Reactions of Haloarenes with Thiolate Anions in Tetraglyme: Cmpetition between Electron Transfer and SNAr Mechanisms

Article abstract of DOI:10.1002/hlca.19880710421

The reaction of the bromo-substituted naphthalene 1 with the alkanethiolate anions 2a-b and arenethiolate 2c in tetraglyme gave the corresponding 1-naphthyl thio-ethers 3a-c.Thio-ethers 3a-c were oxidized to the corresponding sulfones 4a-c with m-chloroperoxybenzoic acid.The reaction of the dichloro-substituted anthracene 5a with 2b gave the disubstitution product 6a.The reaction of 9-bromoanthracene 5c with the alkanethiolate 2b gave 6b, whereas the reaction of 5c with the arenethiolate 2c gave a mixture of aubstitution product 6c and anthracene 7.The observation of the formation of both 6c and 7 is explained by the competition between substitution (S_NAr) and electron-transfer (ET) mechanisms.Consistent with this interpretation, the reaction of the monochloro-substituted 5b, which has a higher-energy ?^* orbital, with 2c gave 6c without the formation of 7.Zn/KOH in tetraglyme was shown to reduce the aryl halides 5b-c and thio-ether 6c to 7.