Sulfur Bond Formation Research Articles

Desulfitative Carbon–Carbon Cross‐Coupling of Thioamide Fragments with Boronic Acids

AbstractA novel and general carbon–carbon cross‐coupling reaction between cyclic thioamides and boronic acids is described. The reaction is catalytic in palladium(0) and requires stoichiometric amounts of a copper(I) carboxylate as metal cofactor. The mode of cross‐coupling in the reaction of cyclic thioamides with boronic acids is easily tunable between carbon–carbon and carbon–sulfur cross‐coupling. While the catalytic palladium(0)/copper(I) system provides carbon–carbon bond formation with extrusion of sulfur, stoichiometric quantities of copper(II) under air mediate carbon–sulfur bond formation.

Scope and limitations of HClO 4–SiO 2 as an extremely efficient, inexpensive, and reusable catalyst for chemoselective carbon–sulfur bond formation

The scope and limitations of perchloric acid adsorbed on silica gel (HClO 4–SiO 2) as a highly efficient, inexpensive, and reusable catalyst for chemoselective carbon–sulfur bond formation by conjugate addition of thiols to α,β-unsaturated ketones under solvent-free conditions and at rt are reported. In the case of 1,3-diphenylpropenone, the reactions were best carried out either at 80 °C under solvent-free conditions or at rt in MeOH. The reaction of aryl, arylalkyl, alkyl thiols, and alkane dithiols with cyclic and acyclic α,β-unsaturated ketones afforded excellent yields of the corresponding β-sulfidocarbonyls after 2 min to 2 h. In the case of dithiols, the bis-thia-Michael adducts were formed. The rate of the reaction was found to be dependent on the electronic and steric factors of the α,β-unsaturated ketones and the thiols. A substituent at the β-carbon of the α,β-unsaturated ketone offered steric hindrance for conjugate addition and such substrates required longer times. In case of aromatic thiols, the presence of the nitro group reduced the nucleophilicity of the sulfhydryl sulfur atom resulting in slower rate of reaction for 4-nitrothiophenol compared to that of thiophenol and 4-methylthiophenol. For alkane thiol, the reaction rate was influenced by the steric crowding of the alkyl group attached to the sulfhydryl moiety. The rate of reaction for alkane thiols was sluggish compared to that of aryl thiols. The influence of the β-substituent on the rate of thia-Michael addition was utilized for selective reaction during inter-molecular competitions of cyclohexen-2-one versus 3-methyl-2-cyclohexenone, cyclohexen-2-one versus 4-methyl-3-penten-2-one, and 4-phenyl-3-buten-2-one versus 4-methyl-3-penten-2-one with thiophenol with 100:0, 91:9, and 70:30 selectivities, respectively. The difference in the rate of reaction of thiophenol and 4-nitrothiophenol was also reflected during the inter-molecular competition for the reaction with cyclohexen-2-one with an excellent selectivity of 100:0. The influence of the steric factor of the alkyl group in alkane thiol resulted in 62:38 selectivity during the inter-molecular competition of ethane thiol and tert-butanethiol with cyclohexen-2-one. During inter- and intra-molecular competitions of thia- versus aza- and thia- versus oxa-Michael addition reactions, chemoselective thia-Michael addition took place. The chemoselective thia-Michael addition over aza-Michael addition during intra-molecular competion reactions with 2-aminothiophenol was utilized for an efficient one-pot synthesis of benzothiazepines.

A highly efficient carbon–sulfur bond formation reaction via microwave-assisted nucleophilic substitution of thiols to polychloroalkanes without a transition-metal catalyst

An efficient carbon–sulfur bond formation reaction has been developed under microwave irradiation. This reaction affords a novel and rapid synthesis of thioacetals and sulfides under mild conditions. This method is particularly noteworthy given its experimental simplicity and high generality, and no transition-metal catalysts were needed under our conditions.Key words: microwave, sulfide, thiol, nucleophilic substitution.

An Efficient Synthesis of a Potent PPARpan Agonist

An efficient synthesis of 2-{4-[({4-{[4-(4-methoxyphenyl)piperazin-1-yl]methyl}-2-[4-(trifluoromethyl)phenyl]-1,3-thiazol-5-yl}methyl)thio]phenoxy}-2-methylpropanoic acid (1), a potent PPARpan agonist, is described. The seven-step synthesis, which afforded 1 in 30% overall yield, includes a highly regioselective carbon-sulfur bond formation via coupling of a bishydroxymethylthiazole (3) with 4-hydroxythiophenol, displacement of the remaining alcohol through a three-step telescoped sequence involving an efficient cleavage of an aryl mesylate, and an efficient and practical method of introducing an isobutyric acid fragment.

A novel environmentally friendly process for carbon–sulfur bond formation catalyzed by montmorillonite clays

Montmorillonite clays are reported as efficient, inexpensive, and reusable catalysts for carbon–sulfur bond formation by conjugate addition of thiols to α,β-unsaturated ketones/ester/nitrile. The reaction of aryl and aryl alkyl thiols with cyclic/acyclic α,β-unsaturated ketones/ester afforded excellent yields after 5 min to 20 h. The reaction rate was found to be influenced by the (i) size of the ring in case of cyclic enone, (ii) electronic nature of the thiol, and (iii) presence of aryl/alkyl substituent at the β position of the acyclic α,β-unsaturated ketone/nitrile. The conjugate addition of thiols took place at faster rates for five-membered and acyclic α,β-unsaturated ketones than the six-membered analogue. Aryl thiols reacted at faster rates than aryl alkyl and alkane thiols and the differential reaction rates were attributed to the relative acidic strength of the thiols. The reaction of α,β-unsaturated ketones having an aryl/alkyl group at the β-carbon took longer times and higher temperature. The difference in the reactivity between six and five membered enones and various thiols was utilized to demonstrate selective thia-Michael addition reaction during intermolecular competition studies.

A new series of iodocarbonyl ruthenium (II) complexes with unsymmetrical phosphine–phosphine sulfide ligands of the type Ph 2P(CH 2) nP(S)Ph 2, n = 1–4: Isolation and structural investigation

Hexa-coordinated chelate complex cis-[Ru(CO) 2I 2(P∩S)] ( 1a) {P∩S = η 2-(P,S)-coordinated} and penta-coordinated non-chelate complexes cis-[Ru(CO) 2I 2(P∼S)] ( 1b– d) {P∼S = η 1-(P)-coordinated} are produced by the reaction of polymeric [Ru(CO) 2I 2] n with equimolar quantity of the ligands Ph 2P(CH 2) n P(S)Ph 2 { n = 1( a), 2( b), 3( c), 4( d)} in dichloromethane at room temperature. The bidentate nature of the ligand a in the complex 1a leads to the formation of five-membered chelate ring which confers extra stability to the complex. On the other hand, 1:2 (Ru:L) molar ratio reaction affords the hexa-coordinated non-chelate complexes cis,cis,trans-[Ru(CO) 2I 2(P∼S) 2] ( 2a– d) irrespective of the ligands. All the complexes show two equally intense terminal ν(CO) bands in the range 2028–2103 cm −1. The ν(PS) band of complex 1a occurs 23 cm −1 lower region compared to the corresponding free ligand suggesting chelation via metal–sulfur bond formation. X-ray crystallography reveals that the Ru(II) atom occupies the center of a slightly distorted octahedral geometry. The complexes have also been characterized by elemental analysis, 1H, 13C and 31P NMR spectroscopy.

Carbon—Sulfur Bond Formation from 2‐Halochalcogenophenes via Copper‐Catalyzed Thiol Cross‐Coupling.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Carbon–Sulfur Bond Formation between a Ruthenium‐Coordinated Thiyl Radical and Methyl Ketones

Ein metallkoordiniertes Thiylradikal entsteht bei der elektrochemischen Oxidation eines Ruthenium(III)-thiolats in Aceton (oder verwandten Ketonen). Die nachfolgende Reaktion des radikalischen Intermediats mit Aceton verläuft unter C-S-Kupplung zum Ruthenium(III)-thioether (siehe Bild). Teil des vorgeschlagenen Mechanismus ist die Reaktion des Enoltautomers von Aceton mit dem Radikal. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2001/2005/z462713_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Carbon–Sulfur Bond Formation between a Ruthenium‐Coordinated Thiyl Radical and Methyl Ketones

Carbon–Sulfur Bond Formation between a Ruthenium‐Coordinated Thiyl Radical and Methyl Ketones

Borane-Catalyzed Hydrosilylation of Thiobenzophenone: A New Route to Silicon−Sulfur Bond Formation

Clean and quantitative B(C6F5)3-catalyzed hydrosilylation of thiobenzophenone by a variety of mono- and disilanes proceeds under mild conditions, at low catalyst loading, to furnish new silyl thioether compounds.

A General Palladium-Catalyzed Coupling of Aryl Bromides/Triflates and Thiols

We have developed an efficient palladium-catalyzed carbon-sulfur bond formation reaction of aryl bromides, triflates, and activated aryl chloride. Using this protocol, we have shown tolerance to a wide variety of aryl thiols and alkyl thiols that can also be used as sulfide equivalents. [reaction: see text]

Cowpea Mosaic Virus as a Scaffold for 3-D Patterning of Gold Nanoparticles

Different mutants of Cowpea Mosaic Virus (CPMV) have been used as scaffolds to bind 2 and 5 nm gold nanoparticles through gold−sulfur bond formation at specific locations on the virus to produce patterns of specific interparticle distances. TEM images confirm that the bound gold particles produce patterns of gold nanoparticles that correlate well with models built from the known locations of the inserted cysteine groups on the capsid. These results demonstrate that it is possible to use CPMV mutants as nanoscale scaffolds to place gold nanoparticles at fixed interparticle distances.

A General, Efficient, and Inexpensive Catalyst System for the Coupling of Aryl Iodides and Thiols.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Controlled polymer synthesis in homogeneous and heterogeneous processes

Research in polymer synthesis can be oriented toward method or structure. This review is intended to document both approaches. Recent examples from our own work as well as future prospectives will be presented. A general concern is to work out the impact from organic and supramolecular chemistry. Examples of method oriented work are (i) a unique polycondensation via carbon sulfur-bond formation providing hybrid structures of, e.g., polyphenylenesulfide and polyaniline; (ii) a triazoline additive establishing a novel self-regulation process in controlled radical polymerization; (iii) a metallocene catalyzed polyolefin synthesis which is performed by using “smart”, reversibly cross-linked polymer resins as support; and (iv) hydrogen-bonded aggregates suggesting new emulsifiers for emulsion polymerization thus leading to functional nanoparticles. Examples of structure oriented work are (i) rod-coil block copolymers (1D case) as a “covalently bound combination” of rigid and flexible segments whereby a key synthetic concern is the chemical modification and quantitative end-functionalization of polyphenylene chains; (ii) discs (2D case) as molecularly defined graphite subunits which are obtained via a remarkably mild intramolecular cyclodehydrogenation; and (iii) dendrimers (3D case) as shape-persistent nanoparticles whose high degree of structural precision results from a new cycloaddition-deprotection protocol.

Nickel mediated sulfur–selenium and sulfur–sulfur bond formation

Electrophilic addition of the PhSeCl to a nickel dithiolate yields S,S′-bis(phenylselenenyl-N,N′-bis(mercaptoethyl)-1,5-diazacyclooctane nickel(II) dichloride and a dimeric, intermolecular bis-disulfide which results from ligand oxidation.

Modeling the Claus Reaction: Preparation of trans-Pt(PPh(3))(2)(phthalimido)S(O)(2)SR.

Treatment of Pt(PPh3)3SO2 with RS-phthalimide, a source of RS+, gives complexes containing ligands of the type RSS(O)2-, the first of their kind. The reaction models the industrially important Claus process (2H2S + SO2 → 3/8S8 + 2H2O) by simulating the attack of H2S on surface coordinated SO2. Sulfur−sulfur bond formation, as observed in this work, is a necessary characteristic of the heterogeneously catalyzed Claus process.

Formation of a nickel(II) complex with a new N2S2macrocyclic ligand by C–Cl bond cleavage and C–S bond formation

Heating a monohelical square-planar nickel(II) complex containing chlorine atoms in the side arms gives a distorted octahedral nickel(II) complex containing the trans-N2S2 macrocyclic ligand by carbon–chlorine bond cleavage and carbon–sulfur bond formation.

Evidence for an insertion–homolysis mechanism for carbon–sulphur bond formation in penicillin biosynthesis

Evidence to support an insertion–homolysis mechanism for the event leading to carbon–sulphur bond formation in penicillin biosynthesis has been obtained by a stereochemical probe.

Ab initio study of the nucleophilic addition of the hydrosulfide anion HS − to formaldehyde

Nucleophilic addition of hydrosulfide ion to formaldehyde has been investigated by ab initio quantum mechanical methods. Contrary to the system HO −+H 2CO, our study reveals that no minimum exists for the tetrahedral structure of the adduct of HS − and H 2CO on the potential surface. Orbital interaction analysis allows one to understand the different behaviors of HO − and HS − towards H 2CO. Moreover it appears that in the case of HS − the only reactive pathway involves simultaneous proton transfer and carbon sulfur bond formation leading to the formation of the H 2C(S, OH) − species.

Intramolecular coupling reaction of phosphino–thioenolato iron(II) complexes with alkynes. Crystal structure of [Fe{η3-Ph2P–CHC(But)S–CCHPh}(CO)(PMe3)2]BF4

[FeCl{η2-Ph2PCHC(R)S}(PMe3)(CO)(L)] complexes, prepared by ligand substitution, react with phenylacetylene in the presence of AgBF4 or NaPF6 and lead to carbon–sulphur bond formation between the β-phosphino–thioenolate ligand and the phenylvinylidene–iron intermediate, as shown by X-ray diffraction analysis.