This chemist erroneously predicted that a certain cyclization undergoes a two-plus-two mechanism followed by a migratory insertion, which was corrected by E. J. Corey’s three-plus-two mechanism in a decade-long feud. A reaction named for this chemist expands on one developed by the Upjohn Company and may use a commercial “AD (“A-D”) mix” containing various potassium salts and a quinine ligand. This chemist is the alphabetically latest of the developers of a copper-catalyzed variant of the (10[1])Huisgen (“HOUSE-gun”) cycloaddition, which reacts an azide with an alkyne. This chemist names an alkene dihydroxylation that uses osmium tetroxide, as well as an asymmetric epoxidation. For 10 points, name this American chemist who coined the term “click chemistry” (10[1])and twice received the Nobel Prize in Chemistry. ■END■ (0[1])