Akin toenamines, enol ethers are electron-rich alkenes by virtue of the electron-donation from the heteroatom viapi-bonding. Enol ethers haveoxonium ion character. By virtue of their bonding characteristics, enol ethers display distinctive reactivity. In comparison with simple alkenes, enol ethers exhibit enhanced susceptibility to attack by electrophiles such as Bronsted acids. Similarly, they undergo inverse demandDiels-Alder reactions.[2]
The reactivity of enol ethers is highly dependent on the presence of substituents alpha to oxygen. The vinyl ethers are susceptible to polymerization to givepolyvinyl ethers.[3] They also react readily withthiols in thethiol-ene reaction to formthioethers. This makes enol ether-functionalized monomers ideal for polymerization with thiol-based monomers to form thiol-ene networks.[4]
Some vinyl ethers find some use asinhalation anesthetics. Enol ethers bearing α substituents do not polymerize readily. They are mainly of academic interest, e.g. as intermediates in the synthesis of more complex molecules.
The acid-catalyzed addition of hydrogen peroxide to vinyl ethers gives the hydroperoxide:[5]
Vinyl ethers can be prepared by reaction ofacetylene andalcohols in presence of a base.[8]
Although enol ethers can be considered theether of the correspondingenolates, they are not prepared by alkylation of enolates. Some enol ethers are prepared from saturated ethers by elimination reactions.[9]
^Milas, Nicholas A.; Peeler, Robert L.; Mageli, Orville L. (1954). "Organic Peroxides. XIX. α-Hydroperoxyethers and Related Peroxides".Journal of the American Chemical Society.76 (9):2322–2325.doi:10.1021/ja01638a012.
^Carl Kaiser; Joseph Weinstock (1976). "Alkenes Via Hofmann Elimination: Use of Ion-exchange Resin for Preparation of Quaternary Ammonium Hydroxides: Diphenylmethyl Vinyl Ether".Org. Synth.55: 3.doi:10.15227/orgsyn.055.0003.
