Carboxylative Cyclization Research Articles

A highly stable polyoxovanadate-based Cu(i)–MOF for the carboxylative cyclization of CO2with propargylic alcohols at room temperature

A POVs-based Cu(i)–MOF was synthesized and utilized as a heterogeneous catalyst for the cyclization of CO2with propargylic alcohols to obtain value-added α-alkylidene cyclic carbonates, exhibiting high catalytic activity and sustainability.

Stereoselective amination via vinyl-silver intermediates derived from silver-catalyzed carboxylative cyclization of propargylamine.

The stereoselective synthesis of aminovinyloxazolidinones based on the electrophilic amination of a vinyl-silver intermediate, generated by silver-catalyzed carbon dioxide incorporation on a propargyl amine, was achieved. The geometry of the aminated product was determined by a single crystal X-ray analysis and NOE measurement and it was elucidated that the geometry was proved to be opposite to the geometry predicted from the previous silver-catalyzed carbon dioxide fixation on a propargyl amine derivative. This unexpected stereoselectivity could be successfully explained by a radical mechanism.

A CO2-induced ROCO2Na/ROCO2H buffer solution promoted the carboxylative cyclization of propargyl alcohol to synthesize cyclic carbonates

A CO2-induced ROCO2Na/ROCO2H buffer solution is developed and employed in the carboxylative cyclization of propargyl alcohol to generate α-alkylene cyclic carbonates.

A DFT study on mechanisms of CO2 coupling with propargylic alcohols using alkali carbonates

AbstractThe mechanisms of CO2 coupling with the propargylic alcohol using alkali carbonates M2CO3 (M = Li, Na, K, Cs) have been investigated by means of density functional theory calculations. The calculations reveal that the target product tetronic acid (TA) is yielded through two stages: (a) the formation of the α‐alkylidene cyclic carbonate (αACC) intermediate via Cs2CO3‐mediated carboxylative cyclization of the propargylic alcohol with CO2, and (b) the conversion of the αACC intermediate with Cs2CO3 to produce the cesium salt of the TA. Since the overall kinetic barriers for the two stages are comparable and affordable, the excellent chemoselectivity to the TA should be primarily originated from the high thermodynamic stability of the cesium salt of the TA. Moreover, relative to the TA, the possibility to yield the by‐product acyclic carbonate can be excluded due to the both kinetics and thermodynamic inferiority. This result is different from the organic base‐mediated reaction. Alternatively, our calculations predict that CsHCO3 together generated with the cesium salt of the TA might also be an available mediating reagent for the incorporation of CO2 with the propargylic alcohol. Compared to other alkali carbonates M2CO3 (M = Li, Na, K), the stronger basicity of Cs2CO3 and the lower ionic potential of cesium ion can raise the effective concentration of the αACC intermediate, and thus the conversion of the αACC intermediate into the cesium salt of the TA can be achieved with high yield.

Silver-Catalyzed Carboxylative Cyclization of Propargylic Alcohols

Key words silver catalysis - carboxylative cyclization - propagylic alcohols - dioxolanones - catalyst support - rose bengal

Pd NPs Decorated on POPs as Recyclable Catalysts for the Synthesis of 2‐Oxazolidinones from Propargylic Amines via Atmospheric Cyclizative CO2 Incorporation

AbstractA novel approach has been taken for the synthesis of a microporous polymeric materials of BBA‐1 and BBA‐2 (benzene−benzylamine), which is a POP (porous organic polymer) with its excellent surface area determined by BET study, via Friedel‐Crafts alkylation of benzene and benzylamine (or 4‐methoxybenzylamine) by utilizing a cross‐linker (formaldehyde dimethyl acetal) and a promoter (anhydrous FeCl3). Pd NPs were decorated over BBA‐1 and modified BBA‐2 to generate the desired catalysts (Pd@BBA‐1 and Pd@BBA‐2 respectively). The characterizations of the synthesized nanomaterials have been conducted by FE‐SEM, wide‐angle powder XRDmethods, N2 adsorption/desorption studies and high resolution transmission electron microscopy (TEM). Pd NPs decorated porous polymers are described here to facilitate the carboxylative cyclization of several propargylamine derivatives leading to the corresponding desired products (2‐oxazolidinone) under the application of ambient conditions (0.1 MPa of CO2, DMSO, 40–80 °C, 30–60 mg nanocatalyst). The Pd NPs‐loaded POP is competitive with previously reported catalytic systems. These pure polymeric microporous catalytic systems exhibited outstanding catalytic performances for the generation of oxazolidinones from several propargylic amines in the absence of organic and inorganic bases through atmospheric cyclizative CO2 incorporation. The modified nanocatalyst (Pd@BBA‐2) displayed exceptional recycling efficiency for the generation of oxazolidinones up to five runs without any noticeable decay in the activity of Pd@BBA‐2.

Cu‐Catalyzed Selective Oxy‐Cyanoalkylation of Allylamines with Cycloketone Oxime Esters and CO2

Summary of main observation and conclusionThe radical‐initiated carboxylative cyclization of allylamines with CO2 represents an efficient and highly promising strategy to afford valuable 2‐oxazolidinones. However, the radical precursors and pathways to generate radicals in such processes are still limited. Herein, we report the first Cu‐catalyzed selective oxy‐cyanoalkylation of allylamines with cycloketone oxime esters and CO2 via C—C bond cleavage. Many cyanoalkyl‐substituted 2‐oxazolidinones are obtained in moderate to good yields with high regio‐ and chemo‐selectivities. The utility of this redox‐neutral and cyanide‐free method is demonstrated with mild conditions, broad substrate scope, good functional group tolerance and easy scalability.

Metal-Free Photocatalytic Synthesis of exo-Iodomethylene 2-Oxazolidinones: An Alternative Strategy for CO2 Valorization with Solar Energy.

A visible-light-promoted metal-free carboxylative cyclization of propargylic amines with CO2 was shown to offer exo-iodomethylene 2-oxazolidinones. Incorporation of both CO2 and iodo moieties into these compounds was realized efficiently. The mechanism study revealed that this carboxylative cyclization proceeds through a radical pathway. Notably, the iodine-functionalized 2-oxazolidinone as a platform molecule could be easily converted into a wide range of value-added chemicals through Buchwald-Hartwig, Suzuki, Sonogashira, photocatalytic ene, and photoreduction reactions. As a result, the plentiful downstream transformations remarkably enhance the range of chemicals derived from CO2 and open a potential avenue for CO2 functionalization to circumvent energy challenges in this field.

Carboxylative Cyclization of Propargylic Amines Catalyzed by Dendrimer-Encapsulated Gold NPs

Key words gold nanoparticles - propargylic amines - carbon dioxide - oxazolidinones - carboxylation - cyclization

Efficient and Recyclable Cobalt(II)/Ionic Liquid Catalytic System for CO2 Conversion to Prepare 2‐Oxazolinones at Atmospheric Pressure

Summary of main observation and conclusionConverting CO2 into value‐added chemicals represents a promising way to alleviate the CO2 derived environmental issues, for which the development of catalysts with high efficiency and recyclability is very desirable. Herein, the catalytic system by combining cobalt source and ionic liquid (IL) has been developed as the efficacious and recyclable catalyst for the carboxylative cyclization of propargylic amine and CO2 to prepare 2‐oxazolinones. In this protocol, various propargylic amines were successfully transformed into the corresponding 2‐oxazolinones with CoBr2 and diethylimidazolium acetate ([EEIM][OAc]) as the catalyst under atmospheric CO2 pressure. It is worth noting that the turnover number (TON) of this transformation can be up to 1740, presumably being attributed to the cooperative effect of the cobalt and IL. Furthermore, the existence of IL enables the catalytic system to be easily recycled to 10 times without losing its activity.

A Versatile Porous Silver-Coordinated Material for the Heterogeneous Catalysis of Chemical Conversion with Propargylic Alcohols and CO2.

The efficient transformation of carbon dioxide into useful chemical feedstock is of great significance, attracting intense research interest. The widely studied porous-coordinated polymers possess large pores to adsorb guest molecules and further allow the contact and to transfer the substrate molecule within their microenvironment. Here we present the synthesis of a silver-based metal-organic frameworks (MOFs) material with a three-dimensional structure by incorporating a tetraphenyl-ethylene moiety as the four-point connected node via the solvothermal method. This polymer exhibits as an efficient heterogeneous catalyst for the carboxylative cyclization of CO2 to α-methylene cyclic carbonates in excellent yields. Moreover, the introduction of silver (Ag (I)) chains in this framework shows the specific alkynophilicity to activate C≡C bonds in propargylic alcohols to greatly accelerate the efficient conversion, and the large pores in the catalyst exhibit a size-selective catalytic performance.

Carboxylative Cyclization of Propargylic Amines with Carbon Dioxide­ Catalyzed by Poly(amidoamine)-Dendrimer-Encapsulated Gold Nanoparticles

We prepared gold nanoparticles encapsulated in poly(amidoamine) (PAMAM) dendrimers as templating agents. The resulting gold nanoparticles were used as catalysts for the carboxylative cyclization of propargylic amines with carbon dioxide to afford the corresponding 1,3-oxazolidin-2-ones in yields of up to 99%.

Zinc (II) incorporated porous organic polymeric material (POPs): A mild and efficient catalyst for synthesis of dicoumarols and carboxylative cyclization of propargyl alcohols and CO2 in ambient conditions

Zinc (II) incorporated porous organic polymer catalyst, Zn@BBAPA has been designed, synthesized and characterized thoroughly by XRD, EDX, SEM, HR-TEM, FTIR spectra, UV–vis spectra, TGA and N2 absorption desorption isotherm. An eco-friendly porous Zn@BBAPA catalyst exhibits highly efficient catalytic performance for the production of α-alkylidene cyclic carbonates by using propargylic alcohols viaCO2 fixation.In addition the catalyst shows outstanding efficiency for the synthesis of various dicoumarol derivatives in green solvent medium (water)from 4-hydroxycoumarin and aromatic aldehydes. Presence of super hydrophobic nature and electron-donation characterof NH2 groups of BBA framework with high surface area is main aspect to be responsible for elevated catalytic performance as well as improvement in catalyst stability and enabling a good recyclability.

Synthesis of α-hydroxy ketones by copper(I)-catalyzed hydration of propargylic alcohols: CO2 as a cocatalyst under atmospheric pressure

Inexpensive and efficient Cu(I) catalysis is reported for the synthesis of α-hydroxy ketones from propargylic alcohols, CO 2 , and water via tandem carboxylative cyclization and nucleophilic addition reaction. Notably, hydration of propargylic alcohols can be carried out smoothly under atmospheric CO 2 pressure, generating a series of α-hydroxy ketones efficiently and selectively. This strategy shows great potential for the preparation of valuable α-hydroxy ketones by using CO 2 as a crucial cocatalyst under mild conditions. Efficient and inexpensive copper(I) catalysis was realized for the synthesis of α-hydroxy ketones via the hydration of propargylic alcohols by using CO 2 as a cocatalyst under atmospheric pressure.

Cobalt-based catalysis for carboxylative cyclization of propargylic amines with CO2 at atmospheric pressure

A cobalt-bicyclic guanidine catalytic system consisting of CoBr2 and 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) for the carboxylative cyclization of terminal propargylic amines with CO2 was firstly developed in this work to produce 2-oxazolinones efficiently. The existence of induction period urged us to understand the reaction mechanism of cobalt catalysis. Investigation on the roles of CoBr2 and TBD was conducted using control experiments and density functional theory (DFT) calculation. TBD presumably acts as a base to activate propargylic amine for favorable CO2 capture, and a ligand to coordinate with CoBr2 via forming bulkier CoBr2(TBD) in the same time. This bulkier complex can enhance the O-nucleophility of the in situ formed carbamate intermediate and then promote subsequent intramolecular cyclization to generate 2-oxazolinone, accounting for the high activity of cobalt catalysis. This protocol enables the synthesis of various 2-oxazolinones from propargylic amines and CO2 under atmospheric pressure in good to excellent yields, representing a simple, cost-effective and practical route for CO2 fixation to 2-oxazolinones under mild conditions.

Silver-catalyzed carboxylative cyclization of alkynic hydrazones with carbon dioxide

The development of new catalytic methodologies to synthesize heterocyclic fine chemicals using carbon dioxide as a synthon has attracted considerable attention. Herein, we report the silver(I)-catalyzed carboxylative cyclization of a variety of alkynic hydrazones with carbon dioxide to produce the corresponding 1,3,4-oxadiazin-2-ones under mild reaction conditions. In this reaction, silver(I) salts play a π-Lewis acid role for the highly efficient activation of the alkyne moiety in the hydrazone substrates. Single-crystal X-ray analysis and NOE experiments confirm that the newly formed oxadiazinone products exhibit Z configuration. Based on control experiments and NMR studies, a mechanism including the formation of a reactive carbazate intermediate, electrophilic cyclization, and subsequent protonation is proposed. This study offers an efficient and atom-economical method for the synthesis of biologically important 1,3,4-oxadiazin-2-ones.

Enantioselective carboxylative cyclization of propargylic alcohol with carbon dioxide under mild conditions

An enantioselective carboxylative cyclization of propargylic alcohols and CO2 was realized under mild conditions, based on a kinetic resolution strategy, which enabled the synthesis of chiral cyclic carbonates and propargylic alcohols with promising yield and enantioselectivity simultaneously.

Transformation of CO2 into α-Alkylidene Cyclic Carbonates at Room Temperature Cocatalyzed by CuI and Ionic Liquid with Biomass-Derived Levulinate Anion

Utilization of carbon dioxide (CO2) as a renewable C1 building block is of great importance. Herein, a series of ionic liquids (ILs) with biomass-derived anions or/and cations were synthesized, and using these prepared ILs as catalytic solvents, CuI could catalyze carboxylative cyclization of propargylic alcohols with CO2 at room temperature (25 °C). Especially, the IL [Bu4P][Levulinate] with cellulose-derived levulinate anion combined with CuI showed the best performance, affording various corresponding α-alkylidene cyclic carbonates in good yields (>90%). In the reaction, CuI and [Bu4P][Levulinate] played synergistic role to activate the C≡C and hydroxyl groups in propargylic alcohols, respectively, leading to the excellent performance of CuI/[Bu4P][Levuliniate]. Additionally, the CuI/[Bu4P][Levuliniate] catalytic system could be reused for five times without noticeable decrease in activity and selectivity.

Silver-Catalyzed Carboxylative Cyclization of Primary Propargyl Alcohols with CO2.

By using silver complexes with bulky ligands such as DavePhos or N-heterocyclic carbenes, propargylic alcohols are smoothly converted with CO2 into a unique class of unexplored cyclic alkylidene carbonates. These systems, for the first time, also achieve the direct carboxylative cyclization of primary propargylic alcohols. The silver-DavePhos catalyst is further applied for the bis-carboxylative cyclization of primary propargyl derivatives, thereby providing an effective route to a series of previously inaccessible and industrially relevant α-alkylidene cyclic carbonates.

Multifunctional 1,3-diphenylguanidine for the carboxylative cyclization of homopropargyl amines with CO2 under ambient temperature and pressure.

Herein, we report that 1,3-diphenylguanidine (DPG) could be utilized for the carboxylative cyclization of homopropargyl amines with CO2 under ambient temperature and pressure, in combination with AgSbF6, which enabled the synthesis of both chiral and achiral 2-oxazinones efficiently. A mechanistic study revealed that the multi-functionality of DPG is critical to the success of the reaction.