Functional group equivalents homoenolates

A CH-group, which bears vinyl and sulfide substituents, is acidic enough to be metallated by strong bases. Other d3-synthons may contain two activating functional groups in Imposition ( homoenolate -equivalents). Only one of the a-carbons is deprotonated under appropiate conditions (e.g. succinic diesters). Ano ther possibility is an acidic carbon and a non-acidic functional group in 1,3-positions (e.g. propargyl derivatives). Silyl ethers of a, -unsaturated alcohols can also be converted to anions, which react as d3-synthons (W. Oppolzer, 1976). 

Ready access to the allylic anion (26) is obtained as a result of the increased kinetic acidity of the proton a- to the carbamate group. The anions react with electrophiles at the y-position (R 5 H), and thus function as homoenolate equivalents. ... 

---