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

Methyl substitution at the double bond of N-alkenyl anilides influences both the preferred conformation and the susceptibility to acidic hydrolysis. The R1-substituted amide favors the trans conformation, whereas amides substituted at R2 or R3 favor the cis conformation. Substitution at the R1 and R3 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 N-alkenyl moiety relative to the amide plane. R1 substitution enhances the susceptibility to acidic hydrolysis, whereas R2 or R3 substitution increases the stability. The effect of the double bond on the conformational effect was showcased by contrasting the preferred conformation of R1-substituted anilide (trans) and hydrogenated N-isopropyl amide (cis)

Crystal Engineering of <i>N</i>,<i>N</i>′‑Diphenylurea Compounds Featuring Phenyl–Perfluorophenyl Interaction

Here, aiming to adopt the phenyl–perfluorophenyl interaction to regulate molecular alignment and arrangement for crystal engineering, we examined and compared in detail the crystal structures of <i>N</i>,<i>N</i>′-diphenylurea compounds <b>1</b>–<b>6</b>. We found that phenyl–perfluorophenyl interaction greatly influenced the intermolecular arrangement in the crystal, and we were able to prepare a cocrystal of <b>1</b> and <b>2</b>, in which the molecules were alternately arranged under the control of the phenyl–perfluorophenyl interaction. This arrangement was driven by the asymmetric geometry of the hydrogen bonds in the cocrystal (<b>1·2</b>), in which <b>2</b>, bearing two perfluorophenyl groups, worked as a better hydrogen bond donor. In contrast, NH connected to the phenyl group in <b>3</b> proved to be a better hydrogen bond donor due to the intramolecular resonance effect. <i>N</i>,<i>N</i>′-Dimethylated derivatives, <b>4</b>–<b>6</b>, existed in <i>cis</i>-<i>cis</i> form in the crystal. Antiparallel carbonyl–carbonyl arrangements were observed in <b>4</b> and <b>6</b>, while an unexpected carbonyl–perfluorophenyl interaction was observed in the crystal of <b>5</b>. These findings will be helpful in the design of diphenylurea-based functional molecules, especially for solid-state application