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)

Synthesis of [2]Rotaxanes by the Copper-Mediated Threading Reactions of Aryl Iodides with Alkynes

The catalytic activity of the macrocyclic phenanthroline–copper(I) complex is utilized for the Sonogashira-type reaction to synthesize [2]rotaxanes. Thus, [2]rotaxanes were prepared by reactions between terminal alkynes and aryl iodides in the presence of the macrocyclic copper complex. Bulky substituents were introduced to the substrates to stabilize the rotaxane. The bond-forming reaction proceeded selectively inside the macrocyclic complex so that the rotaxanes could be synthesized

[5 + 2] Cycloaddition Reaction of 2-Vinylaziridines and Sulfonyl Isocyanates. Synthesis of Seven-Membered Cyclic Ureas

The [5 + 2] cycloaddition reaction of 2-vinylaziridines with sulfonyl isocyanates proceeded smoothly under mild conditions, and various cyclic ureas were isolated in high yields. The remarkable solvent effect on the reaction was observed, and the preferential formation of the seven-membered ring occurred when the reaction was carried out in CH₂Cl₂. The scope and limitation were studied, and the mechanism of this reaction was discussed. This study provides a new and simple method for the synthesis of seven-membered cyclic ureas

Acid-Mediated Ring-Expansion Reaction of <i>N</i>‑Aryl-2-vinylazetidines: Synthesis and Unanticipated Reactivity of Tetrahydrobenzazocines

The aza-Clasen rearrangement of <i>N</i>-aryl-2-vinylazetidines has been explored. <i>N</i>-Aryl-2-vinylazetidines were transformed to corresponding tetrahydrobenzazocines in good yields. Unexpectedly, the tetrahydrobenzazocine was unstable and readily isomerized to vinyltetrahydroquinoline in the presence of acid. The mechanism of this ring contraction was studied in detail

[5 + 2] Cycloaddition Reaction of 2-Vinylaziridines and Sulfonyl Isocyanates. Synthesis of Seven-Membered Cyclic Ureas

The [5 + 2] cycloaddition reaction of 2-vinylaziridines with sulfonyl isocyanates proceeded smoothly under mild conditions, and various cyclic ureas were isolated in high yields. The remarkable solvent effect on the reaction was observed, and the preferential formation of the seven-membered ring occurred when the reaction was carried out in CH₂Cl₂. The scope and limitation were studied, and the mechanism of this reaction was discussed. This study provides a new and simple method for the synthesis of seven-membered cyclic ureas

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

Synthesis of Large [2]Rotaxanes. The Relationship between the Size of the Blocking Group and the Stability of the Rotaxane

[2]­Rotaxanes with large macrocyclic phenanthrolines were prepared by the template method, and the stability of the rotaxanes was examined. Compared to the tris­(biphenyl)­methyl group, the tris­(4-cyclohexylbiphenyl)­methyl group was a larger blocking group, and the rate of the dissociation of the components decreased significantly when the thermal stability of a rotaxane with a 41-memebered ring was examined. We also succeeded in the synthesis of larger rotaxanes by the oxidative dimerization of alkynes with these bulky blocking groups, utilizing the catalytic activity of the macrocyclic phenanthroline–Cu complex