Editing Sharpless epoxidation (section)

==Selectivity==
The [[epoxidation of allylic alcohols]] is a well-utilized conversion in fine chemical synthesis. The chirality of the product of a Sharpless epoxidation is sometimes predicted with the following [[mnemonic]]. A rectangle is drawn around the double bond in the same plane as the carbons of the double bond (the ''xy-plane''), with the allylic alcohol in the bottom right corner and the other substituents in their appropriate corners. In this orientation, the (−) diester tartrate preferentially interacts with the top half of the molecule, and the (+) diester tartrate preferentially interacts with the bottom half of the molecule. This model seems to be valid despite substitution on the olefin. Selectivity decreases with larger R<sup>1</sup>, but increases with larger R<sup>2</sup> and R<sup>3</sup> (see introduction).<ref name = ChemRev/>

[[File:Mnemonic.png|center|400px|The Sharpless epoxidation]]

However, this method incorrectly predicts the product of allylic 1,2-diols.<ref>{{cite journal|author1=Takano, S. |author2=Iwabuchi, Y. |author3=Ogasawara, K. |journal=[[J. Am. Chem. Soc.]]|year=1991|volume=113|pages= 2786–2787| doi=10.1021/ja00007a082|title=Inversion of enantioselectivity in the kinetic resolution mode of the Katsuki-Sharpless asymmetric epoxidation reaction|issue=7|bibcode=1991JAChS.113.2786T }}</ref>
[[File:Sharpless model violation.png|center|Sharpless model violation]]