Pyridinium saccharinate salts as efficient recyclable acylation catalyst: a new bridge between heterogeneous and homogeneous catalysis

Synthesis and catalytic performance of wood cellulose nanofibers grafted with polylactic acid in rare-earth complexes based on tetrazole carboxylic acids

Stannous octanoate [Sn(Oct)2] and 4-dimethylamino pyridine (DMAP) were used to catalyze the synthesis of amphiphilic cellulose-based graft copolymers, but the acute toxicity of tin ions and DMAP prompts the need for the application of less harmful catalysts. Herein, green catalyst complexes 1-3 [M(H0.5L)2(H2O)5]·2(H2O) (M = Sm, 1; M = Nd, 2; M = Eu, 3; H2L = 4-(3-(tetrazol-5-yl)pyridin-5-yl)benzoic acid) were synthesized, and their properties were systematically investigated. Single-crystal X-ray diffraction showed that the complexes possessed a zero-dimensional structure, while the thermogravimetry and scanning electron microscopy results confirmed their stability after heating at 110 °C for 10 h. Using complexes 1-3 and DMAP as the catalysts, CNFs were grafted with l-lactide via homogeneous ring-opening polymerization to form wood cellulose nanofibers grafted with l-lactide (WGLAs), and the effects of the ratio of wood cellulose nanofibers (WCNFs) to l-lactide ([AGU]/[LA]) and catalyst dosage were studied. The polymerization followed the coordination-insertion mechanism. Under comparable reaction conditions, the grafting ratio of WGLA-1 reached 84.7 %, and the grafting ratio of complex 1 was found to be higher than those achieved using DMAP. WGLAs demonstrated good thermal stability without cytotoxicity, and the residual catalysts in the WGLAs exhibited fluorescence characteristics. Overall, amphiphilic cellulose-based materials with fluorescence emission offered a promising modification strategy to prepare high-performance polymer composites for agriculture and biomedical application.

Artificial sugar saccharin and its derivatives: role as a catalyst

The primary objective of this review was to demonstrate the significance of artificial sugar saccharin and its derivatives as catalysts for a wide variety of organic transformations. The application of saccharin and its derivatives represents a greener and superior catalytic approach for reactions. In particular, we were interested in bringing together the literature pertaining to these saccharin derivatives from a catalysis perspective. The present review reports synthesis of saccharin and its derivatives such as saccharin-N-sulfonic acid, sodium saccharin, N-halo saccharin, saccharin lithium-bromide, N-formyl saccharin, N-acyl saccharin, N-nitrosaccharin, N-SCF₃ saccharin, N-fluorosultam, N-phenylselenosaccharin, N-thiocyanatosaccharin palladium saccharin, DMAP-saccharin, and [Bmim]Sac. This catalytic application of saccharin and its derivatives includes reactions such as the Biginelli reaction, Paal-Knorr pyrrole synthesis, azo-coupling reaction, halogenations, domino Knoevenagel, Michael, deoximation reaction, catalytic condensation, functional group protection and oxidation etc. Also, these saccharin derivatives act as a source of CO, NH₂, SCN, SCF₃ and nitro groups. We reported all the available data on saccharin and its derivatives acting as a catalyst from 1957 to date.

Molecular structures of 3-[(2,2,3,3-tetrafluoropropoxy)methyl]- and 3-[(2,2,3,3,3-pentafluoropropoxy)methyl]pyridinium saccharinates

The salts 3-[(2,2,3,3-tetrafluoropropoxy)methyl]pyridinium saccharinate, C₉H₁₀F₄NO⁺·C₇H₄NO₃S^-, (1), and 3-[(2,2,3,3,3-pentafluoropropoxy)methyl]pyridinium saccharinate, C₉H₉F₅NO⁺·C₇H₄NO₃S^-, (2), i.e. saccharinate (or 1,1-dioxo-1λ⁶,2-benzothiazol-3-olate) salts of pyridinium with -CH₂OCH₂CF₂CF₂H and -CH₂OCH₂CF₂CF₃ meta substituents, respectively, were investigated crystallographically in order to compare their fluorine-related weak interactions in the solid state. Both salts demonstrate a stable synthon formed by the pyridinium cation and the saccharinate anion, in which a seven-membered ring reveals a double hydrogen-bonding pattern. The twist between the pyridinium plane and the saccharinate plane in (2) is 21.26 (8)° and that in (1) is 8.03 (6)°. Both salts also show stacks of alternating cation-anion π-interactions. The layer distances, calculated from the centroid of the saccharinate plane to the neighbouring pyridinium planes, above and below, are 3.406 (2) and 3.517 (2) Å in (1), and 3.409 (3) and 3.458 (3) Å in (2).