Mechanochemistry through high‐speed ball milling has become an increasingly popular method for performing organic transformations. This newfound interest in high‐speed ball milling is in part driven by the benefit of performing reactions in the absence of solvent. Mechanochemical reactions are often conducted in stainless‐steel vials with stainless‐steel balls. Since stainless steel is made of several readily oxidizable metals (Fe, Cr, and Ni), reduction reactions using water as a hydrogen source were explored using a temperature‐controlled mixer mill. Mechanistic studies suggest that the reduction proceeds via a single electron transfer (SET) pathway, with iron and nickel being essential components for the reaction.
Insights into Mechanochemical Reactions at Targetable and Stable, Sub‐ambient Temperatures
We provide insights into the effects of stable and verifiable, low‐temperature conditions on mechanochemical reactions. These are made possible by modifications made to a SPEX 8000
- NSF-PAR ID:
- 10074399
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Angewandte Chemie International Edition
- Volume:
- 57
- Issue:
- 40
- ISSN:
- 1433-7851
- Page Range / eLocation ID:
- p. 13062-13065
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
more » « less
Abstract -
more » « less
Abstract Finding a platinum‐free cathode catalyst that effectively models the oxygen reduction reaction (ORR) of a proton‐exchange membrane (PEM) fuel cell cathode better than the current commercial Pt/C catalyst has been a major shortcoming in fuel cell technology. Overall, a promising platinum‐free cathode catalyst must offer great ORR activity, ORR selectivity, and acid stability. Due to their enticing ORR activity and selectivity to the preferred four‐electron ORR pathway, the possible dissolution reactions and oxygen‐intermediate reactions of iron phthalocyanine monolayer supported on a pristine graphene (GFePc) and boron‐doped graphene substrate (BGFePc) have been studied to determine the stability as a function of potential and pH through spin‐polarized density functional theory (DFT) calculations at both infinitesimally low (10−9
m ) and 1m Fe2+/Fe3+ionic concentrations. BGFePc offers higher stability in both concentrations than GFePc. In both cases, the oxygen‐intermediates are more stable than the bare catalytic surface due to the metal d‐band center shifting further away from the Fermi level in the valence band state (higher energy of antibonding). Moreover, at an Fe2+ionic concentration, both catalysts would be stable in the potential and pH regions at the operating conditions of rotating disk electrode (RDE) experiments and PEM fuel cells. -
more » « less
Abstract One-pot reactions that combine non-enzymatic and biocatalytic transformations represent an emerging strategy in chemical synthesis. Some of the most powerful chemoenzymatic methodologies, although uncommon, are those that form a carbon–carbon (C–C) bond and a stereocenter at one of the reacting carbons, thereby streamlining traditional retrosynthetic disconnections. Here we report the one-pot, chemoenzymatic conversion of amides to enantioenriched alcohols. This transformation combines a nickel-catalyzed Suzuki–Miyaura coupling of amides in aqueous medium with an asymmetric, biocatalytic reduction to provide diarylmethanol derivatives in high yields and enantiomeric excesses. The synthetic utility of this platform is underscored by the formal syntheses of both antipodes of the pharmaceutical orphenadrine, which rely on ketoreductase enzymes that instill complementary stereoselectivities. We provide an explanation for the origins of stereoselectivity based on an analysis of the enzyme binding pockets.
-
more » « less
Abstract Here, an environmentally‐friendly and scalable process is reported to synthesize reduced graphene oxide (RGO) thin films for printed electronics applications. The films are produced by inkjet printing GO flakes dispersed binder‐free in aqueous solutions followed by treatment with a nonthermal, radio‐frequency (RF) plasma containing only argon (Ar) gas. The plasma process is found to heat the substrate to temperatures no greater than 138 °C, enabling RGO to be printed directly on a wide range of temperature‐sensitive substrate materials including photo paper. Unlike other low‐temperature methods such as electrochemical reduction, plasma reduction is friendly to moisture absorbent materials. Moreover, the plasma treatment can be performed on nonconducting substrates, eliminating the need for film transfer. From an applications perspective, the printed, plasma‐reduced RGO exhibits excellent electrical, mechanical, and electrochemical properties. As a technology demonstrator, the working electrodes of hydrogen peroxide (H2O2) sensors fabricated from plasma‐reduced GO show a sensitivity of 277 ± 80 µA m
m −1cm−2, which is comparable to RGO working electrodes made by electrochemical reduction. -
more » « less
Abstract The Stille cross‐coupling reaction is one of the most common strategies for the construction of C−C bonds. Despite notable strides in the advancement of the Stille reaction, persistent challenges persist in hindering its greener evolution. These challenges encompass multiple facets, such as the high cost of precious metals and ligands, the demand for various additives, and the slow reaction rate. In comparison to the dominant palladium‐catalysed Stille reactions, cost‐effective nickel‐catalysed systems lag behind, and enantioconvergent Stille reactions of racemic stannanes remain undeveloped. Herein, we present a pioneering instance of nickel‐catalysed enantioconvergent Stille cross‐coupling reactions of racemic stannane reagents, resulting in the formation of C−C bonds in good to high yields with excellent stereoselectivity. This strategy provides a practical, scalable, and operationally straightforward method for the synthesis of C(
sp 3)−C(sp 3), C(sp 3)−C(sp 2 ), and C(sp 3)−C(sp ) bonds under exceptionally mild conditions (without additives and bases, ambient temperature). The innovative use of synergistic photoredox/nickel catalysis enables a novel single‐electron transmetalation process of stannane reagents, providing a new research paradigm of Stille reactions.
