6251-34-9Relevant academic research and scientific papers
A kinetic investigation, supported by theoretical calculations, of steric and ring strain effects on the oxidation of sulfides and sulfoxides by dimethyldioxirane in acetone
Hanson, Peter,Hendrickx, Ramon A. A. J.,Lindsay Smith, John R.
supporting information; scheme or table, p. 65 - 84 (2011/01/07)
The oxidations of alkyl 4-nitrophenyl, and dialkyl, sulfides and sulfoxides by dimethyldioxirane in acetone occur by concerted mechanisms but the sulfides respond differently from the sulfoxides to variation in the alkyl group. The reactions of the sulfides are inhibited by the steric effects of alkyl groups and these predominate over their inductive effects. By contrast, the reactions of these limited sets of sulfoxides are insensitive to alkyl steric effects but there is an indication of steric acceleration when a broader set of sulfoxides is considered. This behaviour is rationalised in terms of the differences in dipolar charge and its solvation between the ground state and transition state for the two types of substrate. The oxidations of cyclic sulfides and sulfoxides also exhibit contrasting behaviour. The reactivity of the sulfides is insensitive to ring strain but is explicable in frontier orbital terms whereas that of the sulfoxides is partly dependent upon the change in ring strain between reactant and product on oxidation, a difference rationalised in terms of the relative positions of the transition states in the reaction coordinates of the two oxidations. The reactivity of 4-, 5- and 6-membered cyclic sulfoxides is also dependent on a ring-size related property of the transition state. Calculations at the B3-LYP/6-31G* level of density functional theory on both ground states and transition states, including simulation of solvation by acetone, strongly support the mechanistic conclusions reached in this and earlier work.
Mechanistic organic chemistry in a microreactor. Zeolite-controlled photooxidations of organic sulfides
Clennan, Edward L.,Zhou, Wenhui,Chan, Jacqueline
, p. 9368 - 9378 (2007/10/03)
The intrazeolite and solution photooxygenations of a series of sulfides have been compared. The unusual zeolite environment enhances the rates of reaction, it suppresses the Pummerer rearrangements, and it has a dramatic effect on the sulfoxide/sulfone ratio. A detailed kinetic study utilizing trapping experiments and intramolecular competition provides evidence for cation complexation to a persulfoxide intermediate as the underlying phenomenon for the unique intrazeolite behavior. For example, the enhanced rate of reaction is traced to the cation stabilization of the persulfoxide toward unproductive decomposition to substrate and triplet oxygen.
SELECTIVE MOLECULAR OXYGEN OXIDATION OF THIOETHERS TO SULFOXIDES CATALYZED BY Ce(IV).
Riley,Smith,Correa
, p. 177 - 180 (2007/10/02)
The selective molecular oxygen conversion of thioethers to sulfoxides is catalyzed by ceric ammonium nitrate (CAN) with rate enhancements that are at least three orders of magnitude greater than the uncatalyzed autoxidation of thioethers. Mechanistic studies (including spectroscopic, labeling, uptake, mixed reactant, and autocatalysis studies) of this novel reaction reveal that both atoms of dioxygen are incorporated into product sulfoxide, that a novel oxygen-driven Ce(IV)/Ce(III) redox cycle gives rise to the catalysis, and that molecular oxygen efficiently traps a sulfur-centered radial cation of the thioether (produced by Ce(IV) oxidation of thioether) to yield the oxygenated radical cation R//2S** plus OO multiplied by (times) , which, it is proposed, reoxidizes Ce(III) to Ce(IV).
Selective Autoxidation of Electron-Rich Substrates under Elevated Oxygen Pressures
Correa, Paul E.,Hardy, Gordon,Riley, Dennis P.
, p. 1695 - 1702 (2007/10/02)
We report here the observation of a novel autoxidation pathway which occurs with electron-rich substrates.Tertiary amines, dialkyl thioethers, olefins, and alkynes under high oxygen pressures (>20 bars of O2), in polar solvents, and at elevated temperatures (>90 deg C) yield in good to excellent selectivity amine oxides, sulfoxides, and site-specific olefin and alkyne cleavage products, respectively.The results of mechanistic studies, including high oxygen pressure electrochemical studies, are discussed.A mechanism for this novel oxygenation reaction pathway that is consistent with the observed results is proposed.It involves an initial unfavorable electron transfer from the electron-rich substrate to oxygen to yield superoxide and the radical cation, which reacts with triplet oxygen to yield the oxygenated radical cation intermediate, a suspected potent oxidant.Electron transfer to the oxygenated radical cation from additional substrate (chain reaction) or superoxide yields a zwitterionic intermediate.This intermediate either reacts with additional substrate (O-atom transfer) to yield product (sulfoxide and N-oxide, in the case of thioethers and tertiary amines) or is converted with unimolecular reactivity to dioxetane-like (in the case of alkenes) or dioxetene-like (in the case alkynes) derived products.
Mechanism of the Oxidation of Sulphides with Sodium Periodate
Ruff, Ferenc,Kucsman, Arpad
, p. 683 - 688 (2007/10/02)
The kinetics of the oxidation of RSAr, R2S, and (CH2)nS sulphides with NaIO4 yielding sulphoxides were investigated in ethanol-water solutions, and the rate equation v = k2 was found to be valid.The observed substituent (ρ -1
PHOTOSENSITIZED OXYGENATION OF CYCLIC SULFIDES. SELECTIVE C-S BOND CLEAVAGE
Takata, Toshikazu,Ishibashi, Koichi,Ando, Wataru
, p. 4609 - 4612 (2007/10/02)
TPP-Senzitized photooxidation of five-membered ring sulfides in aprotic solvent afforded C-S bond cleavage products, unlike six- and seven-membered ring sulfides which gave only S-oxidation products.The products as well as substitution and concentration effects suggest that C-S bond cleavage depends upon acidity of α-proton of persulfoxide intermediate.
The Formation of the Anion from 1-Thiacyclohept-2-ene 1-Oxide and its Reaction with Substituted Benzaldehydes
Crumbie, Robyn L.,Ridley, Damon D.
, p. 1027 - 1035 (2007/10/02)
On treatment with bases 1-thiacyclohept-2-ene 1-oxide affords the 2-metallated derivative which rapidly polymerizes, except in the presence of tetramethylethylenediamine when the pale yellow anion is relatively stable in tetrahydrofuran solution at -78 deg.The anion reacts rapidly with methyl iodide and with benzaldehyde and gives 2-methyl-1-thiacyclohept-2-ene 1-oxide and 2-(1-hydroxy-1-phenylmethyl)-1-thiacyclohept-2-ene 1-oxide respectively in high yields.Substituted benzaldehydes react similarly to benzaldehyde and whilst the ratio of diastereomeric products formed is affected by the nature of the substituent, no clear correlation emerges.The reactions are subject to kinetic control and it is proposed that an unfavourable lone-pair, ?-cloud electronic interaction is responsible for the diastereoselection.
