Facile synthesis of 2-benzimidazolones via carbonylation of o -phenylenediamines with CO 2

The methodology for preparing domperidone: strategies, routes and reaction processes

Domperidone is a powerful peripheral dopamine receptor antagonist; however, a systematic review of the synthetic methods and processes of this drug has not been reported so far. This review summarizes the synthetic strategies, synthetic routes and reaction processes of domperidone in detail. Domperidone can be synthesized from the coupling reaction of two benzimidazolone derivatives (intermediates 1 and 2). Intermediate 1 can be prepared by two synthetic routes: the cyclization of o-phenylenediamine with carbonyl reagents followed by coupling with 1,3-dihalopropane, and the coupling reaction of o-halo or o-amino substituted nitrobenzene with 1,3-disubstituted propane followed by reduction and cyclization. The latter route avoids the production of di-substituted by-products and has higher reaction selectivity. Intermediate 2 is synthesized by coupling substituted nitrobenzene with 4-aminopiperidine followed by reduction and cyclization, which is similar to the synthetic route of intermediate 1. Understanding the advantages and drawbacks of these synthetic methodologies would provide insights for the development of new strategies to prepare domperidone. Moreover, the methods used to synthesize domperidone can provide alternative approaches in the preparation of drugs or compounds with similar structure.

Ionic-Liquid-Catalyzed Approaches under Metal-Free Conditions

ConspectusMetal-free catalysis is a promising protocol to access chemicals without metal contamination. Ionic liquids (ILs) that are entirely composed of organic cations and inorganic/organic anions have emerged as promising alternatives to molecular solvents and metal catalysts due to their unique properties such as structural tunability, the coexistence of multiple interactions among ions (e.g., electrostatic interaction, hydrogen bonding, van de Waals forces, acid/base interactions, hydrophilic/hydrophobic interactions, etc.), unique affinity for a wide range of chemicals, good chemical and thermal stability, and quite low volatility. ILs have shown potential applications in various chemical processes.In this Account, we systematically described our most recent work on IL-catalyzed approaches under metal-free conditions. The first section presents the IL-catalyzed strategies toward the transformation of CO2 to value-added chemicals, focusing on the CO2-reactive IL-catalyzed CO2 transformation to various heterocycles and the IL-catalyzed reductive transformation of CO2 to chemicals. In these approaches, we designed task-specific ILs that are able to chemically capture and activate CO2 via forming anion-based carbonate/carbamate or cation-based carboxylate/carbamate intermediates, thus further accomplishing its transformation to a series of heterocycles including quinazoline-2,4(1H,3H)-diones, cyclic carbonates, 2-oxazolidinones, oxazolones, and benzimidazolones under metal-free conditions. For the IL-catalyzed approaches to reducing CO2 with hydrosilanes to chemicals, we employed ILs capable of activating the Si-H bond in hydrosilanes and the N-H bond in amine substrates via H-bonding, thus achieving the reductive transformation of CO2 to formamides, benzimidazoles, and benzothiazoles via cooperative catalysis. The second section describes our finding on the IL-catalyzed hydration of the C≡C bond in propargylic alcohols. Azolate anion-based ILs that can chemically capture CO2 via the formation of carbamates could serve as robust nucleophiles to attack the C≡C bond in propargylic alcohols and then efficiently catalyze the hydration of propargylic alcohols to produce α-hydroxy ketones with the assistance of atmospheric CO2 gas under metal-free conditions. The third section unveils the cooperative catalysis strategy of hydrogen bond donors and acceptors of ILs for chemical reactions. In the hydrogen-bonding catalysis protocols, cations of the ILs act as H-bond donors and anions, as acceptors, forming H-bonds with the reactant molecules, respectively, in opposite ways, which can cooperatively catalyze the ring-closing C-O/C-O bond metathesis reactions of aliphatic diethers to O-heterocycles, the dehydrative etherification of alcohols to ethers, and direct oxidative esterification of alcohols to esters. We believe that these IL-catalyzed metal-free processes and strategies display promising practical applications, and their commercialization would bring great benefits to the production of the as-afforded value-added chemicals.

Synthesis of benzimidazolones via CO2 fixation and N-phenyl formamides using formic acid in presence of zinc embedded polymer complex

A merrifield supported heterogeneous zinc catalyst [Zn(Meri-Ald-Py)] was synthesized and applied for benzimidazolone synthesis through the fixation of carbon dioxide (CO₂) and for different N-formylated products synthesis under mild reaction conditions.

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.