Catalytic Carboxylation Research Articles

Electrocarboxylation of chloroacetonitrile by a Cobalt(I) complex of terpyridine

The electrocarboxylation of chloroacetonitrile (NC–CH 2–Cl RCl) mediated by [Co IIL 2] 2+ (L = terpyridine) was investigated by cyclic voltammetry. Electrochemical studies under argon atmosphere showed that the monoelectronic reduction of [Co IIL 2] 2+ yielded a Cobalt(I) complex which after the loss of a terpyridine ligand reacted with chloroacetonitrile. The oxidative addition of chloroacetonitrile on [Co IL] + gave an alkylCobalt(III) complex [R–Co IIIL] 2+ which was reduced into an alkylCobalt(II) complex, highly unstable and decomposed into an alkyl anion and a Cobalt(II) complex. Under carbon dioxide atmosphere, Cobalt(I) complex was shown to be unreactive towards CO 2 but CO 2 insertion was observed in the alkylCobalt(III) complex [R–Co IIIL] 2+ giving probably a CO 2 adduct [R–Co IIIL(CO 2)] 2+. This adduct presented a strong adsorption at the carbon electrode and was reduced at potential less cathodic than the one of alkylCobalt(III) complex. After reduction, the carboxylate RCO 2 − (NC–CH 2–CO 2 −) was released and a catalytic bielectronic carboxylation of chloroacetonitrile took place. Controlled potential electrolyses confirmed the catalytic process and gave for cyanoacetic acid faradic yields up to 60% under low overpotential conditions.

ChemInform Abstract: Palladium‐Catalyzed Carboxylation of Allylstannanes and Boranes Using CO2.

A family of well-defined (η3-allyl)Pd(L)(carboxylate) (L = PR3 or NHC) complexes are by far the most efficient catalysts reported to date for the catalytic carboxylation of allylstannanes into allylcarboxylates using CO2. The substrate scope of this reaction is extended to both substituted allylstannanes and allylboranes.

Palladium catalyzed carboxylation of allylstannanes and boranes using CO2

A family of well-defined (η(3)-allyl)Pd(L)(carboxylate) (L = PR(3) or NHC) complexes are by far the most efficient catalysts reported to date for the catalytic carboxylation of allylstannanes into allylcarboxylates using CO(2). The substrate scope of this reaction is extended to both substituted allylstannanes and allylboranes.

Synthesis and characterization of a novel polystyrene-tethered niobium methoxo species. Its application in the CO 2-based carboxylation of methanol to afford dimethyl carbonate

In this paper we describe the synthesis and characterization of a polystyrene-tethered Nb-complex, namely P-C 6H 4-p-CH 2CH 2–NbCl 4, 1 which reacts with CH 3OH to afford P-C 6H 4-p-CH 2CH 2–NbCl(OCH 3) 3 2. The latter inserts CO 2 to afford P-C 6H 4-p-CH 2CH 2–NbCl[O–C(O)OCH 3](OCH 3) 2, 3, active in the catalytic carboxylation of methanol. The insertion of only one mol CO 2 per Nb has been determined both by measuring the CO 2 released upon treatment with HCl and by solid state 13C NMR. 3 is easily recovered from the reaction medium and re-used; it can also be used in a flow reactor without decomposition after days. It shows good recycling properties and is much easier to use than the relevant homogeneous catalyst Nb(OCH 3) 4[O–C(O)OCH 3].

Insertion of CO2into a palladiumallyl bond and a Pd(ii) catalysed carboxylation of allyl stannanes

The complex 2,6-bis[(di-t-butylphosphino)methyl]phenyl allyl palladium (PCP(tBu)Pd-allyl, 3) reacts with CO(2) in a very fast insertion reaction to give the corresponding butenoate complex. The reaction is thought to occur via a cyclic six-membered transition state (7), where the gamma-carbon of the allyl group is linked up with the CO(2)-carbon. A group of related PCP complexes were investigated as catalysts for the carboxylation of tributyl(allyl)stannane. A catalytic cycle is proposed for this reaction where the rate determining step is the transmetallation between tin and palladium. The carboxylation reaction is faster using less sterically crowded catalysts whereas the electron richness of the palladium complexes seems less important for reactivity. Thus, there was no apparent difference in reactivity between 2,6-bis[(di-phenylphosphino)methyl]phenyl palladium triflouroacetate (13) and resorcinolbis(diphenyl)phosphinite palladium triflouroacetate (10). Both of these complexes give high turnovers for the carboxylation of tributyl(allyl)stannane (80% in 16 h using a ca. 5% catalyst loading and 4 atm CO(2) pressure). On the other hand complex 3 was inactive in the catalytic carboxylation reaction.

Insertion of Carbon Dioxide into (PCP)PdII−Me Bonds

A (PCP)PdMe complex has been synthesized and structurally characterized, displaying a very long Pd−Me bond. It is reactive toward CO2 insertion, giving the corresponding acetate in quantitative yield. The methyl complex can be regenerated using ZnMe2, and catalytic carboxylation is possible in benzene.

Process Development for a Herbicide Intermediate via Catalytic Carboxylation of an Aromatic Diazonium Compound

A laboratory process is described for the preparation of 2-sulfo-4-methoxybenzoic acid (SMBA) via diazotization of 2-amino-4-methoxy-sulfonic acid followed by Pd-catalyzed carbonylation in the presence of water. The most important process parameters were the catalyst precursor and water content. Both a two-step procedure using isolated diazonium compound as well as a one-pot reaction proved to be feasible. A yield of >95% SMBA was obtained after 3−4 h, using 1 mol % PdCl2 at 8 bar and 60 °C. This is the first technically feasible catalytic carbonylation of an arene diazonium compound.

Novel Catalytic CO2 Incorporation Reaction: Nickel‐Catalyzed Regio‐ and Stereoselective Ring‐Closing Carboxylation of Bis‐1,3‐dienes.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Novel Catalytic CO(2) Incorporation Reaction: Nickel-Catalyzed Regio- and Stereoselective Ring-Closing Carboxylation of Bis-1,3-dienes.

Novel nickel-catalyzed carboxylation of bis-1,3-dienes using carbon dioxide (CO2) was investigated. In the presence of catalytic amounts of Ni(acac)2 and PPh3, various bis-1,3-dienes smoothly reacted with CO2 and an organozinc reagent (Et2Zn, Me2Zn, or Ph2Zn) under mild conditions. This catalytic carboxylation process was accompanied by carbocyclization of bis-1,3-diene followed by alkylation by an organozinc reagent to afford cyclic carboxylic acid derivatives in high yields with high regio- and stereoselectivities.

Innovation of Hydrocarbon Oxidation with Molecular Oxygen and Related Reactions

An innovation of the aerobic oxidation of hydrocarbons through catalytic carbon radical generation under mild conditions was achieved by using N-hydroxyphthalimide (NHPI) as a key compound. Alkanes were successfully oxidized with O2 or air to valuable oxygen-containing compounds such as alcohols, ketones, and dicarboxylic acids by the combined catalytic system of NHPI and a transition metal such as Co or Mn. The NHPI-catalyzed oxidation of alkylbenzenes with dioxygen could be performed even under normal temperature and pressure of dioxygen. Xylenes and methylpyridines were also converted into phthalic acids and pyridinecarboxylic acids, respectively, in good yields. The present oxidation method was extended to the selective transformations of alcohols to carbonyl compounds and of alkynes to ynones. The epoxidation of alkenes using hydroperoxides or H2O2 generated in situ from hydrocarbons or alcohols and O 2 under the influence of the NHPI was demonstrated and seems to be a useful strategy for industrial applications. The NHPI method is applicable to a wide variety of organic syntheses via carbon radical intermediates. The catalytic carboxylation of alkanes was accomplished by the use of CO and O2 in the presence of NHPI. In addition, the reactions of alkanes with NO2 and SO2 catalyzed by NHPI provided efficient methods for the synthesis of nitroalkanes and sulfonic acids, respectively. A catalytic carbon-carbon bond forming reaction was achieved by allowing carbon radicals generated in situ from alkanes or alcohols to react with alkenes under mild conditions. 1 Introduction 2 Discovery of NHPI as Carbon Radical Producing Catalyst from Alkanes 2.1 Historical Background 2.2 Catalysis of NHPI in Aerobic Oxidation 3 NHPI-Catalyzed Aerobic Oxidation 3.1 Oxidation of Benzylic Compounds 3.2 Alkane Oxidations with Molecular Oxygen 3.3 Oxidation of Alkylbenzenes 3.4 Practical Oxidation of Methylpyridines 3.5 Preparation of Acetylenic Ketones via Alkyne Oxidation 3.6 Oxidation of Alcohols 3.7 Selective Oxidation of Sulfides to Sulfoxides 3.8 Production of Hydrogen Peroxide by Aerobic Oxidation of Alcohols 3.9 Epoxidation of Alkenes using Molecular Oxygen as Terminal Oxidant 4 Carboxylation of Alkanes with CO and O2 5 Utilization of NOx in Organic Synthesis 5.1 First Catalytic Nitration of Alkanes using NO2 5.2 Reaction of NO with Organic Compounds 6 Sulfoxidation of Alkanes Catalyzed by Vanadium 7 Carbon-Carbon Bond Forming Reaction via Catalytic Carbon Radicals Generated from Various Organic Compounds Assisted by NHPI 7.1 Oxyalkylation of Alkenes with Alkanes and Dioxygen 7.2 Synthesis of α-Hydroxy-γ-lactones by Addition of α-Hydroxy Carbon Radicals to Unsaturated Esters 7.3 Hydroxyacylation of Alkenes using 1,3-Dioxolanes and Dioxygen 8 Conclusions

Innovation of Hydrocarbon Oxidation with Molecular Oxygen and Related Reactions

An innovation of the aerobic oxidation of hydrocarbons through catalytic carbon radical generation under mild conditions was achieved by using N-hydroxyphthalimide (NHPI) as a key compound. Alkanes were successfully oxidized with O2 or air to valuable oxygen-containing compounds such as alcohols, ketones, and dicarboxylic acids by the combined catalytic system of NHPI and a transition metal such as Co or Mn. The NHPI-catalyzed oxidation of alkylbenzenes with dioxygen could be performed even under normal temperature and pressure of dioxygen. Xylenes and methylpyridines were also converted into phthalic acids and pyridinecarboxylic acids, respectively, in good yields. The present oxidation method was extended to the selective transformations of alcohols to carbonyl compounds and of alkynes to ynones. The epoxidation of alkenes using hydroperoxides or H2O2 generated in situ from hydrocarbons or alcohols and O 2 under the influence of the NHPI was demonstrated and seems to be a useful strategy for industrial applications. The NHPI method is applicable to a wide variety of organic syntheses via carbon radical intermediates. The catalytic carboxylation of alkanes was accomplished by the use of CO and O2 in the presence of NHPI. In addition, the reactions of alkanes with NO2 and SO2 catalyzed by NHPI provided efficient methods for the synthesis of nitroalkanes and sulfonic acids, respectively. A catalytic carbon-carbon bond forming reaction was achieved by allowing carbon radicals generated in situ from alkanes or alcohols to react with alkenes under mild conditions. 1 Introduction 2 Discovery of NHPI as Carbon Radical Producing Catalyst from Alkanes 2.1 Historical Background 2.2 Catalysis of NHPI in Aerobic Oxidation 3 NHPI-Catalyzed Aerobic Oxidation 3.1 Oxidation of Benzylic Compounds 3.2 Alkane Oxidations with Molecular Oxygen 3.3 Oxidation of Alkylbenzenes 3.4 Practical Oxidation of Methylpyridines 3.5 Preparation of Acetylenic Ketones via Alkyne Oxidation 3.6 Oxidation of Alcohols 3.7 Selective Oxidation of Sulfides to Sulfoxides 3.8 Production of Hydrogen Peroxide by Aerobic Oxidation of Alcohols 3.9 Epoxidation of Alkenes using Molecular Oxygen as Terminal Oxidant 4 Carboxylation of Alkanes with CO and O2 5 Utilization of NOx in Organic Synthesis 5.1 First Catalytic Nitration of Alkanes using NO2 5.2 Reaction of NO with Organic Compounds 6 Sulfoxidation of Alkanes Catalyzed by Vanadium 7 Carbon-Carbon Bond Forming Reaction via Catalytic Carbon Radicals Generated from Various Organic Compounds Assisted by NHPI 7.1 Oxyalkylation of Alkenes with Alkanes and Dioxygen 7.2 Synthesis of α-Hydroxy-γ-lactones by Addition of α-Hydroxy Carbon Radicals to Unsaturated Esters 7.3 Hydroxyacylation of Alkenes using 1,3-Dioxolanes and Dioxygen 8 Conclusions

Allylic Carboxylations and Lactonization Using Benzoquinone and Hydrogen Peroxide or tert-Butyl Hydroperoxide as Oxidants

Two new systems have been developed for catalytic carboxylation of alkenes. Both use palladium(II) as catalyst and benzoquinone as cocatalyst. In the first hydrogen peroxide was used as oxidant in acetic acid solution. Alkenes such as cyclohexene and 5-decene were converted cleanly to allylic acetates, but with 1-decene mainly the methyl ketone was formed. A diene such as 1,3-cyclohexadiene gave the diacetate while cis-1,2-divinylcyclohexane gave the cyclized monoacetate. In the second system, tert-butyl hydroperoxide was used as oxidant, permitting a wider choice of solvents and nucleophiles. Intramolecular reaction to lactones was possible in addition to allylic addition of acids such as benzoic, pivalic, and (S)-O-acetylmandelic acid

Factors influencing the oxidative addition of iodomethane to [Rh(CO) 2I 2] −, the key step in methanol and methyl acetate carbonylation

The oxidative addition of MeI to A + [Rh(CO) 2I 2] − [A = n-Bu 4N, Ph 4P, and Ph 4As], the rate determining step in the Rh and I − catalysed conversion of methanol into acetic acid and of methyl acetate into acetic anhydride, is second order overall, first order in both complex and methyl iodide. The reaction is slower in less polar solvents ( k 2 1.9 × 10 −5 M −1 s −1 in MeOAc, 3.1 × 10 −5 in THF, and 10.0 × 10 −5 M −1 s −1 at 298 K, in MeOH). Protic solvents accelerate the reaction; e.g. adition of ca. 3% water quadruples the rate in THF. Values of Δ G ≠ have been measured in MeOH and MeOAc between 288 and 318 K, and values of Δ H ≠ [60 (MeOH), 46 (MeOAc) kJ mol −1], and Δ S ≠ [−120 (MeOH), −180 (MeOAc) J mol −1 K −1] calculated from them; these numbers are very close to those for the catalytic carboxylation. Iodide also accelerates the reaction in methyl acetate up to two-fold, for addition of 20 equivalents of [I −]; this may be due to a “general” salt effect, stabilising the transition rather than the ground state. LiOAc behaves analogously; this is due to the reaction, MeI + LiOAc ⇌ MeOAc + LiI, which increases the LiI concentration, not to the formation of acetato-complexes of unusual reactivity. n-Bu 4NBF 4 has no effect on the reaction in methyl acetate. The oxidative addition is insensitive to the nature of the counter-ion except for C 12H 25NH + 3[Rh(CO) 2I 2] − in less polar solvents, where the IR spectra and also the slower rates of oxidative addition are consistent with some form of interaction, probably a N ⋯ H ⋯ Rh hydrogen-bond.

Rigid polyurethane foams from diethanolamides of carboxylated oils and fatty acids

AbstractNew polyols of high hydroxyl content and reactivity were made from linseed and soybean oils and acids by catalytic carboxylation followed by reaction with diethanolamine. Urethane foams made with these diethanolamides were stronger than those made with castor oil at equivalent polyol wt. Because of their higher hydroxyl content, a larger amount of diethanolamides could be incorporated in foam formulations than is possible with castor oil. The rigid urethane foams prepared with the new polyols meet the requirements of commercial products with respect to density, compressive strength, and dimensional stability.

Catalytic carboxylation of fats: Carboxy acids from polyunsaturates

AbstractStudies with a palladium chloride‐triphenylphosphine catalyst have been extended to the carboxylation of polyunsaturated fats. Linseed, soybean, and safflower oils, acids, and esters were carboxylated catalytically with water‐carbon monoxide (4000 psig) at 120–160 C with or without acetone as a solvent. Main products were monocarboxy, 1,3‐ and 1,4‐dicarboxy and tricarboxy acids. Minor products were carbomethoxy esters and disubstituted 2‐cyclopentenone. Optimum reaction conditions were determined for the carboxylation of linseed oil and methyl esters by statistically designed experiments. Yields of total carboxy and tricarboxy acids were maximized at low triphenylphosphine and water levels, low temperatures, and high palladium‐chloride concentrations. Carboxylated soybean esters were separated by ether extraction of the palladium catalyst from sodium carbonate or hydroxide carboxylate salts. This salt extraction permits catalyst recycling.

Catalytic carboxylation of fats. Carboxy acids and esters from monounsaturates

AbstractA highly selective catalytic, one‐step synthesis converts oleic acid into 9(10)‐carboxystearic acid in high yields (85–99%). Hydrocarboxylation with water and carbon monoxide under pressure (3000–4000 psi) is catalyzed with a mixture of palladium chloride and triphenylphosphine at 120–150 C with or without acetone or acetic acid solvents. Palladium supported on carbon is also an effective hydrocarboxylation catalyst in the presence of triphenylphosphine and HCl. Methyl 9(10)‐carbomethoxystearate was prepared by catalytic carbomethoxylation of methyl oleate with methanol and carbon monoxide but in lower yields. The carboxystearic acids and esters consisted of the 9 and 10 isomers (87–94%) in approximately equal proportions. This catalytic carboxylation procedure is a more efficient route to carboxystearic acid and ester than the two‐step hydroformylation‐oxidation process reported previously. Carboxylated acids, methyl esters and triglycerides of potential industrial importance have been prepared.

The Carboxylation Reaction using Nickel Catalysts. V. The Catalytic Reaction of Propene with Nickel Carbonyl and Nickel Carbonyl-Triphenylphosphine

Abstract The carboxylation reaction of propene catalyzed by nickel carbonyl was studied undeer various conditions. Iso- and n-butyric acids were obtained in good yields under mild conditions in the presence of a large amount of an organic acid. The catalytic carboxylation area was examined in detail. The carboxylation reaction proceeded smoothly in tetrahydrofuran, acetic acid, and dioxane. The proportion of isobutyric acid was largest in acetic acid (72.5–77.5%). Triphenylphosphine (TPP) had a great effect on the reaction rate, the catalytic reaction area, and the product distribution. On the reaction mechanism, an active species (HNi(CO)(TPP)X) was taken to account for the experimental results.