- Improved Synthesis of Soluble Metal-Free/Metal Phthalocyanine Tetracarboxylic Acids and Their Application in the Catalytic Epoxidation of Cyclohexene
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Soluble metal-free and metal (copper (II), iron (III), and cobalt (II)) phthalocyanine tetracarboxylic acids (5-8) were synthesized using a novel method consisting of improved hydrolysis based on the diazo reaction. The obtained compounds (5-8) were characterized by X-ray diffraction, UV-Vis spectrometry, and FT-IR spectrometry and then utilized as catalysts for the epoxidation of cyclohexene with molecular oxygen as oxidant. Reaction conditions including reaction time, temperature, catalyst amount, and isobutyraldehyde/cyclohexene ratio were optimized to achieve the highest selectivity of cyclohexene oxide. Metal-free phthalocyanine tetracarboxylic acid (5) and metal (copper (II), iron (III), and cobalt (II)) phthalocyanine tetracarboxylic acids (6-8, respectively) were compared. Complexes 6-8 exhibited higher catalytic activity than compound 5 under the optimal conditions. Graphical Abstract: Four soluble metal-free and metal PTCs were synthesized using a novel method, and were utilized as catalysts for the epoxidation of cyclohexene with molecular oxygen as the oxidant. A total of 58.1% selectivity and yield of cyclohexene oxide were achieved under the optimal condition. [Figure not available: see fulltext.]
- Sun, Xiaoling,Wang, Li,Tan, Zhi
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- Highly efficient, mild, bromide-free and acetic acid-free dioxygen oxidation of p-nitrotoluene to p-nitrobenzoic acid with metal phthalocyanine catalysts
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Four metal tetracarboxyl phthalocyanines were synthesized and characterized by elemental analysis and mass spectrometry. p-Nitrobenzoic acid was efficiently prepared in high yield from bromide-free and acetic acid-free aerobic oxidation of p-nitrotoluene using metal phthalocyanines as catalysts under mild conditions in alkali-methanol solution. Up to 88.8% isolated yield of p-nitrobenzoic acid was obtained with the catalysis of tetracarboxyl phthalocyanine cobalt (0.13 mol %, based on the moles of p-nitrotoluene) optionally combined with a small amount of dimethylformamide in the presence of 2.0 MPa dioxygen at 30-60°C. The effect on catalytic performance of a carboxyl group introduced into the phthalocyanine ring was further discussed on the basis of metal coordination chemistry theory.
- Song, Xufeng,She, Yuanbin,Ji, Hongbing,Zhang, Yanhui
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