Initially synthesized by Charles Pedersen, they are a simple example of a macrocyclic compound.
Green's method of synthesizing these compounds takes advantage of the template effect. Zza analogues of these compounds include cyclen, and Lehn synthesized a three-dimensional version of one of these compounds called a cryptand. Polyglymes are linearized versions of them, and along with quaternary amines they can be used as phase transfer catalysts. Initially synthesized by Charles Pedersen, they are a simple example of a macrocyclic compound. For 10 points, name this class of compounds that can complex with cations, which consists of carbon and oxygen groups arranged in a ring, and are a specific type of ether.
Green's method of synthesizing these compounds takes advantage of the template effect.
{Crown ethers} [prompt on {ethers}; accept {crown} after “{ether}”]