Functional Group Transposition: A Palladium-Catalyzed Metathesis of Ar-X σ-Bonds and Acid Chloride Synthesis

Palladium-catalyzed intermolecular transthioetherification of aryl halides with thioethers and thioesters

Functional group transfer reactions are an important synthetic tool in modern organic synthesis. Herein, we developed a new palladium-catalyzed intermolecular transthioetherification reaction of aryl halides with thioethers and thioesters. The synthetic utility and practicality of this catalytic protocol are demonstrated in a wide range of successful transformations (>70 examples). This catalytic protocol is applicable in carbonylative coupling processes as well, and the first example of carbonylative methylthioesterification of aryl halides has been achieved. Notably, this work also provides an approach to using natural products, such as methionine and selenomethionine, as the functional group sources.

Functional group transfer reactions are an important synthetic tool in modern organic synthesis.

Copper-catalysed three-component carboiodination of arynes: expeditious synthesis ofo-alkynyl aryl iodides

A copper-catalysed three-component reaction of arynes, terminal alkynes, and NIS provides an expeditious approach too-alkynyl aryl iodides.

Hydrogen bonding and non-covalent interaction assisted nickel(0) catalysed reversible alkenyl functional group swapping: a computational study

An extensive DFT study is carried out to explore the mechanistic pathways involved in nickel(0) catalysed functional group swapping, where the less substituted N-tosyl allylamine transforms into a more substituted N-tosyl allylamine product.

Redox-Neutral Decarbonylative Cross-Couplings Coming of Age

Major progress has recently been made in the challenging redox-neutral decarbonylative cross-coupling of carboxylic acids. For example, the use of acid fluorides as effective cross-coupling partners has been found to enable control of the decarbonylation selectivity and facilitates challenging Pd⁰ -catalyzed nucleophilic trifluoromethylation and exogenous base-free Suzuki cross-coupling reactions. In another recent advance, the use of acid chlorides in room temperature difluoromethylation and direct decarbonylative cross-coupling of carboxylic acids allows these classical substrates to be used as aryl electrophiles in cross-coupling reactions. Further challenges that are yet to be addressed in redox-neutral decarbonylative cross-couplings are also briefly summarized.

Highly-chemoselective step-down reduction of carboxylic acids to aromatic hydrocarbons via palladium catalysis

Aryl carboxylic acids are among the most abundant substrates in chemical synthesis and represent a perfect example of a traceless directing group that is central to many processes in the preparation of pharmaceuticals, natural products and polymers. Herein, we describe a highly selective method for the direct step-down reduction of carboxylic acids to arenes, proceeding via well-defined Pd(0)/(ii) catalytic cycle. The method shows a remarkably broad substrate scope, enabling to direct the classical acyl reduction towards selective decarbonylation by a redox-neutral mechanism. The utility of this reaction is highlighted in the direct defunctionalization of pharmaceuticals and natural products, and further emphasized in a range of traceless processes using removable carboxylic acids under mild, redox-neutral conditions orthogonal to protodecarboxylation. Extensive DFT computations were conducted to demonstrate preferred selectivity for the reversible oxidative addition and indicated that a versatile hydrogen atom transfer (HAT) pathway is operable.

Enantioselective Cross-Exchange between C-I and C-C σ Bonds

A palladium-catalyzed enantioselective intramolecular σ-bond cross-exchange between C-I and C-C bonds is realized, providing chiral indanones bearing an alkyl iodide group and an all-carbon quaternary stereocenter. Pd/TADDOL-derived phosphoramidite is found to be an efficient catalytic system for both C-C bond cleavage and alkyl iodide reductive elimination. In addition to aryl iodides, aryl bromides can also be used for this transformation in the presence of KI. Density-functional theory (DFT) calculation studies support the ring-opening of cyclobutanones occuring through an oxidative addition/reductive elimination process involving Pd^IV species.

Decarboxylation with Carbon Monoxide: The Direct Conversion of Carboxylic Acids into Potent Acid Triflate Electrophiles

We report a new strategy for the conversion of carboxylic acids into potent acid triflate electrophiles. The reaction involves oxidative carbonylation of carboxylic acids with I₂ in the presence of AgOTf, and is postulated to proceed via acyl hypoiodites that react with CO to form acid triflates. Coupling this chemistry with subsequent trapping with arenes offers a mild, room temperature approach to generate ketones directly from broadly available carboxylic acids without the use of corrosive and reactive Lewis or Bronsted acid additives, and instead from compounds that are readily available, stable, and functional group compatible.

Palladium-Catalyzed Carbon Isotope Exchange on Aliphatic and Benzoic Acid Chlorides

An operationally simple protocol for a palladium-catalyzed ¹³CO and ¹⁴CO exchange with activated aliphatic and benzoic carbonyls is presented. Several ¹³C and ¹⁴C building blocks, natural product derivatives, and pharmaceuticals have been prepared to showcase the method for late-stage carbon isotope incorporation and its functional group compatibility.