Catalytic transfer hydrogenation of ethyl levulinate to γ-valerolactone over zirconium (IV) Schiff base complexes on mesoporous silica with isopropanol as hydrogen source

Chloride‐Bridged Dimeric SalphenZr(IV) Cobaltate Catalyst Unleashes the Potential of Base‐Free Carbonylative Polymerization for Biodegradable PHAs†

“…[ 43 ] Subsequently, the precatalyst salphenZr(IV)Cl 2 ( 1 ) was obtained by adding a methanolic solution of ZrCl 4 dropwise to the methanolic solution of the salphen ligand. [ 44 ] This resulted in an orange‐yellow suspension, which was then filtered, washed, and dried under high vacuum, yielding an orange solid. [ 45 ] To incorporate the cobaltate, anion exchange of the salphenZr(IV)Cl 2 precatalyst with NaCo(CO) 4 ( 2 ) in tetrahydrofuran was performed, leading to the formation of a new cobaltate‐incorporated three‐chloro‐bridged cationic salphenZr(IV) dimeric complex ( 3 ).…”

“…The 1 H NMR spectra of the precatalyst, compared to the ligand, indicated complex formation through a downfield shift of the ligand protons upon coordination via N 2 O 2 chelation. [ 44 ] As shown in Figure 1a, UV‐visible studies on both the ligand and the precatalyst revealed strong absorption bands in the ultraviolet regions of 278—281 nm and 325—334 nm due to intraligand (π‐π*) transitions on the phenyl ring and C=N imine group of the salphen ligand, respectively. [ 44 ] The only absorption band in the visible region of the precatalyst at 417 nm is attributed to ligand‐to‐metal charge transfer (LMCT).…”

Micro/mesoporous LTL derived materials for catalytic transfer hydrogenation and acid reactions of bio-based levulinic acid and furanics

“…Literature studies reported that HPA/HPE may undergo etherification at the alcohol group in position C4, giving 4-alkoxypentanoic acid (APA) and alkyl 4-alkoxypentanoates (APE), respectively ( Tang et al, 2015 ; Li et al, 2016a ; Valekar et al, 2016 ; Wang et al, 2017 ). Although HPA/HPE/APA/APE were not identified for the yHf-H-DL(x) catalysts, one cannot exclude their possible formation and subsequent lactonization (and dealkoxylation in the case of HPE/APE) to give GVL ( Li et al, 2016a ; Wang et al, 2017 ). According to the literature, even the intrinsic acidity of LA may promote relatively fast lactonization of HPA ( Xie et al, 2016 ; Winoto et al, 2019 ).…”

“…The acid-catalyzed esterification of LA gives alkyl levulinates (LE), and the CTH of LA and LE may give 4-hydroxypentanoic acid (HPA) and alkyl 4-hydroxypentanoates (HPE), respectively, i.e., the carbonyl group in position C4 is reduced to an alcohol group. Literature studies reported that HPA/HPE may undergo etherification at the alcohol group in position C4, giving 4-alkoxypentanoic acid (APA) and alkyl 4alkoxypentanoates (APE), respectively (Tang et al, 2015;Li et al, 2016a;Valekar et al, 2016;Wang et al, 2017). Although HPA/HPE/APA/APE were not identified for the yHf-H-DL(x) catalysts, one cannot exclude their possible formation and subsequent lactonization (and dealkoxylation in the case of HPE/APE) to give GVL (Li et al, 2016a;Wang et al, 2017).…”

Sulfonated MCM-41 as potential catalyst to obtain biolubricants from vegetable oil

“…The latter approach involves the surface modification by grafting or coating (Liu et al 2009;Huang et al 2016;Wang et al 2019;Krishna et al 2018;Noda et al 2016). Several studies have described the efficiency in the insertion of acidic groups on the surface of MCM-41 for application in catalysis (Chermahini et al 2015;Díaz et al 2005;Wang et al 2017;Rossetto et al 2018;Mohino et al 2002;Debasish, Jyh-Fu Lee and Cheng 2001). Some studies described that this material has an efficient catalytic performance when applied in esterification reactions, due to the combination of high acidity and proper porous structure (Díaz et al 2005;.…”