In: Chemistry
stereoselective alkene synthesis by the horner-emmons reaction balance equation(s) for important side reactions
In case of Horner–Wadsworth–Emmons reaction chemical reaction a stabilized phosphonate carbanions is reacted with aldehydes (or ketones) to produce predominantly E-alkenes.
The phosphonate-stabilized carbanions are more nucleophilic but less basic and hence, phosphonate-stabilized carbanions can be alkylated.
Whereas,in case of Wittig reaction an unstabilized phosphorous yilied is used.
Unlike phosphonium ylides, the dialkylphosphate salt byproduct is easily removed by aqueous extraction. In the absence of a carbanion-stabilizing group on the anionic carbon the elimination reaction to form the double bond becomes very slow. Apparently the transition state for the syn-elimination resembles the carbanion formed by cleavage of the P-C bond: