trialkylamines, can attack CO-5 of NCAs (Equation 83). The alternative initiation mechanism is, of course, the N-H deprotonation of N-unsubstituted NCAs as formulated for trialkylamines in Equation 40. Bamford and Block71 were the first who became aware that initiation by pyridines may take two different mechanistic courses. In order to differentiate between a nucleophilic and a basic attack on the NCA, γ-O-Bzl-l-Glu-NCA was polymerized in DMF with pyridine, picoline, and 2,6-lutidine as initiators. Whereas the nucleophilicity of pyridines depends largely on position and bulkiness of the substituents98 the basicity is far less sensitive to the steric demands of substituents, because protons are the smallest possible reaction partners. Thus, the basicity slightly increases in the series pyridine <2-picoline <2,6-lutidine whereas the nucleophilicity strongly decreases. The polymerizations conducted by Bamford and Block71 demonstrate that the rate of initiation depends on the basicity of the initiators and not on their nucleophilicity.
Transition-metal-free electrochemical-induced active C(sp3)-H functionalization
Published in Green Chemistry Letters and Reviews, 2023
Xiaolong Ma, Jinfeng Wei, Xu Yang, Huajin Xu, Yi Hu
As we all know, achieving enantioselectivity in the process of transition-metal-catalyzed C–H bond functionalization is a very challenging task. However, electrochemical method provides unprecedented possibilities for realizing the reactivity and selectivity of C–H bond functionalization reactions (43–45). In 2017, Luo and co-workers reported a combination of electrochemistry and chiral primary amine catalysis to efficiently achieve the catalytic asymmetric oxidative coupling of tertiary amines with various ketones including cyclopentanone, cyclohexanone, and cycloheptanone, as well as an acyclic ketone to synthesize diverse C1-alkylated tetrahydroisoquinolines (Scheme 3) (46). To obtain the optimal conditions, phenyltetrahydroisoquinoline (6a) and cyclohexanone (7a) were chosen as model substrates for chiral primary amine catalyst screening, protonic additives screening, as well as electrochemical parameter screening. In this case, compound 8 was chosen as the best primary amine catalyst which was crucial to achieving high enantioselectivity and diastereoselectivity. CF3CH2OH was evaluated as the best protonic additive to significantly improve the yield of model reaction from 38% to 75% with the highest ee value (95%). Additionally, The addition of 2,6-lutidine could further improve the yield to 88% but with the sacrifice of ee to 90%.
Immobilization of polyphosphoesters on poly(ether ether ketone) (PEEK) for facilitating mineral coating
Published in Journal of Biomaterials Science, Polymer Edition, 2019
Shun Kunomura, Yasuhiko Iwasaki
2-Chloro-2-oxo-1,3,2-dioxaphospholane (COP) was supplied by NOF Corporation, Tokyo, Japan. Methanol, toluene, dichloromethane, acetic acid, and diethyl ether were purchased from FUJIFILM Wako Pure Chemical Corporation, Osaka, Japan and used as received. Chloroform-d, dimethyl sulfoxide-d6 and deuterium oxide were purchased from Tokyo Chemical Industry Co., Ltd., Tokyo, Japan and used as received. 2,6-Lutidine and 1,8-diazabicyclo[5.4.0]-7-undecene (DBU) were purchased from FUJIFILM Wako Pure Chemical Corporation, Osaka, Japan and used after distillation under reduced pressure. N-(2-Hydroxypropyl) methacrylamide (HPMA, Sigma-Aldrich, St. Louis, MO, USA), trimethylamine (TMA) aqueous solution (30% TMA, Nacalai Tesque, Inc., Kyoto, Japan), and lithium bromide (LiBr, Kanto Chemical Co., Inc., Tokyo, Japan) were purchased and used as received. PEEK films were purchased from Yasojima Proceed Co., Ltd., Hyogo, Japan.
New synthetic strategies and disconnections in the synthesis of liquid crystals enabled by photoredox cross-coupling reactions
Published in Liquid Crystals, 2019
Richard J. Mandle, John W. Goodby
Several of the chemical intermediates used herein have been described by previously: i3andi4 in Ref. [21]. The photocatalyst [Ir{dF(CF3)ppy}2(dtbbpy)]PF6 was prepared according to Ref [22]. 1,2-Dimethoxy ethane was distilled from CaH prior to use and stored over 4Å molecular sieves under dry nitrogen. 2,6-Lutidine and tris(trimethylsilyl)silane were distilled upon receiving from SigmaAldrich and Fluorochem, respectively. Barton’s base was purchased from Fluorochem and used without purification. i1 was purchased from Fluorochem, i2 was purchased previously from BDH, 4-bromobenzonitrile was purchased from Aldrich and trans 4-pentylcyclohexane carboxylic acid was purchased from Synthon GMBH. Photoredox couplings were performed in 25 ml reaction tubes (Sigma Aldrich, part no. Z515981). Reactions were irradiated two LED emitters (Mouser, part no. LZ1-10UB00-00U8, 410 nm peak output, 1050 mW radiant flux) mounted on anodised aluminium heatsinks (Mouser, part no. 984-ATSEU-077B-C6-R0) at opposite sides of the reaction tube at a distance of approximately 1 cm from the wall of the reaction tube. The LED and reactor assembly was cooled with a fan during operation – failure to cool the reaction leads to reduced yields and increased side products. Full experimental details are given in the Supplementary information.