[73473-51-5] · C9H18NO3P · N-Ethyl(diethoxyphosphinyl)methylketenimine · (MW 219.25)
(ketenimine functionalized with a diethoxyphosphinyl group;1 reacts with nucleophiles to give various phosphonates; an annulation reagent for the synthesis of heterocycles)
Physical Data: bp 86-90 °C/1 mmHg.
Form Supplied in: colorless liquid.
Analysis of Reagent Purity: IR: nC=C=N 2030 cm-1.
Preparative Method: synthesized in 82% yield by the dehydration of diethyl (N-ethylcarbamoylethyl)phosphonate, which is prepared from N-ethyl-a-chloropropionamide and diethyl sodiophosphite (eq 1).
Handling, Storage, and Precautions: use in a fume hood.
Nucleophilic addition of ethanol, diethylamine, or hydrazoic acid to the title ketenimine (1) gives the imidate, amidine, or tetrazole with a phosphonyl residue, respectively, showing typical reactivity of ketenimines (eq 2).
The reactions of (1) with sodium salts of salicylaldehyde, o-hydroxyacetophenone, a-formyl-b-naphthol, 2-formylpyrrole, and 2-acetylpyrrole in DMF give benzopyrans, naphthopyrans, and pyrrolizines with exocyclic imine groups (eqs 3 and 4). These annulation reactions occur via initial nucleophilic attack of the anionic species at the center carbon of the ketenimine followed by the intramolecular Horner-Emmons reaction as seen in the tandem Michael-Horner-Emmons reaction of vinylphosphonates.3
Osaka University, Japan
Shinshu University, Japan