Shinichi Saito

Weak interactions between the macrocyclic phenanthroline derivatives and hydrocarbon moieties were quantitatively evaluated by analyzing the NMR spectra of the rotaxanes. The observed associative interaction between the macrocycle and the 1,3‐diyne moiety was further investigated by DFT calculations. The C─H⋯N interaction and reduced steric bulk of the 1,3‐diyne moiety were assumed to be the origins of the interaction. These findings demonstrate that rotaxane architectures provide a powerful platform for the quantitative analysis of weak interactions.

We synthesized [3]catenanes via intramolecular Sonogashira-type reaction. A macrocyclic phenanthroline-copper(I) iodide complex promoted the cyclization reaction providing [2]- and [3]catenanes. By using acyclic precursors with pyrene or naphthalene diimide (NDI) moieties, we successfully synthesized [3]catenanes with two different ring components (ABB-type) as well as [3]catenanes with three different ring components (ABC-type). In the ABC-type [3]catenane, interactions between the pyrene and NDI moieties were observed. The photophysical properties of the catenanes were examined.

We achieved the synthesis of [2]rotaxane by the reaction of a bulky phenoxide with a macrocyclic iodonium salt, which served as a covalent-bond-tethered precursor. The cleavage of the tether and the formation of the axle component proceeded simultaneously, providing rotaxane in a good yield. The versatility of this approach was demonstrated by the synthesis of [3]rotaxane as well as the synthesis of [2]rotaxane from a medicine.

We report a regio- and stereoselective diboration of the terminal C═C bond of allenes by B₂(dan)₂ (dan = naphthalene-1,8-diaminato) in the presence of a Pt catalyst. This reaction is applicable to a broad range of substrates, including 1-arylallenes and 1,1-disubstituted allenes. The two boryl groups in the product exhibit distinct reactivities, enabling chemoselective transformations.

Oligo( para ‐phenylene) (PPn) is a π‐conjugated compound where phenylene units are directly connected at the 1,4‐positions. Utilizing the catalytic activity of the macrocyclic dihydrodibenzophenanthroline‐Ni complex, we succeeded in the synthesis of [3]‐ and [2]rotaxanes with PPn axles by biaryl coupling. The size of the macrocycle was critical to synthesize [3]rotaxanes, which consist of two oligo( para ‐phenylene) axles, in good yields. The relationship between the length of the PPn structure on the ¹ H NMR spectra of the rotaxanes was studied. The aggregation of a PP8 derivative was suppressed by the presence of the macrocycle in the rotaxanes. A [3]rotaxane could be considered as a model compound of an aggregated PPn, and the photophysical studies disclosed the influence of the aggregation on the properties of PPn.

The diboration of alkynes by 1,8-diaminonaphthalene-protected diboronic acid (B₂(dan)₂) proceeded smoothly in the presence of a platinum catalyst, and 1,2-diborylalkenes were isolated in up to 94% yield. The use of an appropriate solvent and ligand was critical for the progress of the reaction. The derivatization of 1,2-diborylalkenes was briefly examined.

Invited for the cover of this issue are Yusuke Yoshigoe, Hirotaka Shimada, and Shinichi Saito at the Tokyo University of Science, and Takuya Takaki and Yoshitane Imai at Kindai University. The image depicts a witch with a racemic pair of our nanohoops, TB[6]CPPs, chanting words shown in the font of a magical world. Read the full text of the article at 10.1002/chem.202304059.

The synthesis of a new nanohoop containing a stereogenic Tröger's base skeleton tethered to a curved hexaparaphenylene ([6]CPP) is reported. The TB[6]CPP nanohoop possesses a stable C₂ symmetrical structure, which promotes the allowed transition that gives rise to pale blue emission with a quantum yield of ~0.69, surpassing the value of the more symmetrical [8]CPP. Moreover, TB[6]CPP shows chiroptical properties including circular dichroism and circularly polarized luminescence with a moderate dissymmetry factor (|g_lum|) of ~2.1×10⁻³

Oligo(para‐phenylene) (PPn) is a compound composed of directly connected 1,4‐phenylene moieties. The synthesis of PPn composed of six or more phenylene moieties with no substituent at the internal phenylene moiety has been challenging because of its low solubility. Herein we synthesized oligo(para‐phenylene)[2]rotaxanes, including a deca(para‐phenylene)[2]rotaxane, with a defined number of phenylene moieties. Biaryl coupling of iodoarenes mediated by macrocyclic dibenzodihydrophenanthroline‐Ni complex was utilized for the first time to synthesize the [2]rotaxanes. Compared to the non‐interlocked deca(para‐phenylene), the deca(para‐phenylene)[2]rotaxane showed higher solubility. The properties of the oligo(para‐phenylene)[2]rotaxanes and non‐interlocked oligo(para‐phenylene)s were analyzed by spectroscopic methods.