Palladium Catalyzed Dicarbonylation of α-Iodo-Substituted Alkylidenecyclopropanes: Synthesis of Carbamoyl Substituted Indenones

Transition Metal-Catalyzed Aminocarbonylation Reactions

Transition-metal-catalyzed aminocarbonylation reactions using low-cost and accessible CO gas as a C1 building block and amine as a nucleophile have been widely used to prepare amides, which are broadly exist in bioactive drugs, natural products, and polymers. This type of reaction has also been applied to construct various biologically active heterocycles. In this review, we highlight aminocarbonylation reactions involving amine and CO under various transition metal catalysis systems (palladium, rhodium, ruthenium, iridium, iron, copper, and cobalt) over the past decade.

Oxidative [4+2] Annulation of Pyrrole-2-carbaldehyde Derivatives with o-Hydroxyphenyl Propargylamines: Syntheses of 5,6,7-Trisubstituted Indolizines

A base promoted oxidative [4+2] annulation of pyrrole-2-carbaldehyde derivatives with o-hydroxyphenyl propargylamines for the synthesis of highly substituted indolizines has been developed. Using DBN as base, a broad range of 5,6,7-trisubstituted indolizines have been prepared in good to excellent yields under mild conditions, and many useful functional groups can be tolerated.

Novel thiosemicarbazide-based β-carboline derivatives as α-glucosidase inhibitors: Synthesis and biological evaluation

In the quest for potent α-glucosidase inhibitors to combat diabetes, a series of novel thiosemicarbazide-based β-carboline derivatives (CTL1∼36) were synthesized and evaluated. CTL1∼36 exhibited remarkable inhibitory effects against α-glucosidase, with IC50 values ranging from 2.81 to 12.40 μM, significantly surpassing the positive control acarbose (IC50 = 564.28 μM). Notably, CTL26 demonstrated the most potent inhibition (IC50 = 2.81 μM) and was characterized as a non-competitive inhibitor. Through a combination assay with fluorescence quenching, 3D fluorescence spectra, CD spectra, and molecular docking, we elucidated that CTL26 formed a complex with α-glucosidase via hydrogen bondings and hydrophobic interactions, leading to α-glucosidase conformation changes that impaired enzymatic activity. In vivo studies revealed that oral administration of CTL26 (25 and 50 mg/kg/d) reduced fasting blood glucose levels, enhanced glucose tolerance, and ameliorated lipid abnormalities in diabetic mice. These findings positioned CTL26 as a promising candidate for the development of α-glucosidase inhibitors with anti-diabetic potential.

Palladium-Catalyzed Cascade Carbonylation Reaction: Synthesis of Fused Isoindolinones

A palladium-catalyzed cascade carbonylation reaction of 2-bromo-N-(2-iodophenyl)benzamides with benzylidenecyclopropanes for the synthesis of fused isoindolinone derivatives has been developed. A broad range of 6/5/6/6 tetracyclic isoindolinone products were efficiently prepared in moderate to good yields with diverse substitution. Two carbonyl groups were incorporated into the substrates in a single step with the formation of four carbon-carbon bonds and two carbon-heteroatom bonds.

Synthesis of Multisubstituted 2,3-Allenamides via Palladium-Catalyzed Carbonylation of Propargylic Esters

2,3-Allenamides are an important class of unsaturated group-substituted carbonyl compounds. A palladium-catalyzed aminocarbonylation of propargyl acetates with amines for the synthesized tri-/tetrasubstituted 2,3-allenamides has been developed. A broad range of tri-/tetrasubstituted 2,3-allenamides have been prepared from propargyl acetates in good to excellent yields. The reaction featured mild reaction conditions and good functional group tolerance. The applicability of this methodology was further highlighted by the late-stage modification of several natural products and pharmaceuticals.

Enantio- and Regioselective Cascade Hydroboration of Methylenecyclopropanes for Facile Access to Chiral 1,3- and 1,4-Bis(boronates)

Chiral 1, n-bis(boronate) plays a crucial role in organic synthesis and medicinal chemistry. However, their catalytic and asymmetric synthesis has long posed a challenge in terms of operability and accessibility from readily available substrates. The recent discovery of the C═C bond formation through β-C elimination of methylenecyclopropanes (MCP) has provided an exciting opportunity to enhance molecular complexity. In this study, the catalyzed asymmetric cascade hydroboration of MCP is developed. By employing different ligands, various homoallylic boronate intermediate are obtained through the hydroboration ring opening process. Subsequently, the cascade hydroboration with HBpin or B2pin2 resulted in the synthesis of enantioenriched chiral 1,3- and 1,4-bis(boronates) in high yields, accompanied by excellent chemo- and enantioselectivities. The selective transformation of these two distinct C─B bonds also demonstrated their application potential in organic synthesis.

Palladium-Catalyzed Three-Component Cascade Carbonylation Reaction to Construct Benzofuran Derivatives

A novel three-component cyclization carbonylation reaction of iodoarene-tethered propargyl ethers with amine and CO is reported. This palladium-catalyzed cascade reaction undergoes a sequence of oxidative addition, unsaturated bond migration, carbonyl insertion, and nucleophilic attack to deliver the benzofuran skeleton. Both aromatic amines and aliphatic amines could proceed smoothly in this transformation under one atm of CO.

Ruthenium-Catalyzed Carbonylation of α-Aminoaryl-Tethered Alkylidenecyclopropanes: Synthesis of Eight-Membered Benzolactams

The synthesis of medium-sized lactams is a great challenge because of the unfavorable transannular interactions and entropic barriers in the transition state. We have developed a ruthenium-catalyzed carbonylation of α-aminoaryl-tethered alkylidenecyclopropanes (ACPs) that allows for the efficient preparation of valuable eight-membered benzolactams under ligand-free conditions. The amino group served a dual role of both directing group and nucleophile to facilitate the metallacycle formation and the carbonylation.

Palladium-catalyzed Enantio- and Regioselective Ring-Opening Hydrophosphinylation of Methylenecyclopropanes

Transition metal-catalyzed hydrofunctionalization of methylenecyclopropanes (MCP) has presented a considerable challenge due to the difficult manipulation of regioselectivity and complicated reaction patterns. Herein, we report a straightforward Pd-catalyzed ring-opening hydrophosphinylation reaction of MCP via highly selective C-C bond cleavage. This allows for rapid and efficient access to a wide range of chiral allylic phosphine oxides in good yields and high enantioselectivities. Additionally, density functional theory (DFT) calculations were performed to elucidate the reaction mechanism and the origin of product 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.

Pd/Cu catalyzed carbonylation of α-aminoaryl-tethered alkylidenecyclopropanes: synthesis of furoquinoline derivatives

A Pd/Cu catalyzed carbonylation of α-aminoaryl-tethered ACPs for the synthesis of furoquinoline derivatives has been developed. Oxygen was used as the terminal oxidant.