Selectivity of Wohl-Ziegler Brominations of Cyclohexene and trans-2-Hexene

https://openriver.winona.edu/urc2018/1131/thumbnail.jp

Mitochondrial biogenesis and dynamics in the developing and diseased heart

The mitochondrion is a complex organelle that serves essential roles in energy transduction, ATP production, and a myriad of cellular signaling events. A finely tuned regulatory network orchestrates the biogenesis, maintenance, and turnover of mitochondria. The high-capacity mitochondrial system in the heart is regulated in a dynamic way to generate and consume enormous amounts of ATP in order to support the constant pumping function in the context of changing energy demands. This review describes the regulatory circuitry and downstream events involved in mitochondrial biogenesis and its coordination with mitochondrial dynamics in developing and diseased hearts

Formation of a Strong Heterogeneous Aluminum Lewis Acid on Silica

Al(OC(CF 3 ) 3 )(PhF) reacts with silanols present on partially dehydroxylated silica to form well-defined ≡ SiOAl(OC(CF 3 ) 3 ) 2 (O(Si ≡ ) 2 ) ( 1 ). 27 Al NMR and DFT calculations with a small cluster model to approximate the silica surface show that the aluminum in 1 adopts a distorted trigonal bipyramidyl coordination geometry by coordinating to a nearby siloxane bridge and fluorine from the alkoxide. Fluoride ion affinity (FIA) calculations follow experimental trends and show that 1 is a stronger Lewis acid than B(C 6 F 5 ) 3 and Al(OC(CF 3 ) 3 )(PhF), but is weaker than Al(OC(CF 3 ) 3 ) and i Pr 3 Si + . Cp 2 Zr(CH 3 ) 2 reacts with 1 to form [Cp 2 ZrCH 3 ][ ≡ SiOAl(OC(CF 3 ) 3 ) 2 (CH 3 )] ( 3 ) by methide abstraction. This reactivity pattern is similar to reactions of organometallics with the proposed strong Lewis acid sites present on Al 2 O 3 .This is the peer-reviewed version of the following article: Conley, Matthew, Kavyasripriya K. Samudrala, Winn Huynh, Rick W. Dorn, and Aaron J. Rossini. "Formation of a Strong Heterogeneous Aluminum Lewis Acid on Silica," Angewandte Chemie International Edition, which has been published in final form at DOI: 10.1002/anie.202205745. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving. Copyright 2022 Wiley-VCH. Posted with permission

Structural characterization of tin in toothpaste by dynamic nuclear polarization enhanced 119Sn solid-state NMR spectroscopy

Stannous fluoride (SnF2) is an effective fluoride source and antimicrobial agent that is widely used in commercial toothpaste formulations. The antimicrobial activity of SnF2 is partly attributed to the presence of Sn(II) ions. However, it is challenging to directly determine the Sn speciation and oxidation state within commercially available toothpaste products due to the low weight loading of SnF2 (0.454 wt% SnF2, 0.34 wt% Sn) and the amorphous, semi-solid nature of the toothpaste. Here, we show that dynamic nuclear polarization (DNP) enables 119Sn solid-state NMR experiments that can probe the Sn speciation within commercially available toothpaste. Solid-state NMR experiments on SnF2 and SnF4 show that 19F isotropic chemical shift and 119Sn chemical shift anisotropy (CSA) are highly sensitive to the Sn oxidation state. DNP-enhanced 119Sn magic-angle turning (MAT) 2D NMR spectra of toothpastes resolve Sn(II) and Sn(IV) by their 119Sn chemical shift tensor parameters. Fits of DNP-enhanced 1D 1H → 119Sn solid-state NMR spectra allow the populations of Sn(II) and Sn(IV) within the toothpastes to be estimated. This analysis reveals that three of the four commercially available toothpastes contained at least 80% Sn(II), whereas one of the toothpaste contained a significantly higher amount of Sn(IV).This article is published as Dorn, Rick W., Scott L. Carnahan, Chi-yuan Cheng, Long Pan, Zhigang Hao, and Aaron J. Rossini. "Structural characterization of tin in toothpaste by dynamic nuclear polarization enhanced 119Sn solid-state NMR spectroscopy." Nature Communications 14, no. 1 (2023): 7423. doi: https://doi.org/10.1038/s41467-023-42816-z. © The Author(s) 2023.This Open Access article is licensed under a Creative Commons Attribution 4.0 International License

Determination of Rate Constants for Hydrogen Abstraction by Phenyl Radicals from Fatty Acid Esters

Radicals are molecules that contain an unpaired electron in place of a bond. As such they are generally very reactive and only exist as short-lived intermediates in chemical reactions. Phenyl radicals (C6H5•) are well known reactive intermediates that rapidly undergo typical radical reactions such as hydrogen abstraction and double bond addition. Their H-abstraction reactions with lipids and other biomolecules are of particular interest, yet rate constants (kH) for these have not been previously reported. We used the visible photolysis of p-fluorophenylazoisobutyronitrile (FPAIN) to generate p-fluorophenyl radicals, which were allowed to react with a fatty acid ester (FAE) in competition with abstraction of iodine from an iodoarene (m-iodobenzotrifluoride, ArI). The relative yields of the competitively formed products, fluorobenzene and p-fluoroiodobenzene were measured by integration of the fluorine-19 nuclear magnetic resonance (19F NMR) spectrum allowing the relative rate constants (kH/kI) to be determined. A literature derived value for kI (kI = 2.2 x 108M-1 s -1 ) then serves as a kinetic reference point for determining kH. We also report the results of high-level density functional theory (DFT) calculations that support the supposition that the reactivities of p-fluorophenyl and unsubstituted phenyl radicals are very similar

Attached Nitrogen Test by 13C–14N Solid-State NMR Spectroscopy for the Structure Determination of Heterocyclic Isomers

Differentiation of heterocyclic isomers by solution 1H, 13C, and 15N NMR spectroscopy is often challenging due to similarities in their spectroscopic signatures. Here, 13C{14N} solid-state NMR spectroscopy experiments are shown to operate as an “attached nitrogen test”, where heterocyclic isomers are easy to distinguish based on one-dimensional nitrogen-filtered 13C solid-state NMR. We anticipate that these NMR experiments will facilitate the assignment of heterocyclic isomers during synthesis and natural product discovery.This document is the unedited Author’s version of a Submitted Work that was subsequently accepted for publication in Organic Letters, copyright © 2022 American Chemical Society after peer review. To access the final edited and published work see DOI: 10.1021/acs.orglett.2c01576. Posted with permission

A Heterogeneous Palladium Catalyst for the Polymerization of Olefins Prepared by Halide Abstraction Using Surface R3Si+ Species

The silylium-like surface species [iPr3Si][(RFO)3Al–OSi≡)] activates (N^N)Pd(CH3)Cl (N^N = Ar-N=CMeMeC=N-Ar, Ar = 2,6-bis(diphenylmethyl)-4-methylbenzene) by chloride ion abstraction to form [(N^N)Pd–CH3][(RFO)3Al–OSi≡)] (1). A combination of FTIR, solid-state NMR spectroscopy, and reactions with CO or vinyl chloride establish that 1shows similar reactivity patterns as (N^N)Pd(CH3)Cl activated with Na[B(ArF)4]. Multinuclear 13C{27Al} RESPDOR and 1H{19F} S-REDOR experiments show that the (N^N)Pd–CH3+ fragment is weakly coordinated to the [(RFO)3Al–OSi≡)] anion, indicating that the palladium fragment interacts with a siloxane bridge on silica. 1 catalyzes the polymerization of ethylene with similar activities as [(N^N)Pd–CH3]+ in solution and incorporates up to 0.4 % methyl acrylate in copolymerization reactions. 1 produces polymers with significantly higher molecular weight than the solution catalyst, and generates the highest molecular weight polymers currently reported in copolymerization reactions of ethylene and methylacrylate.This is the peer-reviewed version of the following article: Gao, Jiaxin, Rick W. Dorn, Guillaume P. Laurent, Frédéric A. Perras, Aaron J. Rossini, and Matthew Conley. "A Heterogeneous Palladium Catalyst for the Polymerization of Olefins Prepared by Halide Abstraction Using Surface R3Si+ Species." Angewandte Chemie (2022), which has been published in final form at DOI: 10.1002/ange.202117279. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving. Copyright 2022 Wiley-VCH GmbH, Weinheim. Posted with permission. DOE Contract Number(s): AC02-07CH11358; CHE-2101582; CBET-1916809