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Role of Metal-heterogeneous Catalysts in Organic Synthesis
Published in Varun Rawat, Anirban Das, Chandra Mohan Srivastava, Heterogeneous Catalysis in Organic Transformations, 2022
Interestingly, the reaction was chemoselective under different catalyst systems. In the homogeneous medium where Pd(OAc)2 was used as a PdII-source, lactone 5 was the major product whereas heterogeneous PdII-AmP-MCF furnished lactone/lactam 4 as the main product. Mechanistically, simultaneous coordination of the hydroxyl group (or sulfonamide group) allene and olefin unit to the PdII center occurs at the initial step, which would first promote the allenic attack and then CO coordination to form common intermediate A (Int-A) in both catalyst systems (Figure 7.2). If homogeneous Pd-catalyst was used, attack by the XH group on coordinated CO would be favored with the formation of Int-A′ and gives γ-lactones (or γ-lactams) 5 as the major product after reductive elimination (path a). However, the heterogeneous Pd-catalyst would favor CO insertion into the Pd–C bond of Int-A that would lead to Int-B (path b). Next, the selective olefin insertion occurs in Int-B directed by the OH (or NHTs) producing Int-C that undergo CO insertion affording Int-D, which follow lactonization (or lactamization) to give cyclopentenone-fused γ-lactones (or γ-lactams) 4. It is also possible that lactonization or lactamization of Int-B could occur that lead to γ-lactones or γ-lactams with two chiral centers. In Int-C, alkyl-Pd and OH (or NHTs) groups are on the same side of cyclopentenone moiety explaining high diastereomeric ratios.
Selective aqueous-phase hydrogenation of furfural to cyclopentanol over Ni-based CNT catalysts
Published in Environmental Technology, 2023
Haihong Xia, Jing Li, Jun Zhao, Minghao Zhou, Jianchun Jiang
In this paper, we demonstrated the synthesis of a series of Ni-based CNT catalysts for highly efficient hydrogenation of FFA to CPL in an aqueous medium, which showed a good conversion of FFA compared with a single metal catalyst Ni/CNT catalyst. More significantly, only a slight decrease of FFA conversion and CPL yield were detected after up to five runs. It was probably due to the leaching of metal active components on CNT support. In addition, all of the catalysts were characterized by XRD, TEM, XPS, H2-TPR and NH3-TPD analysis, and the reaction pathways were also proposed in the end. Furfural could be hydrogenated into different products. Nevertheless, furfuryl alcohol is the sole suitable substrate for the obtention of cyclopentanic molecules through Piancatelli-type rearrangement. The in-situ hydrogenation of the obtained hydroxy-cyclopentenone could afford mainly cyclopentanone and cyclopentanol, depending on the nature of the catalyst (such as acidity) [36–39]. The generation of those chemicals relying exclusively on the exploitation of fossil carbon, their production from biomass-derived materials appears particularly attractive.
Investigation of cornstalk cellulose liquefaction in supercritical acetone by FT-TR and GC-MS methods
Published in Green Chemistry Letters and Reviews, 2019
Wei Li, Xin-an Xie, Jiao Sun, Di Fan, Xing Wei
Table 1 shows that ketones (Carbon numbers C5∼C20), esters (Carbon numbers C7∼C30), alkanes (Carbon numbers C10∼C30) have a higher content in BO, and alcohols, acids, aldehydes and phenols were lower. Acetates and methyl esters were the dominant compounds of esters, this indicated that CH3· and CH3C = O· radicals were produced from supercritical acetone, the addition and condensation among these methyl and acetyl radicals and cellulose active fragments produced a lot of esters, on the other hand, the esterification between acids and alcohols also have a contribution on esters formation (34). Ketones were composed of aliphatic ketones (4-Hydroxy-4-methyl-2-pentanone, etc.), alicyclic ketones (cyclopentanone, furanone, etc.) and aromatic ketones (cyclopentenone, etc.). In the initial stage, cellulose underwent dehydration, isomerization to form alicyclic ketones, aliphatic ketones were produced from active fragments via ring-cleavage, addition, aromatic ketones were formed from aliphatic ketones and alicyclic ketones underwent cyclization, aromatization and dehydration (25). The carbon numbers of alkanes were between C10∼C30, such as eicosane and heneicosane. Alkanes were formed from cellulose via ring-cleavage, addition, dehydration, hydrogenation, deoxygenation, decarboxylation and decarbonylation (35,36).
Parametric study via full factorial design for glycerol supercritical gasification
Published in Biofuels, 2022
Houcinat Ibtissem, Outili Nawel, Weiss-Hortala Elsa, Meniai Abdeslam-Hassen
The liquid residues recovered after phase separation were analyzed by gas chromatography-mass spectrometry (GCMS-TQ 803, collision-induced dissociation (CID)), with Argon and Helium as the carrier gases and a GC-2010 column to identify and quantify the different intermediates of the solution at the end of the reaction. The major compounds in the final solutions were as follows: butanediol, dimethyl phenol, methyl cyclopentanone, methyl phenol, propylene glycol, glycerin, butene diol, oxime methoxy-phenyl, 2- trimethyl cyclopentenone, ethanone, 1-(1-cyclohexen-1-yl)-, trimethyl cyclopentenone, ethyl phenol.