- Catalytic Activation of Unstrained C(Aryl)-C(Alkyl) Bonds in 2,2′-Methylenediphenols
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Catalytic activation of unstrained and nonpolar C-C bonds remains a largely unmet challenge. Here, we describe our detailed efforts in developing a rhodium-catalyzed hydrogenolysis of unstrained C(aryl)-C(alkyl) bonds in 2,2′-methylenediphenols aided by removable directing groups. Good yields of the monophenol products are obtained with tolerating a wide range of functional groups. In addition, the reaction is scalable, and the catalyst loading can be reduced to as low as 0.5 mol %. Moreover, this method proves to be effective to cleave C(aryl)-C(alkyl) linkages in both models of phenolic resins and commercial novolacs resins. Finally, detailed experimental and computational mechanistic studies show that with C-H activation being a competitive but reversible off-cycle reaction, this transformation goes through a directed C(aryl)-C(alkyl) oxidative addition pathway.
- Dong, Guangbin,Ratchford, Benjamin L.,Xue, Yibin,Zhang, Rui,Zhu, Jun
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p. 3242 - 3249
(2022/02/23)
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- Lignin-based diphenylmethane diisocyanate as well as preparation method and application thereof
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The invention discloses a lignin-based diphenylmethane diisocyanate and a preparation method and application thereof. As shown in Formula I, the lignin-based diphenylmethane diisocyanate is prepared by reacting a lignin-cracking monomer compound II with a carbonyl compound to give compound III, compound III reacts with chloroacetyl ammonia to obtain compound IV, compound IV is subjected Smiles rearrangement reaction to obtain compound V, and compound V is reacted with a compound containing carbon-containing acid to obtain the lignin-based diphenylmethane diisocyanate shown in formula I. The product replaces MDI for synthesis of polyurethane materials, and the toughness of the polyurethane material is improved. Thermal stability and glass transition temperature. When being applied to polyurethane waterproof coating, the water absorption rate is obviously reduced, and the stability of the coating is improved.
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Paragraph 0093-0096; 0103-0106
(2021/11/21)
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- Microwave-assisted synthesis of 6,6′-(aryl(alkyl)methylene)bis(2,4-dialkylphenol) antioxidants catalyzed by multi-sulfonated reduced graphene oxide nanosheets in water
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Sulfonated reduced graphene oxide nanosheets (RGO-SO3H) were characterized using field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, X-ray diffraction (XRD), thermogravimetric analysis (TGA), and acid-base titration. Multi-SO3H supported on reduced graphene oxide nanosheets was found to be an efficient catalyst for the green synthesis of 6,6′-(aryl(alkyl)methylene)bis(2,4-dialkylphenol) derivatives from 2,4-dialkylphenols and aromatic and aliphatic aldehydes in aqueous media under microwave irradiation. The synthesis of 6,6′-(aryl(alkyl)methylene)bis(2,4-dialkylphenol) derivatives were carried out in the presence of a catalytic amount of RGO-SO3H, under thermal and microwave conditions to afford the desired products in high and excellent yields respectively. In addition, the catalyst could be recovered easily and reused several times without any considerable loss of its catalytic activity.
- Naeimi, Hossein,Golestanzadeh, Mohsen
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p. 2697 - 2710
(2015/04/14)
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- Highly sulfonated graphene and graphene oxide nanosheets as heterogeneous nanocatalysts in green synthesis of bisphenolic antioxidants under solvent free conditions
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Sulfonated functionalized graphene and graphene oxide nanosheets were prepared via chemical approaches and their catalytic activities were investigated in the green synthesis of 6,6′-(arylmethylene) bis(2,4-dialkylphenol) antioxidants. In this research, three types of the catalysts including sulfonated reduced graphene oxide nanosheets (catalyst 1a), sulfonated graphene oxide nanosheets (catalyst 1b), and sulfonated propylsilane graphene oxide nanosheets (catalyst 1c) were synthesized and used in the synthesis of target molecules. The catalysts were characterized by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, X-ray diffraction spectroscopy (XRD), and back acid-base titration. The catalyst 1a showed excellent catalytic activity in the green synthesis of 6,6′-(arylmethylene)bis(2,4-dialkylphenol) antioxidants under solvent free conditions and was reused several times without any appreciable loss of its catalytic activity even after eight consecutive cycles. In addition, the high yield of the products and non-toxicity of the catalysts are other worthwhile advantages of the present methods.
- Naeimi, Hossein,Golestanzadeh, Mohsen
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p. 56475 - 56488
(2015/02/05)
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- Polymerization of p-cresol, formaldehyde, and piperazine and structure of monofunctional benzoxazine-derived oligomers
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By using a secondary amine, e g. piperazine, a Mannich base polymer, having similar structure to the traditional polybenzoxazine, is synthesized. Unlike all the reported polybenzoxazines that are colored, the white polymer shows good thermal property that is close to the degradation temperature of the polybenzoxazine derived from difunctional benzoxazine monomers. 31P NMR spectroscopy in combination with facile phosphorus derivatization and previous model compound studies are utilized to clarify the structures of piperazine-based systems as well as the main chain and end group of traditional polybenzoxazines.
- Chutayothin, Papinporn,Ishida, Hatsuo
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experimental part
p. 3897 - 3904
(2012/05/04)
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- Cationic ring-opening polymerization of 1,3-benzoxazines: Mechanistic study using model compounds
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The benzoxazine monomer is used to simplify the study of the benzoxazine initiation mechanism. The HPLC retention time and the 1H NMR spectra of crude products from the benzoxazine reaction are compared with the results from a vast number of pure model compounds, which are synthesized based on the hypothesized mechanisms. Products involved in the process are identified, with species having benzoxazine structures, Mannich base and other components (acetal, nonacetal phenoxy structures, and methylene bridge structure). Initiation mechanisms of benzoxazine, e.g., the oxygen protonation and the nitrogen protonation, are proposed.
- Chutayothin, Papinporn,Ishida, Hatsuo
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experimental part
p. 4562 - 4572
(2011/10/18)
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- Optimization of asymmetric catalysts using achiral ligands: metal geometry-induced ligand asymmetry.
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[reaction: see text] Traditionally, asymmetric catalysts have been optimized by modification of resolved chiral ligands. In this Letter, we optimize the asymmetric addition of diethylzinc to aldehydes by modification of achiral methylene bis(phenol) ligands. Upon coordination of the substrate, the achiral ligand becomes asymmetric, a concept termed Metal Geometry-Induced Ligand Asymmetry. The enantioselectivity of the catalyst formed from a single resolved ligand and several achiral ligands ranged from 9% (R) to 83% (S).
- Davis,Balsells,Carroll,Walsh
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p. 2161 - 2164
(2007/10/03)
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- Magnesium-mediated ortho-Specific Formylation and Formaldoximation of Phenols
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Deprotonation of phenols using magnesium methoxide, followed by distillative removal of free methanol and addition of paraformaldehyde results in ortho-specific magnesium mediated formylation to give the corresponding salicyladehyde magnesium salts, from which the salicylaldehydes can be isolated by acidic work-up.Addition of aq. hydroxylamine sulfate to the salicylaldehyde magnesium salt, in place of the acid work-up, gives the corresponding salicylaldoximes.
- Aldred, Robert,Johnston, Robert,Levin, Daniel,Neilan, James
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p. 1823 - 1832
(2007/10/02)
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- Method of producing 2,2 '-methylenebis(4,6-dialkylphenols)
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A method of producing 2,2'-methylenebis(4,6-dialkylphenols) residing in that 2,4-dialkylphenols interact with acetals in the presence of an acid catalyst at a temperature from 30° C to 140° C with the formation of a reaction mixture containing the desired product and with subsequent separation of the desired product from said mixture, the starting reagents being taken in amounts of 1 mole of 2,4-dialkylphenol per 1-10 moles of acetal. The method is technologically simple and accomplished without the formation of waste water.
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