For ten points, name these highly strained cyclic ethers with three membered rings.
These compounds can be formed enantioselectively from alkyl- and aryl- substituted olefins using manganese in a reaction named for Katsui and Jacobsen, or by reacting sulfur ylides with ketones and aldehydes in the Johnson-Corey-Chaykovsky reaction.  Allylic alcohols are converted to chiral alcohols containing this functional group in a reaction named for Sharpless.  A transition state in the synthesis of these compounds is known as the butterfly mechanism, and these compounds are commonly synthesized by reacting an alkene with a peroxyacid. These compounds can also be synthesized from an intramolecular Williamson reaction. For ten points, name these highly strained cyclic ethers with three membered rings.
These compounds can be formed enantioselectively from alkyl- and aryl- substituted olefins using manganese in a reaction named for Katsui and Jacobsen, or by reacting sulfur ylides with ketones and aldehydes in the Johnson-Corey-Chaykovsky reaction.  
{Epoxides} or {Oxiranes} (prompt on {Ethers} before mentioned)