Catalysis Letters, Vol.145, No.4, 1094-1102, 2015
Improved Synthesis of Soluble Metal-Free/Metal Phthalocyanine Tetracarboxylic Acids and Their Application in the Catalytic Epoxidation of Cyclohexene
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. 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.