cas 765-38-8, 2-Methylpyrrolidine | Articles data

Articles about 765-38-8Total 82 be found

Article title
Article abstract
Author
Journal number and time
Download

Acylative kinetic resolution of racemic methyl-substituted cyclic alkylamines with 2,5-dioxopyrrolidin-1-yl (: R)-2-phenoxypropanoate
The diastereoselective acylation of a number of racemic methyl-substituted cyclic alkylamines with active esters of 2-phenoxypropanoic acid was studied in detail. The ester of (R)-2-phenoxypropanoic acid and N-hydroxysuccinimide was found to be the most selective agent. The highest stereoselectivity was observed in the kinetic resolution of racemic 2-methylpiperidine in toluene at -40 °C (selectivity factor s = 73) with the predominant formation of (R,R)-amide (93.7% de). To explain the observed stereoselectivity, DFT modelling of the transition states in the reactions of the title acylating agent with 2-methylpiperidine and 2-methylpyrrolidine was performed. The calculated values were in good agreement with experimental data. It has been demonstrated that the acylation proceeds via a concerted mechanism, in which the addition of an amine occurs simultaneously with the elimination of the hydroxysuccinimide fragment. The high stereoselectivity of the (R,R)-amide formation is largely ensured by the lower steric hindrances in the transition states as compared to the formation of (R,S)-amide.
Bartashevich, Ekaterina V.,Chulakov, Evgeny N.,Ezhikova, Marina A.,Gruzdev, Dmitry A.,Kodess, Mikhail I.,Korolyova, Marina A.,Krasnov, Victor P.,Levit, Galina L.,Tumashov, Andrey A.,Vakarov, Sergey A.
supporting information
p. 862 - 869
(2022/02/03)

One-Pot Synthesis of Chiral N-Arylamines by Combining Biocatalytic Aminations with Buchwald–Hartwig N-Arylation
The combination of biocatalysis and chemo-catalysis increasingly offers chemists access to more diverse chemical architectures. Here, we describe the combination of a toolbox of chiral-amine-producing biocatalysts with a Buchwald–Hartwig cross-coupling reaction, affording a variety of α-chiral aniline derivatives. The use of a surfactant allowed reactions to be performed sequentially in the same flask, preventing the palladium catalyst from being inhibited by the high concentrations of ammonia, salts, or buffers present in the aqueous media in most cases. The methodology was further extended by combining with a dual-enzyme biocatalytic hydrogen-borrowing cascade in one pot to allow for the conversion of a racemic alcohol to a chiral aniline.
Ahmed, Syed T.,Cosgrove, Sebastian C.,Parmeggiani, Fabio,Thompson, Matthew P.,Turner, Nicholas J.
supporting information
p. 18156 - 18160
(2020/08/13)

Basicities and Nucleophilicities of Pyrrolidines and Imidazolidinones Used as Organocatalysts
The Br?nsted basicities pKaH (i.e., pKa of the conjugate acids) of 32 pyrrolidines and imidazolidinones, commonly used in organocatalytic reactions, have been determined photometrically in acetonitrile solution using CH acids as indicators. Most investigated pyrrolidines have basicities in the range 16 aH aH aH 12.6) and the 2-imidazoliummethyl-substituted pyrrolidine A21 (pKaH 11.1) are outside the typical range for pyrrolidines with basicities comparable to those of imidazolidinones. Kinetics of the reactions of these 32 organocatalysts with benzhydrylium ions (Ar2CH+) and structurally related quinone methides, common reference electrophiles for quantifying nucleophilic reactivities, have been measured photometrically. Most reactions followed second-order kinetics, first order in amine and first order in electrophile. More complex kinetics were observed for the reactions of imidazolidinones and several pyrrolidines carrying bulky 2-substituents, due to reversibility of the initial attack of the amines at the electrophiles followed by rate-determining deprotonation of the intermediate ammonium ions. In the presence of 2,4,6-collidine or 2,6-di-tert-butyl-4-methyl-pyridine, the deprotonation of the initial adducts became faster, which allowed the rate of the attack of the amines at the electrophiles to be determined. The resulting second-order rate constants k2 followed the correlation log?k2(20 °C) = sN(N + E), where electrophiles are characterized by one parameter (E) and nucleophiles are characterized by the two solvent-dependent parameters N and sN. In this way, the organocatalysts A1-A32 were integrated in our comprehensive nucleophilicity scale, which compares n-, -, and σ-nucleophiles. The nucleophilic reactivities of the title compounds correlate only poorly with their Br?nsted basicities.
An, Feng,Maji, Biplab,Min, Elizabeth,Ofial, Armin R.,Mayr, Herbert
supporting information
p. 1526 - 1547
(2020/02/04)

Stereoselective Biotransformations of Cyclic Imines in Recombinant Cells of Synechocystis sp. PCC 6803
Light-driven biotransformations in recombinant cyanobacteria allow to employ photosynthetic water-splitting for cofactor-regeneration and thus, to save the use of organic electron donors. The genes of three recombinant imine reductases (IREDs) were expressed in the cyanobacterium Synechocystis sp. PCC 6803 and eight cyclic imine substrates were screened in whole-cell biotransformations. While initial reactions showed low to moderate rates, optimization of the reaction conditions in combination with promoter engineering allowed to alleviate toxicity effects and achieve full conversion of prochiral imines with initial rates of up to 6.3 mM h?1. The high specific activity of up to 22 U gCDW ?1 demonstrates that recombinant cyanobacteria can provide large amounts of NADPH during whole cell reactions. The excellent optical purity of the products with up to >99 %ee underlines the usefulness of cyanobacteria for the stereoselective synthesis of amines.
Büchsenschütz, Hanna C.,Vidimce-Risteski, Viktorija,Eggbauer, Bettina,Schmidt, Sandy,Winkler, Christoph K.,Schrittwieser, Joerg H.,Kroutil, Wolfgang,Kourist, Robert
p. 726 - 730
(2019/12/27)

Dihydrogen-Driven NADPH Recycling in Imine Reduction and P450-Catalyzed Oxidations Mediated by an Engineered O2-Tolerant Hydrogenase
The O2-tolerant NAD+-reducing hydrogenase (SH) from Ralstonia eutropha (Cupriavidus necator) has already been applied in vitro and in vivo for H2-driven NADH recycling in coupled enzymatic reactions with various NADH-dependent oxidoreductases. To expand the scope for application in NADPH-dependent biocatalysis, we introduced changes in the NAD+-binding pocket of the enzyme by rational mutagenesis, and generated a variant with significantly higher affinity for NADP+ than for the natural substrate NAD+, while retaining native O2-tolerance. The applicability of the SH variant in H2-driven NADPH supply was demonstrated by the full conversion of 2-methyl-1-pyrroline into a single enantiomer of 2-methylpyrrolidine catalysed by a stereoselective imine reductase. In an even more challenging reaction, the SH supported a cytochrome P450 monooxygenase for the oxidation of octane under safe H2/O2 mixtures. Thus, the re-designed SH represents a versatile platform for atom-efficient, H2-driven cofactor recycling in biotransformations involving NADPH-dependent oxidoreductases.
Preissler, Janina,Reeve, Holly A.,Zhu, Tianze,Nicholson, Jake,Urata, Kouji,Lauterbach, Lars,Wong, Luet L.,Vincent, Kylie A.,Lenz, Oliver
p. 4853 - 4861
(2020/08/12)

Synthesis and evaluation of in vivo anti-hypothermic effect of all stereoisomers of the thyrotropin-releasing hormone mimetic: Rovatirelin Hydrate
We discovered the orally active thyrotropin-releasing hormone (TRH) mimetic: (4S,5S)-5-methyl-N-{(2S)-1-[(2R)-2-methylpyrrolidin-1-yl]-1-oxo-3-(1,3-thiazol-4-yl)propan-2-yl}-2-oxo-1,3-oxazolidine-4-carboxamide 1 (rovatirelin). The central nervous system (CNS) effect of rovatirelin after intravenous (iv) administration is 100-fold higher than that of TRH. As 1 has four asymmetric carbons in its molecule, there are 16 stereoisomers. We synthesized and evaluated the anti-hypothermic effect of all stereoisomers of 1, which has the (4S),(5S),(2S),(2R) configuration from the N-terminus to the C-terminus, in order to clarify the structure?activity relationship (SAR) of stereoisomers. The (4R),(5R),(2R),(2S)-isomer 16 did not show any anti-hypothermic effect. Only the (4S),(5S),(2S),(2S)-isomer 10, which has the (2S)-2-methylpyrrolidine moiety at the C-terminus showed the anti-hypothermic effect similar to 1. Stereoisomers, which have the (5R) configuration of the oxazolidinone at the N-terminus and the (2R) configuration at the middle-part, showed a much lower anti-hypothermic effect than that of 1. On the other hand, stereoisomers, which have the (4R) configuration of the oxazolidinone at the N-terminus or the (2S) configuration of the C-terminus, have little influence on the anti-hypothermic effect.
Kobayashi, Naotake,Sato, Norihito,Sugita, Katsuji,Takahashi, Kouji,Sugawara, Tamio,Tada, Yukio,Yoshikawa, Takayoshi
(2019/11/20)

Asymmetric Intra- and Intermolecular Hydroamination Catalyzed by 3,3′-Bis(trisarylsilyl)- and 3,3′-Bis(arylalkylsilyl)-Substituted Binaphtholate Rare-Earth-Metal Complexes
The series of novel 3,3′-bis(trisarylsilyl)- and 3,3′-bis(arylalkylsilyl)-substituted binaphtholate rare-earth-metal complexes 2a-i (SiR3 = Si(o-biphenylene)Ph (a), SiCyPh2 (b), Si-t-BuPh2 (c), Si(i-Pr)3 (d), SiCy2Ph (e), Si(2-tolyl)Ph2 (f), Si(4-t-Bu-C6H4)3 (g), Si(4-MeO-C6H4)Ph2 (h), SiBnPh2 (i)) have been prepared via arene elimination from [Ln(o-C6H4CH2NMe2)3] (Ln = Y, Lu) and the corresponding 3,3′-bis(silyl)-substituted binaphthol. The complexes exhibit high catalytic activity in the hydroamination/cyclization of aminoalkenes, with activities exceeding 1000 h-1 for (R)-2f-Ln, (R)-2g-Ln, and (R)-2h-Ln in the cyclization of 2,2-diphenylpent-4-enylamine (3a) at 25 °C, while the rigid dibenzosilole-substituted complexes (R)-2a-Ln and the triisopropylsilyl-substituted complexes (R)-2d-Ln exhibited the lowest activity in the range of 150-270 h-1. Catalysts (R)-2b-Lu, (R)-2c-Lu, (R)-2f-Lu, and (R)-2i-Lu provide the highest selectivities for the majority of the substrates, while the yttrium congeners are usually less selective. The highest enantioselectivities of 96% ee were observed using (R)-2a-Lu and (R)-2c-Lu in the cyclization of (4E)-2,2,5-triphenylpent-4-enylamine (9). The reactions show apparently zero-order rate dependence on substrate concentration and first-order rate dependence on catalyst concentration, with some reactions exhibiting a slightly accelerated rate at high conversion due to a shift in the equilibrium between a less active, higher coordinate catalyst species in favor of a more active, lower coordinate species as a result of weaker binding of the hydroamination product in comparison to the aminoalkene substrate. The shift in equilibrium from the higher to the lower coordinate species is also entropically favored at elevated temperatures, which results in an unusual increase in selectivity in the cyclization of 2,2-dimethylpent-4-enylamine (3d), presumably due to a higher selectivity of the lower coordinate catalyst species. All binaphtholate yttrium complexes, except (R)-2a-Y, are catalytically active in the intermolecular hydroamination of benzylamines with terminal alkenes. The highest selectivity of 66% ee was observed for the reaction of benzylamine with 4-phenyl-1-butene using (R)-2h-Y at 110 °C.
Nguyen, Hiep N.,Lee, Hyeunjoo,Aud?rsch, Stephan,Reznichenko, Alexander L.,Nawara-Hultzsch, Agnieszka J.,Schmidt, Bernd,Hultzsch, Kai C.
p. 4358 - 4379
(2018/09/27)

Carbon—carbon and carbon—nitrogen bond formation reactions catalyzed by the magnesium and calcium acenaphthene-1,2-diimine complexes
A mixture of allylbromide and diphenylacetonitrile is reduced to afford 2,2-diphenylpentene-4-nitrile as a major product in the presence of catalytic amounts of the magnesium complex (dpp-bian)Mg(thf)3 (dpp-bian is 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene dianion). The overall conversion of nitrile is 71% within 3 h at 85 °С. 4,4-Diphenylbutene-1 and diphenylmethane are by-products in this process. Complexes (dpp-bian)Mg(thf)3 and (dpp-bian)Ca(thf)4 (in an amount of 0.5—5 mol.%) catalyze the intramolecular hydroamination of some aminopentenes and aminohexenes with the conversion from 67 to 99%.
Yakub,Moskalev,Bazyakina,Fedushkin
p. 473 - 478
(2018/07/06)

Sequence-Based In-silico Discovery, Characterisation, and Biocatalytic Application of a Set of Imine Reductases
Imine reductases (IREDs) have recently become a primary focus of research in biocatalysis, complementing other classes of amine-forming enzymes such as transaminases and amine dehydrogenases. Following in the footsteps of other research groups, we have established a set of IRED biocatalysts by sequence-based in silico enzyme discovery. In this study, we present basic characterisation data for these novel IREDs and explore their activity and stereoselectivity using a panel of structurally diverse cyclic imines as substrates. Specific activities of >1 U/mg and excellent stereoselectivities (ee>99 %) were observed in many cases, and the enzymes proved surprisingly tolerant towards elevated substrate loadings. Co-expression of the IREDs with an alcohol dehydrogenase for cofactor regeneration led to whole-cell biocatalysts capable of efficiently reducing imines at 100 mM initial concentration with no need for the addition of extracellular nicotinamide cofactor. Preparative biotransformations on gram scale using these ‘designer cells’ afforded chiral amines in good yield and excellent optical purity.
Velikogne, Stefan,Resch, Verena,Dertnig, Carina,Schrittwieser, Joerg H.,Kroutil, Wolfgang
p. 3236 - 3246
(2018/08/03)

Exploiting the Catalytic Diversity of Short-Chain Dehydrogenases/Reductases: Versatile Enzymes from Plants with Extended Imine Substrate Scope
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.
Roth, Sebastian,Kilgore, Matthew B.,Kutchan, Toni M.,Müller, Michael
p. 1849 - 1852
(2018/09/10)

Switching the Cofactor Specificity of an Imine Reductase
In the last years, imine reductases (IREDs) have gained importance for the formation of chiral amines by catalyzing asymmetric reductions of imines and chemo- and stereoselective reductive aminations. However, all characterized members of this steadily gr
Borlinghaus, Niels,Nestl, Bettina M.
p. 183 - 187
(2017/12/07)

En Route to a Practical Primary Alcohol Deoxygenation
A long-standing scientific challenge in the field of alcohol deoxygenation has been direct catalytic sp3 C-O defunctionalization with high selectivity and efficiency, in the presence of other functionalities, such as free hydroxyl groups and amines widely present in biological molecules. Previously, the selectivity issue had been only addressed by classic multistep deoxygenation strategies with stoichiometric reagents. Herein, we propose a catalytic late-transition-metal-catalyzed redox design, on the basis of dehydrogenation/Wolff-Kishner (WK) reduction, to simultaneously tackle the challenges regarding step economy and selectivity. The early development of our hypothesis focuses on an iridium-catalyzed process efficient mainly with activated alcohols, which dictates harsh reaction conditions and thus limits its synthetic utility. Later, a significant advancement has been made on aliphatic primary alcohol deoxygenation by employing a ruthenium complex, with good functional group tolerance and exclusive selectivity under practical reaction conditions. Its synthetic utility is further illustrated by excellent efficiency as well as complete chemo- and regio-selectivity in both simple and complex molecular settings. Mechanistic discussion is also included with experimental supports. Overall, our current method successfully addresses the aforementioned challenges in the pertinent field, providing a practical redox-based approach to the direct sp3 C-O defunctionalization of aliphatic primary alcohols.
Dai, Xi-Jie,Li, Chao-Jun
supporting information
p. 5433 - 5440
(2016/05/19)

A Novel (R)-Imine Reductase from Paenibacillus lactis for Asymmetric Reduction of 3 H-Indoles
A novel (R)-imine reductase (PlRIR) from Paenibacillus lactis was heterologously overexpressed in Escherichia coli, purified and characterized. The purified PlRIR exhibited relatively high catalytic efficiency (kcat/Km=1.58 s-1 mm-1) towards 2,3,3-trimethylindolenine. A panel of 3H-indoles and 3H-indole iodides were reduced by PlRIR to yield the corresponding products with good-to-excellent enantioselectivity (66-98 % ee). In addition, PlRIR also possesses good activities toward other types of imines such as pyrroline, tetrahydropyridine, and dihydroisoquinoline, indicating a reasonably broad substrate acceptance. In a 100 mg scale preparative reaction, 100 mm 2,3,3-trimethylindolenine was converted efficiently to afford (R)-2,3,3-trimethylindoline with 96 % ee and 81 % yield.
Li, Hao,Zhang, Guang-Xiang,Li, Liu-Mei,Ou, Yu-Shi,Wang, Ming-Yang,Li, Chun-Xiu,Zheng, Gao-Wei,Xu, Jian-He
p. 724 - 727
(2016/03/05)

Stereoselectivity and Structural Characterization of an Imine Reductase (IRED) from Amycolatopsis orientalis
The imine reductase AoIRED from Amycolatopsis orientalis (Uniprot R4SNK4) catalyzes the NADPH-dependent reduction of a wide range of prochiral imines and iminium ions, predominantly with (S)-selectivity and with ee's of up to >99%. AoIRED displays up to 100-fold greater catalytic efficiency for 2-methyl-1-pyrroline (2MPN) compared to other IREDs, such as the enzyme from Streptomyces sp. GF3546, which also exhibits (S)-selectivity, and thus, AoIRED is an interesting candidate for preparative synthesis. AoIRED exhibits unusual catalytic properties, with inversion of stereoselectivity observed between structurally similar substrates, and also, in the case of 1-methyl-3,4-dihydroisoquinoline, for the same substrate, dependent on the age of the enzyme after purification. The structure of AoIRED has been determined in an "open" apo-form, revealing a canonical dimeric IRED fold in which the active site is formed between the N- and C-terminal domains of participating monomers. Co-crystallization with NADPH gave a "closed" form in complex with the cofactor, in which a relative closure of domains, and associated loop movements, has resulted in a much smaller active site. A ternary complex was also obtained by cocrystallization with NADPH and 1-methyl-1,2,3,4-tetrahydroisoquinoline [(MTQ], and it reveals a binding site for the (R)-amine product, which places the chiral carbon within 4 ? of the putative location of the C4 atom of NADPH that delivers hydride to the C? -N bond of the substrate. The ternary complex has permitted structure-informed mutation of the active site, resulting in mutants including Y179A, Y179F, and N241A, of altered activity and stereoselectivity.
Aleku, Godwin A.,Man, Henry,France, Scott P.,Leipold, Friedemann,Hussain, Shahed,Toca-Gonzalez, Laura,Marchington, Rebecca,Hart, Sam,Turkenburg, Johan P.,Grogan, Gideon,Turner, Nicholas J.
p. 3880 - 3889
(2016/07/06)

Structure, activity and stereoselectivity of NADPH-dependent oxidoreductases catalysing the S-selective reduction of the imine substrate 2-methylpyrroline
Oxidoreductases from Streptomyces sp. GF3546 [3546-IRED], Bacillus cereus BAG3X2 (BcIRED) and Nocardiopsis halophila (NhIRED) each reduce prochiral 2-methylpyrroline (2MPN) to (S)-2-methylpyrrolidine with >95 % ee and also a number of other imine substrates with good selectivity. Structures of BcIRED and NhIRED have helped to identify conserved active site residues within this subgroup of imine reductases that have S selectivity towards 2MPN, including a tyrosine residue that has a possible role in catalysis and superimposes with an aspartate in related enzymes that display R selectivity towards the same substrate. Mutation of this tyrosine residue - Tyr169 - in 3546-IRED to Phe resulted in a mutant of negligible activity. The data together provide structural evidence for the location and significance of the Tyr residue in this group of imine reductases, and permit a comparison of the active sites of enzymes that reduce 2MPN with either R or S selectivity.
Man, Henry,Wells, Elizabeth,Hussain, Shahed,Leipold, Friedemann,Hart, Sam,Turkenburg, Johan P.,Turner, Nicholas J.,Grogan, Gideon
p. 1052 - 1059
(2015/05/05)

An (R)-imine reductase biocatalyst for the asymmetric reduction of cyclic imines
Although the range of biocatalysts available for the synthesis of enantiomerically pure chiral amines continues to expand, few existing methods provide access to secondary amines. To address this shortcoming, we have over-expressed the gene for an (R)-imine reductase [(R)-IRED] from Streptomyces sp. GF3587 in Escherichia coli to create a recombinant whole-cell biocatalyst for the asymmetric reduction of prochiral imines. The (R)-IRED was screened against a panel of cyclic imines and two iminium ions and was shown to possess high catalytic activity and enantioselectivity. Preparative-scale synthesis of the alkaloid (R)-coniine (90 % yield; 99 % ee) from the imine precursor was performed on a gram-scale. A homology model of the enzyme active site, based on the structure of a closely related (R)-IRED from Streptomyces kanamyceticus, was constructed and used to identify potential amino acids as targets for
Hussain, Shahed,Leipold, Friedemann,Man, Henry,Wells, Elizabeth,France, Scott P.,Mulholland, Keith R.,Grogan, Gideon,Turner, Nicholas J.
p. 579 - 583
(2015/03/05)

Characterization of three novel enzymes with imine reductase activity
Imine reductases (IRED) are promising catalysts for the synthesis of optically pure secondary cyclic amines. Three novel IREDs from Paenibacillus elgii B69, Streptomyces ipomoeae 91-03 and Pseudomonas putida KT2440 were identified by amino acid or structural similarity search, cloned and recombinantly expressed in E. coli and their substrate scope was investigated. Besides the acceptance of cyclic amines, also acyclic amines could be identified as substrates for all IREDs. For the IRED from P. putida, a crystal structure (PDB-code 3L6D) is available in the database, but the function of the protein was not investigated so far. This enzyme showed the highest apparent E-value of approximately Eapp = 52 for (R)-methylpyrrolidine of the IREDs investigated in this study. Thus, an excellent enantiomeric purity of >99% and 97% conversion was reached in a biocatalytic reaction using resting cells after 24 h. Interestingly, a histidine residue could be confirmed as a catalytic residue by mutagenesis, but the residue is placed one turn aside compared to the formally known position of the catalytic Asp187 of Streptomyces kanamyceticus IRED.
Gand,Müller,Wardenga,H?hne
p. 126 - 132
(2015/02/19)

A method for the racemization of 2-methylpyrrolidine: A histamine H 3 receptor pharmacophore
This paper describes a method for the racemization of unwanted (S)-1 isomer arising from the resolution of (±)-1. The process of racemization involves thiyl radical-mediated reversible hydrogen abstraction at the chiral center, in the presence of AIBN in water. The racemized isomer was subsequently resolved by l-(+)-tartaric acid to get (R)-1, a histamine H3 receptor pharmacophore. We foresee that such an approach of racemization will be industrially useful for recycling waste (S)-1 enantiomer.
Yerande, Swapnil G.,Yerande, Ragini S.,Thakare, Prashant P.,Shendage, Deepak M.,Galave, Sharad,Gangopadhyay, Ashok Kumar
p. 652 - 655
(2014/06/09)

Enzyme Toolbox: Novel Enantiocomplementary Imine Reductases
Reducing reactions are among the most useful transformations for the generation of chiral compounds in the fine-chemical industry. Because of their exquisite selectivities, enzymatic approaches have emerged as the method of choice for the reduction of C=O
Scheller, Philipp N.,Fademrecht, Silvia,Hofelzer, Sebastian,Pleiss, Jürgen,Leipold, Friedemann,Turner, Nicholas J.,Nestl, Bettina M.,Hauer, Bernhard
p. 2201 - 2204
(2016/02/18)

C1-symmetric rare-earth-metal aminodiolate complexes for intra- and intermolecular asymmetric hydroamination of alkenes
A series of novel C1-symmetric aminodiolate rare-earth-metal complexes have been prepared via arene elimination from [Ln(o-C 6H4CH2NMe2)3] (Ln = Y, Lu) and the corresponding aminodiol proligand. The NOBIN-derived aminodiolate ligands feature sterically demanding triphenylsilyl and methyldiphenylsilyl ortho substituents on the naphtholate moiety and substituents of varying steric demand ranging from tert-butyl to tris(3,5-xylyl)silyl on the phenolate moiety. Complexes with a triphenylsilyl substituent on the naphtholate moiety displayed good catalytic activity in the hydroamination/cyclization of aminoalkenes, while complexes with a methyldiphenylsilyl substituent exhibited somewhat lower reactivity. The highest enantioselectivities for five- and six-membered-ring formation were observed utilizing complex 9c-Lu (R1 = Ph, R 2 = Me, R3 = SiPh3) in the cyclization of (2,2-diphenylpent-4-enyl)amine (92% ee, Nt = 200 h-1 at 25 C) and (2,2-diphenylhex-5-enyl)amine (73% ee, Nt = 20 h-1 at 25 C). The complexes can be applied in asymmetric intermolecular hydroaminations of 1-heptene and 4-phenyl-1-butene with benzylamine with enantioselectivities of up to 40% ee using complex 9b-Y (R1 = Ph, R2 = Me, R3 = SiPh2Me). Here the higher catalytic activities are achieved with catalysts having a methyldiphenylsilyl substituent on the naphtholate moiety. Lanthanum aminodiolate catalysts generated in situ from [La{CH(C6H5)NMe2} 3] did not exhibit improved catalytic activity in the intermolecular hydroamination in comparison to the corresponding yttrium and lutetium catalysts. The overall catalytic activities of the aminodiolate complexes are somewhat diminished in comparison to previously studied binaphtholate complexes due to the presence of the additional amine donor site in the ligand framework.
Reznichenko, Alexander L.,Hultzsch, Kai C.
p. 1394 - 1408
(2013/05/21)

Highly enantioselective zirconium-catalyzed cyclization of aminoalkenes
Aminoalkenes are catalytically cyclized in the presence of cyclopentadienylbis(oxazolinyl)borato group 4 complexes {PhB(C5H 4)(OxR)2}M(NMe2)2 (M = Ti, Zr, Hf; OxR = 4,4-dimethyl-2-oxazoline, 4S-isopropyl-5,5- dimethyl-2-oxazoline, 4S-tert-butyl-2-oxazoline) at room temperature and below, affording five-, six-, and seven-membered N-heterocyclic amines with enantiomeric excesses of >90% in many cases and up to 99%. Mechanistic investigations of this highly selective system employed synthetic tests, kinetics, and stereochemistry. Secondary aminopentene cyclizations require a primary amine (1-2 equiv vs catalyst). Aminoalkenes are unchanged in the presence of a zirconium monoamido complex {PhB(C5H 4)(Ox4S-iPr,Me2)2}Zr(NMe2)Cl or a cyclopentadienylmono(oxazolinyl)borato zirconium diamide {Ph2B(C 5H4)(Ox4S-iPr,Me2)}Zr(NMe2) 2. Plots of initial rate versus [substrate] show a rate dependence that evolves from first-order at low concentration to zero-order at high concentration, and this is consistent with a reversible substrate-catalyst interaction preceding an irreversible step. Primary kinetic isotope effects from substrate conversion measurements (k′obs(H)/ k′obs(D) = 3.3 ± 0.3) and from initial rate analysis (k2(H)/k2(D) = 2.3 ± 0.4) indicate that a N-H bond is broken in the turnover-limiting and irreversible step of the catalytic cycle. Asymmetric hydroamination/cyclization of N-deutero-aminoalkenes provides products with higher optical purities than obtained with N-proteo-aminoalkenes. Transition state theory, applied to the rate constant k2 that characterizes the irreversible step, provides activation parameters consistent with a highly organized transition state (ΔS? = -43(7) cal·mol-1 K -1) and a remarkably low enthalpic barrier (ΔH ? = 6.7(2) kcal·mol-1). A six-centered, concerted transition state for C-N and C-H bond formation and N-H bond cleavage involving two amidoalkene ligands is proposed as most consistent with the current data.
Manna, Kuntal,Everett, William C.,Schoendorff, George,Ellern, Arkady,Windus, Theresa L.,Sadow, Aaron D.
supporting information
p. 7235 - 7250
(2013/06/27)

Group IV organometallic compounds based on dianionic "pincer" ligands: Synthesis, characterization, and catalytic activity in intramolecular hydroamination reactions
Neutral ZrIV and HfIV diamido complexes stabilized by unsymmetrical dianionic N,C,N′ pincer ligands have been prepared through the simplest and convenient direct metal-induced Caryl-H bond activation. Simple ligand modification has contributed to highlight the non-innocent role played by the donor atom set in the control of the cyclometallation kinetics. The as-prepared bis-amido catalysts were found to be good candidates for the intramolecular hydroamination/cyclization of primary aminoalkenes. The ability of these compounds to promote such a catalytic transformation efficiently (by providing, in some cases, fast and complete substrate conversion at room temperature) constitutes a remarkable step forward toward catalytic systems that can operate at relatively low catalyst loading and under milder reaction conditions. Kinetic studies and substrate-scope investigations, in conjunction with preliminary DFT calculations on the real systems, were used to elucidate the effects of the substrate substitution on the catalyst performance and to support the most reliable mechanistic path operative in the hydroamination reaction. Changing the order of the "factors" can (somehow) change the result! Neutral ZrIV and HfIV diamido complexes stabilized by unsymmetrical dianionic N,C,N′-pincer ligands have been prepared (see picture) and successfully employed as good catalyst candidates for the efficient and mild intramolecular hydroamination/cyclization of primary aminoalkenes. Copyright
Luconi, Lapo,Rossin, Andrea,Motta, Alessandro,Tuci, Giulia,Giambastiani, Giuliano
p. 4906 - 4921
(2013/05/21)

Asymmetric reduction of cyclic imines catalyzed by a whole-cell biocatalyst containing an (S)-imine reductase
Biocatalytic imine reduction: A whole-cell recombinant E. coli system, producing an (S)-selective imine reductase (IRED) from Streptomyces sp. GF3546, is developed. This biocatalyst is used for the enantioselective reduction of a broad range of substrates such as dihydroisoquinolines and dihydro-β- carbolines as well as iminium ions. Copyright
Leipold, Friedemann,Hussain, Shahed,Ghislieri, Diego,Turner, Nicholas J.
p. 3505 - 3508
(2014/01/06)

Structure and activity of NADPH-dependent reductase Q1EQE0 from streptomyces kanamyceticus, which catalyses the R-selective reduction of an imine substrate
NADPH-dependent oxidoreductase Q1EQE0 from Streptomyces kanamyceticus catalyzes the asymmetric reduction of the prochiral monocyclic imine 2-methyl-1-pyrroline to the chiral amine (R)-2-methylpyrrolidine with >99% ee, and is thus of interest as a potential biocatalyst for the production of optically active amines. The structures of Q1EQE0 in native form, and in complex with the nicotinamide cofactor NADPH have been solved and refined to a resolution of 2.7 A. Q1EQE0 functions as a dimer in which the monomer consists of an N-terminal Rossman-fold motif attached to a helical C-terminal domain through a helix of 28 amino acids. The dimer is formed through reciprocal domain sharing in which the C-terminal domains are swapped, with a substrate-binding cleft formed between the N-terminal subunit of monomer A and the C-terminal subunit of monomer B. The structure is related to those of known β-hydroxyacid dehydrogenases, except that the essential lysine, which serves as an acid/base in the (de)protonation of the nascent alcohol in those enzymes, is replaced by an aspartate residue, Asp187 in Q1EQE0. Mutation of Asp187 to either asparagine or alanine resulted in an inactive enzyme.
Rodriguez-Mata, Maria,Frank, Annika,Wells, Elizabeth,Leipold, Friedemann,Turner, Nicholas J.,Hart, Sam,Turkenburg, Johan P.,Grogan, Gideon
p. 1372 - 1379
(2013/08/23)

A chiral phenoxyamine magnesium catalyst for the enantioselective hydroamination/cyclization of aminoalkenes and intermolecular hydroamination of vinyl arenes
If Grignard had only known! A chiral magnesium complex catalyzes the intramolecular hydroamination/cyclization of aminoalkenes with high efficiency at temperatures as low as -20 °C and enantioselectivities as high as 93 %ee. The high activity of this system also allows the catalytic intermolecular anti-Markovnikov addition of pyrrolidine and benzylamine to vinyl arenes. Copyright
Zhang, Xiaoming,Emge, Thomas J.,Hultzsch, Kai C.
supporting information; experimental part
p. 394 - 398
(2012/03/22)

Rare-earth-metal complexes supported by new chiral tetra-azane chelating ligands: Synthesis, characterization, and catalytic properties for intramolecular asymmetric hydroamination
A number of new chiral tetra-azane proligands (1R,2R)-N,N′-bis(o- arylamino-benzylidene)-1,2-diaminocyclohexane ((1R,2R)-[(ArHN)C 6H4CH=N]2C6H10, Ar = 2,6-Me2C6H3 (L1H2), 2,6-Et2C6H3 (L2H2), 2,6-iPr2C6H3 (L3H 2)) have been synthesized via a nucleophilic displacement of the two fluorine atoms in (o-C6H4FCH=N)2C 6H10 with the lithium salt of the corresponding aniline derivative. Their rare-earth-metal complexes L1ScCl 2Li(THF)3 (1), L1YCl2Li(THF) 3 (2), L2YCl2Li(THF)3 (3), and L3YCl2Li(THF)2 (4) were synthesized in good yields via the salt metathesis of MCl3 (M = Sc, Y) with the dilithium salts of the ligands L1Li2(THF)4, L 2Li2(THF),4, and L3Li 2(THF)4, respectively. Further more, the two diethylamido complexes L1Y(NEt2)ClLi(THF)3 (5) and L 3Y(NEt2)ClLi(THF)2 (6) were also synthesized from reactions of the corresponding chloride complexes 2 and 4 with diethylamidolithium. The new proligands L1H2-L 3H2 and their rare-earth-metal complexes 1-6 have been characterized by elemental analyses and 1H and 13C NMR spectroscopy. The structures of complexes 1, 2, and 4 have been further confirmed by single-crystal X-ray diffraction analysis. The molecular structural analysis reveals that the metal centers in complexes 1, 2, and 4 acquire a distorted-octahedral coordination environment in their solid-state structures by sharing the chloride with a LiCl(THF)n moiety. After in situ treatment with nBuLi or Me3SiCH2Li, complexes 1-4 show reasonable catalytic activity and good enantioselectivity (up to 90%) for intramolecular asymmetric hydroamination reactions of terminal aminoalkenes. The amido complexes 5 and 6 can catalyze the intramolecular hydroamination reaction directly and show catalytic activities and enantioselectivities similar to those of the in situ formed alkyl complexes.
Zhang, Yanyu,Yao, Wei,Li, He,Mu, Ying
experimental part
p. 4670 - 4679
(2012/10/08)

Diamido-ether actinide complexes as catalysts for the intramolecular hydroamination of aminoalkenes
The synthesis and characterization of a series of new diamido-thorium(IV) and diamido-uranium(IV) halide and alkyl complexes supported by three different diamido-ether ligands are reported. Reaction of ThCl4?2DME with [(RNSiMe2)2O]Li2 ([RNON]Li 2) in DME when R = tBu gives [tBuNON]ThCl 5Li3?DME (1), when R = iPr2Ph in diethyl ether [iPr2Ph NON]ThCl3Li?DME (3) is prepared. Reaction of UCl4 with [iPr2Ph NON]Li2 in diethyl ether gives {[iPr2Ph NON]UCl2}2 (4). Reaction of ThCl4?2DME with Li2[( iPr2PhNCH2CH2)2O] ([iPr2Ph NCOCN]Li2) in DME gives [iPr2Ph NCOCN]ThCl2?DME (5). The addition of 2 equiv of LiCH 2SiMe3 to 1 and 5 resulted in salt- and base-free [ tBuNON]Th(CH2SiMe3)2 (7) and [iPr2Ph NCOCN]Th(CH2SiMe3)2 (9), respectively. Complexes 1, 3, 4, 7, and 9, as well as previously reported {[tBuNON]UCl2}2 (2), [tBuNON] U(CH2SiMe3)2 (6), and [iPr2Ph NCOCN]U(CH2SiMe3)2 (8) were examined as catalysts for the intramolecular hydroamination of a series of aminoalkenes. Complexes 6-9 were shown to facilitate the formation of 2-methyl-4,4- diphenylpyrrolidine from 2,2-diphenyl-1-amino-4-pentene at room temperature. For 9, this reaction occurs in less than 15 min, while for other dialkyls 6-8, the reaction takes less than 2 h. Dihalides 1 and 2 facilitated the same reaction at 60 °C in 4 h, while 3 and 4 showed no activity under the same conditions. Dialkyl complexes 7-9 were examined for further reactivity with different substrates. The uranium dialkyl 8 was more active than 7 and 9 for the cyclization of 2,2-diphenyl-1-amino-5-hexene and 2,2-diphenyl-1-amino-6-heptene, as well as more active in the cyclization of N-methyl-2,2-diphenyl-1-amino-4- pentene, a secondary amine. All three dialkyls became less active when the steric bulk of the gem-substituents was decreased from diphenyl to cyclopentyl; reactivity further decreased when the steric bulk of the substituents was decreased further to hydrogen.
Hayes, Cassandra E.,Leznoff, Daniel B.,Platel, Rachel H.,Schafer, Laurel L.
p. 6732 - 6740,9
(2020/09/15)

Amidate ligand design effects in zirconium-catalyzed enantioselective hydroamination of aminoalkenes
In situ generated axially chiral zirconium biphenyl amidate complexes are efficient precatalysts for the enantioselective intramolecular hydroamination of aminoalkenes, generating α-substituted pyrrolidines and piperidine with up to 74% ee. Five new chelating amide proligands and three new zirconium amidate complexes have been prepared and fully characterized in this investigation of ligand structure/catalyst function. Solid-state molecular structures of the complexes suggest that the observed moderate and highly variable enantioselectivities are a consequence of the multiple isomers accessible to this family of complexes, including a κ2-(O,O)- bonding motif. Thermal stability studies of the complexes further revealed the tendency of these complexes to undergo diastereoselective dimerization to afford homochiral dimers. These dimeric precatalysts are less efficient when used for the cyclization of aminoalkenes in comparison to their monomeric precursors. These results illustrate the variable coordination modes accessible to amidate ligands and suggest steric factors that must be considered in advanced ligand design.
Ayinla, Rashidat O.,Gibson, Travis,Schafer, Laurel L.
experimental part
p. 50 - 60
(2011/02/16)

A highly enantioselective zirconium catalyst for intramolecular alkene hydroamination: Significant isotope effects on rate and stereoselectivity
Zirconium catalysts sparkle: A new chiral zirconium complex has been used to catalyze hydroamination reactions to cyclize aminopentenes into 2-methylpyrrolidines (see scheme). The rate law supports a mechanism involving a reversible substrate-catalyst interaction that precedes the rate-determining step. A new mechanism for zirconium-catalyzed hydroamination has been proposed based on kinetic isotope effects and the significant effect of isotopic substitution on enantioselectivity.
Manna, Kuntal,Xu, Songchen,Sadow, Aaron D.
supporting information; experimental part
p. 1865 - 1868
(2011/04/22)

Intramolecular hydroamination of aminoalkenes catalyzed by a cationic zirconium complex
A new cationic [N-O-S]zirconium complex (cat.) was developed to be an excellent catalyst for the intramolecular hydroamination of aminoalkenes with a large substrate scope from terminal alkenes to internal alkenes, and primary amines to secondary amines. The catalyst system can also tolerate various functional groups and perform sequential hydroamination of primary aminodienes.
Wang, Xinke,Chen, Zhou,Sun, Xiu-Li,Tang, Yong,Xie, Zuowei
supporting information; experimental part
p. 4758 - 4761
(2011/10/30)

PROCESS FOR SYNTHESIS OF 2-SUBSTITUTED PYRROLIDINES AND PIPERADINES
The present invention provides a highly efficient, versatile one-step process for asymmetric synthesis of either diastereomer of 2-substituted pyrrolidines from a single starting material with excellent yields and high diastereoselectivety. Also provided is a method for the asymmetric synthesis of both diastereomers of 2-substituted piperidines with good yields and excellent diastereoselectivety. Diasteroselectivity is controlled effectively by choice of reducing agent.
-
Page/Page column 61

(2011/09/19)

Purification and characterization of a novel (R)-imine reductase from Streptomyces sp. GF3587
The (R)-imine reductase (RIR) of Streptomyces sp. GF3587 was purified and characterized. It was found to be a NADPH-dependent enzyme, and was found to be a homodimer consisting of 32 kDa subunits. Enzymatic reduction of 10mM 2-methyl-1-pyrroline (2-MPN) resulted in the formation of 9.8mM (R)-2-methylpyrrolidine ((R)-2-MP) with 99% e.e. The enzyme showed not only reduction activity for 2-MPN at neutral pH (6.5- 8.0), but also oxidation activity for (R)-2-MP under alkaline pH (10-11.5) conditions. It appeared to be a sulfhydryl enzyme based on the sensitivity to sulfhydryl specific inhibitors. It was very specific to 2-MPN as substrate.
Mitsukura, Koichi,Suzuki, Mai,Shinoda, Sho,Kuramoto, Tatsuya,Yoshida, Toyokazu,Nagasawa, Toru
experimental part
p. 1778 - 1782
(2012/02/02)

C2-symmetric zirconium Bis(Amidate) complexes with enhanced reactivity in aminoalkene hydroamination
Binaphthalenedicarboxamide zirconium complexes exhibit significantly enhanced catalytic activity in aminoalkene hydroamination reactions with respect to substrate scope (substrates without gem-dialkyl activation; cyclization of aminoheptenes), catalyst loading (as low as 0.5 mol %) and reaction temperatures (as low as 70 °C) compared to previous group 4 metal-based hydroamination catalyst systems.
Reznichenko, Alexander L.,Hultzsch, Kai C.
scheme or table
p. 24 - 27
(2010/03/04)

A zwitterionic zirconium complex that catalyzes hydroamination of aminoalkenes at room temperature
The zwitterionic cyclopentadienyl-bis(2-oxazolinyl)borate diamidozirconium(iv) complex is a precatalyst for the cyclization of aminoalkenes to five- and six-membered rings under mild conditions.
Manna, Kuntal,Ellern, Arkady,Sadow, Aaron D.
supporting information; experimental part
p. 339 - 341
(2010/05/01)

Intramolecular aminoalkene hydroamination catalyzed by magnesium complexes containing multidentate phenoxyamine ligands
The magnesium complexes L2MgiPr (L2 = 4-tert-butyl-6-(triphenylsilyl)-2-[bis((3-(dimethylamino)propyl)amino)methyl] phenoxyl) and L3MgiPr (L3 = 4-tert-butyl-6-(triphenylsilyl)-2-[benzyl((3-(dimethylamino)propyl)amino)methyl] phenoxyl) supported by potentially tetradentate and tridentate triphenylsilyl-substituted phenoxyamine ligands have been prepared and fully characterized. The X-ray crystallographic analysis of L2Mg iPr confirmed a monomeric structure in which only one of the amine side arms is bound to the four-coordinate magnesium atom. The free and coordinated side arms in L2MgiPr undergo an exchange process at 25 °C in solution, while the phenoxydiamine complex L 3MgiPr, on the other hand, shows no sign of fluxionality. Both complexes, as well as L1MgiPr (L1 = 4,6-di-tert-butyl-2-[bis((3-(dimethylamino)propyl)amino)methyl]phenoxyl), were shown to be competent catalysts in the cyclization of aminoalkenes. L 2MgiPr exhibited the best catalytic activity, and both triphenylsilyl-substituted complexes display zero-order rate dependence on substrate concentration and first-order rate dependence on catalyst concentration, whereas the sterically less hindered complex L1Mg iPr exhibits second-order rate dependence on substrate concentration. No Schlenk-type ligand redistributions were observed, and the catalytically active magnesium species was stable after prolonged heating to 120 °C, according to an NMR spectroscopic study.
Zhang, Xiaoming,Emge, Thomas J.,Hultzsch, Kai C.
experimental part
p. 5871 - 5877
(2011/02/24)

Asymmetric synthesis of chiral cyclic amine from cyclic imine by bacterial whole-cell catalyst of enantioselective imine reductase
Streptomyces sp. GF3587 and 3546 were found to be imine-reducing strains with high R- and S-selectivity by screening using 2-methyl-1-pyrroline (2-MPN). Their whole-cell catalysts produced 91 mM R-2-methylpyrrolidine (R-2-MP) with 99.2%e.e. and 27.5 mM S-2-MP (92.3%e.e.) from 2-MPN at 91-92% conversion in the presence of glucose, respectively.
Mitsukura, Koichi,Suzuki, Mai,Tada, Kazuhiro,Yoshida, Toyokazu,Nagasawa, Toru
supporting information; experimental part
p. 4533 - 4535
(2010/11/19)

A facile asymmetric synthesis of either enantiomer of 2-substituted pyrrolidines
Chemical Reaction Reprentation A new and general method for asymmetric synthesis of either enantiomer of 2-substituted pyrrolidines from a single starting material is described. Reductive cyclization of (Ss)-γ-chloro-N- tertbutanesulfinyl ketimines with LiBHEt3 in THF at -78 to 23 °C afforded (Ss,R)-N-tert-buta.nemnnyl-2-substituted pyrrolidines in excellent yields (88-98%) and with high diastereoselectivity (99:1). The diastereoselectivity is controlled effectively by the choice of reducing agent. Thus, the corresponding epimers of (3 to DIBAL-H/LiHMDS. Deprotection of N-fe/ f-butanesulfinyl-2-substituted pyrrolidines using 4 N HCl in dioxane and MeOH gave the corresponding enantiomers of 2-substituted pyrrolidines in quantative yield. This method was found to be effective for a variety of substrates including aromatic, heteroaromatic, and aliphatic substituents. Extension of this methodology to the formation of 2-substituted piperidines is also illustrated. Reductive cyclization of (5s)-3 in THF at -78 to 23 °C or DIBAL-H/LiHMDS in toluene at -78 to 0 °C afforded the (Ss,R?)-N-tert-butanesulfinyl-2-substituted piperidines in excellent yield (98%) and with high diastereoselectivity (99:1) or (Ss,S)-.N-tert-butanesulfmyl- 2substituted piperidines in good yield (98%) and with high diastereoselectivity (1:99), respectively.
Reddy, Leleti Rajender,Das, Sonia G.,Liu, Yugang,Prashad, Mahavir
supporting information; experimental part
p. 2236 - 2246
(2010/06/15)

Rhodium-catalyzed asymmetric intramolecular hydroamination of unactivated alkenes
(Figure Presented) One for the Rh(oad): The first rhodiumcatalyzed asymmetric intramolecular hydroamination of unactivated olefins was developed by using dialkylbiaryl phosphine ligands (see scheme; cod = 1,5-cyclooctadiene, Cy = cyclohexyl). A variety of 2-methylpyrrolidines have been synthesized with high enantioselectivities.
Shen, Xiaoqiang,Buchwald, Stephen L.
supporting information; experimental part
p. 564 - 567
(2010/04/05)

Facile synthesis of a family of H8BINOL-amine compounds and catalytic asymmetric arylzinc addition to aldehydes
A family of optically active H8BINOL-AM compounds containing 3,3′-bis-tertiary amine substituents are synthesized by using a one-step reaction of H8BINOL with amino methanols that were in situ generated from various cyclic or acyclic secondary amines and paraformaldehyde. The H 8BINOL-AM compounds are used to catalyze the reaction of functional arylzincs, in situ prepared from the reaction of aryliodides with ZnEt 2, with aldehydes to produce chiral diaryl carbinols and a few arylalkyl carbinols. Through this study, highly enantioselective catalysts were identified. It was found that the H8BINOL-AM compounds with sterically less congested cyclic or acyclic amino methyl substituents were more enantioselective than those with more bulky substituents. The pyrrolidinyl derivative (S)-12 in most cases showed greater enantioselectivity than other H8BINOL-AM compounds, especially for the challenging ortho-substituted aromatic aldehydes. A H8BINOL-AM with 3,3′-bis-sec-amine substituents, prepared by a multistep method, was also used to catalyze the arylzinc addition to aldehydes, but it showed enantioselectivity lower than that of the compounds with tertiary amine groups. It was found for the first time that an aryl bromide, 2-bromothiophene, could be used to prepare an arylzinc reagent by reaction with ZnEt2. The addition of this heteroarylzinc reagent to an aldehyde in the presence of (S)-12 proceeded with good enantioselectivity.
Deberardinis, Albert M.,Turlington, Mark,Ko, Jason,Sole, Laura,Pu, Lin
experimental part
p. 2836 - 2850
(2010/08/05)

Intramolecular hydroamination of unbiased and functionalized primary aminoalkenes catalyzed by a rhodium aminophosphine complex
We report a rhodium catalyst that exhibits high reactivity for the hydroamination of primary aminoalkenes that are unbiased toward cyclization and that possess functional groups incompatible with more electrophilic hydroamination catalysts. The rhodium catalyst contains an unusual diaminophosphine ligand (L1) that binds to rhodium in a K3-P,O,P mode. The reactions catalyzed by this complex typically proceed at mild temperatures (room temperature to 70 °C) and occur with primary aminoalkenes lacking substituents on the alkyl chain that bias the system toward cyclization, with primary aminoalkenes containing chloride, ester, ether, enolizable ketone, nitrile, and unprotected alcohol functionality, and with primary aminoalkenes containing internal olefins. Mechanistic data imply that these reactions occur with a turnover-limiting step that is different from that of reactions catalyzed by late-transition-metal complexes of Pd, Pt, and Ir. This change in the turnover-limiting step and resulting high activity of the catalyst stem from favorable relative rates for protonolysis of the M-C bond to release the hydroamination product versus reversion of the aminoalkyl intermediate to regenerate the acyclic precursor. Probes of the origin of the reactivity of the rhodium complex of L1 imply that the aminophosphine groups lead to these favorable rates by effects beyond steric demands and simple electron donation to the metal center.
Julian, Lisa D.,Hartwig, John F.
supporting information; experimental part
p. 13813 - 13822
(2010/11/17)

Organocerium additions to proline-derived hydrazones: Synthesis of enantiomerically enriched amines
The addition of organocerium reagents (from both organolithium and organomagnesium precursors) to chiral aldehyde hydrazones prepared from 1-aminoproline derivatives has been studied. The additions proceed in good yield and high diastereoselectivity and with good nucleophile (Me, n-Bu, i-Pr, t-Bu, Ph, etc.) and substrate scope (alkyl, alkenyl and aryl). The resulting hydrazines can be converted to amines by N-N bond cleavage through hydrogenolysis (Raney nickel) or by acylation and cleavage with Li/NH 3. The influence of the side chain on the diastereoselectivity was investigated through variation of the substituents to include more coordinating atoms (oxygen and nitrogen) as well as the removal of coordinating atoms. The SAMEMP auxiliary bearing a 2-methoxyethoxymethyl group gave the highest diastereoselectivities. Remarkably, auxiliaries bearing simple methyl and isobutyl substituents gave high selectivities as well. Hypotheses for the origin of the selectivity are presented.
Denmark, Scott E.,Edwards, James P.,Weber, Theodor,Piotrowski, David W.
experimental part
p. 1278 - 1302
(2010/11/02)

Base-catalysed intramolecular hydroamination of vinyl sulfiies
Small amounts of n-butyllithium catalyse the highly efficient hydroamination of a large variety of vinyl sulfides. This novel methodology offers an easy access to a wide range of nitrogen heterocycles, including simple pyrrolidines and piperidines, as well as more complex bicyclic compounds. Subsequent transformations of the sulfur group led to the formation of functionalised alkaloid-like substructures. Wiley-VCH Verlag GmbH & Co. KGaA.
Quinet, Coralie,Sampoux, Laetitia,Marko, Istvan E.
supporting information; experimental part
p. 1806 - 1811
(2009/09/06)

Intramolecular hydroamination of aminoalkenes by calcium and magnesium complexes: A synthetic and mechanistic study
The β-diketiminate-stabilized calcium amide complex [{ArNC(Me)CHC(Me)NAr}Ca{N(SiMe3)2}-(THF)] (Ar = 2,6-diisopropylphenyl) and magnesium methyl complex [{ArNC(Me)CHC(Me)NAr}Mg(Me) (THF)] are reported as efficient precatalysts for hydroamination/cyclization of aminoalkenes. The reactions proceeded under mild conditions, allowing the synthesis of five-, six-, and seven-membered heterocyclic compounds. Qualitative assessment of these reactions revealed that the ease of catalytic turnover increases (i) for smaller ring sizes (5 > 6 > 7), (ii) substrates that benefit from favorable Thorpe-Ingold effects, and (iii) substrates that do not possess additional substitution on the alkene entity. Prochiral substrates may undergo diastereoselective hydroamination/cyclization depending upon the position of the existing stereocenter. Furthermore, a number of minor byproducts of these reactions, arising from competitive alkene isomerization reactions, were identified. A series of stoichiometric reactions between the precatalysts and primary amines provided an important model for catalyst initiation and suggested that these reactions are facile at room temperature, with the reaction of the calcium precatalyst with benzylamine proceeding with ΔG°(298 K) = -2.7 kcal mol-1. Both external amine/amide exchange and coordinated amine/amide exchange were observed in model complexes, and the data suggest that these processes occur via low-activation-energy pathways. As a result of the formation of potentially reactive byproducts such as hexamethyldisilazane, calcium-catalyst initiation is reversible, whereas for the magnesium precatalyst, this process is nonreversible. Further stoichiometric reactions of the two precatalysts with 1-amino-2,2-diphenyl-4-pentene demonstrated that the alkene insertion step proceeds via a highly reactive transient alkylmetal intermediate that readily reacts with N-H σ bonds under catalytically relevant conditions. The results of deuterium-labeling studies are consistent with the formation of a single transient alkyl complex for both the magnesium and calcium precatalysts. Kinetic analysis of the nonreversible magnesium system revealed that the reaction rate depends directly upon catalyst concentration and inversely upon substrate concentration, suggesting that substrate-inhibited alkene insertion is rate-determining.
Crimmin, Mark R.,Arrowsmith, Merle,Barrett, Anthony G. M.,Casely, Ian J.,Hill, Michael S.,Procopiou, Panayiotis A.
supporting information; experimental part
p. 9670 - 9685
(2011/03/20)

Highly efficient, base-catalysed, intramolecular hydroamination of non-activated olefins
The intramolecular hydroamination of a large variety of non-activated alkenes can be efficiently catalysed by small amounts of lithium bases, providing smoothly and in high yields the corresponding five- and six-membered ring heterocycles. Fused and bridged bicyclic amines, of varying ring sizes, can be readily prepared either by a sequential hydroamination process or by a tandem, double addition reaction.
Quinet, Coralie,Jourdain, Pierre,Hermans, Christophe,Ates, Ali,Lucas, Isabelle,Markó, István E.
p. 1077 - 1087
(2008/09/17)

Constrained geometry organoactinides as versatile catalysts for the intramolecular hydroamination/cyclization of primary and secondary amines having diverse tethered C-C unsaturation
A series of "constrained geometry" organoactinide complexes, (CGC)An(NMe)2 (CGC = Me2-Si(η5-Me 4C5)(tBuN); An = Th, 1; U, 2), has been prepared via efficient in situ, two-step protodeamination routes in good yields and high purity. Both 1 and 2 are quantitatively converted to the neutrally charged, solvent-free dichlorides (1-Cl2, 2-Cl2) and slightly more soluble diiodides (1-I2, 2-I2) with excess Me3Si-X (X = Cl, I) in non-coordinating solvents. The new complexes were characterized by NMR spectroscopy, elemental analysis, and (for 1 and 2) single-crystal X-ray diffraction, revealing substantially increased metal coordinative unsaturation vs the corresponding Me2SiCp″ 2AnR2 (Cp″ = η5-Me4C 5; An = Th, R = CH2-(SiMe3), 3; An = U, R = CH2Ph, 4) and Cp′2AnR2 (Cp′ = η5-Me5C5 ; An = Th, R = CH 2(SiMe3), 5; An = U, R = CH2(SiMe3), 6) complexes. Complexes 1-6 exhibit broad applicability for the intramolecular hydroamination of diverse C-C unsaturations, including terminal and internal aminoalkenes (primary and secondary amines), aminoalkynes (primary and secondary amines), aminoallenes, and aminodienes. Large turnover frequencies (N t up to 3000 h-1) and high regioselectivities (≥95%) are observed throughout, along with moderate to high diastereoselectivities (up to 90% trans ring closures). With several noteworthy exceptions, reactivity trends track relative 5f ionic radii and ancillary ligand coordinative unsaturation. Reactivity patterns and activation parameters are consistent with a reaction pathway proceeding via turnover-limiting C=C/C=C insertion into the An-N σ-bond.
Stubbert, Bryan D.,Marks, Tobin J.
p. 4253 - 4271
(2008/02/01)

CHROMANE ANTAGONIST OF THE H-3 RECEPTOR
This invention is directed to a compound of formula (I), as defined herein, or a pharmaceutically acceptable salt thereof; a pharmaceutical composition containing a compound of formula (I), a process of preparation of a compound of formula (I), a method of treatment of a disorder or condition that may be treated by antagonizing histamine H3 receptors, the method comprising administering to a mammal in need of such treatment a compound of formula (I) as described above, and a method of treatment of a disorder or condition selected from the group consisting of depression, mood disorders, schizophrenia, anxiety disorders, Alzheimer's disease, attention-deficit hyperactivity disorder (ADHD), psychotic disorders, cognitive disorders, sleep disorders, obesity, dizziness, epilepsy, motion sickness, respiratory diseases, allergy, allergy-induced airway responses, allergic rhinitis, nasal congestion, allergic congestion, congestion, hypotension, cardiovascular disease, diseases of the GI tract, hyper and hypo motility and acidic secretion of the gastro-intestinal tract, the method comprising administering to a mammal in need of such treatment a compound of formula (I) as described above.
-
Page/Page column 32-33; 34

(2008/06/13)

3,3′-Bis(trisarylsilyl)-substituted binaphtholate rare earth metal catalysts for asymmetric hydroamination
Chiral 3,3′-bis(trisarylsilyl)-substituted binaphtholate rare earth metal complexes (R)-[Ln{Binol-SiAr3}(o-C6H 4CH2NMe2)(Me2NCH2Ph)] (Ln = Sc, Lu, Y; Binol-SiAr3 = 3,3′-bis(trisarylsilyl)-2,2′- dihydroxy-1,1′-binaphthyl; Ar = Ph (2-Ln), 3,5-xylyl (3-Ln)) and (R)-[La{Binol-Si(3,5-xylyl)3}{E(SiMe3)2}(THF) 2] (E = CH (4a), N (4b)) are accessible via facile arene, alkane, and amine elimination. They are efficient catalysts for the asymmetric hydroamination/cyclization of aminoalkenes, giving TOF of up to 840 h -1 at 25 °C for 2,2-diphenyl-pent-4-enylamine (5c) using (R)-2-Y. Enantioselectivities of up to 95% ee were achieved in the cyclization of 5c with (R)-2-Sc. The reactions show apparently zero-order rate dependence on substrate concentration and first-order rate dependence on catalyst concentration, but rates depend on total amine concentrations. Activation parameters for the cyclization of pent-4-enylamine using (R)-2-Y (ΔH(S)? = 57.4-(0.8) kJ mol-1 and ΔS(S)? = -102(3) J K-1 mol-1; ΔH(R)? = 61.5(0.7) kJ mol-1 and ΔS(R)? = -103(3) J K-1 mol -1) indicate a highly organized transition state. The binaphtholate catalysts were also applied to the kinetic resolution of chiral α-substituted aminoalkenes with resolution factors f of up to 19. The 2,5-disubstituted aminopentenes were formed in 7:1 to ≥50:1 trans diastereoselectivity, depending on the size of the α-substituent of the aminoalkene. Rate studies with (S)-1-phenyl-pent-4-enylamine ((S)-15e) gave the activation parameters for the matching (ΔH? = 52.2(2.8) kJ mol -1, ΔS? = -127(8) J K-1 mol-1 using (S)-2-Y) and mismatching (ΔH? = 57.7(1.3) kJ mol -1, ΔS? = -126(4) J K-1 mol-1 using (R)-2-Y) substrate/catalyst combination. The absolute configuration of the Mosher amide of (2S)-2-methyl-4,4-diphenyl-pyrrolidine and (2R)-methyl-(5S)- phenyl-pyrrolidinium chloride, prepared from (S)-15e, were determined by crystallographic analysis. Catalyst (R)-4a showed activity in the anti-Markovnikov addition of n-propylamine to styrene.
Gribkov, Denis V.,Hultzsch, Kai C.,Hampel, Frank
p. 3748 - 3759
(2007/10/03)

Internal alkene hydroaminations catalyzed by zirconium(IV) complexes and asymmetric alkene hydroaminations catalyzed by yttrium(III) complexes
The thiophosphinic amide 2 was prepared in 68% yield by the reaction of 2,2-dimethyl-1,3-propanediamine with diisopropylchlorophosphine followed by the addition of sulfur. Attachment of the proligand 2 to zirconium was achieved by direct metalation with Zr(NMe2)4 in benzene-d6 or toluene-d8 to afford complex 3 via elimination of dimethylamine. The neutral Zr(IV) complex 3 has been shown to be an effective precatalyst for intramolecular alkene hydroaminations that provide cyclic amines in good to excellent yields. A variety of chiral ligands (20, 22, 24, and 25-30) were prepared for asymmetric internal alkene hydroaminations. Metalation of chiral ligands to yttrium was accomplished with Y[N-(TMS)2]3 in benzene-d6 or toluene-d8 to give complexes. Treatment of 7 with 5 mol% of 33 in benzene-d6 (25°C, 18 h) or toluene-d 8 (25°C, 15 h) afforded 2,4,4-trimethylpyrrolidine 14 in 95% yield (61% ee).
Kim, Hyunseok,Kim, Young Kwan,Shim, Jun Hwan,Kim, Misook,Han, Mijung,Livinghouse, Tom,Lee, Phil Ho
p. 2609 - 2618
(2007/10/03)

Enantioselective intramolecular alkene hydroaminations catalyzed by yttrium complexes of axially chiral bis(thiolate) ligands
(Chemical Equation Presented) A yttrium(III) complex derived from proligand 7c has been shown to be a superior catalyst for enantioselective intramolecular alkene hydroaminations that provide cyclic amines with ee's ranging from 69% to 89%.
Joon, Young Kim,Livinghouse, Tom
p. 1737 - 1739
(2007/10/03)

Calcium-mediated intramolecular hydroamination catalysis
The calcium-catalyzed intramolecular hydroamination of alkenes and alkynes is reported. The β-diketiminato complex [{HC(C(Me)2N-2,6-iPr2C6H3)2}-Ca{N(SiMe3)2}(THF)] affects catalytic cyclization of a range of aminoalkenes and aminoalkynes with activities that are broadly commensurate to those of established rare earth catalysts. Copyright
Crimmin, Mark R.,Casely, Ian J.,Hill, Michael S.
p. 2042 - 2043
(2007/10/03)