Inter-and intramolecular cyclopropanations of a series of diazo Weinreb amides and transallylic diazo Weinreb amide derivatives have been achieved using chiral ruthenium(II)-Amm-Pheox catalyst to give the corresponding chiral cyclopropyl Weinreb amides in excellent yield (up to 99%) with excellent enantioselectivity (up to 99% ee). The chiral products could easily undergo useful synthetic transformations to give the corresponding aldehydes, alcohols and ketones in high yields and enantioselectivities.
The first highly stereoselective cyclopropanation of diazo Weinreb amides with olefins was accomplished using chiral Ru(ii)-Amm-Pheox complex to give the corresponding chiral cyclopropyl Weinreb amides in high yields (up to 99%) with excellent diastereoselectivities (up to 99 : 1 dr) and enantioselectivities (up to 96% ee).
A reusable and highly enantioselective catalyst for the intramolecular cyclopropanation of various diazo ester and Weinreb amide derivatives was developed. The reactions catalyzed by a water-soluble Ru(II)-Amm-Pheox catalyst proceeded smoothly at room temperature, affording the corresponding bicyclic cyclopropane ring-fused lactones and lactams in high yields (up to 99%) with excellent enantioselectivities (up to 99% ee). After screening of various catalysts, the Ru(II)-Amm-Pheox complex having an ammonium group proved to be crucial for the intramolecular cyclopropanation reaction in a water/ether biphasic medium. The water-soluble catalyst could be reused at least six times with little loss in yield and enantioselectivity.
Derivatives of formyl pyrazole were synthesized by the reaction of acetophenone, 4-methyl acetophenone, 3-acetyl furan, 3-acetyl thiophen and phenyl hydrazine derivatives. The product was treated with Vilsmeier reagent producing different formyl pyrazole derivatives which were characterized by FT-IR, 1HNMR, Elemental analysis and Mass spectroscopy. The formyl pyrazole derivatives were reacted with chitosan to produce chitosan/ pyrazole Schiff base. These Schiff bases were characterized by FT-IR and TGA.The antimicrobial activity of chitosan/ pyrazol Schiff base (CSB) was evaluated against Gram-positive bacteria (Staphylococcus aureus and Bacillus cereus), gram negative bacterium (Escherichia coli) and fungus (Aspergillus niger). Results indicated agood inhibitory activity for CSB-14 when tested against B.cereus that gave inhibition zone of 7.5 ± 0.6 (mm), however CSB-18 gave a pronounced inhibitory activity against S. aureus and recorded 25 ± 2.0 (mm). All synthesized derivatives have no inhibitory activity against Gram negative E. coli. CSB-14, and CSB-15 exhibited inhibitory activity against tested A. niger that was used as a fungal model which gave 19 ± 0.9 and 18 ± 1.0 inhibition zone (mm) respectively. Thus, these results showed that, functionalization of chitosan with the hetero-cyclic compounds created biological activities of the synthesized derivatives; hence the synthesized pyrazole derivatives have not recorded any inhibitory activity before its immobilization onto chitosan.
Platinum nanoparticles (PAA-Pt) stabilized by polyacrylic acid (PAA) of a polymeric stabilizer were adsorbed on an indium tin oxide (ITO) surface from their colloidal solution due to the chemical adsorption...
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