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Allylic oxidation of olefins with a manganese-based metal–organic framework
- Chen, Jingwen, Chen, Minda, Zhang, Biying, Nie, Renfeng, Huang, Ao, Goh, Tian Wei, Volkov, Alexander, Zhang, Zhiguo, Ren, Qilong, Huang, Wenyu
- Green chemistry 2019 v.21 no.13 pp. 3629-3636
- catalysts, catalytic activity, cost effectiveness, cyclohexanones, cyclohexenes, green chemistry, ligands, manganese, oxidants, oxidation, oxygen
- Selective oxidation of olefins to α,β-unsaturated ketones under mild reaction conditions has attracted considerable interest, since α,β-unsaturated ketones can serve as synthetic precursors for various downstream chemical products. The major inherent challenges with this chemical oxidation are chemo- and regio-selectivity as well as environmental concerns, i.e. catalyst recycle, safety and cost. Using atmospheric oxygen as an environmentally friendly oxidant, we found that a metal–organic framework (MOF) constructed with Mn and a tetrazolate ligand (CPF-5) showed good activity and selectivity for the allylic oxidation of olefins to α,β-unsaturated ketones. Under the optimized conditions, we could achieve 98% conversion of cyclohexene and 87% selectivity toward cyclohexanone. The combination of a substoichiometric amount of TBHP (tert-butylhydroperoxide) and oxygen not only provides a cost effective oxidation system but significantly enhances the selectivity to α,β-unsaturated ketones, outperforming most reported oxidation methods. This catalytic system is heterogeneous in nature, and CPF-5 could be reused at least five times without a significant decrease in its catalytic activity and selectivity.