Giving the same products as the Peterson reaction, unlike the Knoevenagel and aldol reactions, it is stereoselective and regiospecific.  
Giving the same products as the Peterson reaction, unlike the Knoevenagel and aldol reactions, it is stereoselective and regiospecific.  Beta-carotene is synthesized from vitamin A using this reaction in which an aldehyde or ketone reacts with a phosphonium ylide to form an alkene. For ten points, name this eponymous reaction which won its German discoverer a share of a Nobel Prize.
Giving the same products as the Peterson reaction, unlike the Knoevenagel and aldol reactions, it is stereoselective and regiospecific.  
Wittig reaction