Transition Metal-Catalyzed Transformations of Chalcones

Chalcones are a class of naturally occurring flavonoid compounds associated to a variety of biological and pharmacological properties. Several reviews have been published describing the synthesis and biological properties of a vast array of analogues. However, overviews on the reactivity of chalcones has only been explored in a few accounts. To fill this gap, a systematic survey on the most recent developments in the transition metal-catalyzed transformation of chalcones was performed. The chemistry of copper, palladium, zinc, iron, manganese, nickel, ruthenium, cobalt, rhodium, iridium, silver, indium, gold, titanium, platinum, among others, as versatile catalysts will be highlighted, covering the literature from year 2000 to 2023, in more than 380 publications.

Construction of Functionalized α-Imino Ketones via Pd-Catalyzed C-H Addition to Nitriles/Aerobic Oxidation Sequences

Pd(II)-catalyzed addition of sp2 C-H to nitrile/aerobic oxidation sequences for the preparation of functionalized α-imino ketones is described in which readily available heteroarenes and O-acyl cyanohydrins were employed. Various functionalized targeted molecules can be prepared in good yields with high atom and step economy. Moreover, a broad substrate scope and the ready manipulation and availability of the reaction partners enable this protocol to be appealing to explore the chemical space of the construction of functionalized α-imino ketones with high efficiency.

Moderately lipophilic 2-(Het)aryl-6-dithioacetals, 2-phenyl-1,4-benzodioxane-6-dithioacetals and 2-phenylbenzofuran-5-dithioacetals: Synthesis and primary evaluation as potential antidiabetic AMPK-activators

Since the 1950's, AMP-kinase (AMPK) has been used as a promising target for the development of antidiabetic drugs against Type 2 diabetes mellitus (T2D). Indeed, the canonical antidiabetic drug metformin recruits, at least partially, AMPK activation for its therapeutic effect. Herein we present design and synthesis of 20 novel relatively polar cyclic and acyclic dithioacetals of 2-(Het)arylchroman-6-carbaldehydes, 2-phenyl-1,4-benzodioxane-6-carbaldehyde, and 2-phenylbenzofuran-5-carbaldehyde, which were developed as potential AMPK activators. Three of the synthesized dithioacetals demonstrated significant enhancement (≥70%) of glucose uptake in rat L6 myotubes. Noteworthy, one of the dithioacetals, namely 4-(6-(1,3-dithian-2-yl)chroman-2-yl)pyridine, exhibited high potency comparing to other molecules. It increased the rate of glucose uptake in rat L6 myotubes and augmented insulin secretion from rat INS-1E cells in pharmacological relevant concentrations (up to 2 μM). Both effects were mediated by activation of AMPK. In addition, the compound showed excellent pharmacokinetic profile in healthy mice, including maximal oral bioavailability. Such bifunctionality (increased glucose uptake and insulin secretion) can be used as a starting point for the development of a novel class of antidiabetic drugs with dual activity that is relevant for T2D treatment.

Tf2O-Mediated Direct Synthesis of 4-Sulfenylated Oxazoles from β-Keto Sulfoxides and Nitriles

A general and efficient method for the synthesis of 4-sulfenylated oxazoles is described. Trisubstituted oxazoles are obtained in good to excellent yields from β-keto sulfoxides and nitriles. The mechanistic study suggests that the reaction proceeds via the nucleophilic addition of nitriles to the in situ formed α-carbonyl cation followed by intramolecular cyclization.

Palladium-catalyzed direct construction of oxazoline-containing polycyclic scaffolds via tandem addition/cyclization of nitriles and arylboronic acids

An efficient construction of oxazoline-containing polycyclic scaffolds through a Pd-catalyzed addition/cyclization of (hetero)arene tethered O-acyl cyanohydrin units and arylboronic acids is described.

Recent Advances in Transition-Metal-Catalyzed C–H Addition to Nitriles

Transition-metal-catalyzed C–H bond addition to nitriles has emerged as a powerful synthetic approach for the construction of C–C bonds in organic synthesis. Due to the merits of atom- and step-economy, as well the easy availability of the starting materials, these transformations not only deliver acyclic aryl ketone products with nitriles­ as C-building blocks, but can also be utilized for the highly efficient­ assembly of azaheterocyclic skeletons using nitriles as C–N building blocks. This short review summarizes recent progress on transition-metal-catalyzed C–C bond-forming reactions based on C(sp2)–H and C(sp3)–H additions to nitriles.

1 Introduction

2 Palladium-Catalyzed C–H Addition to Nitriles

2.1 Palladium-Catalyzed C–H Addition to Nitriles for the Preparation of Ketone (Imine) Products

2.2 Palladium-Catalyzed C–H Addition to Nitriles for the Preparation of Azaheterocycles

2.3 Palladium-Catalyzed C–H Addition to Nitriles/1,2-Rearangement

3 Other Transition-Metal-Catalyzed C–H Additions to Nitriles

4 Summary and Outlook

Palladium(II)-Catalyzed C(sp)–C(sp2) Coupling: A Direct Approach to Multi-Substituted Pyrrolo[1,2-a]pyrazines

A direct synthesis of multi-substituted pyrrolo[1,2-a]pyrazines via palladium(II)-catalyzed C(sp)–C(sp2) cascade coupling and intramolecular cyclization in the presence of ligand was developed. This reaction originates from phenylboronic acids and readily synthesized 2-carbonyl- or 2-formylpyrroloacetonitriles, and affords products in good to excellent yields for a diversity of substrates. Additionally, a possible mechanism for the transformation is proposed.

α-Iminol Rearrangement Triggered by Pd-Catalyzed C-H Addition to Nitriles Sequences: Synthesis of Functionalized α-Amino Cyclopentanones

A α-iminol rearrangement triggered by Pd-catalyzed C-H addition of electronic-rich heteroarenes to cyclobutanone-derived O-acyl cyanohydrins was described, which provided a practical and efficient protocol for the preparation of functionalized α-amino cyclopentanones in an atom- and step-economic fashion. In addition, further synthetic transformations of products have also been demonstrated.

Palladium-catalyzed C-H activation of simple arenes and cascade reaction with nitriles: access to 2,4,5-trisubstituted oxazoles

An efficient and straightforward protocol for the assembly of the pharmaceutically and biologically valuable oxazole skeleton is achieved for the first time from readily available simple arenes and functionalized aliphatic nitriles. This transformation involves palladium-catalyzed C-H activation, carbopalladation and a tandem annulation sequence in one pot. Notably, the reaction proceeds efficiently under redox-neutral conditions, and exhibits high atom-economy. Deuterium-labeling experiments suggested that C-H bond cleavage of the simple arenes might be the rate-determining step.

Synthesis of benzofuro- and benzothieno[2,3-c]pyridines via copper-catalyzed [4 + 2] annulation of ketoxime acetates with acetoacetanilide

An efficient copper-catalyzed annulation of ketoxime acetates with acetoacetanilide has been developed for the facile synthesis of benzofuro- and benzothieno[2,3-c]pyridines.

Palladium(ii)-catalyzed three-component tandem reactions: synthesis of multiply substituted quinolines

The three-component tandem reaction of 2-aminobenzonitriles, arylboronic acids and ketones as available reagents allowing the synthesis of polysubstitution quinolines is reported.

Selective Synthesis of β-Ketonitriles via Catalytic Carbopalladation of Dinitriles

A practical, convenient, and highly selective method of synthesizing β-ketonitriles from the Pd-catalyzed addition of organoboron reagents to dinitriles has been developed. This method provides excellent functional-group tolerance, a broad scope of substrates, and the convenience of using commercially available substrates. The method is expected to show further utility in future synthetic procedures.

Fe3O4@GlcA@Cu-MOF: A Magnetic Metal-Organic Framework as a Recoverable Catalyst for the Hydration of Nitriles and Reduction of Isothiocyanates, Isocyanates, and Isocyanides

A novel magnetic metal-organic framework (Fe₃O₄@GlcA@Cu-MOF) has been prepared and characterized by spectroscopic, microscopic, and magnetic techniques. This magnetically separable catalyst exhibited high catalytic activity for nitrile hydration and the ability to reduce isothiocyanates, isocyanates, and isocyanides with excellent activity and selectivity without any additional reducing agent.

Palladium-catalyzed tandem reaction of epoxynitriles with arylboronic acids in aqueous medium: divergent synthesis of furans and pyrroles

A palladium-catalyzed controllable divergent synthesis of furans and pyrroles through a cascade reaction of epoxynitriles with arylboronic acids has been developed in the aqueous phase.