Functionally substituted vinyl carbanions, 25. Heteroatom influence on vinylic deprotonation

Abstract

Abstract Direct lithiation of ( E )‐(phenylvinyl)phosphonate 2 with LDA takes place at 1‐position; with electrophiles compounds 3 were obtained. The ( Z )‐1‐(ethylsulfinyl)‐2‐(ethylthio)ethylene 7 delivers on reaction with methyllithium mainly the 1‐lithiated species ( Z )‐ 7A . According to reactions with electrophiles, this functionally substituted vinyllithium species is configurationally labile. Depending on reaction temperature and time with electrophiles either ( Z )‐or ( E )‐products were obtained. Depending on substituents the 1,3‐dithioles 10a – c were lithiated either in 2‐ or 5‐position; higher reaction temperature or prolonged reaction time leads to fragmentation of the lithiated species. The 1,3‐dioxole 14b gave only a product of vinylic lithiation.