Search Results (5)

Ionic liquids (ILs) and deep eutectic solvents (DESs) have emerged as effective solvents for poorly soluble materials such as natural polysaccharides, including chitin. This review describes recently developed efficient chitin derivatization methods that harness the solubilizing power of ILs and DESs. It covers chitin acylation approaches, including acylation and mixed ester formation, as well as chitin etherification protocols. For example, the ILs 1-allyl-3-methylimidazolium bromide (AMIMBr) and 1-allyl-2,3-dimethylimidazolium bromide serve as effective media for chitin acylation and etherification, respectively, yielding single esters and benzyl derivatives with high degrees of substitution (DS). The use of DESs comprising AMIM chloride (AMIMCl) as a hydrogen bond acceptor and several hydrogen bond donors for chitin acylation are presented. In an optimized system, acylation using acyl chlorides proceeded smoothly without additives, such as a base/catalyst, in a DES comprising AMIMCl and 1,1,3,3-tetramethylguanidine, affording high-DS ester derivatives. The method was extended to the synthesis of mixed chitin esters bearing both long and bulky acyl substituents at appropriate substitution ratios, which exhibit thermoplasticity. Full article

Easily accessible and inexpensive potassium carbonate (K₂CO₃) has been applied as the base-catalyst for the synthesis of novel classes of functionalized nanomaterials. This eco-friendly approach has been proven to be effective for a wide range of substrates, leading to nine isocyanate derivatives of silsesquioxanes (SQs) with yields exceeding 90% in mild and transition metal-free conditions. The application potential of chosen products was assessed on the basis of thermogravimetric analyses and photochemical measurements. Full article

Mesoporous silica nanostructures (MSNs) attract high interest due to their unique and tunable physical chemical features, including high specific surface area and large pore volume, that hold a great potential in a variety of fields, i.e., adsorption, catalysis, and biomedicine. An essential feature for biomedical application of MSNs is limiting MSN size in the sub-micrometer regime to control uptake and cell viability. However, careful size tuning in such a regime remains still challenging. We aim to tackling this issue by developing two synthetic procedures for MSN size modulation, performed in homogenous aqueous/ethanol solution or two-phase aqueous/ethyl acetate system. Both approaches make use of tetraethyl orthosilicate as precursor, in the presence of cetyltrimethylammonium bromide, as structure-directing agent, and NaOH, as base-catalyst. NaOH catalyzed syntheses usually require high temperature (>80 °C) and large reaction medium volume to trigger MSN formation and limit aggregation. Here, a successful modulation of MSNs size from 40 up to 150 nm is demonstrated to be achieved by purposely balancing synthesis conditions, being able, in addition, to keep reaction temperature not higher than 50 °C (30 °C and 50 °C, respectively) and reaction mixture volume low. Through a comprehensive and in-depth systematic morphological and structural investigation, the mechanism and kinetics that sustain the control of MSNs size in such low dimensional regime are defined, highlighting that modulation of size and pores of the structures are mainly mediated by base concentration, reaction time and temperature and ageing, for the homogenous phase approach, and by temperature for the two-phase synthesis. Finally, an in vitro study is performed on bEnd.3 cells to investigate on the cytotoxicity of the MNSs. Full article

Cyanation reactions of carbonyl compounds with methyl cyanoformate or acetyl cyanide catalyzed by 5 mol % of 1,5,7-triazabicyclo[4,4,0]dec-5-ene (TBD) were examined. Using methyl cyanoformate, the corresponding cyanohydrin carbonates were readily obtained in high yield for aromatic and aliphatic aldehydes and ketones. Similar results were obtained when acetyl cyanide was used as the cyanide source. The polymer-supported catalyst, PS-TBD, also acted as a good catalyst for this reaction. PS-TBD was easily recovered and reused with minimal activity loss. Full article

The ring-opening of N-tosylaziridines with various acid anhydrides catalyzed by 5 mol % of 1,5,7-triazabicyclo[4,4,0]dec-5-ene (TBD) afforded the corresponding β-amino esters in excellent yields under mild reaction conditions. Polymer-supported catalyst, PS-TBD also acts as a good catalyst for this reaction. PS-TBD was easily recovered and reused with minimal loss of activity. Full article