The Shi epoxidation is a chemical reaction described as the asymmetric epoxidation of alkenes with oxone (potassium peroxymonosulfate) and a fructose-derived catalyst (1). This reaction is thought to proceed via a dioxirane intermediate, generated from the catalyst ketone by oxone (potassium peroxymonosulfate). The addition of the sulfate group by the oxone facilitates the formation of the dioxirane by acting as a good leaving group during ring closure. It is notable for its use of a non-metal catalyst and represents an early example of organocatalysis. The reaction was first discovered by Yian Shi (史一安, pinyin: Shǐ Yī-ān) of Colorado State University in 1996. History Many attempts at the synthesis of an efficient non-metal catalyst were made before one was discovered. The problem with previous catalysts was the rapid decomposition/oxidation of the dioxirane intermediate and lack of electrophilicity of the reactive ketone. Aromatic ketones were proposed, and many subsequent variations of oxoammonium salts were used, but were ineffective in promoting epoxidation because of the oxidative instability of the amide groups and high flexibility of the seven-membered rings. Enantioselectivity of these early catalysts were also lowered because of large distances between the asymmetric subunits and reaction centers, yielding less than 10 percent in enantiomeric excess. The catalyst discovered by Yian Shi's group in 1996 was derived from D-fructose, and has a stereogenic center close to the reacting center (ketone)- the rigid six-membered ring structure of the catalyst and adjacent quaternary ring group minimizes epimerization of this stereocenter. Oxidation by the active dioxirane catalyst takes place from the si-face, due to steric hindrance of the opposing re-face. This catalyst functions efficiently as an asymmetric catalyst for unfunctionalized trans-olefins. Dioxirane catalyst formation Under normal pH conditions, an excess of 3 stoichiometric amounts of ketone catalyst are needed due to a high rate of decomposition. At basic pH conditions greater than 10 (pH 10.5) substoichiometric amounts (0.2–0.3) are needed for epoxidations, lowering the decomposition of reagents by disfavoring the Baeyer-Villiger side reaction. Higher temperatures result in further decomposition; thus a low temperature of zero degrees Celsius is used. Decomposition of reagents is bimolecular (second-order reaction rate), so low amounts of oxone and catalyst are used. The reaction is mediated by a D-fructose derived catalyst, which produces the (R,R) enantiomer of the resulting epoxide. Solubilities of olefin organic substrate and oxidant (oxone) differ, and thus a biphasic medium is needed. The generation of the active catalyst species