Homoenolate dianions of secondary amides via tin/lithium exchange

Treatment of N-phenyl- a well as N-methyl-3-(tri-bar|n-butylstannyl)-propionamide with 2 equiv of bar|n-butyllithium in the presence of 1,4-diazabicyclo2.2.2]octane at ?78°C in tetrahydrofuran produced the corresponding dilithio derivatives (homoenolate dianions) $\text{4}$ and $\text{8}$ respectively. Reaction with various electrophiles (1 equiv) gave the terminally substituted amides in good yields.