In 2012, Byrne and Gilheany affirmed this reaction progresses differently in salt-containing and salt-free conditions, with the latter scenario being susceptible to “stereochemical drift.” In one mechanism, (15[1])this reaction begins with a [2+2] cycloaddition followed by a fragmentation step. One reagent is replaced with a resonance-stabilized ester carbanion in a variant of this reaction partly named for Leopold Horner. In a modification (15[1])to this reaction, the (15[1])use of (*) phenyllithium leads to the preferential formation of (E)-isomers. This reaction’s intermediate exists in an equilibrium between betaine (10[1])(“bay-tah-een”) and oxaphosphetane (“ock-sah-FOSS-fuh-tain”) forms. This is the most popular reaction used to convert a carbonyl into an alkene. A German chemist names, for 10 points, what reaction that makes use of triphenyl phosphonium ylide reagents? ■END■