Nickel-Catalyzed Decarbonylative Thioetherification of Carboxylic Acids with Thiols

Samarium(II) Diiodide-Mediated Deoxygenation of Sulfoxides

Samarium diiodide-mediated deoxygenative activation of sulfoxides by selective S-O cleavage to construct thioethers under mild room temperature conditions has been achieved. A broad variety of sulfoxides, including aryl-aryl, aryl-alkyl, aryl-alkenyl, and alkyl-alkyl sulfoxides, can be readily converted to the corresponding thioethers using the highly chemoselective, operationally simple, and benign SmI2/Et3N reagent system. Extensive studies on the effect of additives indicate that typical samarium(II) iodide additives, such as water, alcohols, HMPA or nickel, have a negative impact on this valuable deoxygenation, while triethylamine promotes the deoxygenation in a versatile manner to afford synthetically useful thioether products.

Highly efficient esterification of carboxylic acids with O-H nucleophiles through acid/iodide cooperative catalysis

The esterification of carboxylic acids is an important reaction for preparing esters which find wide applications in various research fields. In this manuscript, we report an acid/iodide cooperative catalytic method which enables highly efficient esterification of carboxylic acids with a wide range of equivalent O-H nucleophiles including both alcohols and weak nucleophilic phenols. Under the reaction conditions, both aromatic and aliphatic carboxylic acids including those bearing functional groups work well, furnishing the corresponding esters in good to high yields. Moreover, this reaction is scalable and applicable to the modification of bioactive molecules. These results demonstrate the synthetic value of this new reaction in organic synthesis.

Palladium-catalyzed Suzuki-Miyaura cross-coupling of carboxylic-phosphoric anhydrides via C-O bond cleavage

A robust palladium-catalyzed Suzuki-Miyaura reaction of carboxylic-phosphoric anhydrides via highly selective C(O)-O bond cleavage under inorganic base-free conditions has been reported. Carboxylic-phosphoric anhydrides, generated through activating carboxylic acids using phosphates by esterification or direct dehydrogenative reaction with phosphites, have been employed as highly reactive electrophiles for Suzuki-Miyaura cross-coupling reactions. Broad substrate scope and excellent functional group tolerance have been demonstrated to be a general and practical approach for the synthesis of highly valuable ketones.

Decarbonylative borylation of aryl anhydrides via rhodium catalysis

Decarbonylative borylation of aryl anhydrides by rhodium catalysis has been reported. A base-free system with Rh(PPh3)3Cl as a catalyst enables the efficient synthesis of various arylboronate esters from readily available aryl anhydrides. The reaction involves the cleavage of C(O)-O bonds and the formation of C-B bonds. The experimental results demonstrated that compared with carboxylic acids, amides, and esters, anhydrides have higher reactivity in the decarbonylative borylation reaction under the current conditions. Furthermore, compared with the reported palladium-catalyzed borylation reaction of aryl anhydrides, the present rhodium-catalyzed method has the advantages of a shorter reaction time and a lower reaction temperature.

Palladium-Catalyzed Decarbonylative Sonogashira Alkynylation of Carboxylic-Phosphoric Anhydrides

We report the first palladium-catalyzed decarbonylative alkynylation of carboxylic-phosphoric anhydrides via highly selective C(O)-O bond cleavage. Carboxylic-phosphoric anhydrides are highly active carboxylic acid derivatives, which are generated through activating carboxylic acids using phosphates by esterification or direct dehydrogenative coupling with phosphites. Highly valuable internal alkynes have been generated by the present method, and the efficiency of this approach has been demonstrated through a wide substrate scope and excellent functional group tolerance.

Heterogeneously catalyzed decarbonylation of thioesters by supported Ni, Pd, or Rh nanoparticle catalysts

Decarbonylation of thioesters has been actively studied using homogeneous metal catalysts as an attractive approach for synthesizing thioethers, which are widely utilized in various fields, because decarbonylation ideally requires no additives and produces CO as the sole theoretical byproduct. However, heterogeneously catalyzed decarbonylation of thioesters has not been reported to date, despite its importance for the construction of environmentally-friendly and practical catalytic systems. This study demonstrated a heterogeneously catalyzed system for the decarbonylation of various aryl thioesters to produce thioethers and CO by utilizing CeO2- or hydroxyapatite-supported Ni, Pd, or Rh nanoparticle catalysts. The Ni catalysts showed high catalytic activity, while the Pd catalysts possessed excellent functional group tolerance. The Rh catalysts were suitable for the selective decarbonylation of unsymmetrically substituted thioesters.

Synthesis of acyl fluorides through deoxyfluorination of carboxylic acids

A direct deoxyfluorination of carboxylic acids by utilizing inorganic potassium fluoride (KF) as a safe and inexpensive fluoride source has been developed. Both aryl carboxylic acids and cinnamyl carboxylic acids could be efficiently transformed into valuable acyl fluorides in moderate to high yields with good functional group tolerance. A scale-up reaction could be carried out smoothly under solvent-free conditions, which further demonstrated the practicality of this reaction in organic synthesis.

Palladium-Catalyzed Decarbonylative Annulation of 2-Arylbenzoic Acids with Internal Alkynes toward Phenanthrenes

A palladium-catalyzed decarbonylative annulation of 2-arylbenzoic acids with internal alkynes via C(sp2)-H activation has been developed. A series of phenanthrenes were produced in moderate to good yield with good functional group tolerance. The mechanism study indicated that the C(sp2)-H activation should be the rate-determining step during the reaction.

Synthesis and Functionalization of Thiophosphonium Salts: A Divergent Approach to Access Thioether, Thioester, and Dithioester Derivatives

Herein, we report a straightforward practical method for efficiently obtaining a diverse range of thiophosphonium salts. This method involves the direct coupling of commercially available thiols and aldehydes with Ph3P and TfOH. The setup is simple and carried out in a metal-free manner. The synthetic utility of these salts is demonstrated through various examples of C-P bond functionalizations, enabling the synthesis of thioether, deuterated thioether, thioester, and dithioester derivatives. These products, which serve as valuable building blocks, are obtained in high yields.

Visible-Light/Nickel-Catalyzed Carboxylation of C(sp2) Bromides via Formate Activation

A new visible-light-driven method for the carboxylation of (hetero)aryl/vinyl bromides has been developed using catalytic 4CzIPN, nickel, phenyl triflimide, and sodium formate as a carboxylation agent. Interestingly, we found catalytic phenyl triflimide plays an essential role in promoting the reaction. While many C(sp²) carboxylation reactions require harsh reagents or gaseous carbon dioxide, we demonstrate the mild and facile construction of carboxylic acids from readily available starting materials.

Metal-free highly chemo-selective bisphosphorylation and deoxyphosphorylation of carboxylic acids

Carboxylic acids are readily available in both the natural and synthetic world. Their direct utilization for preparing organophosphorus compounds would greatly benefit the development of organophosphorus chemistry. In this manuscript, we describe a novel and practical phosphorylating reaction under transition metal-free reaction conditions that can selectively convert carboxylic acids into the P-C-O-P motif-containing compounds through bisphosphorylation, and the benzyl phosphorus compounds through deoxyphosphorylation. This strategy provides a new route for carboxylic acid conversion as the alkyl source, enabling highly efficient and practical synthesis of the corresponding value-added organophosphorus compounds with high chemo-selectivity and wide substrate scope, including the late modification of complex APIs (active pharmaceutical ingredients). Moreover, this reaction also indicates a new strategy for converting carboxylic acids into alkenes by coupling this work and the subsequent WHE reaction with ketones and aldehydes. We anticipate that this new mode of transforming carboxylic acids will find wide application in chemical synthesis.

Nonbasic Synthesis of Thioethers via Nickel-Catalyzed Reductive Thiolation Utilizing NBS-Like N-Thioimides as Electrophilic Sulfur Donors

The nonbasic synthesis of unsymmetrical thioethers via nickel-catalyzed reductive thiolation between aryl(hetero) iodides and N-thioimides is illustrated. N-Bromosuccinimide (NBS)-like N-thioimides were found quite reactive toward thiolation with carbon electrophiles, and a series of structurally varied thioethers were successfully prepared under mild reaction conditions. The transformation was featured with the new application of the NBS-like reagents, good functional group tolerance, and late-stage modification of biologically active scaffolds, thus providing an expeditious and efficient platform to construct polyfunctional thioethers.

Palladium-catalysed deaminative/decarboxylative cross-coupling of organoammonium salts with carboxylic acids

A palladium-catalysed carbon-carbon bond-forming reaction via deaminative/decarboxylative cross-coupling of organoammonium salts with carboxylic acids was developed. Under the reaction conditions, polyfluoroaromatic carboxylic acids, propiolic acids and α-cyano benzyl carboxylic acid reacted smoothly with benzyl ammonium salts to produce the corresponding carbon-carbon coupling products in good-to-excellent yields.

Palladium-Catalyzed Decarbonylative Cyanation of Carboxylic Acids with TMSCN

The direct decarbonylative cyanation of benzoic acids with TMSCN was achieved through palladium catalysis. By this strategy, a wide range of nitriles including those with functional groups was synthesized in good to high yields. Moreover, this reaction applied to modifying bioactive molecules such as adapalene, probenecid, telmisartan, and 3-methylflavone-8-carboxylic acid. These results demonstrate that this new reaction has potential synthetic value in organic synthesis.