Carbon-sulfur bonds 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. 

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... 

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

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. 

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

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]... 

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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