Three types of products by carbon nucleophiles toward methoxyphenylacetylenic sulfones

Methoxy-arylacetylenic sulfones were examined to react with various carbanion nucleophiles to result in the three types of products; thus, (i) nucleophiles (MeLi·LiBr, Vinyl MgBr, LiCH2CN) showed the α-addition, however, (ii) Li–Ctriple bond; length of mdashC–TMS afforded β-addition (conjugate addition) products. The (iii) displacement reaction through α-addition/isomerization/trans-elimination was enhanced by the presence of ortho-methoxy group at high temperature. The heteroatom nucleophiles (nitrogen, oxygen or sulfur atom) in a protic solvent provided only conjugate addition products as reported.