Reaction of the bromo- and fluoronaphthalenes with butyl mercaptide in dimethyl sulfoxide

Abstract

Fluoro-and 1-bromonaphthalenes reacted with «-butyl mercaptide in DMSO to give «-butyl 1-naphthyl sulfide in good yields. 2-Fluoroand 2-bromonaphthalenes reacted in a similar manner to yield «-butyl 2naphthyl sulfide. ieri-Butyl mercaptide reacted with the fluoroand bromonaphthalenes to give the corresponding ieri-butyl naphthyl sulfides. These reactions proved to be direct aromatic nucleophilic substitution reactions.In a continuation of our interest in the base-catalyzed reactions of the halonaphthalenes,3•4 we have treated the bromoand fluoronaphthalenes with n-butyl and ferf-butyl mercaptides in dimethyl sulfoxide (DMSO).The products of these reactions were the corresponding alkyl naphthyl sulfides.Although there is much knowledge concerning the reactions of thiophenoxide and thiocyanate with aromatic halogen compounds5-7 very little work has been done with the alkyl mercaptides. Miller has reported that methyl mercaptide is a much stronger nucleophile in aromatic nucleophilic substitution than thiophenoxide.8'9 Caubere and coworkers have studied the reactions of ethyl mercaptide with bromoand fluorobenzene in hexamethylphosphotriamide (H-MPT).10'11 Results and DiscussionA mixture of the halonaphthalene, butanethiol, sodium methoxide, and DMSO was heated at reflux for 1 hr. Sodium methoxide was used as the base since the thiol is a much stronger acid than methanol.12 Thus the solution would contain methanol and sodium butyl mercaptide. The completed mixture was added to water. The neutral fraction was separated and the products were analyzed by vapor phase chromatography (vpc).The products proved to be the appropriate alkyl naphthyl sulfide and the dibutyl disulfide. For example, w-butyl 2-naphthyl sulfide was obtained in the reaction using n-butyl mercaptide and 2-bromoor 2-fluoronaphthalene. No methyl naphthyl ether was observed in any of these reactions. Also no evidence of the 1,2-dehydronaphthalene intermediate, previously observed,3'4 was detected. This was shown by the fact that no 2-napththyl sulfide was isolated from 1bromoor l-fluoronaphthalene.