- A capped trigonal pyramidal molybdenum hydrido complex and an unusually mild sulfur-carbon bond cleavage reaction
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DFT calculations reveal that a reported molybdenum hydride complex has an unprecedented geometry with the molybdenum in the base of trigonal pyramid defined by three thiolate ligands with a phosphine ligand on the apex and a hydride capping a PS2 face. This complex reacts with methanol to produce a sulfido complex by a new reaction: the protonation of an ipso carbon of a thiolate ligand by coordinated methanol.
- Morris, Robert H.
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- A general thiolation of magnesium organometallics using tetramethylthiuram disulfide
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The reaction of various functionalized aryl and heteroaryl bromides with i-PrMgCl·LiCl produces highly reactive Grignard reagents complexed by LiCl, which react with tetramethylthiuram disulfide [(Me2NCS 2)2] leading to th
- Krasovskiy, Arkady,Gavryushin, Andrey,Knochel, Paul
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- Electrophilic alkylation of pseudotetrahedral nickel(II) arylthiolate complexes
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A kinetic study is reported for reactions of pseudotetrahedral nickel(II) arylthiolate complexes [(TpR,Me)Ni-SAr] (TpR,Me = hydrotris{3-R-5-methyl-1-pyrazolyl}borate, R = Me, Ph, and Ar = C6H5, C6H4-4-Cl, C6H4-4-Me, C6H4-4-OMe, 2,4,6-Me3C6H2, 2,4,6-iPr3C6H2) with organic electrophiles R'X (i.e., MeI, EtI, BzBr) in low-polarity organic solvents (toluene, THF, chloroform, dichloromethane, or 1,2-dichloroethane), yielding a pseudotetrahedral halide complex [(TpR,Me)Ni-X] (X = Cl, Br, I) and the corresponding organosulfide R'SAr. Competitive reactions with halogenated solvents and adventitious air were also examined. Akin to reactions of analogous and biomimetic zinc complexes, a pertinent mechanistic question is the nature of the reactive nucleophile, either an intact thiolate complex or a free arylthiolate resulting from a dissociative pre-equilibrium. The observed kinetics conformed to a second-order rate law, first order with respect to the complex and electrophile, and no intermediate complexes were observed. In the absence of a mechanistically diagnostic rate law, a variety of mechanistic probes were examined, including kinetic effects of varying the metal, solvent, electrophile, and temperature, as well as the 3-pyrazolyl and arylthiolate substituents. Compared to zinc analogues, the effect of Ni-SAr covalency is also of interest herein. The results are broadly interpreted with respect to the disparate mechanistic pathways.
- Deb, Tapash,Jensen, Michael P.
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supporting information
p. 87 - 96
(2015/03/03)
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- Synthesis, structure and reactivity of Ni site models of [NiFeSe] hydrogenases
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A series of structural models of the Ni centre in [NiFeSe] hydrogenases has been developed which exhibits key structural features of the Ni site in the H2 cycling enzyme. Specifically, two complexes with a hydrogenase-analogous four-coordinate 'NiS3Se' primary coordination sphere and complexes with a 'NiS2Se2' and a 'NiS 4' core are reported. The reactivity of the complexes towards oxygen and protons shows some relevance to the chemistry of [NiFeSe] hydrogenases. Exposure of a 'NiS3Se' complex to atmospheric oxygen results in the oxidation of the selenolate group in the complex to a diselenide, which is released from the nickel site. Oxidation of the selenolate ligand on Ni occurs approximately four times faster than oxidation with the analogous sulfur complex. Reaction of the complexes with one equivalent of HBF4 results in protonation of the monodentate chalcogenolate and the release of this ligand from the metal centre as a thiol or selenol. Unrelated to their biomimetic nature, the complexes serve also as molecular precursors to modify electrodes with Ni-S-Se containing particles by electrochemical deposition. The activated electrodes evolve H2 in pH neutral water with an electrocatalytic onset potential of -0.6 V and a current density of 15 μA cm-2 at -0.75 V vs. NHE.
- Wombwell, Claire,Reisner, Erwin
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p. 4483 - 4493
(2014/03/21)
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- Facile introduction of SH group on aromatic substrates via electrophilic substitution reactions
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Herein, we describe a mild and efficient two-step procedure to introduce a thiol group on aromatic substrates. First, reaction with an activated sulfoxide leads to an arylsulfonium salt intermediate. Then, two successive β-elimination-based dealkylation reactions afford the desired arylthiols in good to excellent yields.
- Becht, Jean-Michel,Wagner, Alain,Mioskowski, Charles
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p. 5758 - 5761
(2007/10/03)
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- Rhodium-Catalyzed Rearrangement of α-Diazo Thiol Esters to Thio-Substituted Ketenes. Application in the Synthesis of Cyclobutanones, Cyclobutenones, and β-Lactams
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Exposure of α-diazo thiol esters (1) to the action of catalytic rhodium(II) acetate leads to a remarkably facile "thia-Wolff rearrangement", producing thio-substituted ketenes which combine with a variety of ketenophiles to provide access to α-thiocyclobutanones, cyclobutenones, and β-lactams. Reductive desulfurization of these cycloadducts takes place under mild conditions and in excellent yield, and this sequence thus represents a useful new alternative to the existing dichloroketene-based methodology for the synthesis of four-membered carbocycles and heterocycles.
- Lawlor, Michael D.,Lee, Thomas W.,Danheiser, Rick L.
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p. 4375 - 4384
(2007/10/03)
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- Formation by SRN1 reactions and 1H N.M.R. properties of sterically encumbered 2,4,6-triaIkyIphenyl p-nitrobenzyl sulfides
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Sterically hindered p-nitrobenzylic chlorides (1) and (2) react with the sodium salts of 2,4,6-trialkylbenzenethiols (3a)-(5a) by the SRN1 reaction to give good yields of the corresponding p-nitrobenzylic aryl sulfides (6)-(10). For example, th
- Look, Kai,Norris, Robert K.
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p. 1077 - 1083
(2007/10/03)
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- Catalytic kinetic resolution of 5-alkoxy-2(5H)-furanones
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The kinetic resolution of racemic 5-alkoxy-2(5H)-furanones, using a chiral aminoalcohol catalyzed 1,4-addition of arylthiols, was examined. Using various butenolides it was shown that a γ-alkoxy substituent appears to be essential to reach high enantioselectivities whereas electron-donating substituents in the arylthiols also increase the selectivity. Cinchona alkaloids are the preferred catalysts for the kinetic resolution, with quinine and quinidine leading to the most efficient and selective thiol additions. A remarkable dilution effect and a strong dependency on the mode of addition of reactants were observed. Optimization studies are presented of the kinetic resolution of 5-methoxy-2(5H)-furanone 2 resulting in (R)-2 or (S)-2 with enantiomeric excesses exceeding 90%. A mechanism for the quinine (quinidine) catalyzed kinetic resolution is given.
- Faber, Wijnand S.,Kok, Johan,De Lange, Ben,Feringa, Ben L.
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p. 4775 - 4794
(2007/10/02)
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- RADIKALIONEN 89. EINELEKTRONEN-OXIDATIONEN VON DIARYLDISULFIDEN MIT AlCl3/H2CCl2
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The single electron oxidation of 14 alkyl and alkoxy substituted diaryldisulfides by AlCl3/H2CCl2 has been investigated by ESR/ENDOR spectroscopy.The radical cations observed prove the following skeletal rearrangements: Those with ring hydrogens in ortho positions to the disulfide bridge preferentially form thianthrene derivatives.The isomeric dinaphthyl disulfides react differently, the 2,2'-isomer yielding the dibenzothianthrene radical cation and the 1,1'-isomer the well-known naphthalene-1,8-disulfide radical cation.For all diaryl disulfides with completely alkyl- or methoxy-blocked ortho positions, oxidative desulfuration is observed.As substantiated by additional (2)D and (33)S isotope marking, the bis(2,5-dimethoxyphenyl)disulfide reacts both to the corresponding thianthrene derivative as well as via desulfuration to the radical cation of the monosulfide.Accompanying cyclovoltammetric and photoelectron spectroscopic measurements prove that all ESR spectroscopically detected radical cations result from compounds Ar-S-Ar, Ar-SS-Ar and Ar(S)2Ar with rather low oxidation or ionisation potentials and thus suggest that each the most easily oxidized paramagnetic species is observed in the rather complex product mixtures, which form on AlCl3/H2CCl2 oxidation of diaryldisulfides. Key words: Diaryl disulfides; one-electron oxidation; radical cations; ESR/ENDOR spectra.
- Bock, Hans,Rittmeyer, Peter
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p. 261 - 292
(2007/10/02)
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- Process for phenol alkylthiolation and its application to the synthesis of 4-acyl-2-alkylthiophenols
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The invention relates to the preparation of alkylthiophenols by reaction of a dialkyl disulphide with a phenol. In the process according to the invention, the reaction is carried out in the presence of aluminum chloride or of ferric chloride in a solvent of the alkylbenzene type or, soley in the case of methylthiolation, in an excess of dimethyl disulphide. This process makes it possible, in particular to obtain, with a selectivity and in a yield which are excellent, 2-alkylthiophenols which may then be converted into 4-acyl-2-alkylthiophenols by means of a reaction at a temperature ranging from 40° to 100° C. with a complex BF3 :2RCOOH where R denotes an alkyl or propenyl radical, in a proportion of 10 to 15 moles of complex per mole of 2-alkylthiophenol.
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- Synthesis, Crystal Structure and Electronic Properties of a 2Fe-2S Complex with a Bulky Thiolato Ligand, 2
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The complex 2 (tmbt = 2,4,6-trimethylbenzenethiolate) was synthesised and its molecular structure determined.The crystal system is monoclinic with a = 15.241(6), b = 16.174(5), c = 16.768(6) Angstroem, β = 135.84(2) deg and Z = 2, in s
- Ueyama, Norikazu,Ueno, Satoru,Sugawara, Takashi,Tatsumi, Kazuyuki,Nakamura, Akira,Yasuoka, Noritake
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p. 2723 - 2728
(2007/10/02)
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- Quantitative Structure-Activity Analysis in Dihydropteroate Synthase Inhibition by Sulfones. Comparison with Sulfanilamides
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A set of 25 4'-, eight 2',4'-, and five 2',4',6'-substituted 4-aminodiphenyl sulfones were tested for their inhibitory activity on dihydropteroate synthase of Escherichia coli.Linear regression analysis shows that enzymic inhibition indices correlate well with both quantum chemical and spectroscopic descriptors of the electronic structure of the common moiety 4-NH2-C6H4-SO2 of the sulfones (the above descriptors being expressed in relation to the electronic structure of the enzyme substrate, p-aminobenzoate).Therefore, the biological activity of the sulfones can be related to the electronic structural resemblance between these inhibitors and the substrate of the target enzyme.Since a similar result was previously obtained for a wide series of sulfanilamides in their different (amidic, imidic, and anionic) forms, it appears possible to consider the antibacterial sulfones and sulfanilamides as a congeneric chemical series.On the basis of the present results, the classical theory of antimetabolites would appear to take on a quantitative and sound rationale.
- Benedetti, Pier G. De,Iarossi, Dario,Menziani, Cristina,Caiolfa, Valeria,Frassineti, Chiara,Cennamo, Carlo
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p. 459 - 464
(2007/10/02)
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- Rhenium Nitrosyl Complexes with Simple and with Sterically Demanding Aromatic Thiolate Ligands: X-Ray Crystal Structures of *CH2Cl2 and i2-2,6)4(NO)>
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Reaction of with a range of thiophenols under basic conditions gives one of two classes of products depending on the steric requirements of the thiols.A representative member of each class has been characterised by an X-ray crystal
- Blower, Philip J.,Dilworth, Jonathan R.,Hutchinson, John P.,Zubieta, Jon A.
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p. 1533 - 1542
(2007/10/02)
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- CONVERSION OF α ACETYLENIC ALCOHOLS INTO αβ UNSATURATED ALDEHYDES
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Very mild conditions have been found for the efficient regioselective addition of phenylthiol to ethynyl carbinols.A biphasic aqueous acid hydrolysis then leads to αβ-unsaturated aldehydes.The Meyer-Schuster rearrangement is thus brought about in two steps.
- Julia, Marc,Lefebvre, Christian
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p. 189 - 192
(2007/10/02)
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- BIOMIMETIC REDUCTION OF SULFURIC ACID.
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Sulfuric acid and sodium sulfate were readily reduced to elemental sulfur and hydrogen sulfide upon treatment with a mixture of either one of polyphosphoric acid derivatives, PPE, PPA, and P//4O//1//0, which can form a mixed anhydride having -P-O-S- linkage, and iodide or thiol. Sulfur dioxide, which is undoubtedly one of the important intermediates, was trapped by p-tolyllithium to afford p-toluenesulfinic acid which was converted to p-tolyl methyl sulfone upon treatment with methyl iodide, though the yield was low. Sulfur trioxide which has been postulated as the key intermediate in the biological reduction of inorganic sulfate, was also trapped by mesitylene to give mesitylenesulfonic acid in a high yield. The reduction of sulfate to elemental sulfur and hydrogen suylfide is considered to proceed through the course which resembles the biological reaction path involved in the assimilatory metabolism of inorganic sulfate in microorganisms and plants.
- Oae,Togo
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p. 3818 - 3823
(2007/10/02)
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- Electrophilic additions to allenes. VI. The role of steric versus electronic effects in the reactions of arenesulphenyl halides with allenes
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The role of steric and electronic effects during the rate and product determining steps for the addition of arenesulphenyl chlorides to 1,3-disubstituted allenes has been briefly examined.Both effects appear to be generally of minimal importance during the rate determinig step.The available rate data indicate the presence of little, if any, build up of positive charge on sulphur.These results are interpreted in terms of an SN2 attack on bivalent sulphur leading to an alkylidenethiiranium ion intermediate.Steric effects are of greater importance in the product determinig step, particularly when the sulphenyl chlorides possess two bulky ortho substituents, as in the case of 2,4,6-triisopropylbenzenesulphenyl chloride.
- Garratt, Dennis G.,Beaulieu, Pierre L.
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p. 2738 - 2744
(2007/10/02)
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