Palladium-catalyzed Carbonylation Research Articles

Highly Diastereoselective Palladium-Catalyzed Oxidative Cascade Carbonylative Carbocyclization of Enallenols.

A palladium-catalyzed oxidative cascade carbonylative carbocyclization of enallenols was developed. Under mild reaction conditions, a range of cis-fused [5,5] bicyclic γ-lactones and γ-lactams with a 1,3-diene motif were obtained in good yields with high diastereoselectivity. The obtained lactone/lactam products are viable substrates for a stereoselective Diels-Alder reaction with N-phenylmaleimide, providing polycyclic compounds with increased molecular complexity.

Palladium-catalyzed oxidative dehydrogenative carbonylation reactions using carbon monoxide and mechanistic overviews.

Carbon monoxide, which is an abundant and inexpensive carbonyl source, has been widely applied to synthesize carbonyl-containing compounds, for example ketones, esters, and amides. These types of compounds are ubiquitous in natural products, pharmaceuticals, as well as in functional materials. This review focuses on the palladium-catalyzed dehydrogenative C-H/X-H (X = C, N, O) carbonylation transformations under oxidative conditions. The related C-H bonds here include C(sp)-H, C(sp2)-H, and C(sp3)-H bonds. From a step- and atom-economy perspective, transition metal-catalyzed oxidative dehydrogenative C-H/X-H carbonylation reactions with CO constitute one of the most efficient strategies for the construction of versatile carbonyl groups, without the requirement of pre-functionalized substrates.

Palladium-catalyzed three-component carbonylative synthesis of 2-(trifluoromethyl)quinazolin-4(3H)-ones from trifluoroacetimidoyl chlorides and amines

An efficient and practical approach for the synthesis of 2-(trifluoromethyl)quinazolin-4(3H)-ones through palladium-catalyzed three-component carbonylative reaction has been developed.

Pd-Catalyzed External-CO-Free Carbonylation: Preparation of 2,4,6-Trichlorophenyl 3,4- Dihydronaphthalene-2-Carboxylate

Palladium-catalyzed carbonylation of organic (pseudo)halides has received much attention because of its versatility for the synthesis of carbonyl-containing compounds. This article discusses the preparation of 2,4,6-trichlorophenyl 3,4-dihydronaphthalene-2-carboxylate using Pd-catalyzed external-CO-free carbonylation. It also discusses the characterization data of 2,4,6-trichlorophenyl 3,4-dihydronaphthalene-2-carboxylate. Keywords: Pd-Catalysis; 2,4,6-Trichlorophenyl formate; 2,4,6-Trichlorophenyl 3,4-dihydronaphthalene-2-carboxylate; 3,4-Dihydronaphthalen-2-yl trifluoromethanesulfonate

Palladium-catalyzed carbonylative synthesis of arylacetamides from benzyl formates and tertiary amines

A palladium-catalyzed carbonylative synthesis of arylacetamides via a C–N bond cleavage of tertiary amines with benzyl formates as the CO source has been disclosed. A variety of arylacetamides were obtained in very good yields under oxidant-free conditions.

Palladium-catalyzed carbonylations of highly substituted olefins using CO-surrogates

CO surrogate chemistry: General protocols for alkoxycarbonylations of highly substituted olefins with paraformaldehyde and methyl formate are reported, allowing the performance of carbonylation reactions in all labs and for all kinds of substrates.

Benzene-1,3,5-triyl Triformate (TFBen)-Promoted Palladium-Catalyzed Carbonylative Synthesis of 2-Oxo-2,5-dihydropyrroles from Propargyl Amines.

In this letter, we developed a palladium-catalyzed procedure for the cyclocarbonylation of propargyl amines. Benzene-1,3,5-triyl triformate (TFBen) has been explored as the CO source and also as the key promotor. Various substituted 2-oxo-dihydropyrroles were produced in a facile manner in good yields (up to 90%).

Direct synthesis of adipic acid esters via palladium-catalyzed carbonylation of 1,3-dienes.

The direct carbonylation of 1,3-butadiene offers the potential for a more cost-efficient and environmentally benign route to industrially important adipic acid derivatives. However, owing to the complex reaction network of regioisomeric carbonylation and isomerization pathways, a selective practical catalyst for this process has thus far proven elusive. Here, we report the design of a pyridyl-substituted bidentate phosphine ligand (HeMaRaphos) that, upon coordination to palladium, catalyzes adipate diester formation from 1,3-butadiene, carbon monoxide, and butanol with 97% selectivity and 100% atom-economy under industrially viable and scalable conditions (turnover number > 60,000). This catalyst system also affords access to a variety of other di- and triesters from 1,2- and 1,3-dienes.

Total Synthesis of (-)-Graminin A Based on Asymmetric Cyclization Carbonylation of Propargyl Acetate.

The first total synthesis of (-)-graminin A is described. Key features of our synthetic approach involve a palladium-catalyzed asymmetric cyclization carbonylation of prochiral propargylic acetate, conversion of the orthoester product into methyl 4-oxo-3-furancarboxylate, and copper complex-mediated aldol condensation of (+)-gregatin B bearing a diene moiety. A new synthesis of (+)-gregatin B and the first synthesis of (-)-graminin A were achieved.

Palladium-catalyzed four-component carbonylation of allenes, alcohols and nitroarenes

In this communication, a highly selective palladium-catalyzed carbonylative four components procedure for the transformation of allenes, alcohols and nitroarenes has been developed. The desired 2-aminomethyl substituted 3-arylacrylates were produced in good yields with Mo(CO)6 as the solid CO source. Furthermore, nitroarenes have been used as reaction partners and oxidant in this catalytic system. Additionally, further synthetic application of our obtained products has been realized as well and α-alkylidene β-lactams were prepared.

Carbonylation of Aryl Halides in the Presence of Heterogeneous Catalysts

Palladium-catalyzed carbonylation in the presence of organic and organometallic nucleophiles serves as a powerful tool for the conversion of aryl/alkenyl halides or halide equivalents to carbonyl compounds and carboxylic acid derivatives. To circumvent the difficulties in product separation and recovery and reuse of the catalysts, associated with homogeneous reactions, supported counterparts of the homogeneous palladium catalysts were developed. The review intends to summarize the huge development that has been witnessed in recent years in the field of heterogeneous carbonylation. A great plethora of supports, organic modifiers on solid surfaces stabilizing metal particles, transition metal precursors, as well as alternative sources for CO was investigated. In most cases, careful optimization of reaction conditions was carried out. Besides simple model reactions, the synthesis of carbonyl compounds and carboxylic acid derivatives from substrates with different functionalities was performed. In some cases, causes of palladium leaching were clarified with detailed investigations. The advantages of immobilized catalysts were shown by several examples. The possibility of catalystrecycling was proved besides proving that metal contamination of the products could often be kept below the detection limit. At the same time, detailed investigations should be carried out to gain a better insight into the real nature of these processes.

Palladium-catalyzed reductive carbonylation of nitrobenzene for producing phenyl isocyanate

Direct reductive carbonylation of nitrobenzene to phenyl isocyanate with carbon monoxide was performed using various types of palladium catalysts together with many types of N-donor ligands. The effect of reaction time, pressure, temperature, ligand amount, and molar ratio to establish the optimized conditions was also investigated. With this, we were able to achieve up to 100% conversion and 63.5% yield with PdCl2 and alkylimidazole system (1:3) within 2 h at 220 °C and 1400 psi of CO in toluene.

Carboxyboronate: A Versatile C1 Building Block.

The synthesis and applications of carboxy-MIDA-boronate, a novel C1 building block, are described. This molecule is accessible via a ruthenium tetraoxide-mediated cleavage of commercially available ethynyl-MIDA-boronate. In the course of this study, carboxy-MIDA-boronate was found to possess ambident reactivity towards nucleophiles. Carboxylic acid derivatization produces a broad range of previously unknown carbamoyl-, oxycarbo- and thiocarboboronates. Carboxy-MIDA-boronate and its derivatives undergo condensations to access borylated heterocycles with boron at positions that are difficult to access using alternate methods. The resulting heterocycles participate in the Suzuki-Miyaura cross-coupling reaction, enabling entry into diverse bis(heteroaryl) motifs. The carbon monoxide-releasing capacity of carboxy-MIDA-boronate was also examined and applied in palladium-catalyzed carbonylation.

Two-Photon Absorption and Cell Imaging of Fluorene-Functionalized Epicocconone Analogues.

Epicocconone 1 is a natural chromophore isolated from the fungus Epicoccum nigrum that has shown applications in proteomics and fluorescent microscopy thanks to its unique pro-fluorescence properties. The modification of the skeleton of the natural product by replacing the triene side chain by a fluorenyl scaffold can noticeably increase the fluorophore's absorption coefficient. The synthesis of the analogues of the natural product has been made possible by the use of a palladium-catalyzed carbonylation reaction, allowing the construction of the β-keto-dioxinone key intermediate. Two-photon absorption cross-section measurements of the fluorenyl epicocconone analogues show a structure dependency with values ranging from 60 to 280 GM and live cell imaging show intense staining of intracellular vesicle-like structures around the nucleus.

Selectivity controllable divergent synthesis of α,β-unsaturated amides and maleimides from alkynes and nitroarenes via palladium-catalyzed carbonylation

A tunable procedure on palladium-catalyzed carbonylative divergent synthesis of α,β-unsaturated amides and maleimides from symmetrical internal alkynes and nitroarenes has been developed. By using Pd(acac)2/dppp/4-ClBSA/DMF and Pd(TFA)2/DPEphos/PTSA/H2O/toluene as the catalytic systems, a range of multi-substituted maleimides and α,β-unsaturated amides were selectively prepared in moderate to good yields with Mo(CO)6 as the solid CO source and nitroarene as a cheap and abundant nitrogen source.

Direct Access to 1,1-Dicarbonyl Sulfoxonium Ylides from Aryl Halides or Triflates: Palladium-Catalyzed Carbonylation.

The synthesis of 1,1-dicarbonyl sulfoxonium ylides by palladium-catalyzed carbonylation of aryl halides or triflates with α-carbonyl sulfoxonium ylides has been developed for the first time. This method provides a general approach to synthetically useful 1,1-dicarbonyl sulfoxonium ylides in high efficiency. The protocol displays a wide substrate scope, showing that the resulting 1,1-dicarbonyl sulfoxonium ylides have been converted into the corresponding 1,3-dicarbonyl compounds.

Palladium-Catalyzed Carbonylative Dearomatization of Indoles.

An interesting palladium-catalyzed dearomative carbonylation of N-(2-bromobenzoyl)indoles has been developed. The catalytic system is composed of commercially available Pd(OAc)2 and DPPP and uses alcohols and anilines as nucleophiles to afford moderate to good yields of the desired products. This method provides a straightforward access to diverse fused indoline esters and amides with good functional group tolerance. Remarkably, this is the first example of carbonylative dearomatization.

Palladium-Catalyzed Cyclocarbonylation Approach to Thiadiazafluorenones: A Correction.

The palladium-catalyzed carbonylation of 2-(propynylthio)benzimidazoles bearing a terminal triple bond leads to 2-methyl-1-thia-4a,9-diazafluoren-4-ones instead of the previously reported 3-methyl isomers, as unequivocally established by XRD analysis of a representative product. A correction is therefore provided here in order to rectify the previous erroneous assignment of the position of the methyl group. Moreover, the process has been generalized to substrates bearing an internal triple bond, which lead to 3-alkyl-2-methyl-1-thia-4a,9-diazafluoren-4-ones, whose structure was confirmed by XRD analysis of two representative derivatives.

Catalytic Generation of C1 Ammonium Enolates from Halides and CO for Asymmetric Cascade Reactions.

A general strategy for the design of asymmetric cascade reactions using readily available halides and carbon monoxide (CO) as substrates is developed. The key is the catalytic generation of C1-ammonium enolates for the subsequent asymmetric cascade reactions through the combination of palladium-catalyzed carbonylation and chiral Lewis base catalysis. Utilizing this strategy, we have established asymmetric formal [1+1+4] and [1+1+2] reactions to afford chiral dihydropyridones and β-lactams with high yields and high enantio- and diastereoselectivities.

Carbonylated Indoles from PdII-Catalyzed Intermolecular Reactions of Indolyl Cores

This review summarizes palladium-catalyzed carbonylation, transmetalation, and cross-coupling reactions that lead to carbonylated indoles from indoles and indolyl compounds. Special attention is drawn to procedures involving the C(sp2)–H substitution of free (NH)-indoles or (N-substituted)-indoles. Proposed mechanisms are described with, in some cases, personal comments.1 Introduction2 Carbonylative Reactions2.1 Indolyl Halides as Starting Substrates2.2 Indolyl Iodides as Intermediates2.3 Indolylborates as Intermediates2.4 C(sp2)–H Reactions2.4.1 Carboxylation2.4.2 Carbonylative Alkoxylation2.4.3 Carbonylative Arylation2.4.4 Carbonylative Alkenylation2.4.5 Carbonylative Alkylation2.4.6 Double Carbonylation3 Cross-Coupling of Stannyl- or Mercurioindoles4 Cross-Coupling of Indoles4.1 Aldehydes4.2 Alcohols4.3 α-Diketones4.4 α-Oxo Esters4.5 α-Oxocarboxylic Acids4.6 Nitriles4.7 Isocyanides4.8 Isothiocyanates and Isocyanates4.9 α-Aminocarbonyl Compounds4.10 Vinyl Ethers or Vinyl Amides4.11 Toluene and Substituted Toluenes4.12 Bromodichloromethane5 Conclusion