24965-94-4Relevant academic research and scientific papers
Expedient Synthesis of Bridged Bicyclic Nitrogen Scaffolds via Orthogonal Tandem Catalysis
Bheemireddy, Narendraprasad Reddy,Biswas, Sovan,Evano, Gwilherm,Maes, Bert U. W.,Van Steijvoort, Ben F.,Waeterschoot, Marjo
, p. 21988 - 21996 (2021/08/13)
Bridged nitrogen bicyclic skeletons have been accessed via unprecedented site- and diastereoselective orthogonal tandem catalysis from readily accessible reactants in a step economic manner. Directed Pd-catalyzed γ-C(sp3)-H olefination of aminocyclohexane with gem-dibromoalkenes, followed by a consecutive intramolecular Cu-catalyzed amidation of the 1-bromo-1-alkenylated product delivers the interesting normorphan skeleton. The tandem protocol can be applied on substituted aminocyclohexanes and aminoheterocycles, easily providing access to the corresponding substituted, aza- and oxa-analogues. The Cu catalyst of the Ullmann-Goldberg reaction additionally avoids off-cycle Pd catalyst scavenging by alkenylated reaction product. The picolinamide directing group stabilizes the enamine of the 7-alkylidenenormorphan, allowing further product post functionalizations. Without Cu catalyst, regio- and diastereoselective Pd-catalyzed γ-C(sp3)-H olefination is achieved.
Crossing the Border: From Keto- to Imine Reduction in Short-Chain Dehydrogenases/Reductases
Roth, Sebastian,Stockinger, Peter,Steff, Jakob,Steimle, Simon,Sautner, Viktor,Tittmann, Kai,Pleiss, Jürgen,Müller, Michael
, p. 2615 - 2619 (2020/07/06)
The family of NAD(P)H-dependent short-chain dehydrogenases/reductases (SDRs) comprises numerous biocatalysts capable of C=O or C=C reduction. The highly homologous noroxomaritidine reductase (NR) from Narcissus sp. aff. pseudonarcissus and Zt_SDR from Zephyranthes treatiae, however, are SDRs with an extended imine substrate scope. Comparison with a similar SDR from Asparagus officinalis (Ao_SDR) exhibiting keto-reducing activity, yet negligible imine-reducing capability, and mining the Short-Chain Dehydrogenase/Reductase Engineering Database indicated that NR and Zt_SDR possess a unique active-site composition among SDRs. Adapting the active site of Ao_SDR accordingly improved its imine-reducing capability. By applying the same strategy, an unrelated SDR from Methylobacterium sp. 77 (M77_SDR) with distinct keto-reducing activity was engineered into a promiscuous enzyme with imine-reducing activity, thereby confirming that the ability to reduce imines can be rationally introduced into members of the “classical” SDR enzyme family. Thus, members of the SDR family could be a promising starting point for protein approaches to generate new imine-reducing enzymes.
A Practical and Stereoselective In Situ NHC-Cobalt Catalytic System for Hydrogenation of Ketones and Aldehydes
Zhong, Rui,Wei, Zeyuan,Zhang, Wei,Liu, Shun,Liu, Qiang
supporting information, p. 1552 - 1566 (2019/06/14)
Homogeneous catalytic hydrogenation of carbonyl groups is a synthetically useful and widely applied organic transformation. Sustainable chemistry goals require replacing conventional noble transition metal catalysts for hydrogenation by earth-abundant base metals. Herein, we report how a practical in situ catalytic system generated by easily available pincer NHC precursors, CoCl2, and a base enabled efficient and high-yielding hydrogenation of a broad range of ketones and aldehydes (over 50 examples and a maximum turnover number [TON] of 2,610). This is the first example of NHC-Co-catalyzed hydrogenation of C=O bonds using flexible pincer NHC ligands consisting of a N-H substructure. Diastereodivergent hydrogenation of substituted cyclohexanone derivatives was also realized by fine-tuning of the steric bulk of pincer NHC ligands. Additionally, a bis(NHCs)-Co complex was successfully isolated and fully characterized, and it exhibits excellent catalytic activity that equals that of the in-situ-formed catalytic system. Catalytic hydrogenation is a powerful tool for the reduction of organic compounds in both fine and bulk chemical industries. To improve sustainability, more ecofriendly, inexpensive, and earth-abundant base metals should be employed to replace the precious metals that currently dominate the development of hydrogenation catalysts. However, the majority of the base-metal catalysts that have been reported involve expensive, complex, and often air- and moisture-sensitive phosphine ligands, impeding their widespread application. From a mixture of the stable CoCl2, imidazole salts, and a base, our newly developed catalytic system that formed easily in situ enables efficient and stereoselective hydrogenation of C=O bonds. We anticipate that this easily accessible catalytic system will create opportunities for the design of practical base-metal hydrogenation catalysts. A practical in situ catalytic system generated by a mixture of easily available pincer NHC precursors, CoCl2, and a base enabled highly efficient hydrogenation of a broad range of ketones and aldehydes (over 50 examples and up to a turnover number [TON] of 2,610). Diastereodivergent hydrogenation of substituted cyclohexanone derivatives was also realized in high selectivities. Moreover, the preparation of a well-defined bis(NHCs)-Co complex via this pincer NHC ligand consisting of a N-H substructure was successful, and it exhibits equally excellent catalytic activity for the hydrogenation of C=O bonds.
Exploiting the Catalytic Diversity of Short-Chain Dehydrogenases/Reductases: Versatile Enzymes from Plants with Extended Imine Substrate Scope
Roth, Sebastian,Kilgore, Matthew B.,Kutchan, Toni M.,Müller, Michael
, p. 1849 - 1852 (2018/09/10)
Numerous short-chain dehydrogenases/reductases (SDRs) have found biocatalytic applications in C=O and C=C (enone) reduction. For NADPH-dependent C=N reduction, imine reductases (IREDs) have primarily been investigated for extension of the substrate range. Here, we show that SDRs are also suitable for a broad range of imine reductions. The SDR noroxomaritidine reductase (NR) is involved in Amaryllidaceae alkaloid biosynthesis, serving as an enone reductase. We have characterized NR by using a set of typical imine substrates and established that the enzyme is active with all four tested imine compounds (up to 99 % conversion, up to 92 % ee). Remarkably, NR reduced two keto compounds as well, thus highlighting this enzyme family's versatility. Using NR as a template, we have identified an as yet unexplored SDR from the Amaryllidacea Zephyranthes treatiae with imine-reducing activity (≤95 % ee). Our results encourage the future characterization of SDR family members as a means of discovering new imine-reducing enzymes.
Chemo-Enzymatic Oxidative Rearrangement of Tertiary Allylic Alcohols: Synthetic Application and Integration into a Cascade Process
Brenna, Elisabetta,Crotti, Michele,De Pieri, Matteo,Gatti, Francesco G.,Manenti, Gabriele,Monti, Daniela
, p. 3677 - 3686 (2018/06/04)
A chemo-enzymatic catalytic system, comprised of Bobbitt's salt and laccase from Trametes versicolor, allowed the [1,3]-oxidative rearrangement of endocyclic allylic tertiary alcohols into the corresponding enones under an Oxygen atmosphere in aqueous media. The yields were in most cases quantitative, especially for the cyclopent-2-en-1-ol or the cyclohex-2-en-1-ol substrates without an electron withdrawing group (EWG) on the side chain. Transpositions of macrocyclic alkenols or tertiary alcohols bearing an EWG on the side chain were instead carried out in acetonitrile by using an immobilized laccase preparation. Dehydro-Jasmone, dehydro-Hedione, dehydro-Muscone and other fragrance precursors were directly prepared with this procedure, while a synthetic route was developed to easily transform a cyclopentenone derivative into trans-Magnolione and dehydro-Magnolione. The rearrangement of exocyclic allylic alcohols was tested as well, and a dynamic kinetic resolution was observed: α,β-unsaturated ketones with (E)-configuration and a high diastereomeric excess were synthesized. Finally, the 2,2,6,6-tetramethyl-1-piperidinium tetrafluoroborate (TEMPO+BF4?)/laccase catalysed oxidative rearrangement was combined with the ene-reductase/alcohol dehydrogenase cascade process in a one-pot three-step synthesis of cis or trans 3-methylcyclohexan-1-ol, in both cases with a high optical purity. (Figure presented.).
New p-tolylimido rhenium(v) complexes with carboxylate-based ligands: Synthesis, structures and their catalytic potential in oxidations with peroxides
Gryca,MacHura,Malecki,Shul'Pina, Lidia S.,Pombeiro, Armando J. L.,Shul'Pin, Georgiy B.
, p. 5759 - 5776 (2014/04/03)
Novel p-tolylimido rhenium(v) complexes trans-(Cl,Cl)-[Re(p-NC 6H4CH3)Cl2(pyz-2-COO)(PPh 3)]·MeCN (1), trans-(Cl,Cl)-[Re(p-NC6H 4CH3)Cl2(pyz-2-COO)(PPh
Ruthenium-catalyzed asymmetric transfer hydrogenation of allylic alcohols by an enantioselective isomerization/transfer hydrogenation mechanism
Wu, Ruoqiu,Beauchamps, Marie G.,Laquidara, Joseph M.,Sowa Jr., John R.
experimental part, p. 2106 - 2110 (2012/04/11)
Reducing hazards: A asymmetric transfer hydrogen reaction was developed to reduce prochiral allylic alcohols in high yield and excellent enantioselectivity (see example). Mechanistic studies indicate a novel enantioselective isomerization/transfer hydrogenation mechanism. This new reaction is much safer than high-pressure hydrogenation using H2 gas. Copyright
CYCLIC AMINE-1-CARBOXYLIC ACID ESTER DERIVATIVE AND PHARMACEUTICAL COMPOSITION CONTAINING THE SAME
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, (2012/02/06)
Provided is a compound useful as a therapeutic drug for pain and inflammation caused by various pathological conditions such as neuropathic pain and rheumatoid arthritis. The compound of the formula (I) or a salt thereof [wherein R1 is a methyl group or a hydrogen atom, R2 represents a hydrogen atom, an alkyl group, an alkylcarbonyl group or an aryl carbonyl group, A represents a cycloalkyl group, a cycloalkenyl group, an aryl group or a heteroaryl group (each group may be substituted with a substituent selected from the group consisting of alkyl, alkenyl, cycloalkyl and halogen), n and m each represent an integer of 1, 2 or 3, and p represents an integer of 0, 1, 2 or 3].
Miniaturizing biocatalysis: Enzyme-catalyzed reactions in an aqueous/organic segmented flow capillary microreactor
Karande, Rohan,Schmid, Andreas,Buehler, Katja
experimental part, p. 2511 - 2521 (2011/11/07)
A segmented flow capillary microreactor was used to perform the enzyme-catalyzed conversion of 1-heptaldehyde to 1-heptanol in a two liquid-liquid phase system. These reactor formats are established for chemical reactions but so far data describing the relevant system parameters for enzymatic catalysis are lacking. This work now addresses the impact of important parameters such as capillary diameter, flow velocity, phase ratio, and enzyme as well as substrate concentration on the performance of the enzymatic reaction under segmented flow conditions. All key parameters governing reaction performance have been correlated in a novel operational window for an easy assessment of the various system constraints. Such systems are characterized by high productivities and easy phase separation facilitating downstream processing. This work underscores the importance of segmented flow systems as a promising tool to perform multiphasic enzymatic catalysis. Abbreviations/ Nomenclature: Da: Damkoehler number; kcat: turnover number (s-1); eo: enzyme concentration (mM); I?: phase ratio; kL: mass transfer coefficient (m s-1); a: interfacial area per volume (m-1); CAe: equilibrium substrate concentration in the aqueous phase (mM); CAL: substrate concentration in the bulk aqueous phase (mM); rA: rate of reaction in the aqueous phase; mA: substrate mass transfer into the aqueous phase; STY: space time yield. Copyright
CYCLIC AMINE-1-CARBOXYLIC ACID ESTER DERIVATIVE AND PHARMACEUTICAL COMPOSITION CONTAINING THE SAME
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Page/Page column 24, (2011/02/19)
Provided is a compound useful as a therapeutic drug for pain and inflammation caused by various pathological conditions such as neuropathic pain and rheumatoid arthritis. The compound of the formula (I) or a salt thereof [wherein R1 is a methyl group or a hydrogen atom, R2 represents a hydrogen atom, an alkyl group, an alkylcarbonyl group or an aryl carbonyl group, A represents a cycloalkyl group, a cycloalkenyl group, an aryl group or a heteroaryl group (each group may be substituted with a substituent selected from the group consisting of alkyl, alkenyl, cycloalkyl and halogen), n and m each represent an integer of 1, 2 or 3, and p represents an integer of 0, 1, 2 or 3].
