Carboxylative Cyclization Of Propargylic Alcohols Research Articles

ChemInform Abstract: Zinc(II)‐Catalyzed Reactions of Carbon Dioxide and Propargylic Alcohols to Carbonates at Room Temperature.

AbstractAlkylidiene cyclic carbonates are prepared by carboxylative cyclization of propargylic alcohols with CO2 using ZnI2/NEt3 as synergistic catalytic system.

Green Catalytic Process for Cyclic Carbonate Synthesis from Carbon Dioxide under Mild Conditions.

As a renewable and abundant C1 resource possessing multiple attractive characteristics, such as low cost, nontoxicity, non-flammability, and easy accessibility, CO2 conversion into value-added chemicals and fuels can contribute to green chemistry and sustainable development. Since CO2 is a thermodynamically inert molecule, the activation of CO2 is pivotal for its effective conversion. In this regard, the formation of a transition-metal CO2 complex through direct coordination is one of the most powerful ways to induce the inert CO2 molecule to undergo chemical reactions. To date, numerous processes have been developed for efficient synthesis of cyclic carbonates from CO2 . On the basis of mechanistic understanding, we have developed efficient metal catalysts and green processes, including heterogeneous catalysis, and metal-free systems, such as ionic liquids, for cyclic carbonate synthesis. The big challenge is to develop catalysts that promote the reaction under low pressure (preferably at 1 bar). In this context, bifunctional catalysis is capable of synergistic activation of both the substrate and CO2 molecule, and thus, could render CO2 conversion smoothly under mild conditions. Alternatively, converting CO2 derivatives, that is, the captured CO2 as an activated species, would more easily take place at low pressure in comparison with gaseous CO2 . The aim of this Personal Account is to summarize versatile catalytic processes for cyclic carbonate synthesis from CO2 , including epoxide/CO2 coupling reaction, carboxylation of 1,2-diol with CO2 , oxidative cyclization of olefins with CO2 , condensation of vicinal halohydrin with CO2 , carboxylative cyclization of propargyl alcohols with CO2 , and conversion of the CO2 derivatives.

Metalated Mesoporous Poly(triphenylphosphine) with Azo Functionality: Efficient Catalysts for CO2 Conversion

Mesoporous poly(triphenylphosphine) with azo functionality (poly(PPh3)-azo) is reported, which was synthesized via oxidative polymerization of P(m-NH2Ph)3 at ambient conditions. This kind of polymer could strongly coordinate with metal ions (e.g., Ru3+) and could reduce Ag+ in situ to metallic form. The resultant metalated poly(PPh3)-azo (e.g., poly(PPh3)-azo-Ag or -Ru) were discovered to be highly efficient catalysts for CO2 transformation. Poly(PPh3)-azo-Ag showed more than 400 times higher site-time-yield (STY) for the carboxylative cyclization of propargylic alcohols with CO2 at room temperature compared with the best heterogeneous catalyst reported. Poly(PPh3)-azo-Ru also exhibited good activity for the methylation of amines with CO2. It was demonstrated that the high performances of the catalysts originated from the cooperative effects between the polymer and the metal species. In addition, both catalysts showed good stability and easy recyclability, thus demonstrating promising potential for practi...

A comparative computational study of N-heterocyclic olefin and N-heterocyclic carbene mediated carboxylative cyclization of propargyl alcohols with CO2.

The carboxylative cyclization of a propargyl alcohol with CO2 mediated by a N-heterocyclic olefin (NHO) or N-heterocyclic carbene (NHC) has been comparatively studied using density functional theory (DFT) calculations. The calculations show that the advantageous catalytic performance of the NHO in the title reaction can be attributed to two aspects: (i) the active site of the NHO extends outside the imidazolium ring, which enhances the reactivity and stability of the [NHOH]+[carbonate]- ionic pair intermediate. Thus, the turnover frequency (TOF)-determining intramolecular cyclization step is kinetically more favorable in the NHO system. (ii) As the basicity of the NHO is weaker than the NHC, deprotonation of the propargyl alcohol by the NHO is relatively more difficult. Consequently, the side reaction of ring-opening transesterification of the α-alkylidene cyclic carbonate with the nucleophilic [NHOH]+[alkoxide]- ionic pair intermediate can be inhibited using the NHO system. The present mechanistic study provides a basis for further application of these promising organocatalysts in more organic transformations.

Front Cover Picture: Robust Silver(I) Catalyst for the Carboxylative Cyclization of Propargylic Alcohols with Carbon Dioxide under Ambient Conditions (Adv. Synth. Catal. 8/2016)

The front cover picture, provided by Qing-Wen Song and Liang-Nian He, illustrates a silver-catalyzed carboxylative cyclization of propargylic alcohols/propargylic amines with CO2 for the synthesis of α-alkylidene cyclic carbonates/oxazolidinones under ambient conditions without employing any additional organic base and ligand. The synergistic effect of Lewis basic and Lewis acidic species in conjunction with the bulkier counterion, via the alkyl carbonate intermediate, leads to the excellent efficiency. The picture shows an outline of exhaust gas and chemical conversion via a sustainable CO2 recycling process into value-added products using a green catalytic method. Details can be found in the full paper on pages 1251–1258 (Q.-W. Song and L.-N. He, Adv. Synth. Catal.­ 2016, 358, 1251–1258; DOI: 10.1002/adsc.201500639).

Robust Silver(I) Catalyst for the Carboxylative Cyclization of Propargylic Alcohols with Carbon Dioxide under Ambient Conditions

AbstractInspired by the bulkier bis(triphenylphosphine)–silver cation‐induced mechanism of propargylic alcohols and carbon dioxide through the alkyl carbonate intermediate, a robust dual‐component catalytic system consisting of silver acetate and tetraheptylammonium bromide was rationally developed for the synthesis of α‐methylene cyclic carbonates under ambient conditions without employing any additional organic base and ligand. This is one of the most effective catalysts reported to date for this conversion, with a very high turnover number of up to 6024, probably due to the synergistic effect of Lewis basic and Lewis acidic species for the activation of both propargylic alcohol and carbon dioxide by the formation of the alkyl carbonate with a bulkier counterion. Notably, this catalyst also worked well for the carboxylative cyclization of propargylic amines with carbon dioxide with the highest turnover number of 544.magnified image

Synthesizing Ag Nanoparticles of Small Size on a Hierarchical Porosity Support for the Carboxylative Cyclization of Propargyl Alcohols with CO2 under Ambient Conditions.

Both immobilization of Ag nanoparticles (AgNPs) of very small size on hierarchical porosity supports and carboxylative cyclization of propargyl alcohols with CO2 under ambient conditions are very interesting. In this work, we synthesized AgNPs supported on sulfonated macroreticular resin (SMR) with hierarchical pores in water/alcohol solutions. It was shown that the size of the AgNPs on the SMR could be tailored easily by altering the synthetic solutions, and very small AgNPs with narrow size distribution (1-3 nm) could be obtained in water/methanol solution. It was found that the AgNPs/SMR with small AgNPs was highly efficient and an easily recyclable catalyst for the synthesis of α-alkylidene cyclic carbonates by carboxylative cyclization of propargyl alcohols with CO2 at ambient pressure and temperature, which was the first work to use metal nanoparticles as the catalysts for the reaction.

ChemInform Abstract: Bifunctional Silver(I) Complex‐Catalyzed CO2 Conversion at Ambient Conditions: Synthesis of α‐Methylene Cyclic Carbonates and Derivatives.

AbstractThe Ph3P complex of Ag2CO3, which can be prepared in situ, is found to be a robust bifunctional catalyst for the carboxylative cyclization of propargylic alcohols (I) with CO2.

Bifunctional silver(I) complex-catalyzed CO2 conversion at ambient conditions: synthesis of α-methylene cyclic carbonates and derivatives.

The chemical conversion of CO2 at atmospheric pressure and room temperature remains a great challenge. The triphenylphosphine complex of silver(I) carbonate was proved to be a robust bifunctional catalyst for the carboxylative cyclization of propargylic alcohols and CO2 at ambient conditions leading to the formation of α-methylene cyclic carbonates in excellent yields. The unprecedented performance of [(PPh3)2Ag]2CO3 is presumably attributed to the simultaneous activation of CO2 and propargylic alcohol. Moreover, the highly compatible basicity of the catalytic species allows propargylic alcohol to react with CO2 leading to key silver alkylcarbonate intermediates: the bulkier [(Ph3P)2Ag(I)](+) effectively activates the carbon-carbon triple bond and enhances O-nucleophilicity of the alkylcarbonic anion, thereby greatly promoting the intramolecular nucleophilic cyclization. Notably, this catalytic protocol also worked well for the reaction of propargylic alcohols, secondary amines, and CO2 (at atmospheric pressure) to afford β-oxopropylcarbamates.

Efficient chemical fixation of CO2 promoted by a bifunctional Ag2WO4/Ph3P system

An efficient heterogeneous silver-catalyzed reaction for construction of the α-methylene cyclic carbonate motif was developed through carboxylative assembly of propargyl alcohols and CO2. Such a CO2 fixation protocol proceeded smoothly with only 1 mol% of Ag2WO4 and 2 mol% of PPh3 as well as atmospheric CO2 at room temperature under solvent-free conditions, in an environmentally benign and low energy manner along with an easy operating procedure. Notably, up to 98% isolated yields of carbonates could be attained with exclusive chemo-selectivity. In addition, the dual activation capacity of Ag2WO4 towards both the propargylic substrate and CO2 is based on which cooperative catalytic mechanism by the silver cation and the tungstate anion is proposed. Recycling trials on carboxylative cyclization of propargyl alcohols and CO2 illustrate that the catalyst can be reused at least 4 times with retention of high catalytic activity and selectivity. Especially, it allows the direct and effective application in the one-pot synthesis of various oxazolidinones bearing exocyclic alkenes and carbamates in moderate to high yields upon the alternative introduction of primary or secondary amines.

Stereoselective Formation of α‐Alkylidene Cyclic Carbonates via Carboxylative Cyclization of Propargyl Alcohols in Supercritical Carbon Dioxide.

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Stereoselective Formation of α-Alkylidene Cyclic Carbonates via Carboxylative Cyclization of Propargyl Alcohols in Supercritical Carbon Dioxide

Carboxylative cyclization of propargyl alcohols in supercritical carbon dioxide (scCO2) containing P(n-C4H9)3 as a catalyst proceeded smoothly to give alpha-alkylidene-1,3-dioxolan-2-ones. Internal propargyl alcohols afforded Z-alkyl-idene cyclic carbonates exclusively. CO2 incorporation was markedly promoted under supercritical conditions, possibly due to the facile formation of a putative P(n-C4H9)3-CO2 adduct as a key intermediate.