Efficient synthesis of [2]- and higher order rotaxanes via the transition metal-catalyzed hydrosilylation of alkyne

A novel end-capping method of pseudorotaxanes via the hydrosilylation of the alkyne of the axle terminal was developed. RuHCl(CO)(PPh₃)₃ and RhCl(CO)(PPh₃)₃ complexes catalyzed the hydrosilylation reactions of the alkyne moiety of several pseudorotaxanes at ambient temperature to give the corresponding [2]- and higher order rotaxanes in high yields with excellent regio- and stereoselectivity.     

Is the tert-butyl group bulky enough to end-cap a pseudorotaxane with a 24-crown-8-ether wheel?

Although rotaxane chemists have long believed that the tert-butyl group is bulkier than the cavity of dibenzo-24-crown-8-ether (DB24C8), it is essentially smaller than the cavity of DB24C8. The tert-butyl (or 4-tert-butylphenyl) group can actually function as an end-cap of DB24C8-based rotaxanes when the intercomponent interaction is effectively operative. When such attractive interaction is removed, deslippage occurs. [structure: see text]     

Novel benzyl sulfonium salt having an aromatic group on sulfur atom as a latent thermal initiator

Three benzyl p-hydroxyphenyl methylsulfonium salts with different counter anions were synthesized as novel latent thermal initiators. Syntheses of the sulfonium salts ( 2 ) were performed by the reaction of p-hydroxyphenyl methyl sulfide with benzyl chloride followed by exchange of the counter anion (Cl^?) with SbF^?₆ ( 2a ), PF^?₆ ( 2b ), or BF^?₄ ( 2c ). In the bulk polymerization of glycidyl phenyl ether (PGE) with 2 , initiator activity of the sulfonium salts was evaluated by comparison with that of benzyl tetramethylenesulfonium hexafluoroantimonate ( 1 , R = H). Among the initiators, 2a showed the highest activity, and was much more active than 1 (R = H). Since the polymerization of PGE with 2a proceeded efficiently at more than 80°C but not at all at less than 60°C, 2a was suggested to be a good latent thermal initiator.     

Model reactions of functionalization of polycarbonate. Reactions of phenyl chloroformate with nucleophiles and cationic polymerization behavior of bicyclo orthoesters containing carbonate group

Some model experiments for functionalization of a polycarbonate were carried out. At first, reactivity of phenyl chloroformate with a few nucleophiles was examined. Reaction with alkyl amines gave corresponding carbamates, but in the case of aniline, formation of a byproduct diarylurea was observed. Reactions with alcohols and phenols afforded carbonates in moderate yields, in which p-nitrophenol and isopropyl alcohol were less reactive. On the basis of these results, 1-ethyl-4-phenoxycarboxymethyl-2,6,7-trioxabicyclo[2.2.2]octane (2) and 1-ethyl-4-ethoxycarboxymethyl-2,6,7-trioxabicyclo[2.2.2]octane (3) were prepared by the reaction of phenyl and ethyl chloroformates with 1-ethyl-4-hydroxymethyl-2,6,7-trioxabicyclo[2.2.2]octane in the presence of tert-amine. 2 polymerized cationically with BF₃OEt₂ at more than 80°C to give a polyether containing both ester and carbonate groups in the side chain, with contamination of a gelled polymer.     

Technetium-99m complexes with steroid-2-aminooxyethyliminodiacetic acid conjugates

Conjugates of 2-aminooxyethyliminodiacetic acid with estrone, testosterone, epiandrosterone, 17-alpha-hydroxy-progesterone and progesterone were synthesized and their complexes with Tc-99m were successfully prepared in good yields, which indicated the agent to be promising for metal-labeling of biomolecules and related substances containing one or more carbonyl groups. The biodistribution and scintigraphic studies in mice bearing Ehrlich tumor and mammary tumor showed that the radioactivity accumulated considerably in the tumor tissues, but the tumor images were somewhat obscured.     

Novel adducts of sulfides and 4-substituted 1,2,4-triazoline-3,5-diones ( TAD ) A similarity of TAD and singlet oxygen( 1O2 )

The 4-substituted 1,2,4-triazoline-3,5-diones( $\text{2}$ ) afford with sulfides( $\text{1}$ ) having acidic α-hydrogens the 1,4-disubstituted urazoles( $\text{3}$ ). Reactivity of the triazolinedione shows similarity in possible reaction modes with that of singlet oxygen.     

Screening of matrix suitable for immobilization of microbial cells

To find a suitable matrix for immobilization of microbial cells, synthetic and natural polymers were screened. As a result,kappa-carrageenan,iota-carrageenan, furcellaran, sodium alginate, ethyl succinylated cellulose, succinylated zein, and 2-methyl-5-vinyl-pyridine-methylacrylate-methacrylic acid copolymer were studied. These polymers were induced to gel under mild conditions.Streptomyces phaeochromogenes cells having glucose isomerase activity were successfully immobilized in these polymer matrices. If a gelinducing reagent were added to a substrate solution, these gel matrices could be stabilized. The microbial cells did not leak out from the gel lattice. When these immobilized cells were treated with hardening reagents such as glutaraldehyde or tannins, the gel matrices were strengthened, and the glucose isomerase activity became stable for a long period even in the absence of gel-inducing reagents. Among these polymer matrices tested,kappa -carrageenan was most suitable for immobilization of microbial cells.     

Water reduction and oxidation on Pt-Ru/Y2Ta2O5N2 catalyst under visible light irradiation

Y(2)Ta(2)O(5)N(2) is presented as a novel photocatalyst with high activity for water splitting under visible-light irradiation in the presence of appropriate sacrificial reagents; the activity for reduction to H(2) is increased by the incorporation of Pt or Ru as a co-catalyst, with a significant increase in production efficiency when both Pt and Ru are present.