Stobbes Condensation

Stobbes Condensation

            This is a mixed Claisen condensation reaction between dialkyl succinatees and carbonyl group of aldehyde or ketone in the presence of base like sodium hydride (NaH), potassium tert-butoxide (KOC(CH3)3) or sodium ethoxide(NaOC2H5). The product is α-β-unsaturated half ester. For example, diethyl succinate is condensed with benzophenone using tert-butoxide (a strong base) followed by aqueous acid gives the product shown.

Mechanism

  •             The enolate from diethyl succinate attacks the carbonyl group, followed by cylization to lactone intermediate.
  •             Lactone then undergoes base catalysed ring opening to give salt of unsaturated half eatser, one of easter group is hydrolyzed in the course of reaction.
  •             This reaction is limited to those di esters which not undergo Dieckmann Condensation.