Carbonylation Of Epoxides Research Articles

Cobalt-catalyzed carbonylation of epoxides to β-lactones promoted by gallium porphyrin

Oxophilic Ga(III) porphyrin complexes were developed to replace Al(III) or toxic Cr(III) complexes as the Lewis acid catalyst to achieve the Co-catalyzed carbonylation of epoxides to β-lactones. Its performance is comparable to the state-of-the-art catalyst systems consisting of Al(III) or Cr(III). Large-scale reaction using the combination of (TPP)GaCl and Co2(CO)8 in low loading revealed its potential application for the preparation of β-butyrolactone from propylene oxide and CO.

Cr-Phthalocyanine Porous Organic Polymer as an Efficient and Selective Catalyst for Mono Carbonylation of Epoxides to Lactones

A facile, one-pot design strategy to construct chromium(III)-phthalocyanine chlorides (Pc’CrCl) to form porous organic polymer (POP-Pc’CrCl) using solvent knitting Friedel-Crafts reaction (FCR) is described. The generated highly porous POP-Pc’CrCl is functionalized by post-synthetic exchange reaction with nucleophilic cobaltate ions to provide an heterogenized carbonylation catalyst (POP-Pc’CrCo(CO)4) with Lewis acid-base type bimetallic units. The produced porous polymeric catalyst is identical to that homogeneous counterpart in structure and coordination environments. The catalyst is very selective and effective for mono carbonylation of epoxide into corresponding lactone and the activities are comparable to those observed for a homogeneous Pc’CrCo(CO)4 catalyst. The (POP-Pc’CrCo(CO)4) also displayed a good catalytic activities and recyclability upon successive recycles.

Carbonylative, Catalytic Deoxygenation of 2,3-Disubstituted Epoxides with Inversion of Stereochemistry: An Alternative Alkene Isomerization Method.

Reactions facilitating inversion of alkene stereochemistry are rare, sought-after transformations in the field of modern organic synthesis. Although a number of isomerization reactions exist, most methods require specific, highly activated substrates to achieve appreciable conversion without side product formation. Motivated by stereoinvertive epoxide carbonylation reactions, we developed a two-step epoxidation/deoxygenation process that results in overall inversion of alkene stereochemistry. Unlike most deoxygenation systems, carbon monoxide was used as the terminal reductant, preventing difficult postreaction separations, given the gaseous nature of the resulting carbon dioxide byproduct. Various alkyl-substituted cis- and trans-epoxides can be reduced to trans- and cis-alkenes, respectively, in >99:1 stereospecificity and up to 95% yield, providing an alternative to traditional, direct isomerization approaches.

Direct Heterogenization of Salphen Coordination Complexes to Porous Organic Polymers: Catalysts for Ring-Expansion Carbonylation of Epoxides

Salen and salphens are important ligands in coordination chemistry due to their ability to form various metal complexes that can be used for a variety of organic transformations. However, salen/salphen complexes are difficult to separate from the reaction mixture, thereby limiting their application to homogeneous systems. Accordingly, considerable effort has been spent to heterogenize the metallosalen/salphen complexes; however, this has resulted in compromised activities and selectivities. Direct heterogenization of metallosalens to form porous organic polymers (POPs) shows promise for heterogeneous catalysis, because it would allow easy separation while retaining catalytic function. Thus, a facile synthetic strategy for preparing metallosalen/salphen-based porous organic polymers through direct molecular knitting using a Friedel-Crafts reaction is presented herein for the first time. As representative candidates, salphenM(III)Cl (M = Al3+ and Cr3+) complexes are knitted by covalent cross-linking using this facile, scalable, one-pot method to synthesize highly POPs in high yields. When incorporated with [Co(CO)4]- anions, the resulting heterogeneous Lewis acidic metal (Al3+ and Cr3+) POPs exhibit propylene oxide ring-expansion carbonylation activity on par with those of their homogeneous counterparts.

Hyper-Cross-Linked Porous Porphyrin Aluminum(III) Tetracarbonylcobaltate as a Highly Active Heterogeneous Bimetallic Catalyst for the Ring-Expansion Carbonylation of Epoxides.

Development of an industrially viable catalyst for the ring-expansion carbonylation of epoxides remains challenging in the view of facile product separation and recyclability. Herein, we report a heterogenized porous porphyrin Al(III) tetracarbonylcobaltate bimetallic catalyst for the ring-expansion carbonylation of epoxides. The catalyst was synthesized using a hyper-cross-linking strategy involving methylene bridges introduced by the Friedel-Crafts reaction and incorporated with cobaltate anions. The catalyst effectively converts epoxides into the corresponding β-lactones with an excellent site time yield of 360 h-1, which is comparable to that of the corresponding homogeneous catalysts and is the highest of any heterogeneous catalyst reported so far for this reaction.

Tin(IV)-Porphyrin Tetracarbonyl Cobaltate: An Efficient Catalyst for the Carbonylation of Epoxides

Cationic tin(IV) porphyrins with tetracarbonyl cobaltates were synthesized, exhibiting bifunctional catalytic reactivity. The Lewis acidic tin-porphyrin center activated epoxides; concurrently, cobalt carbonyl anions efficiently opened epoxides and delivered carbonyl moieties. Thus, a series of β-lactones with a high synthetic value were obtained. This catalytic system showed excellent efficiency exceeding a turnover number of one thousand with a broad substrate scope. In addition, the presented tin porphyrin-based catalyst exhibited exclusive chemoselectivity to terminal epoxides over internal ones. The selective carbonylation of di-epoxides demonstrated the usefulness of these catalysts in the synthesis of complex molecular structures.

Balancing between Heterogeneity and Reactivity in Porphyrin Chromium-Cobaltate Catalyzed Ring Expansion Carbonylation of Epoxide into β-Lactone.

The synthesis of a unique heterogeneous catalyst that combines the functionality of a homogeneous catalyst and the advantages of a heterogeneous catalytic process is a continuing goal in various industrially applicable reactions. Here, we report heterogenization of homogeneous catalyst for lactone production from epoxide carbonylation through a facile polymerization using Friedel-Crafts reaction. A correlation between reactivity and degree of heterogeneity has been deduced by synthesizing different sized polymeric catalysts. The partially polymerized catalyst showed a remarkable initial turnover frequency of 400 h-1, and the fully polymerized catalyst displayed excellent selectivity during recycling with a total turnover number of 4100.

An aluminum(iii) picket fence phthalocyanine-based heterogeneous catalyst for ring-expansion carbonylation of epoxides

An effective heterogeneous catalyst for ring-expansion carbonylation of epoxides may have additional advantages over the homogeneous counterpart in terms of facile product separation and recyclability.

Double Ring‐Expanding Carbonylation Using an In Situ Generated Aluminum Phthalocyanine Cobalt Carbonyl Complex

AbstractThe ring‐expanding carbonylation of epoxides provides an efficient one‐step procedure for synthesizing β‐lactones and succinic anhydride derivatives. Although porphyrin‐based catalysts generally show excellent catalytic activities in the ring‐expanding carbonylation of epoxides, the application of porphyrin catalysts is limited owing to the low yield and high cost of preparing porphyrins. This study aims to propose a new and highly efficient catalytic system for the carbonylation of propylene oxide (PO) using an in situ generated active catalyst from cost‐effective and readily available aluminum phthalocyanine chloride (AlPcCl) and dicobalt octacarbonyl (Co2(CO)8). The catalyst showed not only excellent catalytic activities of single carbonylation but also double carbonylation resulting in anhydride by judicious choice of reaction parameters, such as reaction temperature and the ratio of PO to catalyst. This is the first report on the use of an in situ generated catalyst for the one‐pot double carbonylation of epoxide to anhydride.

Cobalt carbonyl ionic liquids based on the 1,1,3,3-tetra-alkylguanidine cation: Novel, highly efficient, and reusable catalysts for the carbonylation of epoxides

A series of novel cobalt carbonyl ionic liquids based on 1,1,3,3-tetra-alkyl-guanidine, such as [1,1-dimethyl-3,3-diethylguanidinium][Co(CO)4] (3a), [1,1-dimethyl-3,3-dibutylguanidinium][Co(CO)4] (3b), [1,1-dimethyl-3,3-tetramethyleneguanidinium][Co(CO)4] (3c), and [1,1-dimethyl-3,3-pentamethyleneguanidinium] [Co(CO)4] (3d), were synthesized in good yields and were also characterized using infrared spectroscopy, ultraviolet-visible spectroscopy, 1H nuclear magnetic resonance (NMR) spectroscopy, 13C NMR spectroscopy, high–resolution mass spectrometry, differential scanning calorimetry, and thermogravimetric analysis. The four compounds exhibited high thermal and chemical stability. In addition, the catalytic performance of these compounds was investigated in the carbonylation of epoxides, with 3a exhibiting the best catalytic activity without the aid of a base as the additive. The catalyst could be reused at least six times without significant decreases of the selectivity or conversion rate. Moreover, the catalyst system exhibited good tolerance with terminal epoxides bearing alkyl, alkenyl, aryl, alkoxy, and chloromethyl functional groups.

Heterogeneous Epoxide Carbonylation by Cooperative Ion-Pair Catalysis in Co(CO)4--Incorporated Cr-MIL-101.

Despite the commercial desirability of epoxide carbonylation to β-lactones, the reliance of this process on homogeneous catalysts makes its industrial application challenging. Here we report the preparation and use of a Co(CO)4–-incorporated Cr-MIL-101 (Co(CO)4⊂Cr-MIL-101, Cr-MIL-101 = Cr3O(BDC)3F, H2BDC = 1,4-benzenedicarboxylic acid) heterogeneous catalyst for the ring-expansion carbonylation of epoxides, whose activity, selectivity, and substrate scope are on par with those of the reported homogeneous catalysts. We ascribe the observed performance to the unique cooperativity between the postsynthetically introduced Co(CO)4– and the site-isolated Lewis acidic Cr(III) centers in the metal–organic framework (MOF). The heterogeneous nature of Co(CO)4⊂Cr-MIL-101 allows the first demonstration of gas-phase continuous-flow production of β-lactones from epoxides, attesting to the potential applicability of the heterogeneous epoxide carbonylation strategy.

ChemInform Abstract: Ring‐expanding Carbonylation of Epoxides

AbstractReview: 216 refs.

Metal-Support Cooperative Catalysts for Environmentally Benign Molecular Transformations.

Metal-support cooperative catalysts have been developed for sustainable and environmentally benign molecular transformations. The active metal centers and supports in these catalysts could cooperatively activate substrates, resulting in high catalytic performance for liquid-phase reactions under mild conditions. These catalysts involved hydrotalcite-supported gold and silver nanoparticles with high catalytic activity for organic reactions such as aerobic oxidation, oxidative carbonylation, and chemoselective reduction of epoxides to alkenes and nitrostyrenes to aminostyrenes using alcohols and CO/H2 O as reducing reagents. This high catalytic performance was due to cooperative catalysis between the metal nanoparticles and basic sites of the hydrotalcite support. To increase the metal-support cooperative effect, core-shell nanostructured catalysts consisting of gold or silver nanoparticles in the core and ceria supports in the shell were designed. These core-shell nanocomposite catalysts were effective for the chemoselective hydrogenation of nitrostyrenes to aminostyrenes, unsaturated aldehydes to allyl alcohols, and alkynes to alkenes using H2 as a clean reductant. In addition, these solid catalysts could be recovered easily from the reaction mixture by simple filtration, and were reusable with high catalytic activity.

ChemInform Abstract: The Asymmetric Synthesis of Tetrahydrolipstatin

AbstractReview: [73 refs.

The Asymmetric Synthesis of Tetrahydrolipstatin

AbstractThe various syntheses of the over‐the‐counter anti‐obesity drug tetrahydrolipstatin (also known as Orlistat) are reviewed. The 31 various syntheses cover the development of enantioselective natural products synthesis since the first synthesis of tetrahydrolipstatin (THL) by Schneider in 1987. After Schneider's landmark synthetic effort there have been numerous total and formal syntheses of THL, which have involved a diverse range of approaches. These various syntheses can be classified by the methods that were used to install the stereochemistry, for instance, chiral auxiliary, asymmetric aldol, asymmetric allylation/crotylation, asymmetric reductions, asymmetric resolutions, asymmetric oxidations, and chiron approach. These routes also feature the elegant use of a chiral phosphate template, a tandem [2+2]‐Mukaiyama aldol‐lactonization, an anti‐aldol segment via a non‐aldol route, a Prins cyclization, and an epoxide carbonylation.

Carbonylation of cis-disubstituted epoxides to trans-β-lactones: catalysts displaying steric and contrasteric regioselectivity.

trans-β-Lactones are a versatile and useful class of compounds, but reliable methods for their direct synthesis are still limited. Addressing this problem, we present herein two catalysts for the regioselective carbonylation of cis-disubstituted epoxides. The two catalysts show high activities and opposing regioselectivities so that either one of the two possible β-lactone regioisomers can be obtained selectively.

Synthesis of Tetrahydrolipstatin

Key words tetrahydrolipstatin - pancreatic lipase inhibitors - epoxide carbonylation - epoxyhomoallylic alcohols

Regioselective Carbonylation of trans-Disubstituted Epoxides to β-Lactones: A Viable Entry into syn-Aldol-Type Products

Two new catalysts are reported for the regioselective carbonylation of trans-disubstituted epoxides to cis-β-lactones. The two catalysts display high and opposing selectivities, which generally are difficult to achieve for this class of epoxides. The resulting β-lactones are well-defined precursors for a wide variety of aldol-type compounds. Altogether, carbonylation of disubstituted epoxides is established as a viable and economical entry into syn- and anti-aldol products.

Recent Progress in Carbonylation of Epoxides

Recent Progress in Carbonylation of Epoxides

De novo asymmetric synthesis of fridamycin E.

A de novo asymmetric synthesis of (R)- and (S)-fridamycin E has been achieved. The entirely linear route required only nine steps from commercially available starting materials (16% overall yield). Key transformations included a Claisen rearrangement, a Sharpless dihydroxylation and a cobalt-catalyzed epoxide carbonylation to give a β-lactone intermediate. Antibacterial activities were determined for both enantiomers using two strains of E. coli, with the natural (R)-enantiomer showing significant inhibition against a Gram-(+)-like imp strain (MIC = 8 μM).