Collaborative effect of Mn-porphyrin and mesoporous SBA-15 in the enantioselective epoxidation of olefins with oxygen

• Published in: Inorganica Chimica Acta 2018-02, Vol.471, p.113-120
• Main Authors: Berijani, Kayhaneh, Hosseini-Monfared, Hassan
• Format: Article
• Language: English
• Subjects: Alkenes; Asymmetric epoxidation; Biomimetics; Catalysis; Catalysts; Chemical synthesis; Chiral Mn(III) porphyrin; Coordination compounds; Design for recycling; Dioxygen; Enantiomers; Enantioselective; Epoxidation; Manganese; Mesoporous silica support; Organic chemistry; Oxidation; Oxygen; Polyolefins; Silica; Transition metal compounds
• ISSN: 0020-1693; 1873-3255
• DOI: 10.1016/j.ica.2017.10.037

[Display omitted] •Mn-TPyP complex was grafted into SBA15-Cl.•SBA15-Mn-TPyP performed high selective epoxidation of olefins with iPrCHO/O2.•Mn-TPyP and SBA-15 showed remarkable collaborative effect to increase TOF and ee.•TON of 47,400, epoxide selectivity 86% and ee 86% was obtained for styrene. The rational design of heterogeneous, low cost transition metal complexes that can catalyze olefin with high enantioselectivity and activity has been a challenging goal for the synthetic chemist. In this study a chiral ion pair strategy was used for the synthesis of a biomimetic efficient manganese-tetrapyridylporphyrin (H2TPyP) catalyst for the asymmetric epoxidation of olefins with O2. Complex Mn-TPyP was covalently linked to mesoporous SBA-15 in heme-type environments and its counter ion was replaced by l-tartrate anion (SBA15-[Mn(TPyP)TA]). Chiral and achiral homogeneous analogous of Mn-TPyP were also prepared. The Mn-porphyrin confined in nanoreactors of SBA-15 exhibited enhanced activity (TOF = 652 h−1) and enantiomeric excess (ee 93%) compared with the value obtained when the same chiral catalyst functioned in homogeneous solution (TOF 97 h−1 and ee 83%) in the oxidation of 1-decene with O2/isobutyraldehyde. The high specific surface area, uniformly sized pore channels and site isolated active centers of the catalyst may contribute to the high activity and enantioselectivity. SBA15-[Mn(TPyP)TA] was structurally stable and could be recycled for repeated use. Total turnover number in the oxidation of styrene after five cycles was 47,400 with 86% epoxide selectivity and ee 86%.