Green and Efficient: Iron-Catalyzed Selective Oxidation of Olefins to Carbonyls with O₂

A mild and operationally simple iron-catalyzed protocol for the selective aerobic oxidation of aromatic olefins to carbonyl compounds is described. Catalyzed by a Fe­(III) species bearing a pyridine bisimidazoline ligand at 1 atm of O₂, α- and β-substituted styrenes were cleaved to afford benzaldehydes and aromatic ketones generally in high yields with excellent chemoselectivity and very good functional group tolerance, including those containing radical-sensitive groups. With α-halo-substituted styrenes, the oxidation took place with concomitant halide migration to afford α-halo acetophenones. Various observations have been made, pointing to a mechanism in which both molecular oxygen and the olefinic substrate coordinate to the iron center, leading to the formation of a dioxetane intermediate, which collapses to give the carbonyl product

Dehydrogenative α‑Oxygenation of Ethers with an Iron Catalyst

Selective α-oxidation of ethers under aerobic conditions is a long-pursued transformation; however, a green and efficient catalytic version of this reaction remains challenging. Herein, we report a new family of iron catalysts capable of promoting chemoselective α-oxidation of a range of ethers with excellent mass balance and high turnover numbers under 1 atm of O₂ with no need for any additives. Unlike metalloenzymes and related biomimetics, the catalyst produces H₂ as the only byproduct. Mechanistic investigations provide evidence for an unexpected two-step reaction pathway, which involves dehydrogenative incorporation of O₂ into the ether to give a peroxobisether intermediate followed by cleavage of the peroxy bond to form two ester molecules, releasing stoichiometric H₂ gas in each step. The operational simplicity and environmental friendliness of this methodology affords a useful alternative for performing oxidation, while the unique ability of the catalyst in oxygenating a substrate via dehydrogenation points to a new direction for understanding metalloenzymes and designing new biomimetic catalysts

Dehydrogenative α‑Oxygenation of Ethers with an Iron Catalyst

Selective α-oxidation of ethers under aerobic conditions is a long-pursued transformation; however, a green and efficient catalytic version of this reaction remains challenging. Herein, we report a new family of iron catalysts capable of promoting chemoselective α-oxidation of a range of ethers with excellent mass balance and high turnover numbers under 1 atm of O₂ with no need for any additives. Unlike metalloenzymes and related biomimetics, the catalyst produces H₂ as the only byproduct. Mechanistic investigations provide evidence for an unexpected two-step reaction pathway, which involves dehydrogenative incorporation of O₂ into the ether to give a peroxobisether intermediate followed by cleavage of the peroxy bond to form two ester molecules, releasing stoichiometric H₂ gas in each step. The operational simplicity and environmental friendliness of this methodology affords a useful alternative for performing oxidation, while the unique ability of the catalyst in oxygenating a substrate via dehydrogenation points to a new direction for understanding metalloenzymes and designing new biomimetic catalysts

A New Phenoxide Chelated Ir^III N‑Heterocyclic Carbene Complex and Its Application in Reductive Amination Reactions

A new phenoxide chelated [Ir­(NHC)­Cp*Cl] (NHC = N-heterocyclic carbene; Cp* = pentamethylcyclopentadienyl) complex (<b>3</b>) has been prepared by reaction of [IrCp*Cl₂]₂ with an in situ prepared NHC–Ag complex in dichloromethane at ambient temperature. The Ir^III complex was stable toward air and moisture and was fully characterized by ¹H, ¹³C NMR, HRMS, and single-crystal X-ray diffraction. The new complex was found to be an active catalyst for transfer hydrogenative reductive amination under aqueous conditions with formate as hydrogen source as well as hydrogenative reductive amination reactions using H₂. Various carbonyl compounds such as aliphatic and aromatic ketones and aldehydes were successfully reacted with amines to give new amines. In comparison with transfer hydrogenative reductive amination, the reductive amination with H₂ is faster and permits higher molar ratios of the substrate to the catalyst (S/C)

Divergent Dehydrogenative Coupling of Indolines with Alcohols

The dehydrogenative coupling of indolines with alcohols catalyzed by an iridium complex has been achieved to afford both N- and C3-alkylated indoles selectively, by simply changing the addition time of a base additive. The iridacycle catalyst plays multiple roles in these reactions, which dehydrogenates both amines and alcohols and catalyzes the coupling reactions. Mechanistic studies reveal that a borrowing hydrogen-dehydrogenation process and a dehydrogenation-borrowing hydrogen process are involved in N-alkylation and C3-alkylation reactions, respectively. The C3-alkylation reaction involves the direct coupling of two sp3 carbon centers

Palladium-Catalyzed Ylidyl-Carbonylation of Aryl Halides To Produce α‑Acylphosphoranes

An efficient synthesis of α-acylphosphoranes by palladium-catalyzed carbonylation of aryl iodides with carbon monoxide and stabilized phosphonium ylides has been developed. Featuring 44 examples, the protocol displayed a wide substrate scope under mild reaction conditions, showcasing its potential in synthetic organic chemistry

Story of an Age-Old Reagent: An Electrophilic Chlorination of Arenes and Heterocycles by 1‑Chloro-1,2-benziodoxol-3-one

By the use of 1-chloro-1,2-benziodoxol-3-one, an age-old reagent, the practical and efficient chlorination method is achieved. This hypervalent iodine reagent is amenable not only to the chlorination of nitrogen-containing heterocycles but also to selected classes of arenes, BODIPY dyes, and pharmaceuticals. In addition, the advantages, such as easy preparation and recyclable, air- and moisture-stable, in combination with the success in a gram-scale experiment grant this reagent great potential for industrial application

Interaction between Poly(vinyl alcohol) and Layered Double Hydroxide (LDH) Particles with Different Topological Shape and Their Application in Electrospinning

To explore the influence of filler topological shape on the rheological behavior of poly­(vinyl alcohol) (PVA) aqueous solution, three kinds (nanosized layered crystals, microsized layered crystals, and nanoscrolls) of layered double hydroxides (LDHs) were synthesized. Except for nanosized layered crystals, both LDH microsized layered crystals and nanoscrolls filled system showed distinct “N” shape viscosity curves with increasing LDH loadings. Notably, the one-dimensional LDH nanoscrolls could increase or decrease the viscosity of PVA solution by only changing the loadings. With combined theoretical calculation with dynamic mechanical analyses, the adsorbed state of PVA chains on surface of the three LDH particles was proposed, in which PVA chains exhibited various adsorbed states due to different interactions between PVA chains and LDH particles with disparate topological shape. Taking the advantage of remarkable rheological modulation and adsorption capacity, LDH nanoscrolls were introduced into PVA aqueous solution to broaden effectively its electrospinnable concentration window from 8.5–11.3 wt % to 6.5–18.0 wt %. More importantly, the adsorption capacity of LDH nanoscrolls was well preserved in the as-electrospun composite nanofibers, implying a superior adsorbent for methyl orange from wastewater was obtained

Story of an Age-Old Reagent: An Electrophilic Chlorination of Arenes and Heterocycles by 1‑Chloro-1,2-benziodoxol-3-one

By the use of 1-chloro-1,2-benziodoxol-3-one, an age-old reagent, the practical and efficient chlorination method is achieved. This hypervalent iodine reagent is amenable not only to the chlorination of nitrogen-containing heterocycles but also to selected classes of arenes, BODIPY dyes, and pharmaceuticals. In addition, the advantages, such as easy preparation and recyclable, air- and moisture-stable, in combination with the success in a gram-scale experiment grant this reagent great potential for industrial application

DMF as Carbon Source: Rh-Catalyzed α‑Methylation of Ketones

An unprecedented Rh-catalyzed direct methylation of ketones with <i>N</i>,<i>N</i>-dimethyl­formamide (DMF) is disclosed. The reaction shows a broad substrate scope, tolerating both aryl and alkyl ketones with various substituents. Mechanistic studies suggest that DMF delivers a methylene fragment followed by a hydride in the methylation process