Reactions of 5-(alkoxy)thianthrenium perchlorates (1) with weakly basic nucleophiles Br ร , I ร and PhS ร (X ร ) in MeCN and DMSO led to S N 2 substitution, E2C elimination, and reaction at sulfonium sulfur to extents depending on the structure of the alkoxy group (RO) in 1 and the nucleophile. Three types of reaction occurred with R = cyclopentyl (1a), cyclohexyl (1b), cis-(1c) and trans-4-methylcyclohexyl (1d) and cycloheptyl (1e), and X ร = Br ร and I ร . That is, S N 2 reaction gave RX and thianthrene 5-oxide (ThO), E2C reaction gave cycloalkene and ThO and reaction at sulfonium sulfur gave X 2 , thianthrene (Th) and cycloalkanol (ROH). Earlier work with R = Me (1f) and Et (1g) and X ร = I ร , Br ร had shown that only S N 2 reaction occurred. In contrast with reactions of halide ions, reactions of PhS ร with 1b-g occurred only at sulfonium sulfur, giving Th, ROH and PhSSPh (DPDS). For comparison with 1, reactions of Ph 2 S OMe (2) with I ร and PhS ร were carried out. Reaction with I ร gave only Ph 2 S=O and MeI (S N 2). Reaction with PhS ร gave very little PhSMe (S N 2) but mainly Ph 2 S, MeOH, and DPDS from reaction at sulfonium sulfur. The differences in nucleophilic pathways (PhS ร vs Br ร and I ร ) in reactions with 1 and 2 are attributed to differences in thiophilicities of the nucleophiles. The thiophilicity of PhS ร dominates its reactions with 1 and 2. The direction toward products (Th, ROH and DPDS) in these reactions is compounded by the ease of displacement of alkoxide from 1 and 2 by PhS ร , and the ease with which, subsequently, thiophilic PhS ร attacks sulfenyl sulfur in the resulting phenylthiosulfonium ion.