Abstract
Treatment of acetylenic sulfonium salts, dimethyl 3-phenyl-2-propynylsulfonium bromide (VII), dimethyl 2-butynylsulfonium bromide (XII) and methyl bis (3-phenyl-2-propynyl) sulfonium methyl sulfate (XIX), with base gave SNi'reaction products, methyl 2-phenyl-2, 3-butadienyl sulfide (VIII), methyl 2-methyl-2, 3-butadienyl sulfide (XIII) and methyl 1-(2-phenylethynyl)-2-phenyl-2, 3-butadienyl sulfide (XXII), respectively. Similarly, methyl (2-propenyl) (3-phenyl-2-propynyl) sulfonium methyl sulfate (XXIII) was converted to methyl 1-(2-phenylethynyl)-3-butenyl sulfide (XXVII) by SNi'reaction. The reaction of methyl benzyl 3-phenyl-2-propynylsulfonium methyl sulfate (XXXIII) with base, however, afforded the usual Stevens type rearrangement product, methyl 1-benzyl 3-phenyl-2-propynyl sulfide (XXXVI). A mechanistic assumption for the rearrangements of acetylenic sulfonium salts was given.
