Metal-Organic Frameworks Containing N-hydroxyphthalimide as Efficient Heterogeneous Catalysts for Allylic Oxidation
Nine metal-organic frameworks, [M(PDA), M(BTC), M(PTC)] (M=Cu, Co, Mn; H2PDA= pyridine-2,6-
dicarboxylic, H3BTC= 1,3,5-benzenetricarboxylic acid , H3PTC= pyridine-2,4,6-tricarboxylate), containing respectively
Cu2+, Co2+, Mn2+ ions and carboxylate ligands (H2PDA, H3BTC, H3PTC). They can be used as valuable heterogeneous
catalysts since they are easily separated and reused from the reaction systems, and possess single catalytic active sites in
their frameworks which are characteristic of the homogenous catalysts. In addition, N-hydroxyphthalimide (NHPI) has
been also revealed to be valuable organocatalyst for free-radical processes and found ample applications in promoting the
aerobic oxidation of a wide range of organic compounds. We present here a heterogeneous protocol by adsorbing NHPI in
MOFs to obtain the novel NHPI/MOFs catalytic system. The allylic oxidation of α-isophorone (α-IP) into ketoisophorone
(KIP) utilizing the NHPI/MOFs as heterogeneous catalysts with moleular oxygen as primary terminal oxidant under solvent-
free condition was conducted. The results show that NHPI/Co(BTC) obtain optimum catalytic efficiency affording
36.6% conservation of α-IP and 81.7% KIP selectivity. The catalyst can be isolated easily from the reaction system by
simple filtration and recycle without significant degradation in activity. The oxidations fulfill the requirement of green
chemistry concept in terms of environmental benignity and sustainability.
Keywords: Allylic oxidation, dioxygen, heterogeneous, metal-organic frameworks, N-hydroxyphthalimide, solvent-free.
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