N-Substituent effects on the stability of ketenimines

A homodesmotic reaction was designed to study N-substituent effects on the stability of ketenimines. A good correlation (SE1 = −12.27χBE + 29.81) between N-substituted ketenimine stabilization energies (SE1) and substituent group electronegativity has been found. Both N-substituted and Cβ-substituted ketenimine stabilization energies (SE1 and SE2) have good correlations with Taft’s dual-substituent-parameters and modified Swain–Lupton constants. As to N-substituent and Cβ-substituent effects on the stability of ketenimines, σ-donors stabilize ketenimines while σ-acceptors destabilize them; π-acceptors stabilize ketenimines while π-donors destabilize them.