- A general and efficient method for the palladium-catalyzed cross-coupling of thiols and secondary phosphines
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The general and efficient cross-coupling of thiols with aryl halides was developed utilizing Pd(OAc)2/1,1′-bis(diisopropylphosphino) ferrocene as the catalyst. The substrate scope is broad and includes a variety of aryl bromides and chlorides,
- Murata, Miki,Buchwald, Stephen L.
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Read Online
- Carbon-sulfur bond formation of challenging substrates at low temperature by using Pd-PEPPSI-IPent
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Aryl thiols made cool and quick: The coupling of alkyl, aryl, and silyl thiols to hindered, deactivated aryl bromides and chlorides has been achieved under the most mild temperatures yet reported (i.e., room temperature to 40°C). The bulk afforded by the di-2,6-(3-propylphenyl)imidazolium-derived Pd-PEPPSI-IPent catalyst is believed to actively promote the critical reductive elimination step of the catalytic cycle, thereby eliminating the formation of poisonous off-cycle dimeric resting states that have plagued Pd-catalyzed sulfination reactions.
- Sayah, Mahmoud,Organ, Michael G.
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supporting information; experimental part
p. 11719 - 11722
(2011/11/29)
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- A general, efficient, and functional-group-tolerant catalyst system for the palladium-catalyzed thioetherification of aryl bromides and iodides
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The cross-coupling reaction of aryl bromides and iodides with aliphatic and aromatic thiols catalyzed by palladium complexes of the bisphosphine ligand CyPF-tBu (1) is reported. Reactions occur in excellent yields, broad scope, high tolerance of functional groups, and with turnover numbers that exceed those of previous catalysts by 2 or 3 orders of magnitude. These couplings of bromo- and iodoarenes are more efficient than the corresponding reactions of chloroarenes and could be conducted with less catalyst loading and/or milder reaction conditions. Consequently, limitations regarding scope and functional group tolerance previously reported in the coupling of aryl chlorides are now overcome.
- Fernandez-Rodriguez, Manuel A.,Hartwig, John F.
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experimental part
p. 1664 - 1672
(2009/07/17)
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- CATALYSTS FOR ARYL SULFIDE SYNTHESIS AND METHOD OF PRODUCING ARYL SULFIDES
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The present invention relates to the formation of aryl sulfides and aryl thiols from aryl halides and thiols, thiolates or thiolate equivalents. The present invention provides a catalyst for the coupling of aryl halides with alkyl or aryl thiols or a hydrogen sulfide equivalent to form aryl alkyl, aryl silyl or diaryl sulfides. The reaction encompasses bromoarenes and other similar compounds containing leaving groups as well as nitrile, ester, keto, free hydroxyl, free amino, free carboxylic acid and other common functionalities. The invention can be used to prepare pharmaceutical compounds, especially including their intermediates, agricultural agents and aryl sulfide polymers.
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Page/Page column 20; 29; 36; 48
(2008/06/13)
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- Highly efficient and functional-group-tolerant catalysts for the palladium-catalyzed coupling of aryl chlorides with thiols
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The cross-coupling reaction of aryl chlorides with aliphatic and aromatic thiols catalyzed by palladium complexes of the strongly binding bisphosphine CyPF-tBu ligand (1) is reported. Most of the reactions catalyzed by complexes of ligand 1 occur with turnover numbers that exceed those of previous catalysts by two orders of magnitude. The reactions occur with excellent yields, broad scope and high tolerance of functional groups. Coupling of aryl halides with thiols in the presence of low loadings of catalysts derived from other Josiphos type ligands, as well as ligands of other structural types, are also described.
- Fernandez-Rodriguez, Manuel A.,Shen, Qilong,Hartwig, John F.
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p. 7782 - 7796
(2007/10/03)
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- Carbon-sulfur bond-forming reductive elimination involving sp-, sp2-, and sp3-hybridized carbon. Mechanism, steric effects, and electronic effects on sulfide formation
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Palladium thiolato complexes [(L)Pd(R)(SR')], within which L is a chelating ligand such as DPPE, DPPP, DPPBz, DPPF, or TRANSPHOS, R is a methyl, alkenyl, aryl, or alkynyl ligand, and R' is an aryl or alkyl group, were synthesized by substitution or proton-transfer reactions. All of these thiolato complexes were found to undergo carbon-sulfur bond-forming inductive elimination in high yields to form dialkyl sulfides, diaryl sulfides, alkyl aryl sulfides, alkyl alkenyl sulfides, and alkyl alkynyl sulfides. Reductive eliminations forming alkenyl alkyl sulfides and aryl alkyl sulfides were the fastest. Eliminations of alkynyl alkyl sulfides were slower, and elimination of dialkyl sulfide was the slowest. Thus the relative rates for sulfide elimination as a function of the hybridization of the palladium-bound carbon follow the trend sp2 > sp >> sp3. Rates of reductive elimination were faster for cis-chelating phosphine ligands with larger bite angles. Kinetic studies, along with results from radical trapping reactions, analysis of solvent effects; and analysis of complexes with chelating phosphines of varying rigidity, were conducted with [Pd(L)(S-tert-butyl)(Ar)] and [Pd(L)(S- tert-butyl)(Me)]. Carbon-sulfur bond-forming reductive eliminations involving both saturated and unsaturated hydrocarbyl groups proceed by an intramolecular, concerted mechanism. Systematic changes in the electronic properties of the thiolate and aryl groups showed that reductive elimination is the fastest for electron deficient aryl groups and electron rich arenethiolates, suggesting that the reaction follows a mechanism in which the thiolate acts as a nucleophile and the aryl group an electrophile. Studies with thiolate ligands and hydrocarbyl ligands of varying steric demands favor a migration mechanism involving coordination of the hydrocarbyl ligand in the transition state.
- Mann, Grace,Baranano, David,Hartwig, John F.,Rheingold, Arnold L.,Guzei, Ilia A.
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p. 9205 - 9219
(2007/10/03)
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- Chemistry of Sulfenic Acids. 3. Studies of Sterically Hindered Sulfenic Acids Using Flash Vacuum Pyrolysis
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Flash vacuum pyrolysis (FVP) of sulfoxides containing β-hydrogen atoms affords sulfenic acids (RSOH) in good concentration under conditions where they are stable.The application of this technique to the synthesis and study of sterically hindered sulfenic acids 12a-e is described.The principal or primary reaction of simple sulfenic acids prepared in this manner is dehydration to thiosulfinates 13 (eq 1).Steric inhibition to dehydration (eq 1) appears to only be of importance for 2-methyl-2-propanesulfenic acid (12a) which was trapped in good yield with methyl propiolate to afford 16a. 2,4,6-Tri-tert-butylbenzenesulfenic acid (12e) appears to be destabilized as a consequence of interaction between the SOH and adjacent tert-butyl groups.In the pyrolysis section of the apparatus, 12e decomposes to phenol 21 and aryl radical 22, which reacts further.Thermolysis of sulfoxides generates the sulfenic acids 12a-e in very low concentration at any one time.The products of sulfenic acids generated in this way result from secondary reactions of the corresponding thiosulfinates.
- Davis, Franklin A.,Jenkins, Robert H.,Rizvi, Syed Q. A.,Yocklovich, Steven G.
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p. 3467 - 3474
(2007/10/02)
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