Recent developments in the synthesis of heterocyclic derivatives by PdI2-catalyzed oxidative carbonylation reactions

A simple catalytic system, consisting of PdI₂ in conjunction with an excess of KI, has proven to be very valuable for the direct one-step synthesis of a variety of heterocyclic derivatives by oxidative carbonylation of suitably functionalized alkynes. The same catalyst also promoted the oxidative carbonylation of β-amino alcohols to oxazolidin-2-ones with unprecedented catalytic efficiencies for this kind of reaction.     

Palladium-catalyzed oxidative heterocyclodehydration-alkoxycarbonylation of 3-yne-1,2-diols: a novel and expedient approach to furan-3-carboxylic esters

A novel and convenient approach to furan-3-carboxylic esters 2 is presented, based on palladium-catalyzed direct oxidative carbonylation of readily available 3-yne-1,2-diols 1. The process, corresponding to a sequential combination between a 5-endo-dig heterocyclodehydration step and an oxidative alkoxycarbonylation stage, is catalyzed by PdI₂ in conjunction with an excess of KI under relatively mild conditions (100 °C in ROH under 40 atm of a 4:1 mixture of CO-air).     

Oxidative Carbonylation of Alkynes in an Oscillation Mode: I. Concentration Limits for Oscillations in the Course of Phenylacetylene Carbonylation and Possible Mechanisms of the Process

An oscillating reaction of alkyne oxidative carbonylation is studied in a PdI₂–KI–CH₃OH catalytic system. Concentration limits for oscillations are found. A tentative kinetic model for the process is proposed. The mechanism of oscillations is discussed.     

Synthesis of cyclic carbonates from epoxides or olefins and CO2 catalyzed by metal-organic frameworks and quaternary ammonium salts

Catalytic properties of the metal-organic framework Cr-MIL-101 in solvent-free cycloaddition of CO₂ to epoxides to produce cyclic carbonates using tetrabutylammonium bromide as co-catalyst have been explored under mild reaction conditions (8 bar CO₂, 25 ⁰C). Styrene and propylene carbonates were formed with high yields (95% and 82%, respectively). Catalytic performance of Cr-MIL-101 was compared with other MOFs: Fe-MIL-101, Zn-MOF-5 and HKUST-1. The catalytic properties of different quaternary ammonium bromides, Cr-MIL-101 as well as PW₁₂/Cr-MIL-101 composite material have been assessed in oxidative carboxylation of styrene in the presence of both tert-butyl hydroperoxide and H₂O₂ as oxidants at 8–100 bar CO₂ and 25–80 ⁰C with selectivity to styrene carbonate up to 44% at 57% substrate conversion.     

CO2 Fixation with Epoxides under Mild Conditions with a Cooperative Metal Corrole/Quaternary Ammonium Salt Catalyst System

The cooperative catalytic activity of several metal corrole complexes in combination with tetrabutyl‐ammonium bromide (TBAB) has been investigated for the reaction of epoxides with CO₂ leading to cyclic carbonates. It was found that the use of just 0.05 mol % of a manganese(III)corrole with 2 mol % TBAB exhibits excellent catalytic activity under an atmosphere of CO₂.     

5-membered cyclic acyl phosphates : A new class of extremely reactive phosphorylating agents

The reaction of phosgene with the oxyphosphorane made from biacetyl and trimethyl phosphite gives an α-(dimethylphosphato)-β-ketoacid chloride, which undergoes an intramolecular loss of methyl chloride under catalysis; by CuSO₄, and yields the first reported 5-membered cyclic acyl phosphate. The acyl phosphate is attacked exclusively at phosphorus by water, alcohols and phenols, at an extraordinarily rapid rate. In contrast, tertiary amines attack only the Me carbon of the exocyclic OMe group of the acyl phosphate to give quaternary ammonium salts of 5-membered cyclic acyl phosphates. These cyclic mixed anhydrides of phosphoric acid are the most powerful phosphorylating agents for oxygen-containing nucleophiles known at present. The end-products of the phosphorylations are phosphotriesters, phosphodiesters, and phosphomonoesters, containing the easily removable acetoinyl group, [(CH₃CO)(CH₃)CHO]P(O)(OR)(OR′).     

Enantioselective microbial hydrolysis of dissymmetrical cyclic carbonates with disubstitution

Enantioselective microbial hydrolysis of C₁ and C₂ dissymmetrical cyclic carbonates with disubstitution (methyl and another groups) has been developed. Pseudomonas diminuta (FU0090), a bacterium, efficiently catalyzes the hydrolysis of five-membered cyclic carbonates. While the trans-substrates are hydrolyzed with low enantioselectivities and/or reactivities, the microbe hydrolyzes the cis-substrates with very high enantioselectivities to afford the corresponding almost optically pure anti-(2R,3S)-diols. On the other hand, six-membered trans-cyclic carbonates are enantioselectively hydrolyzed to afford the corresponding optically active syn-(2R,4R)-diols, although the hydrolysis of the cis-substrates gives racemic compounds. In all cases, the enzyme prefers the (R)-enantiomer for the carbon atom bearing a methyl group.     

Concentration oscillations in the oxidative carbonylation of non-1-yne in the PdI2-KI-CO-O2-CH3OH and PdI2-KI-CO-O2-phenylacetylene-CH3OH systems

The oscillatory mode of the oxidative carbonylation of non-1-yne in the PdI₂-KI-CO-O₂-CH₃OH system has been observed for the first time. Triethylamine affects the formation and development of concentration oscillations in this system. It has been discovered that the character of oscillations of the non-1-yne concentration is changed by the simultaneous introduction of another alkyne (phenylacetylene) into the system.     

A Practical and General Base‐Catalyzed Carbonylation of Amines for the Synthesis of N‐Formamides

A highly practical and general base‐catalyzed carbonylation of amines to the corresponding N‐formamides has been realized. Cheap inorganic bases, including Group IA and IIA metal hydroxides, alkoxides, carbonates, and phosphates, were effective catalysts for the transformation. In the presence of 10–40 mol % of KOH or K₂CO₃, various amines were converted into the corresponding N‐formamides in good‐to‐excellent yields using CO as the formylation reagents.     

Low Pressure Carbonylation of Benzyl Carbonates and Carbamates for Applications in 13C Isotope Labeling and Catalytic CO2 Reduction

Herein, we report a methodology to access isotopically labeled esters and amides from carbonates and carbamates employing an oxygen deletion strategy. This methodology utilizes a decarboxylative carbonylation approach for isotope labeling with near stoichiometric, ex situ generated ¹²C, or ¹³C carbon monoxide. This reaction is characterized by its broad scope, functional group tolerance, and high yields, which is showcased with the synthesis of structurally complex molecules. A complementary method that operates by the catalytic in situ generation of CO via the reduction of CO₂ liberated during decarboxylation has also been developed as a proof-of-concept approach that CO₂-derived compounds can be converted to CO-containing frameworks. Mechanistic studies provide insight into the catalytic steps which highlight the impact of ligand choice to overcome challenges associated with low-pressure carbonylation methodologies, along with rational for the development of future methodologies.     

Isolation and characterization of an iodide bridged dimeric palladium complex in carbonylation of methanol

Palladium-catalyzed carbonylation of methanol in presence of iodide promoters was investigated. Iodide bridged palladium dimeric complex, [PPh₃CH₃]₂[Pd₂I₆] was isolated from the carbonylation reaction mixture and characterized using X-ray crystallography. Reaction mechanism was proposed based on IR and UV spectroscopic characterizations of catalytic species involved in the catalytic cycle. The isolated dimeric palladium species, [Pd₂I₆]²⁻ underwent carbonylation to give monomeric species [PdI₃CO]⁻ at atmospheric pressure of carbon monoxide. It was also observed that PPh₃ plays an important role to avoid catalyst deactivation at higher temperatures. Turnover frequency (TOF) of 1052 h⁻¹ was achieved using Pd(OAc)₂-HI-PPh₃ catalyst system at 175 °C.     

Efficient and Reusable Iron Catalyst to Convert CO2 into Valuable Cyclic Carbonates

The production of cyclic carbonates from CO₂ cycloaddition to epoxides, using the C-scorpionate iron(II) complex [FeCl₂{κ³-HC(pz)₃}] (pz = 1H-pyrazol-1-yl) as a catalyst, is achieved in excellent yields (up to 98%) in a tailor-made ionic liquid (IL) medium under mild conditions (80 °C; 1–8 bar). A favorable synergistic catalytic effect was found in the [FeCl₂{κ³-HC(pz)₃}]/IL system. Notably, in addition to exhibiting remarkable activity, the catalyst is stable during ten consecutive cycles, the first decrease (11%) on the cyclic carbonate yield being observed during the 11th cycle. The use of C-scorpionate complexes in ionic liquids to afford cyclic carbonates is presented herein for the first time.     

Cu/活性炭催化剂：水合肼还原制备及催化甲醇氧化羰基化

以活性炭为载体,水合肼为还原剂制备了负载型Cu/活性炭催化剂,考察了水合肼/硝酸铜物质的量的比对催化甲醇气相氧化羰基化性能的影响,并采用XRD、XPS、H2-TPR和SEM等手段对催化剂进行了表征。结果表明,不加入还原剂水合肼时,催化剂中仅有CuO;随着水合肼/硝酸铜物质的量的比的增加,二价铜逐步被还原为Cu2O和/或单质Cu0,未被还原的Cu(OH)2在催化剂干燥过程中分解形成分散态CuO存在于催化剂表面。当水合肼/硝酸铜物质的量的比为0.75时,催化剂的催化性能最好,碳酸二甲酯的时空收率为120.62 mg.(g.h)-1,选择性为74.51%,甲醇转化率达到3.88%。在93 h反应时间内,催化剂都保持了较高的反应活性和选择性。此时铜物种以Cu2O和分散态CuO为主,Cu2O是主要的活性物种。     

Codimerization and carbonylation of normal alkenes and isobutylene

Conclusions An equimolar mixture of a normal (or cyclic) alkene and an alkene with a branch at the double bond (or a tertiary alcohol) in the presence of the BF₃·H₂O -liquid-SO₂ catalytic system under 1 atm of CO at a temperature of –30 to –40°C undergoes selective codimerization followed by carbonylation and the formation of codimeric carboxylic acids with 70 to 93% yields.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1057–1063, May, 1978.     

Parallel synthesis of 19-membered ring macro-heterocycles via intramolecular thioether formation

Starting from resin-bound orthogonally protected lysine, the generation of 19-membered ring macro-heterocycles via intramolecular thioether formation is described. The on resin cyclization occurred by the coupling of p-fluoro-m-nitro benzoic acid or bromo acetic acid followed by intramolecular substitution S_NAr or S_N2 displacement of the fluoro and bromo groups, respectively. The described approaches present versatile synthetic routes toward the synthesis of libraries of macro-heterocycles in an attempt to establish lead drug candidates. The desired cyclic products were obtained in good yields and good purities.     

Hydrogenation of CO2‐Derived Carbonates and Polycarbonates to Methanol and Diols by Metal–Ligand Cooperative Manganese Catalysis

The first base‐metal‐catalysed hydrogenation of CO₂‐derived carbonates to alcohols is presented. The reaction proceeds under mild conditions in the presence of a well‐defined manganese complex with a loading as low as 0.25 mol %. The non‐precious‐metal homogenous catalytic system provides an indirect route for the conversion of CO₂ into methanol with the co‐production of value‐added (vicinal) diols in yields of up to 99 %. Experimental and computational studies indicate a metal–ligand cooperative catalysis mechanism.     

The promoting effect of chelating ligands in the oxidative carbonylation of phenol to diphenyl carbonate catalyzed by Pd–Co–benzoquinone system

The system Pd(OAc)₂/BQ/Co(acac)₃ (BQ=benzoquinone), in combination with tetrabutylammonium bromide (TBAB) as a surfactant agent and a chelating ligand such as 2,9-dimethyl-1,10-phenanthroline (dmphen) or 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (dmdpphen), is an efficient catalyst for the oxidative carbonylation of phenol to diphenyl carbonate (DPC). The best results have been obtained using the system Pd(OAc)₂/BQ/Co(acac)₃/dmphen=1/30/8/5 (molar ratio) in which [Pd]=10⁻³ mol l⁻¹ and TBAB/Pd=60/1. This system gives the maximum productivity of 700 mol DPC/mol Pd h at 135°C and under P_tot=60 atm (CO/O₂=10/1 molar ratio). The role of each component of the catalytic system is discussed and a catalytic cycle is proposed.     

Soluble polymer-supported catalysts containing pendant quaternary onium salts for the addition reaction of oxiranes with carbon dioxide

The addition reaction of oxiranes ( 15a-d ) with carbon dioxide (CO₂) was carried out using 1 mol % of soluble polymer-supported quaternary onium salts as catalysts under atmospheric pressure. The reaction of 15a-d with CO₂ proceeded very smoothly to give the corresponding five-membered cyclic carbonates ( 16a-d ) in high yields at 90-100°C. The catalytic activity of the soluble polymer-supported quaternary onium salts was strongly affected by the following factors: kind of reaction solvent, degree of introduction of the pendant onium salt residues in the polymer chain, and type of alkyl group on the onium salts due to the balance between lipophilicity and steric hindrance of the onium salt residue. Furthermore, these soluble polymer-supported quaternary onium salts were found ordinarily to have higher catalytic activity than low molecular weight quaternary onium salts under the same reaction conditions. It was also found that the rate of reaction was proportional both to catalyst concentration and to oxirane concentration. © 1995 John Wiley & Sons, Inc.     

Co2(CO)8-catalyzed carbonylation of acetals using N-silylamines

Formaldehyde dialkyl acetals and cyclic acetal, 1,3-dioxolane, are smoothly carbonylated using N-silylamines at 140–160 °C under 70–88 kg cm⁻² CO pressure in the presence of a catalytic amount of Co₂(CO)₈ to give the corresponding 2-alkoxyamides in moderate to good yields. In the carbonylation of formaldehyde dialkyl acetals using N-silylamines, addition of pyridine drastically enhances the catalytic activity.     

Synthesis of 2-oxazolidinones by direct palladium-catalyzed oxidative carbonylation of 2-amino-1-alkanols

[reaction: see text] 2-Oxazolidinones 2 are obtained in excellent yields (up to 100%) and with unprecedented catalytic efficiencies (up to 2000 mol of product/mol of catalyst used) by direct PdI2/KI-catalyzed oxidative carbonylation of the readily available 2-amino-1-alkanols 1. Reactions are carried out in MeOH as the solvent at 100 degrees C using a 1/6/5 CO/O2/air mixture (60 atm total pressure at 25 degrees C).