Carbon-sulfur cross-coupling

Recently, interest in copper-catalyzed carbon-heteroatom bond-forming reactions has shifted to the use of boronic acids as reactive coupling partners [133], One example of carbon-sulfur bond formation is displayed in Scheme 6.65. Lengar and Kappe have reported that, in contrast to the palladium(0)/copper(l)-mediated process described in Scheme 6.55, which leads to carbon-carbon bond formation, reaction of the same starting materials in the presence of 1 equivalent of copper(II) acetate and 2 equivalents of phenanthroline ligand furnishes the corresponding carbon-sulfur cross-coupled product [113]. Whereas the reaction at room temperature needed 4 days to reach completion, microwave irradiation at 85 °C for 45 min in 1,2-dichloroethane provided a 72% isolated yield of the product. 

Scheme6.65 Copper(ll)-mediated carbon—sulfur cross-coupling.

Scheme 6.66 Palladium-catalyzed carbon-sulfur cross-coupling.

Zhang and coworkers have reported on a palladium-catalyzed carbon-sulfur cross-coupling of aryl perfluoroalkoxysulfonates with thiols (Scheme 7.78) [91]. The fluorous substrates were obtained from commercially available phenols by treatment with perfluorooctanesulfonyl fluoride (C8F17S02F) under basic conditions. Various thiols were reacted with a slight excess of the perfluorinated sulfonates in a... 

A Pd(0)-catalyzed/Cu(l)-mediated carbon-carbon cross-coupling of 3,4-dihydropyrimidine-2-thiones 520 and boronic acids occurs under microwave-assisted conditions to give 2-aryl-l,4-dihydropyrimidines 521 in moderate to high yield <20040L771>. In contrast, Gu(ll)-mediated reaction of the same substrates leads to carbon-sulfur cross-coupling. 

Keywords Carbon-sulfur Cross-coupling Catalysis Bond activation... 

CARBON-SULFUR AND CARBON-SELENIUM BOND-FORMING CROSS-COUPLINGS 384... 

M. Miyasaka, A. Rajca, Synthesis of a Short Carbon—Sulfur Helicene Pd-cata-lyzed Cross-coupling at the >-Positioris of Thiophenes, Synlett 2004, 177—182. 

In the presence of 5-10% palladium catalyst 34,20-45% Nal, and 4-6 equiv K2CO3, various boronic acids underwent cross-coupling with thio esters 32 in dimethylacetamide at 90-95 °C for 12-24 h to give the desired ketones in moderate to high yields. Tetrahydrothiophene, detected by GC/MS, was formed by intramolecular nucleophilic attack at the terminal carbon by a sulfur atom. Interestingly, in the absence of Nal, the bromobutyl thiol ester 32a gave only a trace amount of benzophenone when treated with phenylboronic acid in the presence of 34 in DMA at 95 °C for 22 h. In the presence of Nal, the bromide atom at the terminal carbon is replaced by an iodide atom, leading to sulfonium formation via intramolecular S-alkylative activation. 

Abstract The transition metal mediated synthesis of carbon-sulfur (C-S) bonds is possible with a variety of simple and tailored metal complexes. This chapter serves to illustrate developments over the last decade involving the catalytic synthesis of C-S bonds with various transition metals, focusing on cross-coupling reactions and addition to ti-bonds. 

An alternate approach to the asymmetric synthesis of axially chiral biaryls has been developed based on the nickel-catalysed Kumada cross coupling of dibenzothiophenes. Cleavage of the carbon—sulfur bond of achiral dibenzoth-iophene (10.25) with the nickel catalyst generated from ligand (10.26) leads to the... 

M. Miyasaka and A. Rajca, Synthesis of functionalized carbon-sulfur [5]helicene Pd-catalyzed Negishi cross-coupling between the beta-positions of thiophenes, Synlett, 177-181 (2004). 

Utility of Enol and Aryl Triflates. Enol and aryl triflates are extensively used for cross-coupling reactions, the formation of carbon-carbon, carbon-tin, carbon-nitrogen, carbon-sulfur, carbon-phosphorus, and carbon-halogen bonds, and reduction/ deoxygenation. In recent examples, they were used to form enamines or enamides or were eliminated to cyclooctynes for copper-free cycloadditions in biological systems. 

Metal-catalyzed cross-coupling of aryl halides with thiols remains one of the more popular routes to the synthesis of sulfur-carbon(sjP) bonds [23-25, 71]... 

Turks M, Exner CJ, Hamel C, Vogel P. Umpolung with sulfur dioxide carbon-carbon cross-coupling of electron-rich 1,3-dienes and alkenes application to the enantioselective synthesis of long-chain polyketide fragments. Synthesis 2009 ... 

The poisonous components of the most deadly mushroom Amanita phalloides (the Death Cap) are bicyclic heptapeptides which have an additional covalent bond that connects the ( -sulfur atom of an l-cysteine residue with the carbon atom in position 2 of the indole ring of the L-tryptophan. Phalloidin (or phalloidine) is the most abundant member of a whole family of related cyclic heptapeptides called phallotoxins (for a review, see Wieland1 1). These poisonous peptides, therefore, contain a cross-linking moiety consisting of L-tryptophan coupled to L-cysteine, designated tryptathionine (1), alternatively called 5-(trypto-phan-2-yl)cysteine or 2-(L-3-alanylsulfenyl)-L-tryptophan (Scheme 1). 

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