Marnix van der Kolk

A non-directed ortho-olefination reaction was developed using tri-isobutyl silicon-protected phenols as substrates, palladium acetate as the catalyst, and inexpensive pyridine derivatives as ligands. Importantly, bioactive molecules such as hydroquinone, hexylresorcin, and estradiol were able to be modified to increase the applicability of the reaction. Finally, simple reaction conditions were adopted to remove the protective group, which further demonstrates the practical applicability of the reaction.

Abstract

Herein, we report an undirected ortho-olefination reaction using tri-isobutyl silicon-protected phenol as the substrate, palladium acetate as the catalyst, and inexpensive pyridine derivatives as ligands. Various phenols were tolerated well, affording the olefinated product in moderate to good yields. Importantly, bioactive compounds such as hexyl-methoxyphenol and estradiol were tolerated, highlighting the synthetic importance of this method.

The arylation of azaheterocycles can be considered as one of the most important processes for the preparation of various biologically active compounds. In the present work, we describe a method for the copper-catalyzed N-arylation of hindered oxazolidinones using diaryliodonium salts. The method succeeds in good to excellent yields for the arylation of 4-alkyloxazolidinones, including sterically hindered isopropyl- and tert-butyl-substituted representatives. The efficiency of the method was demonstrated for a wide range of diaryliodonium salts - symmetric and unsymmetric as well as ortho-substituted. The developed approach can provide an important contribution in the development and preparation of novel drugs and bioactive molecules containing oxazolidinone moieties.

Publication date: 1 December 2022

Source: Catalysis Today, Volumes 405–406

Author(s): Yumeng Xia, Zehua Li, Ying Li, Kai Cai, Yunduo Liu, Jing Lv, Shouying Huang, Xinbin Ma

Living systems can perceive and respond to environmental stimuli through multiple reaction pathways. Mimicking such adaptability from nature is highly envisioned in artificial intelligent chemical devices. However, the inconsistency of reaction conditions hampers the effective coupling of hybridized system with multiple reaction pathways. Herein, we reported a CuSAC6N6 single-atom catalyst with multiple oxygen-oriented reaction pathways that emerged as an intriguing way to address the challenges of conditions inconsistency. CuSAC6N6 could not only drive primary substrate oxidation with Cu-bound oxygen as intermediates but also undertake a second gain reaction under light stimuli, involving intermediates of free reactive oxygen species (ROS) under the same conditions. Notably, CuSAC6N6 demonstrated remarkable primary activity and a superb gain of up to 3.6 times under light stimuli. It was significantly higher by a factor of 80% than that under acknowledged temperature inducement with an increase of 30 oC from room temperature. As a proof-of-concept application, under light stimuli of different intensities, CuSAC6N6 was successfully applied to a single glucose sensor with adjustable sensitivity (5×10^-6 - 6×10^-3 M) and limit of detection (1.20-195.02 μM) precisely response to a diverse range of concentrations in vitro.

In metal hydride-catalyzed alkene hydrofunctionalization reactions via hydrogen atom transfer (HAT), simple carbonyl groups have been well recognized as good somophiles at the carbon for C–C bond formation. Here we report an alternative pathway exploring the carbonyl as an O-nucleophile to make new C–O bonds during the CoH-catalyzed oxidative cyclization of alkenyl aldehydes. This reaction provides a rapid, mild, modular, and stereoselective (up to > 20:1) entry to saturated O-heterocycles via nucleophilic trapping of an in situ formed oxocarbenium intermediate. The key to overriding the carbonyl’s innate somophilicity was found to be promoting the formation of organocobalt species and suppressing degenerative transfer.

In the presence of KI, aryl diazonium salts are suitable substrates for Catellani-type ortho arylation and amination reactions, allowing for the quick construction of multifunctionalized aromatic products.

Abstract

The palladium/norbornene co-catalyzed difunctionalization of haloarenes provides a facile and efficient method for the synthesis of polyfunctional aromatic compounds. However, the suitable substrates for such a transformation have been strictly limited to haloarenes. We here demonstrate that aryl diazonium salts could be well employed as substrates in these reactions, enabling arylbromides with electron-withdrawing groups to be used as cross-coupling partners.

Single-Atom Alloys (SAAs) have recently emerged as highly active and selective alloy catalysts. Unlike pure metals, SAAs escape the well-established conceptual framework developed nearly three decades ago for predicting catalytic performance. Here, based on high throughput density functional theory calculations, we reveal a 10-electron count rule for the binding of adsorbates on the dopant of SAA surfaces. A simple molecular orbital approach rationalises this rule and the nature of the adsorbate/dopant interaction. In addition, our intuitive model can accelerate the rational design of SAA catalysts. Indeed, we illustrate how the unique insights provided by the electron count rule help identify the most promising dopant for an industrially relevant hydrogenation reaction, thereby reducing the number of potential materials by more than one order of magnitude.

The functionalization of unactivated C-H bonds at will for the strategic introduction of bonds or functionalities have been a matter of extensive investigation for the last couple of decades. We have come across a substrate namely, 5-benzoyl-pyrrolo[2,1-a]isoquinoline in which three different functionalizable C-H bonds were identified that could be judiciously transformed site selectively for the generation of complex polyring fused N-heterocycles. At first, we attempted a Pd-catalyzed cross-dehydrogenative coupling in 5-benzoyl-pyrrolo[2,1-a]isoquinoline towards the synthesis of 8H-indeno-pyrrolo[2,1-a]isoquinolinones. Later, we identified a hitherto unknown oxygen induced palladium catalyzed selective C-H amination in 5-benzoyl-pyrrolo[2,1-a]isoquinoline towards a pentacene viz., 9H-indolo-pyrrolo[2,1-a]isoquinoline. Finally, we came across an unexpected site selective C-H amination towards the formation of multiring fused benzazepine which is believed to form due to its stability and to the higher electron density at the reaction centre on isoquinoline ring.

Publication date: November 2022

Source: Journal of Catalysis, Volume 415

Author(s): Yang Chen, Qiang Wan, Liru Cao, Zhe Gao, Jian Lin, Lin Li, Xiaoli Pan, Sen Lin, Xiaodong Wang, Tao Zhang

N-Boc-N-propargylthiazol-2-amines can be converted in one step and in multicomponent fashion to high value added imidazo[2,1-b]thiazole derivatives, when allowed to react with CO, a secondary amine, and O₂ under the catalysis of PdI₂/KI. The process, leading to 2-(imidazo[2,1-b]thiazol-5-yl)-N,N-dialkylacetamides in yields up to 87 %, occurs through an ordered sequence of steps, involving N-deprotection, oxidative aminocarbonylation of the triple bond, dearomative cyclization, and aromative isomerization.

Abstract

We report a direct, multicomponent approach to an important class of fused-ring heterocycles, namely, imidazo[2,1-b]thiazole derivatives starting from simple and readily available building blocks (N-Boc-N-propargylthiazol-2-amines, carbon monoxide, a secondary amine, and oxygen). The process takes place under the catalysis of the simple PdI₂/KI system under relatively mild conditions (100 °C under 20 atm of a 4 : 1 mixture of CO-air), and leads to 2-(imidazo[2,1-b]thiazol-5-yl)-N,N-dialkylacetamides in yields up to 87 %. The mechanistic pathway leading to carbonylated imidazo[2,1-b]thiazole occurs through an ordered sequence of steps, involving amine-induced N-deprotection, oxidative aminocarbonylation of the triple bond (with Csp−H activation and formation of a 2-ynamide intermediate), dearomative cyclization (by intramolecular conjugate addition of thioazolic nitrogen to the 2-ynamide moiety) and aromatization by proton-shift isomerization. When starting from N-Boc-N-(propargyl)benzo[d]thiazol-2-amine, tricyclic benzimidazothiazoles were formed in moderate yields.

Dimethyl carbonate (DMC), an environmental-benign compound prepared from CO₂, shows diverse reactivity. In this communication, a palladium-catalyzed Intramolecular carbopalladation and Carbonylation has been explored for the synthesis of functionalized isoquinoline-1,3-diones and oxindoles by using DMC as both green solvent and reactant. Moreover, formic acid is employed as the CO source in this reaction.

Abstract

Dimethyl carbonate (DMC), a non-toxic liquid, which shows diverse and tunable reactivity in organic synthesis. Herein, we report a nice study on using DMC as both solvent and reactant in palladium-catalyzed intramolecular Heck/Carbonylation for the synthesis of functionalized isoquinoline-1,3-diones and oxindoles. To avoid the usage of toxic CO gas, formic acid is employed as the CO source, and a variety of functionalized isoquinoline-1,3-diones and oxindoles were obtained in very good yields.