Palladium-catalyzed regioselective carbonylation of 2-amino-2,3-diphenylpropanoate to 5/6-membered benzolactams

Five/six-membered benzolactams are significant blocks in both organic and medicinal chemistry. Achieving 5/6-membered benzolactams from the same starting compound under varying reaction conditions presents a significant challenge. Herein, palladium-catalyzed free amine-oriented regioselective C-H activations/carbonylations mediated by hexacarbonylmolybdenum, leading to diverse sizes of benzolactams, respectively, have been developed. Six-membered dihydroisoquinolinones can be obtained selectively in acetic acid using benzoquinone as an oxidant. While unfavorable five-membered isoindolinones were formed in the presence of Cu(II) as an oxidant and dihydrooxazole ligands in 1,2-dichlorobenzene. The substituents on the phenyl ring also had a great influence on the regioselectivity of the reaction. In addition, an asymmetric version of the reaction has also been attempted preliminarily.

De Novo Synthesis of α-Ketoamides via Pd/TBD Synergistic Catalysis

Precisely controlling the product selectivity of a reaction is an important objective in organic synthesis. α-Ketoamides are vital intermediates in chemical transformations and privileged motifs in numerous drugs, natural products, and biologically active molecules. The selective synthesis of α-ketoamides from feedstock chemicals in a safe and operationally simple manner under mild conditions is a long-standing catalysis challenge. Herein, an unprecedented TBD-switched Pd-catalyzed double isocyanide insertion reaction for assembling ketoamides in aqueous DMSO from (hetero)aryl halides and pseudohalides under mild conditions is reported. The effectiveness and utility of this protocol are demonstrated by its diverse substrate scope (93 examples), the ability to late-stage modify pharmaceuticals, scalability to large-scale synthesis, and the synthesis of pharmaceutically active molecules. Mechanistic studies indicate that TBD is a key ligand that modulates the Pd-catalyzed double isocyanide insertion process, thereby selectively providing the desired α-ketoamides in a unique manner. In addition, the imidoylpalladium(II) complex and α-ketoimine amide are successfully isolated and determined by X-ray analysis, confirming that they are probable intermediates in the catalytic pathway.

Pd-catalyzed CO-free double carbonylation for the synthesis of 1,4-ketoesters with Mo(CO)6 as the carbonyl source

An unprecedented Pd-catalyzed CO-free double carbonylation using Mo(CO)6 as a safe carbonyl source for the efficient synthesis of 1,4-ketoesters in an atom- and step-economic manner has been developed. The current method features operational safety, a wide substrate range, good functional group compatibility and easy scale-up. The application of carbonylation using a safe carbonyl source for the synthesis of biologically and synthetically useful carbonyl-containing molecules is underway in our lab.

P-Stereogenic Phosphorus Ligands in Asymmetric Catalysis

Chiral phosphorus ligands play a crucial role in asymmetric catalysis for the efficient synthesis of useful optically active compounds. They are largely categorized into two classes: backbone chirality ligands and P-stereogenic phosphorus ligands. Most of the reported ligands belong to the former class. Privileged ones such as BINAP and DuPhos are frequently employed in a wide range of catalytic asymmetric transformations. In contrast, the latter class of P-stereogenic phosphorus ligands has remained a small family for many years mainly because of their synthetic difficulty. The late 1990s saw the emergence of novel P-stereogenic phosphorus ligands with their superior enantioinduction ability in Rh-catalyzed asymmetric hydrogenation reactions. Since then, numerous P-stereogenic phosphorus ligands have been synthesized and used in catalytic asymmetric reactions. This Review summarizes P-stereogenic phosphorus ligands reported thus far, including their stereochemical and electronic properties that afford high to excellent enantioselectivities. Examples of reactions that use this class of ligands are described together with their applications in the construction of key intermediates for the synthesis of optically active natural products and therapeutic agents. The literature covered dates back to 1968 up until December 2023, centering on studies published in the late 1990s and later years.

Recent advances in Pd-catalyzed asymmetric cyclization reactions

Over the past few decades, there have been major developments in transition metal-catalyzed asymmetric cyclization reactions, enabling the convenient access to a wide spectrum of structurally diverse chiral carbo- and hetero-cycles, common skeletons found in fine chemicals, natural products, pharmaceuticals, agrochemicals, and materials. In particular, a plethora of enantioselective cyclization reactions have been promoted by chiral palladium catalysts owing to their outstanding features. This review aims to collect the latest advancements in enantioselective palladium-catalyzed cyclization reactions over the past eleven years, and it is organized into thirteen sections depending on the different types of transformations involved.

Enantioselective Palladium-Catalyzed Domino Carbonylative Heck Esterification of o-Iodoalkenylbenzenes with Arylboronic Acids

The current investigation presents an innovative palladium-catalyzed asymmetric carbonylative Heck esterification method. This approach facilitates the efficient synthesis of various chiral γ-ketoacid esters by utilizing o-alkenyliodobenzenes and arylboronic acids as primary substrates. This reaction achieves the creation of three carbon-carbon bonds, two carbon-oxygen bonds, and the establishment of a quaternary carbon center within a single step. The α-chiral γ-ketoacid esters were obtained in yields ranging from good to high yields, displaying enantiomeric excesses (ee's) levels up to 92% under mild reaction conditions.

Photoinduced Five-Component Radical Relay Aminocarbonylation of Alkenes

Radical single carbonylation reactions with CO constitute a direct and robust strategy toward various carbonyl compounds from readily available chemicals, and have been extensively studied over the past decades. However, realizing highly selective catalytic systems for controlled radical double carbonylation reactions has remained a substantial challenge, particularly for the more advanced multicomponent variants, despite their great potential value. Herein, we report a visible-light-driven radical relay five-component radical double aminocarbonylation reaction of unactivated alkenes using CO under metal-free conditions. This protocol provides direct access to valuable γ-trifluoromethyl α-ketoamides with good yields and high chemoselectivity. Crucial was the identification of distinct dual roles of amine coupling partners, sequentially acting as electron donors for the formation of photoactive electron donor-acceptor (EDA) complexes with radical precursors and then as a CO acceptor via nitrogen radical cations to form carbamoyl radicals. Cross-coupling of carbamoyl radicals with the acyl radicals that are formed in an alkene-based relay process affords double aminocarbonylation products.

Palladium-Catalyzed Carbonylative Dearomatization of Indoles to Achieve Carbonyl-Containing Spirocyclic Indolenines Bearing an All-Carbon Quaternary Center

A Pd-catalyzed carbonylative dearomatization via an acyl Pd complex has been developed. Diversified carbonyl-containing spirocyclic indolenines with an all-carbon quaternary center were constructed in an efficient and straightforward way with good to excellent yields. The protocol features a simple catalytic system, operational simplicity, a broad substrate scope, easy scale-up, and versatile transformations. In addition, the asymmetric reaction was initially explored with moderate enantioselectivity.

Regioselective C-H Active Carbonylation via 1,4-Palladium Migration

We report a highly regioselective three-component coupling reaction of styrene, CO gas, and an amine compound to synthesize multisubstituted α,β-unsaturated amides, which involves a palladium-catalyzed sequential 1,4-palladium migration, C(sp²)-H activation, carbonylation, and amination. Salient features of this strategy include the use of 1 atm of CO, excellent stereochemistry, and good functional group tolerance. Further, a series of control experiments and density functional theory calculations were performed to afford some insights for the transfer mechanism.

Palladium-Catalyzed Carbonylative Hiyama-Denmark Reaction toward the Synthesis of Aryl Carbonyl-Containing Oxindoles

A palladium-catalyzed domino Heck cyclization/carbonylative Hiyama-Denmark cross-coupling reaction between alkene-tethered aryl iodides and silylcarboxylic acids is presented. This reaction proceeds well without toxic carbon monoxide (CO) gas and has good functional group tolerance, providing an alternative access to carbonyl-containing oxindoles. In this transformation, silylcarboxylic acids play a dual role as a CO source and a nucleophile.

Synthesis of 7-Arylthiomethyl Dibenzo[b,d]azepines through Imidoylative Heck Cyclization and CPA-Catalyzed Thio-Michael Addition/Enantioselective Protonation

A chiral phosphoric acid-catalyzed thio-Michael addition/enantioselective protonation has been developed for the first time. The reaction applies 7-methylene-6-aryl-7H-dibenzo[b,d]azepines, products of Pd-catalyzed imidoylative Heck cyclization, as Michael acceptors in reactions with a wide range of aryl thiols. Diversified 7-[(arylthio)methyl]-7H-dibenzo[b,d]azepines bearing a benzylic stereocenter and a thermodynamically regulated biaryl axis were produced with good to excellent enantioselectivity and 14-25:1 diastereoisomeric ratios.

Copper-Catalyzed Substrate-Controlled Carbonylative Synthesis of α-Keto Amides and Amides from Alkyl Halides

Controllable production of α-keto amides and amides from the same substrates is an attractive goal in the field of transition-metal-catalyzed (double-)carbonylation. Herein, a novel copper-catalyzed highly selective double carbonylation of alkyl bromides has been developed. Moderate to good yields of α-keto amides were obtained as the only products. In the case of alkyl iodides, double- and mono-carbonylation can be achieved controllably under different conditions.