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.” A [2+2] cycloaddition begins one of this reaction’s two mechanisms that sees the formation of a “closed” four-membered ring intermediate. One reagent is replaced with an ester carbanion in a variant of this reaction partly named for Leopold Horner. This reaction’s intermediate exists in an equilibrium between (*) betaine (“bay-tah-een”) and oxaphosphetane (“ock-sah-FOSS-fuh-tain”) forms. (10[1])Phenyllithium aids in the preferential formation of (E)-isomers in this reaction’s (10[1])Schlosser modification. 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■