This reaction is the basis for a modification that uses electron-deficient reagents in a mixture of KHMDS and 18-crown-6. Semi-stabilized aryl reagents in this reaction do not achieve stereoselectivity, unlike stabilized ester or unstabilized alkyl reagents. Maryanoff and Reitz coined the term (10[1])“stereochemical drift” (10[2])to describe the interconversion of betaine intermediates in this reaction, which can be controlled (10[1])using the Schlosser modification. A modification of this reaction that uses carbanion reagents to preferentially synthesize E products was proposed by Leopold Horner. In lithium-free conditions, this reaction proceeds via a four-atom oxaphosphetane intermediate. For 10 points, name this reaction that uses a triphenyl phosphonium ylide (“ILL-id”) reagent (10[1])to convert a carbonyl group into an alkene. ■END■ (0[2])