Tandem Isomerization-Decarboxylation for Converting Alkenoic Fatty Acids into Alkenes

Copper-Catalyzed Decarboxylative Elimination of Carboxylic Acids to Styrenes

A copper-catalyzed decarboxylative elimination reaction of (hetero)aromatic propionic acids to vinyl (hetero)arenes has been developed. This method furnishes alkenes from carboxylic acids without the need for stochiometric Pb or Ag additives or expensive or specialized photocatalysts. A series of mechanistic experiments indicate that the reaction proceeds via benzylic deprotonation and subsequent radical decarboxylation; a pathway that is distinct from the single-electron-transfer mechanisms implicated in related decarboxylative elimination reactions.

Parts-per-million of ruthenium catalyze the selective chain-walking reaction of terminal alkenes

The chain–walking of terminal alkenes (also called migration or isomerization reaction) is currently carried out in industry with unselective and relatively costly processes, to give mixtures of alkenes with significant amounts of oligomerized, branched and reduced by–products. Here, it is shown that part–per–million amounts of a variety of commercially available and in–house made ruthenium compounds, supported or not, transform into an extremely active catalyst for the regioselective migration of terminal alkenes to internal positions, with yields and selectivity up to >99% and without any solvent, ligand, additive or protecting atmosphere required, but only heating at temperatures >150 °C. The resulting internal alkene can be prepared in kilogram quantities, ready to be used in nine different organic reactions without any further treatment.

The chain-walking of terminal alkenes is an industrially relevant reaction. Here, the authors show that part-per-million amounts of a variety of ruthenium compounds catalyze the reaction in yields and selectivity up to >99%, without any solvent or additive.

A donor-acceptor complex enables the synthesis of E-olefins from alcohols, amines and carboxylic acids

Olefins are prevalent substrates and functionalities. The synthesis of olefins from readily available starting materials such as alcohols, amines and carboxylic acids is of great significance to address the sustainability concerns in organic synthesis. Metallaphotoredox-catalyzed defunctionalizations were reported to achieve such transformations under mild conditions. However, all these valuable strategies require a transition metal catalyst, a ligand or an expensive photocatalyst, with the challenges of controlling the region- and stereoselectivities remaining. Herein, we present a fundamentally distinct strategy enabled by electron donor-acceptor (EDA) complexes, for the selective synthesis of olefins from these simple and easily available starting materials. The conversions took place via photoactivation of the EDA complexes of the activated substrates with alkali salts, followed by hydrogen atom elimination from in situ generated alkyl radicals. This method is operationally simple and straightforward and free of photocatalysts and transition-metals, and shows high regio- and stereoselectivities.

Transition metal-catalyzed alkene isomerization as an enabling technology in tandem, sequential and domino processes

One-pot reactions based on catalytic isomerization of alkenes not only offer the inherent advantages of atom-, step- and redox-economy but also enable the preparation of value-added products that would be difficult to access by conventional methods.

Pd-Catalyzed Synthesis of Vinyl Arenes from Aryl Halides and Acrylic Acid

Acrylic acid is presented as an inexpensive, non-volatile vinylating agent in a palladium-catalyzed decarboxylative vinylation of aryl halides. The reaction proceeds through a Heck reaction of acrylic acid, immediately followed by protodecarboxylation of the cinnamic acid intermediate. The use of the carboxylate group as a deciduous directing group ensures high selectivity for monoarylated products. The vinylation process is generally applicable to diversely substituted substrates. Its utility is shown by the synthesis of drug-like molecules and the gram-scale preparation of key intermediates in drug synthesis.

Do dihydroxymagnesium carboxylates form Grignard-type reagents? A theoretical investigation on decarboxylative fragmentation

Dihydroxymagnesium carboxylates [(OH)₂MgO₂CR] were probed for decarboxylation on a theoretical level, by utilizing both Møller-Plesset perturbation theory (MP2) and density functional theory (B3LYP-DFT) computations. This study is connected to the question of whether this recently introduced, astrobiologically relevant chemical class may form Grignard-type reagent molecules. To extract trends for a broad molecular mass range, different linear alkyl chain lengths between C₄ and C₁₁ were computed. The forward energy barrier for decarboxylation reactions increases linearly as a function of the ligand's chain length. Decarboxylation-type fragmentations of these organomagnesium compounds seem to be improbable in non-catalytic, low energetic environments. A high forward energy barrier (E_MP2 > 55 kcal mol^-1) towards a described transition state restricts the release of CO₂. Nevertheless, we propose the release of CO₂ on a theoretical level, as been revealed via an intramolecular nucleophilic attack mechanism. Once the challenging transition state for decarboxylation is overcome, a stable Mg-C bond is formed. These mechanistic insights were gained by help of natural bond orbital analysis. The Cα atom (first carbon atom in the ligand chain attached to the carboxyl group) is thought to prefer binding towards the electrophilic magnesium coordination center, rather than towards the electrophilic CO₂-carbon atom. Additionally, the putatively formed Grignard-type OH-bearing product molecules possess a more polarized Mg-C bond in comparison to RMgCl species. Therefore, carbanion formation from OH-bearing Grignard-type molecules is made feasible for triggering C-C bond formation reactions. Graphical abstract This study asks whether recently introduced, astrobiologically dihydroxymagnesium carboxylates form Grignard-type reagent molecules via decarboxylative fragmentation.

Dual-catalytic decarbonylation of fatty acid methyl esters to form olefins

The homogeneous dehydrative decarbonylation of fatty acid methyl esters (FAMEs) to form olefins is reported.

Selective production of linear α-olefins via catalytic deoxygenation of fatty acids and derivatives

Various homogeneous, heterogeneous, and enzyme catalysis strategies for the selective synthesis of linear α-olefins from fatty acids and their derivatives are reviewed.

Decarboxylation of Fatty Acids with Triruthenium Dodecacarbonyl: Influence of the Compound Structure and Analysis of the Product Mixtures

Recently, the decarboxylation of oleic acid (9(Z)-octadecenoic acid) catalyzed by triruthenium dodecacarbonyl, Ru₃(CO)₁₂, to give a mixture of heptadecenes with concomitant formation of other hydrocarbons, heptadecane and C17 alkylbenzenes, was reported. The product mixture, consisting of about 77% heptadecene isomers, 18% heptadecane, and slightly >4% C17 alkylbenzenes, possesses acceptable diesel fuel properties. This reaction is now applied to other fatty acids of varying chain length and degree of saturation as well as double-bond configuration and position. Acids beyond oleic acid included in the present study are lauric (dodecanoic), myristic (tetradecanoic), palmitic (hexadecanoic), stearic (octadecanoic), petroselinic (6(Z)-octadecenoic), elaidic (9(E)-octadecenoic), asclepic (11(Z)-octadecenoic), and linoleic (9(Z),12(Z)-octadecadienoic) acids. Regardless of the chain length and degree of unsaturation, a similar product mixture was obtained in all cases with a mixture of alkenes predominating. Monounsaturated fatty acids, however, afforded the alkane with one carbon less than the parent fatty acid as the most prominent component in the mixture. Alkylbenzenes with one carbon atom less than the parent fatty acid were also present in all product mixtures. The number of isomeric alkenes and alkylbenzenes depends on the number of carbons in the chain of the parent fatty acid. With linoleic acid as the starting material, the amount of alkane was reduced significantly with alkenes and alkylaromatics enhanced compared to the monounsaturated fatty acids. Two alkenes, 9(E)-tetradecene and 1-hexadecene, were also studied as starting materials. A similar product mixture was observed but with comparatively minor amount of alkane formed and alkene isomers dominating at almost 90%. The double-bond position and configuration in the starting material do not influence the pattern of alkene isomers in the product mixture. The results underscore the multifunctionality of the Ru₃(CO)₁₂ catalyst, which promotes a reaction sequence including decarboxylation, isomerization, desaturation, hydrogenation, and cyclization (aromatization) to give a mixture of hydrocarbons simulating petrodiesel fuels. A reaction pathway is proposed to explain the existence of these products, in which alkenes are dehydrogenated to alkadienes and then, under cyclization, to the observed alkylaromatics. The liberated hydrogen can then saturate alkenes to the corresponding alkane.

Catalytic decarbonylation of biosourced substrates

Linear α-olefins (LAO) are one of the main targets in the field of surfactants, lubricants, and polymers. With the depletion of petroleum resources, the production of LAO from renewable feedstocks has gained increasing interest in recent years. In the present study, we demonstrated that Ir catalysts were suitable to decarbonylate a wide range of biosourced substrates under rather mild conditions (160 °C, 5 h reaction time) in the presence of potassium iodide and acetic anhydride. The resulting LAO were obtained with good conversion and selectivity provided that the purity of the substrate, the nature of the ligand, and the amounts of the additives were controlled accurately. The catalytic system could be recovered efficiently by using a Kugelrohr distillation apparatus and recycled.

A Direct Metal-Free Decarboxylative Sulfono Functionalization (DSF) of Cinnamic Acids to α,β-Unsaturated Phenyl Sulfones

A metal-free room temperature decarboxylative cross-coupling between cinnamic acids and arylsulfonyl hydrazides has been realized for the first time for the synthesis of (E)-vinyl sulfones. The scope and versatility of the reaction has been demonstrated by the regio- and stereoselective synthesis of 22 derivatives with diverse structural features.

Olefins from biomass feedstocks: catalytic ester decarbonylation and tandem Heck-type coupling

Catalytic method employs “masked” carboxylic acids to yield alkenes, via decarbonylation and/or C–C coupling of activated esters.

Cu, Al and Ga based metal organic framework catalysts for the decarboxylation of oleic acid

Herein we demonstrate the catalytic decarboxylation and conversion of oleic acid to paraffins and hydrocarbons over bare and Pt supported Cu, Al and Ga based metal organic frameworks.