Enhancement of Acid‐Catalyzed Esterification by the Addition of Base

General acid‐catalyzed reaction can be enhanced by the addition of base. Self‐catalyzed esterification of benzoic acid and octan‐1‐ol was enhanced by the addition of certain base such as imidazole. The rate of the esterification was accelerated as the concentration of imidazole increased. Trans‐esterification of 4‐nitrophenyl acetate was promoted in chloroform by the mixture of benzoic acid and imidazole, but not by benzoic acid or imidazole alone.     

Deprotection of dithioacetals with 30% hydrogen peroxide catalyzed by tantalum(V) chloride–sodium iodide or niobium(V) chloride–sodium iodide

The reaction of dithioacetals with 30% hydrogen peroxide in the presence of catalytic amounts of tantalum(V) and iodide ion effectively produced carbonyl compounds in high yields. Dithioacetals also can be deprotected using the niobium(V) catalyzed oxidation of iodide ion by hydrogen peroxide under mild conditions.     

The First Rotational Isomers of Stable Selenobenzaldehydes and their η1-Tungsten Complexes

The first rotational isomers of stable selenoaldehydes are synthesized by deselenation of cyclic polyselenides having an efficient steric protection group, 2, 4, 6-tris[bis(trimetylsilyl)methyl]phenyl (Tbt). Reactions of these selenoaldehydes with W(CO)₅.THF gives the corresponding η¹-selenoaldehyde tungsten complexes, the structures of which are established by X-ray crystallography.     

Synthesis and Antibacterial Activity of 3‐(Substituted arylmethyl)‐4‐acylaminomethyloxazolidin‐2‐ones and Derivatization to Symmetrical Twin‐Drug Type Molecules

In connection with our studies on antibacterial active compounds in the class of new oxazolidinones against Gram‐positive (Staphylococcus aureus) and Gram‐negative (Escherichia coli) strains, some molecular modifications were attempted. In this study, molecular modifications of 4‐aminomethyloxazolidin‐2‐ones ( 3a ) to the corresponding 4‐acylaminomethyloxazolidin‐2‐one derivatives ( 3c–d ) and preparations of the represented twin‐drug type molecules ( 10–14 ) were investigated. Some additional 4‐dialkylaminomethyloxazolidin‐2‐ones ( 2 ) were also synthesized. The synthesized compounds were evaluated for antibacterial activity with Gram‐positive (S. aureus) and Gram‐negative (E. coli) strains.     

Synthesis and photophysical properties of 2,2′-binaphthalene-based receptor bearing trimethylsilyl groups to improve the solubility

Two trimethylsilyl groups were introduced at 5- and 5′-positions of 2,2′-binaphthalene to improve the solubility of 2,2′-binaphthalene-based receptors. The X-ray crystallographic analysis revealed the twisted structure of 2 in the solid state. The solubility of 2 was moderately improved by 3.1-fold comparing with mother skeleton 1. As a practical example of 2, receptor 8 bearing two aza-15-crown-5 moieties was prepared and the selective binding of 8 with Ba²⁺ can be observed by the formation of sandwich-like complex, which shows no prevention of binding ability of the receptor by introduction of the bulky substituents.