Controlling selectivity in the hydrogenation of compounds with several functional groups remains a challenging task in heterogeneous catalysis.We report herein the design and use of simple catalysts composed of Pt nan...Controlling selectivity in the hydrogenation of compounds with several functional groups remains a challenging task in heterogeneous catalysis.We report herein the design and use of simple catalysts composed of Pt nanoparticles confined in Silicalite-1(S-1,MFI type zeolite)for the inversion of the inherent C[double bond,length as m-dash]O selective hydrogenation of cinnamaldehyde over Pt.The encapsulated catalyst achieved an unconventional 98%hydrocinnamaldehyde selectivity at high conversion levels(88%),which bypasses the inherent selectivity of Pt for C[double bond,length as m-dash]O versus C[double bond,length as m-dash]C hydrogenation.This high selectivity originates from the combination of the low polarity of the S-1 support and the toluene solvent that favor interaction of the catalyst with the C[double bond,length as m-dash]C over the C[double bond,length as m-dash]O group,and to the efficient encapsulation of the platinum in the zeolite channels which restricts the growth of the nanoparticles and consequently decreases the number of undesirable Pt(111)facets active for C[double bond,length as m-dash]O hydrogenation.展开更多
Static one-handed helical polymers can serve as an ideal catalytic platform toward chiral synthesis.As a demonstration of helical polyisocyanides in asymmetric catalysis,we report a novel strategy to facilitate asymme...Static one-handed helical polymers can serve as an ideal catalytic platform toward chiral synthesis.As a demonstration of helical polyisocyanides in asymmetric catalysis,we report a novel strategy to facilitate asymmetric cooperative catalysis for the kinetic resolution of epoxides with TMSN_(3) using one-handed polyisocyanide-supported Co(III)-salen catalysts.Co(III)-salen is decorated with polyisocyanides to produce the polymer-supported catalyst P1-Co-N_(3).Owing to the rigid helical backbone of the polyisocyanide skeleton,spatially adjacent Co(III)-salen pendants are arranged with a distance of~1.2 nm so that the epoxide and TMSN_(3) can undergo dual activation in an amplified chiral environment.The catalytic performance is investigated via the kinetic resolution for a series of terminal epoxides through enantioselective ring-opening with TMSN_(3).P1-Co-N_(3) exhibits high catalytic activity and enantioselectivity,producing the desired products in high enantiomeric excesses and good yields at a low catalyst loading(0.6 mol%).In contrast,a small molecular control,S1-Co-N_(3),performs poorly owing to the absence of a preorganized catalytic dimer.Moreover,this polyisocyanide-based catalyst exhibits good functional group tolerance and stable activity in multiple recycles.To demonstrate its potential application in the asymmetric synthesis of chiral drugs,we conducted a gram-scale asymmetric synthesis ofβ-amino acid derivatives via this kinetic resolution method as the essential step.展开更多
基金Funding for this work was provided by baseline grant(BAS/1/1402-01-01)from King Abdullah University of Science and Technology(KAUST).
文摘Controlling selectivity in the hydrogenation of compounds with several functional groups remains a challenging task in heterogeneous catalysis.We report herein the design and use of simple catalysts composed of Pt nanoparticles confined in Silicalite-1(S-1,MFI type zeolite)for the inversion of the inherent C[double bond,length as m-dash]O selective hydrogenation of cinnamaldehyde over Pt.The encapsulated catalyst achieved an unconventional 98%hydrocinnamaldehyde selectivity at high conversion levels(88%),which bypasses the inherent selectivity of Pt for C[double bond,length as m-dash]O versus C[double bond,length as m-dash]C hydrogenation.This high selectivity originates from the combination of the low polarity of the S-1 support and the toluene solvent that favor interaction of the catalyst with the C[double bond,length as m-dash]C over the C[double bond,length as m-dash]O group,and to the efficient encapsulation of the platinum in the zeolite channels which restricts the growth of the nanoparticles and consequently decreases the number of undesirable Pt(111)facets active for C[double bond,length as m-dash]O hydrogenation.
基金supported by the National Natural Science Foundation of China(Grant No.21771049,22071041,and 92256201)the Fundamental Research Funds for the Central Universities of China(Grant No.PA2020GDJQ0028 and PA2021GDSK0063).
文摘Static one-handed helical polymers can serve as an ideal catalytic platform toward chiral synthesis.As a demonstration of helical polyisocyanides in asymmetric catalysis,we report a novel strategy to facilitate asymmetric cooperative catalysis for the kinetic resolution of epoxides with TMSN_(3) using one-handed polyisocyanide-supported Co(III)-salen catalysts.Co(III)-salen is decorated with polyisocyanides to produce the polymer-supported catalyst P1-Co-N_(3).Owing to the rigid helical backbone of the polyisocyanide skeleton,spatially adjacent Co(III)-salen pendants are arranged with a distance of~1.2 nm so that the epoxide and TMSN_(3) can undergo dual activation in an amplified chiral environment.The catalytic performance is investigated via the kinetic resolution for a series of terminal epoxides through enantioselective ring-opening with TMSN_(3).P1-Co-N_(3) exhibits high catalytic activity and enantioselectivity,producing the desired products in high enantiomeric excesses and good yields at a low catalyst loading(0.6 mol%).In contrast,a small molecular control,S1-Co-N_(3),performs poorly owing to the absence of a preorganized catalytic dimer.Moreover,this polyisocyanide-based catalyst exhibits good functional group tolerance and stable activity in multiple recycles.To demonstrate its potential application in the asymmetric synthesis of chiral drugs,we conducted a gram-scale asymmetric synthesis ofβ-amino acid derivatives via this kinetic resolution method as the essential step.
