AbstractIrradiation of N‐stearoylimidazole (1) gave hexadec‐1‐ene (4) in 45% yield, whereas irradiation of N‐(4‐methylstearoyl)imidazole (13) possessing a tertiary hydrogen atom γ to the carbonyl group led to 2‐methylhexadec‐1‐ene (14) in 62% yield. These results are explained by a two‐stage process: acyl migration, followed by Norrish Type II eliminatior. The reaction has been utilized for the side chain degradation of bile acids and of lanosterol, in which the second stage of the reaction was shown to proceed in up to 70% yield.