(±)-Camphor-10-sulfonic acid as recyclable and efficient catalyst for the synthesis of some novel coumarin derivatives

A highly competent-diversity oriented synthesis of coumarin core derivatives using a Knoevenagel condensation followed by Michael addition and subsequent cyclization in the presence of (±)-camphor-10-sulfonic acid in a water/ethanol (1:1) solvent system is depicted. Furthermore, easy workup procedures with good yield, rapid reactions with high atom economy, and catalyst recyclability are the fascinating features of the procedure.     

Photocatalytic activity and characterization of sol-gel-derived Cr(III)-doped TiO2-coated active carbon composites

Cr(III)-doped, TiO₂-coated active carbon (Cr–TiO₂/AC) were prepared by a sol–gel method. The effect of supports, including TiO₂ and active carbon (AC), on the molecular structure and photocatalytic activity of chromium oxide for complete decomposition of EDTA has been examined with respect to the content of Cr on the catalyst surface. The photocatalytic activity of the Cr–TiO₂/AC composites was evaluated in the decomposition of EDTA solution under UV irradiation. The results indicate that Cr–TiO₂/AC has a higher efficiency in decomposition of EDTA than TiO₂, TiO₂/AC or active carbon. This was attributed to the different functions of active carbon and chromate species. (1) Nanosize TiO₂ particles on composites were not reunited, possible because active carbon retards transformation of anatase into rutile and decreases the crystallite size. (2) Production of high concentrations of organic compound near Cr–TiO₂. (3) Carbon in active carbon causes some of the TiO₂ to reduce to Ti³⁺ ions, which prevents electron–hole pair recombination. (4) Formation of polychromate species, with a stronger redox capability, on the surface of TiO₂/AC. It was found that the addition of Cr to TiO₂ sol could suppress the grain growth of TiO₂ crystals and increase the hydroxyl content on the surface of TiO₂/AC. The photocatalytic efficiency and activity of the composites remained good, even after three cycles.     

Action of Trichloromethyl Chloroformate on Sustituted Ureas: Preparation of Some Alkylcarbamoylureas

Trichloromethyl chloroformate (TCF) reacts with substituted ureas to give the intermediate trichlorodiazapentadiene (4) which decomposes in water to yield the corresponding alkylcarbamoylurea.     

Synthesis of Substituted (±)-3,4-Dihydrocoumarins Using H-Y Zeolite

Synthesis of substituted (±)-3,4 Dihydrocoumarins were prepared with the reaction between substituted cinnamic acid and phenol catalysed by ecofriendly solid-acid catalyst H-Y zeolite involving esterification followed by ring closure.     

Novel Selectivity in Carbohydrate Reactions,IV: DABCO-Mediated Regioselective Primary Hydroxyl Protection of Carbohydrates

An efficient procedure for the regioselective tritylation of primary hydroxyl group of aldohexopyranosides and nucleosides using trityl chloride in the presence of 1,4-diazabicyclo[2.2.2]octane (DABCO) in dichloromethane has been developed. Subsequent acetylation of the tritylated products in the same pot has been made possible, thereby providing an efficient route to the fully protected carbohydrate derivatives that can be discriminated chemoselectively.     

Synthesis and Characterization of 2, 3-Dihydroxypropylcellulose

Water-soluble 2,3-dihydroxypropylcellulose (DHPC) was successfully synthesized by the reaction of 3-chloro-1,2-propanediol with alkali cellulose in dioxane, or with glycidol in acetone. DHPC from the glycidol reaction was shown to have better solubility and yield. DHPC made from cotton wool and glycidol possesses the highest intrinsic visocisty (up to 4.05 dL/g). Quantitative ¹³ C-NMR analysis was utilized to estimate the molar substitution and degree of substitution of the resulting DHPC. Since the ratios of molar substitution to degree of substitution were found to be 2 or less, the substituents on the cellulose probably consist of monomer, dimer, or trimer of the alkylation agents used. Above the critical concentration of DHPC, the solution viscosity was found to be increased tremendously upon treating with boric acid under basic conditions.