Ryu Yamasaki

Synthesis of [2]Catenanes by Oxidative Intramolecular Diyne Coupling Mediated by Macrocyclic Copper(I) Complexes†

Mechanically interlocked compounds, such as catenanes and rotaxanes, are challenging synthetic targets which are expected to be important components of molecular machines and switches. Although catenanes were initially synthesized in low yields by the statistical approach and the “directed” approach, efficient synthesis of more complex molecules was achieved only when the components were preorganized by various interactions. Thus, a large number of catenanes were synthesized by the assembly of two or more components by template strategies. For example, Sauvage and co-workers achieved a high yield catenane synthesis by preorganization of the constituent parts as ligands around a Cu template. The groups of Stoddart and Fujita applied p–p donor–acceptor interactions in very efficient syntheses of interlocked molecules. Hydrogen bonding was also utilized in the process of self-assembly by the groups of V gtle and Leigh (Scheme 1). However, these methods

Nickel-Catalyzed [3+2+2] Cycloaddition of Ethyl Cyclopropylideneacetate and Heteroatom-Substituted Alkynes: Application to Selective Three-Component Reaction with 1,3-Diynes

Heteroatom-substituted alkynes such as ynol ethers and ynamines turned out to be decent substrates for the Ni-catalyzed [3 + 2 + 2] cocyclization of ethyl cyclopropylideneacetate (1). The three-component cocyclization of 1, 1,3-diynes, and heteroatom-substituted alkynes also proceeded selectively. The study provided an efficient method for the synthesis of heteroatom-substituted cycloheptadiene and related compounds.

Synthesis of Vinylcycloheptadienes by the Nickel-Catalyzed Three-Component [3 + 2 + 2] Cocyclization. Application to the Synthesis of Polycyclic Compounds

The nickel-catalyzed [3 + 2 + 2] cycloaddition of ethyl cyclopropylideneacetate and conjugated enynes proceeded smoothly and divinylcycloheptadienes were isolated in high yields. The three-component cocyclization of ethyl cyclopropylideneacetate, conjugated enynes, and (trimethylsilyl)acetylene also proceeded in a highly selective manner to afford vinylcycloheptadienes, which were reacted with various dienophiles. This study provided a new, short-step synthesis of polycyclic compounds with cycloheptane skeleton.

Cycloaddition Reaction of 2-Vinylazetidines with Benzyne: A Facile Access to 1-Benzazocine Derivatives

The cycloaddition reaction of 2-vinylazetidines with benzyne proceeded smoothly without a catalyst, and various benzazocine derivatives were isolated in good to high yields. The scope of the reaction, as well as the reactions of other arynes, has been studied.

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.

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.

Ni-catalyzed [4+3+2] cycloaddition of ethyl cyclopropylideneacetate and dienynes: scope and mechanistic insights.

A detailed study of the Ni-catalyzed [4+3+2] cycloaddition reaction between ethyl cyclopropylideneacetate and dienynes has been conducted, resulting in the development of a new method for the synthesis of compounds containing nine-membered rings. We studied the reactivity of various dienynes, together with their substituent and conformational effects. The mechanism of the reaction was probed by examining the stoichiometric reactions of the Ni complexes and dienynes.

[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 CH(2)Cl(2). 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.

Selective Synthesis of Eight-Membered Cyclic Ureas by the [6 + 2] Cycloaddition Reaction of 2-Vinylazetidines and Electron-Deficient Isocyanates

The [6 + 2] cycloaddition reaction of 2-vinylazetidines with electron-deficient isocyanates such as tosyl isocyanate proceeded smoothly in the absence of the catalyst at room temperature, and various cyclic ureas were isolated in good to high yields. Electron-deficient allenes also reacted with the 2-vinylazetidine, and the corresponding azocine derivatives were isolated.

Synthesis, structure and catalytic activity of macrocyclic NHC Pd pincer complexes

- We synthesized a series of new N-heterocyclic carbene (NHC) macrocyclic Pd pincer complexes (17-22) by the reaction of Pd(OAc) 2 or Pd 2 (dba) 3 with the corresponding macrocycles, which were prepared by the coupling reaction of dibromides with bisimidazoles. The complex adopted twisted conformation, and the activation energy of the conformational interconversion of the macrocycle was determined by VT-NMR. We also examined the catalytic activity of these Pd complexes in Mizoroki-Heck and oxidative alkynyl-alkynyl homocoupling reactions.