The catalytic hydrogenation of 2-nitro-4-acetylamino anisole(NMA)is a less-polluting and efficient method to produce 2-amino-4-acetamino anisole(AMA).However,the kinetics of catalytic hydrogenation of NMA to AMA remai...The catalytic hydrogenation of 2-nitro-4-acetylamino anisole(NMA)is a less-polluting and efficient method to produce 2-amino-4-acetamino anisole(AMA).However,the kinetics of catalytic hydrogenation of NMA to AMA remains obscure.In this work,the kinetic models including power-law model and Langmuir-Hinshelwood-Hougen-Watson(LHHW)model of NMA hydrogenation to AMA catalyzed by Raney nickel catalyst were investigated.All experiments were carried out under the elimination of mass transfer resistance within the temperature range of 70–100°C and the hydrogen pressure of 0.8–1.5 MPa.The reaction was found to follow 0.52-order kinetics with respect to the NMA concentration and 1.10-order kinetics in terms of hydrogen pressure.Based on the LHHW model,the dual-site dissociation adsorption of hydrogen was analyzed to be the rate determining step.The research of intrinsic kinetics of NMA to AMA provides the guidance for the reactor design and inspires the catalyst modification.展开更多
The direct reductive amination of 2,5-diformylfuran (DFF) with ammonia to 2,5-bis(aminomethyl)furan (BAF) was demonstrated, for the first time, over the commercial type Nickel-Raney and acid treated Nickel-Raney catal...The direct reductive amination of 2,5-diformylfuran (DFF) with ammonia to 2,5-bis(aminomethyl)furan (BAF) was demonstrated, for the first time, over the commercial type Nickel-Raney and acid treated Nickel-Raney catalysts. The effects of reaction parameters such as reaction medium, temperature and hydrogen pressure were described. The acid treated Nickel-Raney catalyst exhibited the highest BAF yield in the THF-water mixed reaction medium. The relatively higher Ni0 species composition and larger surface area of the acid treated Nickel-Raney catalyst with specific reaction conditions contributed greatly to the BAF formation. The oligomeric species, such as furanic imine trimers and tetramers confirmed by MALDI-MS analysis were presented as the intermediates of DFF reductive amination.展开更多
Asymmetric migratory hydrofunctionalization of isomeric mixtures of alkenes provides a complementary approach for the selective introduction of a functional group into a remote C(sp3)-H position.However,the simultaneo...Asymmetric migratory hydrofunctionalization of isomeric mixtures of alkenes provides a complementary approach for the selective introduction of a functional group into a remote C(sp3)-H position.However,the simultaneous control of both regio-and enantioselectivity in this migratory process is a challenge.Enantioenrichedα-alkyl-substituted azacycles are key motifs in pharmaceuticals,natural products,and agrochemicals.Here,we report a NiH-catalyzed asymmetric migratory hydroalkylation process for their efficient and selective construction.In this process,easily available isomeric mixtures of N-heterocyclic alkenes can be directly employed as starting materials,convergently delivering a variety of enantioenrichedα-alkylated azacycles with high levels of regio-and enantioselectivity.The synthetic utility of this transformation is demonstrated by the facile synthesis of two bioactive alkaloids,(+)-connine and(R)-pipecoline.The obtained chiralα-alkylated azacycles also readily undergo diverse derivatization,such as deconstructive halogenation and ring contraction.展开更多
Though transition metal-catalyzed cage BH methylation has been well documented, catalytic alkylation of cage BH bonds remained elusive because transition metal alkyl complexes are prone to undergo β-H elimination. We...Though transition metal-catalyzed cage BH methylation has been well documented, catalytic alkylation of cage BH bonds remained elusive because transition metal alkyl complexes are prone to undergo β-H elimination. We report herein a highly efficient 8-aminoquinoline-assisted nickel-catalyzed regioselective cage B(3,4,5,6)-H tetra-alkylation of o-carboranes employing unactivated alkyl bromides as alkylating agents in the absence of any oxidants, leading to the preparation of a class of tetra-alkylated o-carboranes with a broad substrate scope in good to very high yields. This method opens new avenues for oxidant-free, direct, efficient, sustainable, and regioselective multiple B–H alkylation of carboranes via base metal catalysis.展开更多
基金the National Natural Science Foun-dation of China(22022802 and 22288102).
文摘The catalytic hydrogenation of 2-nitro-4-acetylamino anisole(NMA)is a less-polluting and efficient method to produce 2-amino-4-acetamino anisole(AMA).However,the kinetics of catalytic hydrogenation of NMA to AMA remains obscure.In this work,the kinetic models including power-law model and Langmuir-Hinshelwood-Hougen-Watson(LHHW)model of NMA hydrogenation to AMA catalyzed by Raney nickel catalyst were investigated.All experiments were carried out under the elimination of mass transfer resistance within the temperature range of 70–100°C and the hydrogen pressure of 0.8–1.5 MPa.The reaction was found to follow 0.52-order kinetics with respect to the NMA concentration and 1.10-order kinetics in terms of hydrogen pressure.Based on the LHHW model,the dual-site dissociation adsorption of hydrogen was analyzed to be the rate determining step.The research of intrinsic kinetics of NMA to AMA provides the guidance for the reactor design and inspires the catalyst modification.
文摘The direct reductive amination of 2,5-diformylfuran (DFF) with ammonia to 2,5-bis(aminomethyl)furan (BAF) was demonstrated, for the first time, over the commercial type Nickel-Raney and acid treated Nickel-Raney catalysts. The effects of reaction parameters such as reaction medium, temperature and hydrogen pressure were described. The acid treated Nickel-Raney catalyst exhibited the highest BAF yield in the THF-water mixed reaction medium. The relatively higher Ni0 species composition and larger surface area of the acid treated Nickel-Raney catalyst with specific reaction conditions contributed greatly to the BAF formation. The oligomeric species, such as furanic imine trimers and tetramers confirmed by MALDI-MS analysis were presented as the intermediates of DFF reductive amination.
基金the National Key R&D Program of China(grant no.2022YFA1503200)NSFC(grant nos.92156004,22271146,and 22271143)+1 种基金the Open Research Fund of School of Chemistry and Chemical Engineering,Henan Normal University,the Open Research Fund of the Shanghai Key Laboratory for Molecular Engineering of Chiral Drugs,the China Postdoctoral Science Foundation(grant no.2021M701655)the Jiangsu Funding Program for Excellent Postdoctoral Talent(grant no.20220ZB24).
文摘Asymmetric migratory hydrofunctionalization of isomeric mixtures of alkenes provides a complementary approach for the selective introduction of a functional group into a remote C(sp3)-H position.However,the simultaneous control of both regio-and enantioselectivity in this migratory process is a challenge.Enantioenrichedα-alkyl-substituted azacycles are key motifs in pharmaceuticals,natural products,and agrochemicals.Here,we report a NiH-catalyzed asymmetric migratory hydroalkylation process for their efficient and selective construction.In this process,easily available isomeric mixtures of N-heterocyclic alkenes can be directly employed as starting materials,convergently delivering a variety of enantioenrichedα-alkylated azacycles with high levels of regio-and enantioselectivity.The synthetic utility of this transformation is demonstrated by the facile synthesis of two bioactive alkaloids,(+)-connine and(R)-pipecoline.The obtained chiralα-alkylated azacycles also readily undergo diverse derivatization,such as deconstructive halogenation and ring contraction.
基金supported by the Research Grants Council of the Hong Kong Special Administration Region (SRFS20214S05)。
文摘Though transition metal-catalyzed cage BH methylation has been well documented, catalytic alkylation of cage BH bonds remained elusive because transition metal alkyl complexes are prone to undergo β-H elimination. We report herein a highly efficient 8-aminoquinoline-assisted nickel-catalyzed regioselective cage B(3,4,5,6)-H tetra-alkylation of o-carboranes employing unactivated alkyl bromides as alkylating agents in the absence of any oxidants, leading to the preparation of a class of tetra-alkylated o-carboranes with a broad substrate scope in good to very high yields. This method opens new avenues for oxidant-free, direct, efficient, sustainable, and regioselective multiple B–H alkylation of carboranes via base metal catalysis.
