A DFT-metadynamics study disclosing key properties of ring-opening polymerization catalysts to produce polyethercarbonate polyols from cyclic ethylene carbonate as part of an emerging CCU technology.

The ring opening polymerization of cyclic carbonates made from epoxide and CO2 to CO2-containing polymers constitutes an emerging technology of particular industrial interest. Considering the reaction of ring-opening polymerization of cyclic ethylene carbonate to produce polyethercarbonate polyols, several types of catalysts were tested experimentally and mechanistic pathways were proposed, but a detailed analysis of structure property relationship including the CO2-liberation pathways is still lacking. This contribution is using computational methods to investigate reported benchmark catalysts with the lead structure AxMyOz (A: alkali metal or alkyl, M: main group element or transition metal) that are particularly approved as effiecient catalysts for industrial purpose. Employing DFT-metadynamics simulations, free energy surfaces (FESs) for the key-steps in the catalytic polymerization of cyclic ethylene carbonate (cEC) are generated. Important structural criteria and characteristics of the catalysts that influence the catalytic performance and (side)reaction pathways are determined. It turns out that less nucleophilicity of the catalyst anion and more labile cations remain major criteria for prohibiting CO2 liberation during polymerization. The key learnings of this contribution currently serve as a basis to develop the next generation of catalysts to bring this emerging carbon capture and use (CCU) technology into industrial application.

Interaction of formaldehyde with a water-tolerant frustrated Lewis pair.

A facile complexation of formaldehyde with the water-tolerant frustrated Lewis pair (FLP) B(C6F5)3/PtBu3 and its Al-analog under ambient conditions is reported. Unprecedented formaldehyde adducts 1, 2 and 4 have been identified and crystallographically characterized.

Transparent Films from CO2 -Based Polyunsaturated Poly(ether carbonate)s: A Novel Synthesis Strategy and Fast Curing.

Transparent films were prepared by cross-linking polyunsaturated poly(ether carbonate)s obtained by the multicomponent polymerization of CO2 , propylene oxide, maleic anhydride, and allyl glycidyl ether. Poly(ether carbonate)s with ABXBA multiblock structures were obtained by sequential addition of mixtures of propylene oxide/maleic anhydride and propylene oxide/allyl glycidyl ether during the polymerization. The simultaneous addition of both monomer mixtures provided poly(ether carbonate)s with AXA triblock structures. Both types of polyunsaturated poly(ether carbonate)s are characterized by diverse functional groups, that is, terminal hydroxy groups, maleate moieties along the polymer backbone, and pendant allyl groups that allow for versatile polymer chemistry. The combination of double bonds substituted with electron-acceptor and electron-donor groups enables particularly facile UV- or redox-initiated free-radical curing. The resulting materials are transparent and highly interesting for coating applications.

Electrochemical functionalization of 1,3-diisopropylbenzene.

The anodic oxidation of 1,3-diisopropylbenzene in methanol gave exclusively the desired dimethoxy-functionalized product in excellent yield when potassium bromate was utilized as supporting electrolyte. Similar electrochemical conversions in other alcoholic solvents were not successful based on the low conductivity of the mixture. The introduction of other alcohols could then be realized when the dimethoxy derivative was converted under S(N)1 conditions in alcohols used as solvent. Thereby, higher alcohols could be introduced in moderate yields and acceptable selectivities.

[4 + 2]-Cycloaddition Reactions between beta-Acceptor-Substituted Enamines and 2-Vinylindole Radical Cations Acting as Hetero-Dienes.

[4 + 2]-Cycloaddition reactions between 2-vinylindoles acting as hetero-dienes and beta-acceptor substituted cyclic and acyclic enamines can be induced by formation of 2-vinylindole radical cations either via anodic oxidation or photoelectron transfer (PET) using catalytic amounts of triarylpyrylium tetrafluoroborates as sensitizers. In this way, pyrido[1,2-a]indoles or indolo[1,2-a]hexahydro-1,8-naphthyridines are formed in one step with complete regio- and stereochemical control.