α-Amino carbene or carbenoid formation in the reaction of a tertiary amide with PhMe2SiLi and its insertion into the Si-Li bond of a second equivalent

PhMe2SiLi reacts with tertiary amides, RCONMe2, to give a carbene, RCNMe2, or an equivalent carbenoid, which gives enediamines, R(Me2N) C=C (NMe2)R, in the absence of a strong nucleophile, but is attacked by strong nucleophiles, NuLi, to give lithium reagents R(Me2N)CLiNu.