Substrate-Triggered Stereoselective Preparation of Highly Substituted Organic Carbonates

Intensified Continuous Flow Process for the Scalable Production of Bio-Based Glycerol Carbonate

A subtle combination of fundamental and applied organic chemistry toward process intensification is demonstrated for the large-scale production of bio-based glycerol carbonate under flow conditions. The direct carbonation of bio-based glycidol with CO2 is successfully carried out under intensified flow conditions, with Barton's base as a potent homogeneous organocatalyst. Process metrics for the CO2 coupling step (for the upstream production, output: 3.6 kg day-1 , Space Time Yield (STY): 2.7 kg h-1  L-1 , Environmental factor (E-factor): 4.7) outclass previous reports. High conversion and selectivity are achieved in less than 30 s of residence time at pilot scale with a stoichiometric amount of CO2 . Supporting DFT computations reveal the unique features of the mechanism in presence of Brønsted bases.

Catalytic Ring-Opening Copolymerization of Fatty Acid Epoxides: Access to Functional Biopolyesters

Fatty acid epoxies serve as valuable starting materials for the development of bio-based polyesters. Here we present a new and efficient catalytic process that allows for the copolymerization of fatty acid-based epoxides and various cyclic anhydrides under attractive process conditions affording functional polyesters. The degree of functionalization and the nature of the polymer backbone can be modulated via monomer design. Postpolymerization cross-linking processes were examined to create rigid macromolecular networks that build on orthogonal polyester functionality, creating possible entries for materials with switchable thermal and mechanical properties.

The Al(iii)-based polydentate chelate complex catalyzed cycloaddition of carbon dioxide and epoxides: synthetic optimization and mechanistic study

Aimed at greenhouse gas CO2 high value-added utilization, a N,N′-(propane-1,3-diyl)dipicolinamide (PPPA) supported Al(iii) metal–organic polydentate chelate complex (Al-PPPA) was designed and used to efficiently catalyze CO2 to cyclic carbonates.

Can Primary Arylamines Form Enamine? Evidence, α-Enaminone, and [3+3] Cycloaddition Reaction

The formation of enamine from primary arylamines was detected and confirmed by nuclear magnetic resonance spectroscopy. The presence of a radical quencher, e.g., (2,2,6,6-tetramethylpiperidin-1-yl)oxidanyl, was found to be essential for the detection of enamine formation. A direct synthesis of α-enaminones from primary arylamines and ketones was also developed. Mechanistic investigation of α-enaminone formation suggests that an amine radical cation generated through O₂ singlet energy transfer was involved in initiating α-enaminone formation. The reactivity and utility of α-enaminones were explored with a [3+3] cycloaddition reaction of enones affording dihydropyridines in good yields (58-85%). α-Enaminones displayed a set of reactivities that is different from that of enamines. The knowledge gained in this work advances our basic understanding of organic chemistry, providing insights and new opportunities in enamine catalysis.

Unlocking the Potential of Substrate-Directed CO2 Activation and Conversion: Pushing the Boundaries of Catalytic Cyclic Carbonate and Carbamate Formation

The unparalleled potential of substrate-induced reactivity modes in the catalytic conversion of carbon dioxide and alcohol or amine functionalized epoxides is discussed in relation to more conventional epoxide/CO₂ coupling strategies. This conceptually new approach allows for a substantial extension of the substitution degree and functionality of cyclic carbonate/carbamate products, which are predominant products in the area of nonreductive CO₂ transformations. Apart from the creation of an advanced library of CO₂ -based heterocyclic products and intermediates, also the underlying mechanistic reasons for this novel reactivity profile are debated with a prominent role for the design and structure of the involved catalysts.

Organocatalytic Trapping of Elusive Carbon Dioxide Based Heterocycles by a Kinetically Controlled Cascade Process

A conceptually novel approach is described for the synthesis of six-membered cyclic carbonates derived from carbon dioxide. The approach utilizes homoallylic precursors that are converted into five-membered cyclic carbonates having a β-positioned alcohol group in one of the ring substituents. The activation of the pendent alcohol group through an N-heterocyclic base allows equilibration towards a thermodynamically disfavored six-membered carbonate analogue that can be trapped by an acylating agent. Various control experiments and computational analysis of this manifold are in line with a process that is primarily dictated by a kinetically controlled acylation step. This cascade process delivers an ample diversity of six-membered cyclic carbonates in excellent yields and chemoselectivities under mild reaction conditions.

Mechanistic guidelines in nonreductive conversion of CO2: the case of cyclic carbonates

This perspective provides general mechanistic guidelines for the catalytic formation of cyclic organic carbonates from CO₂ and cyclic ethers.

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.

High conversion of CO2 into cyclic carbonates under solvent free and ambient pressure conditions by a Fe-cyanide complex

Methods of converting carbon dioxide into valuable chemicals are of great demand but their development is still challenging.

Diphenyl Carbonate: A Highly Reactive and Green Carbonyl Source for the Synthesis of Cyclic Carbonates

A practical, safe, and highly efficient carbonylation system involving a diphenyl carbonate, an organocatalyst, and various diols is presented herein and produces highly valuable cyclic carbonates. In reactions with a wide range of diols, diphenyl carbonate was activated by bicyclic guanidine 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) as a catalyst, which successfully replaced highly toxic and unstable phosgene or its derivatives while maintaining the desired high reactivity. Moreover, this new system can be used to synthesize sterically demanding cyclic carbonates such as tetrasubstituted pinacol carbonates, which are not accessible via other conventional methods.

Synthesis and characterization of trimetallic cobalt, zinc and nickel complexes containing amine-bis(benzotriazole phenolate) ligands: efficient catalysts for coupling of carbon dioxide with epoxides

New trimetallic cobalt, nickel and zinc complexes 1-3 coordinated by amine-bis(benzotriazole phenolate) ligands and ancillary acetate groups have been developed for the use of CO₂/epoxide coupling. All complexes were structurally characterized by single crystal X-ray crystallography; tri-Co complex 1 is the first solid-state example in which three different geometrical configurations exist in the same benzotriazole phenoxide metal complex. Tri-nuclear complexes 1 and 2 with cobalt and zinc metal centers were demonstrated to be very active catalysts for cycloaddition of cyclohexene oxide with CO₂ in the presence of ammonium salt co-catalysts to give cis-cyclohexene carbonate under the conditions of 80 °C and 300 psi initial CO₂ pressure. Particularly, tri-cobalt complex 1 was found to efficiently couple CO₂ with epoxides showing broad substrate scope, producing the corresponding cyclic organic carbonates with good activities and high selectivities. This is a successful example of catalysis for cyclic carbonate synthesis using one cobalt(ii) complex as a homogeneous catalyst.

Current advances in the catalytic conversion of carbon dioxide by molecular catalysts: an update

Recent advances (2015–) in the catalytic conversion of CO₂ by metal-based and metal-free systems are discussed.