Hiroshi Danjo

Back to back twin bowls of D3-symmetric tris(spiroborate)s for supramolecular chain structures.

A new class of D(3)-symmetric tris(spiroborate) cyclophanes has been designed and prepared for the construction of supramolecular chain structures by iterative host-guest interaction with ditopic guest molecules. The treatment of these compounds with [Ir(tpy)(2)](PF(6))(3) complex in solution led to the formation of the chain structure, which was confirmed by (1)H NMR and CSI-MS studies. The chain structure exhibited rapid temperature-responsive gelation behavior in their HMPA solution.

Assembly Modulation by Adjusting Countercharges of Heterobimetallic Supramolecular Polymers Composed of Tris(spiroborate) Twin Bowls

Heterobimetallic supramolecular polymers were prepared by treatment of the supramolecular polymers composed of tris(spiroborate) type molecular connecting modules with a potassium cation. On the other hand, the addition of a barium cation led to dissociation of the supramolecular polymer chain. Modulation of polymer formation was realized by the use of small metal cations as a control factor.

Tris(spiroborate)-type anionic nanocycles.

Full circle: New cyclic tris(spiroborate)s were prepared as molecular recognition modules for nanometer-sized cationic guests. These cyclophanes were simply prepared by treating corresponding bis(2,3-dihydroxynaphthalene)s with an equimolar amount of boric acid. The molecular recognition ability of these cyclic spiroborates was estimated in solution and crystal phases by the use of [Ir(tpy(2))](3+) as a typical example of a cationic guest.

Nestable Tetrakis(spiroborate) Nanocycles

Multicomponent construction of the tetrakis(spiroborate) anionic nanocycles was achieved by reacting bis(dihydroxynaphthalene)s with tetrahydroxyanthraquinone in the presence of boric acid in a self-organized manner. These nanocycles exhibited selective molecular recognition behavior toward cationic guests such as methyl viologen derivatives. Formation of a supramolecular ring@ring and a guest@ring@ring structure was observed by combining the anionic nanocycle and the vinylogous analog of cyclobis(paraquat-p-phenylene).

Chemoselective acylation of (hydroxyalkyl)phenols catalyzed by Candida antarctica lipase B

Acylation of (hydroxyalkyl)phenols with vinyl esters by lipase B from Candida antarctica proceeded smoothly in a highly chemoselective manner, affording their alkyl esters exclusively or at least predominantly. The enzyme therefore discriminates between an alcoholic hydroxyl from a phenolic hydroxyl in addition to having versatile catalytic abilities for organic synthesis.

Preparation of Tris(spiroorthocarbonate) Cyclophanes as Back to Back Ditopic Hosts

Twin-bowl-shaped tris(spiroorthocarbonate) cyclophanes were designed and prepared as ditopic hosts for electrically neutral or electron-rich guests. Preparation of the desired cyclophanes was achieved by cyclotrimerization of 2,2,3,3-tetrahydroxy-1,1-binaphthyl (THB) via the transesterification of tetraphenyl orthocarbonate or dichlorodiphenoxymethane. In those reactions, bis(spiroorthocarbonate) cyclophane containing two THB units was also formed as the kinetically favored product. The spiroorthocarbonate twin bowl exhibited ditopic molecular recognition toward fullerene C60 in the crystalline state.

Selective acylation of the phenolic hydroxyl of (hydroxyalkyl)phenols by using vinyl carboxylates as acyl donors in the presence of rubidium fluoride

Highly selective acylation of the phenolic hydroxy group can be achieved with (hydroxyalkyl)phenols carrying both alcoholic and phenolic hydroxyls by the use of vinyl carboxylates as acyl donors in the presence of rubidium fluoride.Graphical Abstract

Multilayered Inclusion Nanocycles of Anionic Spiroborates

Multilayered spiroborate nanocycles were prepared from tris- or tetrakis(dihydroxynaphthalene) and tetrahydroxyanthraquinone as pillar and crossbar units via the reversible formation of a spiroborate linkage. The four-layered spiroborate nanocycle recognized two cationic aromatic guests simultaneously and exhibited the ability to form a supramolecular one-dimensional array by combining with methyl viologen dimer as the ditopic guest.