Basic Salt-Lake Brine: An Efficient Catalyst for the Transformation of CO2 into Quinazoline-2,4(1 H,3 H)-diones

Synthesis of new DFNS/ZnTiO3 nanoparticles as a nanocatalyst for the reaction of quinazoline-2, 4(1H, 3H)-dione with CO2

The conversion of CO2 into valuable materials through multicomponent reactions in the presence of nanocatalysts with high surface area and suitable efficiency has garnered significant attention. Herein, this study is focused on the synthesis and catalytic activity of DFNS-supported zinc titanate nanoparticles for the conversion of CO2 into quinazoline-2,4(1H,3H)-dione derivatives. ZnTiO3 was prepared by a sol-gel process, presenting a novel dandelion-like morphology that allows a significant increase in the surface area and catalytic activity. Detailed characterizations such as EDX for elemental composition, XRD for crystallinity, TEM and SEM for morphology, TGA for thermal stability, and FT-IR for bonding characteristics confirmed the excellent integration of ZnTiO3 into the DFNS. Under optimized conditions, our catalytic protocol achieved a maximum yield of 92% at 70 °C over 3 h in DMF solvent. Systematic optimization of reaction parameters such as solvent type and nanocatalyst loading showed the remarkable efficiency of this nanocatalyst under mild conditions, hence proving to be a strong alternative in the practices of green synthesis. Further tests for heterogeneity confirmed the effective operation of DFNS/ZnTiO3 as an enduring heterogeneous nanocatalyst, recyclability tests showing an 87% efficiency retention after ten cycles. These findings confirm the economic and ecological viability of the nanocatalyst; hence, DFNS/ZnTiO3 represents a versatile platform toward the advancement of CO2 conversion technologies into valued chemical precursors.

Synthesis of diversely substituted quinazoline-2,4(1H,3H)-diones by cyclization of tert-butyl (2-cyanoaryl)carbamates

The synthesis of diversely substituted quinazoline-2,4(1H,3H)-diones by cyclization of tert-butyl (2-cyanoaryl)carbamates using readily accessible Boc protected o-amino nitriles is reported. The reaction proceeds smoothly at room temperature using 1 equiv. of H2O2 under basic conditions. This reaction is compatible with a variety of aromatic/heteroaromatic substrates with different functional groups. This strategy can be utilized for the simplified synthesis of goshuyuamide II and an alkaloid isolated from Zanthoxylum arborescens in good yields. This method was also applied to the synthesis of quinazoline-2,4(1H,3H)-diones that are precursors of medicinally important compounds: alfuzosin, terazosin, prazosin, IAAP, doxazosin, FK 366 (zenarestat) and KF31327.

Ionic liquid [DBUH][BO2]: an excellent catalyst for chemical fixation of CO2 under mild conditions

The basic IL [DBUH][BO2] was easily synthesized and used for the chemical fixation of CO₂ at atmospheric pressure and room temperature.

Pivotal Role of the Basic Character of Organic and Salt Catalysts in C-N Bond Forming Reactions of Amines with CO2

Organocatalysts promote a range of C-N bond forming reactions of amines with CO₂ . Herein, we review these reactions and attempt to identify the unifying features of the catalysts that allows them to promote a multitude of seemingly unrelated reactions. Analysis of the literature shows that these reactions predominantly proceed by carbamate salt formation in the form [BaseH][RR'NCOO]. The anion of the carbamate salt acts as a nucleophile in hydrosilane reductions of CO₂ , internal cyclization reactions or after dehydration as an electrophile in the synthesis of urea derivatives. The reactions are enhanced by polar aprotic solvents and can be either promoted or hindered by H-bonding interactions. The predominant role of all types of organic and salt catalysts (including ionic liquids, ILs) is the stabilization of the carbamate salt, mostly by acting as a base. Catalytic enhancement depends on the combination of the amine, the base strength, the solvent, steric factors, ion pairing and H-bonding. A linear relationship between the base strength and the reaction yield has been demonstrated with IL catalysts in the synthesis of formamides and quinazoline-2,4-diones. The role of organocatalysts in the reactions indicates that all bases of sufficient strength should be able to catalyze the reactions. However, a physical limit to the extent of a purely base catalyzed reaction mechanism should exist, which needs to be identified, understood and overcome by synergistic or alternative methods.

Recent Advances in the Chemical Fixation of Carbon Dioxide: A Green Route to Carbonylated Heterocycle Synthesis

Carbon dioxide produced by human activities is one of the main contributions responsible for the greenhouse effect, which is modifying the Earth’s climate. Therefore, post-combustion CO2 capture and its conversion into high value-added chemicals are integral parts of today’s green industry. On the other hand, carbon dioxide is a ubiquitous, cheap, abundant, non-toxic, non-flammable and renewable C1 source. Among CO2 usages, this review aims to summarize and discuss the advances in the reaction of CO2, in the synthesis of cyclic carbonates, carbamates, and ureas appeared in the literature since 2017.

Efficient transformation of CO2 into quinazoline-2,4(1H,3H)-diones at room temperature catalyzed by a ZnI2/NEt3 system

The readily available ZnI₂/NEt₃ system promotes the efficient transformation of CO₂ and 2-aminobenzonitriles into quinazoline-2,4(1H,3H)-diones at room temperature and low CO₂ pressure.