A rare example of a rearrangement involving four structural isomers: alpha-phosphinonitrile/C-phosphinoketenimine/1-aza-4- phosphabutadiene/1,2-dihydro-1,2-azaphosphete

The stable compound [bis(dicyclohexylamino)phosphino](trimethylsilyl)-carbene (1) reacts with dimethyl cyanamide to afford the original 1,2-dihydro-1,2-azaphosphete 4a (51% yield). The surprising formation of this heterocycle involves the transient formation of a nitrile, a keteneimine, and a 1-aza-4 lambda 3-phosphabutadiene derivative. By using substituent effects and different synthetic routes, all of these structural isomers have been isolated.