The reaction of the hromo-substituted naphthalene 1 with the alkanethiolate anions 2a-b and arenethiolate 2c in tetraglyme gave the corresponding 1 -naphthyl thio-ethers 3a*. Thio-ethers 3a-e were oxidized to the corresponding sulfones 4a* with m-chloroperoxybenzoic acid. The reaction of the dichloro-substituted anthracene 5a with Zb gave the disubstitution product 6a. The reaction of 9-bromoanthracene 5c with the alkanethiolate 2b gave 6b, whereas the reaction of 5c with the arenethialate 2c gave a mixture of substitution product 6c and anthracene 7. The observation of the fornation of both 6c and 7 is explained by the competition between substitution (S,Ar) and electron-transfer (ET) mechanisms. Consistent with this interpretation, the reaction of the monochloro-substituted Sb, which has a higher-energy u* orbital, with 2c gave 6c without the formation of 7. Zn/KOH in tetraglyme was shown to reduce the aryl halides 5 b c and thio-ether 6c to 7.
Introduction. -Considerable research effort continues towards the development of methodologies for the substitution of aryl halides by thiolate anions because the substitution products are currently of considerable theoretical interest. Alkyl-and arylthiobenzenes, for example, have been used in the design of inclusion compounds [l]. Recent advances in the technology of organic metal conductors have spurred the use of arylthioethers as intermediates for the synthesis of polyfulvalenes with extended conjugation [2]. Quite recently, Cox et al. have reported a novel photochromic tetraalkylthiobenzene [3].
Results from our laboratory have shown that tetraglyme (2,5,8,1I,Il-pentaoxapentadelecane) is a suitable solvent for the substitution of unactivated halobenzenes by arene and alkanethiolate anions [4-71, which provides an alternative to N,N-dimethylacetamide [8], N,N-dimethylformamide [9], and the suspected carcinogen hexamethylphosphoric triamide (HMPT) [lo]. In tetraglyme [6], limited mechanistic study suggested that a S,Ar mechanism [ 111 is operative in the substitution of unactivated halobenzenes by alkanethiolates. Similarly, the results of Tiecco and coworkers [lob] suggested that a S,Ar mechanism is operative in HMPT. The substitution of iodobenzenes with arenethiolate anions by a S,,1 mechanism [1212) has been reported in the photostimulated reaction by Bunnett and Creary [13], whereas Rossi and coworkers [14] reported the competition between electron transfer (ET) and fragmentation of the radial anion intermediate of analogous SR,l reactions with thiolate anions.
The substitution of naphthyl and anthryl halides by thiolate anions has received considerably less attention [15], although evidence for an SR,l mechanism under certain ') *)