Metal-Organic Frameworks Containing N-Hydroxyphthalimide as Efficient Heterogeneous Catalysts for Allylic Oxidation
Peng Yu, Guiyin Liu and Ruiren TangAffiliation:
School of Chemistry and Chemical Engineering, Central South University, Hunan, 410083, China.
AbstractNine metal-organic frameworks, [M(PDA), M(BTC), M(ptc)] (M=Cu, Co, Mn; PDA= pyridine-2,6-dicarboxylic, BTC= 1,3,5-benzenetricarboxylic acid , ptc= pyridine-2,4,6-tricarboxylate ), containing respectively Cu2+, Co2+, Mn2+ ions and carboxylate ligands (pyridine-2,6-dicarboxylic, 1,3,5-benzenetricarboxylic acid, pyridine-2,4,6-tricarboxylate, respectively ). They are valuable heterogeneous catalysts since they could be easily separated and reused from the reaction systems, and possess single catalytic active sites in their frameworks which is characteristic of the homogenous catalysts. In addition, N-hydroxyphthalimide (NHPI) has been also revealed to be valuable organocatalyst for free-radical processes and has found ample applications in promoting the efficient aerobic oxidation of a wide range of organic compounds. We present here a heterogeneous protocol by adsorbing NHPI in MOFs. The allylic oxidation of α-isophorone (α-IP) into ketoisophorone (KIP) utilizing the NHPI/MOFs as heterogeneous catalyst with moleular oxygen as primary terminal oxidant under solvent-free condition was conducted. NHPI/Co(BTC) obtained optimum catalytic efficiency affording 36.6% conservation of α-IP and 81.7% KIP selectivity. The catalyst could be easily isolated from the reaction system by simple filtration and recycled without significant degradation in activity. The oxidations fulfill the requirements of green chemistry concept in terms of environmental benignity and sustainability.
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