In organic chemistry, Eschenmoser's salt (named for Albert Eschenmoser) is the ionic, organic compound . It is the iodide salt of the dimethylaminomethylene cation .
The dimethylaminomethylene cation is a strong dimethylaminomethylating agent, used to prepare derivatives of the type . Enolates, silyl enol ethers, and even more acidic ketones undergo efficient dimethylaminomethylation. Once prepared, such tertiary amines can be further methylated and then subjected to base-induced elimination to afford methylidenated ketones. The salt was first prepared by the group of Albert Eschenmoser after whom the reagent is named.
Dimethylaminomethylene cation is described as a resonance hybrid of the carbocation and an iminium cation:
The atoms are coplanar. The cation is isoelectronic with isobutene.
Pyrolysis of iodomethyltrimethylammonium iodide affords the desired salt:
An alternative route starts with bis(dimethylamino)methane:
Other salts of the dimethylaminomethylene cation: