Structures and Reactivities of N‑Alkenyl-Substituted Anilides: The “Magic” Methyl Effect on Alkene

Methyl substitution at the double bond of -alkenyl anilides influences both the preferred conformation and the susceptibility to acidic hydrolysis. The R-substituted amide favors the trans conformation, whereas amides substituted at R or R favor the cis conformation. Substitution at the R and R positions increases the ratio of the trans conformer. DFT study indicated that these conformational preferences can be explained in terms of substituent-induced torsion twisting of the -alkenyl moiety relative to the amide plane. R substitution enhances the susceptibility to acidic hydrolysis, whereas R or R substitution increases the stability. The effect of the double bond on the conformational effect was showcased by contrasting the preferred conformation of R-substituted anilide (trans) and hydrogenated -isopropyl amide (cis).