Charles K. Mann

Bio: Charles K. Mann is an academic researcher. The author has contributed to research in topics: Chemical reaction & Anhydrous. The author has an hindex of 1, co-authored 3 publications receiving 68 citations.

Electrochemical Oxidation of Aliphatic Sulfides under Nonaqueous Conditions

Abstract: The anodic oxidation of aliphatic sulfides has been investigated, using cyclic voltammetry and controlled potential electrolysis. Reactions of dimethyl sulfide in acetonitrile have been studied in detail, considering the effects of variation of water content and of type of supporting electrolyte. With as much as 1% water in , dimethyl sulfide is completely oxidized to dimethyl sulfone. In anhydrous , the products are and . It is suggested that the electrochemical reaction involves formation of protons and , which condenses with to form . When perchlorate is present as supporting electrolyte, it is involved in a slow chemical reaction which produces Cl−, , and . The reaction of benzyl methyl sulfide is very similar, leading to benzaldehyde and .

1,2-Dications in Organic Main Group Systems

Abstract: IV. Se−Se, Te−Te, and Mixed Dications 248 V. Trischalcogen Dications 251 VI. Polyatomic Chalcogen Dications 254 A. Preparation 255 B. Chemical Properties 256 VII. N−N Dications 257 A. Hydrazinium Dications 257 1. Synthesis of Hydrazinium Dications 257 2. Properties of Hydrazinium Dications 259 3. Heteroaromatic N,N-Dications 262 B. Diazenium and Diazonium Dications 262 1. Synthesis of Diazenium Dications 262 2. Reactions of Diazenium Dications 263 3. Diazonium Dications 265 4. Mixed Dications 266 VIII. P−P Dications 266 A. Synthesis of Diphosphonium Dications 266 B. Reactions of Diphosphonium Dications: Nucleophilic Substitution 267

Studies Leading to the Development of a Single-Electron Transfer (SET) Photochemical Strategy for Syntheses of Macrocyclic Polyethers, Polythioethers, and Polyamides

Abstract: Organic photochemists began to recognize in the 1970sthat a new mechanistic pathway involving excited-state single-electron transfer (SET) could be used to drive unique photochemical reactions. Arnold’s seminal studies demonstrated that SET photochemical reactions proceed by way of ion radical intermediates, the properties of which govern the nature of the ensuing reaction pathways. Thus, in contrast to classical photochemical reactions, SET-promoted excited-state processes are controlled by the nature and rates of secondary reactions of intermediate ion radicals. In this Account, we discuss our work in harnessing SET pathways for photochemical synthesis, focusing on the successful production of macrocyclic polyethers, polythioethers, and polyamides.One major thrust of our studies in SET photochemistry has been to develop new, efficient reactions that can be used for the preparation of important natural and non-natural substances. Our efforts with α-silyl donor-tethered phthalimides and naphthalimides hav...

Phenyl-to-Oxo Migration in an Electrophilic Rhenium(VII) Dioxo Complex

Abstract: Reaction of (HBpz3)ReO(Ph)(OTf) with oxygen atom donors leads to oxidation of the phenyl group [HBpz3 = hydrotris(1-pyrazolyl)borate, OTf = triflate, OSO2CF3]. Reaction with Me2SO gives the adduct [(HBpz3)ReO(Ph)(OSMe2)]OTf, which undergoes phenyl-to-oxo migration at 25 °C to give the phenoxide complex [(HBpz3)ReO(OPh)(OSMe2)]OTf and Me2S. The Me2SO adduct readily and reversibly loses Me2S (k = 2.9(4) s-1 at 25 °C) as indicated by isotope exchange reactions and magnetization transfer. The Me2SO adduct also slowly oxidizes Me2SO to Me2SO2. These reactions all proceed via an intermediate rhenium(VII) dioxo complex, [(HBpz3)ReO2(Ph)]OTf. This dioxo complex can be observed at low temperature on reaction of (HBpz3)ReO(Ph)(OTf) with pyridine N-oxide. It rearranges at 0 °C by phenyl-to-oxo migration to give phenoxide products and the catecholate complex (HBpz3)ReO(O2C6H4). The kinetics of this migration have been measured (ΔH⧧ = 14.8(7) kcal/mol, ΔS⧧ = −20.5(25) eu). From these data and the activation parameters...

The photochemistry of polydonor-substituted phthalimides: Curtin-Hammett-type control of competing reactions of potentially interconverting zwitterionic biradical intermediates.

Abstract: The results of studies designed to obtain information about the factors that control the chemical efficiencies/regioselectivities and quantum yields of single electron transfer (SET)-promoted reactions of acceptor-polydonor systems are reported. Photochemical and photophysical investigations were carried out with bis-donor tethered phthalimides and naphthalimides of general structure N-phthalimido- and N-naphthalimido-CH2CH2-D-CH2CH2-NMsCH2-E (E = SiMe3 or CO2NBu4 and D = NMs, O, S, and NMe). These substrates contain common terminal donor groups (NMsCH2SiMe3 or NMsCH2CO2NBu4) that have known oxidation potentials and cation radical fragmentation rates. Oxidation potentials and fragmentation rates at the other donor site in each of these substrates are varied by incorporating different heteroatoms and/or substituents. Photoproduct distribution, reaction quantum yield, and fluorescence quantum yield measurements were made. The results show that photocyclization reactions of alpha-trimethylsilylmethansulfonamide (E = SiMe3)- and alpha-carboxymethansulfonamide (E = CO2NBu4)-terminated phthalimides and naphthalimides that contain internal sulfonamide, ether, and thioether donor sites (D = NMs, O, or S) are chemically efficient (80-100%) and that they take place exclusively by a pathway involving sequential photoinduced SET (zwitterionic biradical desilylation or decarboxylation) biradical cyclization. In contrast, photoreactions of alpha-trimethylsilylmethansulfonamide- and alpha-carboxymethansulfonamide-terminated phthalimides and naphthalimides that that contain an internal tertiary amine donor site (D = NMe) are chemically inefficient and follow a pathway involving alpha-deprotonation at the tertiary amine radical cation center in intermediate, iminium radical-containing, zwitterionic biradicals. In addition, the quantum efficiencies for photoreactions of alpha-trimethylsilylmethansulfonamide- and alpha-carboxymethansulfonamide-terminated phthalimides are dependent on the nature of the internal donor (eg., phi = 0.12 for D = NMs, E = SiMe3; phi = 0.02 for D = S, E = SiMe3; phi = 0.04 for D = NMe, E = SiMe3). The results of this effort are discussed in terms of how the relative energies of interconverting zwitterionic biradical intermediates and the energy barriers for their alpha-heterolytic fragmentation reactions influence the chemical yields and quantum efficiencies of SET promoted photocyclization reactions of acceptor-polydonor substrates.