Neighboring-Group Participation by Hydroxyl Oxygen in Nucleophilic Aromatic Substitution. Smiles Rearrangements of (ω-Hydroxyalkyl)methyl(p-nitrophenyl)sulfonium Perchlorates in Aqueous Alkali

Article abstract of DOI:10.1021/jo01312a028

(2-Hydroxyethyl)- (1), (3-hydroxy-n-propyl)- (2), and (4-hydroxy-n-butyl)methyl(p-nitrophenyl)sulfonium perchlorates (3) were prepared.Products by Smiles rearrangements (intramolecular S_NAr reactions) were obtained from 1 as β-(methylthio)ethyl p-nitrophenyl ether (9) in 37-42percent yield and from 2 as γ-(methylthio)propyl p-nitrophenyl ether (8) in quantitative yields, and none were obtained from 3.The rearrangement rates and yields were compared with an intermolecular S_N2 reaction of dimethyl(p-nitrophenyl)sulfonium perchlorate (4) (displacement of the sulfonium group by a n-propoxy group) to estimate participation by the ω-hydroxyl oxygen.The rate ratios between the rearrangements (first order) and the S_N2 n-propoxy attack (second order), effective molarities, were obtained as 6.02 * 10³ M for 1 vs. 4 and 4.64 * 10³ M for 2 vs. 4.