Copper-Catalyzed Thiol Arylation

Although thiols are generally stronger nucleophiles than alcohols and amines, the sensitivity of sulfides towards oxidation as well as the formation of disulfide made the cross-coupling between aryl halides and thiols difficult. From all previously reported results, it was foimd that only aryl iodides were suitable for this copper-catalyzed coupling process. 

An SN2-type ring-opening of N-activated aziridines 105 with a 2-bromobenzyl alcohol/thiol 106, followed by a copper-catalyzed intramolecular N-arylation reaction, afforded the corresponding tetrahydrobenzox(thi)azepines 107 in good yields (14JOC6468). 

Copper-Catalyzed Coupling of Aryl Halides with Alcohols and Thiols... 

Fukuzawa, S.-L, Shimizu, E., Atsuumi, Y., Haga, M. and Ogata, K. 2009. Copper-catalyzed direct thiolation of benzoxazole with diaryl disulfides and aryl thiols. Tetrahedron Lett. 50(20) 2374-2376. 

Some of the advantages of copper catalysts are that they are inexpensive, abundant etc. In 2013, Fu, Peters and their co-workers reported a copper-catalyzed coupling of aryl halides with thiols via a single-electron transfer pathway. In order to prove the reaction mechanism, they performed the reaction of allyl-o-iodophenol with thiophenol as well. No cyclized product could be produced when the reactions were performed in the dark, while 57% of dihydrobenzofuran was formed when hv was introduced (Scheme 2.40). 

Arylations. Copper(II) acetate catalyzes the reaction of arylboronic acids with thiols and of amines with hypervalent arylsiloxanes. 4-Substituted imidazoles react with aryllead(IV) reagents (in dichloromethane at room temperature) to afford N-1 arylatcd derivatives regioselectively under catalysis of Cu(OAc)2. ... 

A common feature of the above described processes is that only aryl substituents are tolerated on the side of the acid chloride 4 and aryl iodide 6 due to ketene formation and jd-H elimination from aliphatic derivatives. However, primary alkyl-substituted alkynones 1 can be obtained by a palladium-catalyzed cross-coupling of corresponding thiol-esters 9 with terminal alkynes 5 in the presence of overstoichiometric amounts of copper (2003SL1512, 2010SL1239) (Scheme 4). 

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