cas 112068-01-6, (S)-(?)-α,α-Diphenyl-2-pyrrolidinemethanol

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London Dispersion Interactions Rather than Steric Hindrance Determine the Enantioselectivity of the Corey–Bakshi–Shibata Reduction
The well-known Corey–Bakshi–Shibata (CBS) reduction is a powerful method for the asymmetric synthesis of alcohols from prochiral ketones, often featuring high yields and excellent selectivities. While steric repulsion has been regarded as the key director of the observed high enantioselectivity for many years, we show that London dispersion (LD) interactions are at least as important for enantiodiscrimination. We exemplify this through a combination of detailed computational and experimental studies for a series of modified CBS catalysts equipped with dispersion energy donors (DEDs) in the catalysts and the substrates. Our results demonstrate that attractive LD interactions between the catalyst and the substrate, rather than steric repulsion, determine the selectivity. As a key outcome of our study, we were able to improve the catalyst design for some challenging CBS reductions.
Eschmann, Christian,Song, Lijuan,Schreiner, Peter R.
supporting information
p. 4823 - 4832
(2021/02/01)

Preparation method of duloxetine
To the method, 1 - naphthol and 3 - (2 - thienyl) -2 - acrolein serve as starting materials, and (S)-3 - (1 - naphthyloxy) -3 - (2 - thienyl) propanal is obtained through addition reaction under the action of a catalyst. The raw materials are cheap and easily available, and 1 - fluoronaphthalene which is expensive is not needed. Sodium hydride and operation are tedious, the cost is low, the process operation is safe and convenient, the three wastes are small in generation amount, and green and environment-friendly. The reaction atom economy is high, the reaction selectivity of each step is high, the side reaction is small, the optical purity and yield of the target product are high, and the green industrial production is facilitated.
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Paragraph 0054-0059

(2021/09/26)

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)

Isosteric expansion of the structural diversity of chiral ligands: Design and application of proline-based N,N′-dioxide ligands for copper-catalyzed enantioselective Henry reactions
Chiral N,N′-dioxide catalysts were designed based on isosteric approach. Using L-Proline as the starting material, a variety of chiral N,N′-dioxide ligands were obtained via conventional functional group transformations and were utilized in asymmetric Henry reactions between nitromethane and aromatic aldehydes. Using the N,N′-dioxide-copper(II) complexes as the catalysts, asymmetric Henry reaction produced the corresponding β-nitroalcohols in up to 66% yields and up to 83% ee's under mild conditions. The reactions were easy to carry out, and special care such as air or moisture-free conditions was not required.
Gao, En,Li, Meng,Duan, Lili,Li, Lin,Li, Yue-Ming
(2019/08/16)

Intramolecular [2+2] Photocycloaddition of Cyclic Enones: Selectivity Control by Lewis Acids and Mechanistic Implications
The intramolecular [2+2] photocycloaddition of 3-alkenyl-2-cycloalkenones was performed in an enantioselective fashion (nine representative examples, 54–86 % yield, 76–96 % ee) upon irradiation at λ=366 nm in the presence of an AlBr3-activated oxazaborolidine as the Lewis acid. An extensive screening of proline-derived oxazaborolidines showed that the enantioface differentiation depends strongly on the nature of the aryl group at the 3-position of the heterocycle. DFT calculations of the Lewis acid–substrate complex indicate that attractive dispersion forces may be responsible for a change of the binding mode. The catalytic [2+2] photocycloaddition was shown to proceed on the triplet hypersurface with a quantum yield of 0.05. The positive effect of Lewis acids on the outcome of a given intramolecular [2+2] photocycloaddition was illustrated by optimizing the key step in a concise total synthesis of the sesquiterpene (±)-italicene.
Poplata, Saner,Bauer, Andreas,Storch, Golo,Bach, Thorsten
supporting information
p. 8135 - 8148
(2019/05/29)

Synthesis process of chiral catalyst
The invention relates to a low-cost efficient synthesis process of both a chiral catalyst chiral (R)-(+)-2-(Diphenylhydroxymethyl)pyrrolidine and a hydrochloride thereof. According to the process, rawmaterials which can be commercially obtained easily and are environmentally friendly are used; a one-kettle method is used for operation; through esterification reaction, Boc protecting group addition on amino group, Grignard reaction and Boc protecting group removal, high-optical-purity (R)-(+)-2-(Diphenylhydroxymethyl)pyrrolidine hydrochloride is obtained. The process is simplified; the production cost is reduced; the requirements of green chemistry at present are met. The content of (R)-(+)-2-(Diphenylhydroxymethyl)pyrrolidine and the hydrochloride thereof, prepared by the process, is higher than 99.0 percent; the optical purity is not smaller than 99.5 percent; the total yield is higher than 80 percent.
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Paragraph 0090; 0091; 0094-0096; 0099-0101; 0102; 0105-0107

(2019/02/17)

COMPOUNDS, COMPOSITIONS AND METHODS FOR SYNTHESIS
The present disclosure, among other things, provides technologies for synthesis, including reagents and methods for stereoselective synthesis. In some embodiments, the present disclosure provides compounds useful as chiral auxiliaries. In some embodiments, the present disclosure provides reagents and methods for oligonucleotide synthesis. In some embodiments, the present disclosure provides reagents and methods for chirally controlled preparation of oligonucleotides. In some embodiments, technologies of the present disclosure are particularly useful for constructing challenging internucleotidic linkages, providing high yields and stereoselectivity.
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Paragraph 001345; 001346; 001349; 001350

(2019/01/10)

NITROGEN RING LINKED DEOXYURIDINE TRIPHOSPHATASE INHIBITORS
Provided herein are dUTPase inhibitors, compositions comprising such compounds and methods of using such compounds and compositions.
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Paragraph 0684

(2018/06/12)

Aluminium, gallium and indium complexes supported by a chiral phenolato-prolinolato dianionic ligand
Congeneric complexes (S)-{?O}MCH2SiMe3 (M=Al, 3; Ga, 5; In, 6) of the triel metals supported by an enantiomerically pure phenolato-alkoxo {?O}2- dianionic tridentate ligand derived from prolinol, along with their chloro derivatives, have been prepared and characterised. The aluminium-alkyl species (S)-{?O}AlMe and 3 form four-coordinate complexes with slightly distorted tetrahedral geometries, whereas the geometry in the Lewis acidic five-coordinate (S)-{?O}GaCl·THF is a distorted trigonal bipyramid. These alkyl complexes do not react cleanly, if at all, with protic sources. The indium(III) compound 6, which is for instance inert towards iPrOH or BnOH even after hours at 70°C, catalyses at 95°C the controlled, immortal ring-opening polymerisation of racemic lactide (up to 1000 equivalents) in the presence of excess BnOH as a chain transfer agent. It affords atactic, monodisperse polylactides with predictable molecular weights.
Maudoux, Nicolas,Tan, Eric,Hu, Yuya,Roisnel, Thierry,Dorcet, Vincent,Carpentier, Jean-Fran?ois,Sarazin, Yann
p. 131 - 143
(2016/12/14)

(S)-1,1-diphenylprolinol trimethylsilyl ether
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Boeckman, Robert K.,Tusch, Douglas J.,Biegasiewicz, Kyle F.
p. 309 - 319
(2016/08/23)

Towards a General Understanding of Carbonyl-Stabilised Ammonium Ylide-Mediated Epoxidation Reactions
The key factors for carbonyl-stabilised ammonium ylide-mediated epoxidation reactions were systematically investigated by experimental and computational means and the hereby obtained energy profiles provide explanations for the observed experimental results. In addition, we were able to identify the first tertiary amine-based chiral auxiliary that allows for high enantioselectivities and high yields for such epoxidation reactions.
Novacek, Johanna,Roiser, Lukas,Zielke, Katharina,Robiette, Rapha?l,Waser, Mario
supporting information
p. 11422 - 11428
(2016/08/03)

Organocatalytic enantioselective α-hydroxymethylation of aldehydes: Mechanistic aspects and optimization
Further studies of the direct enantioselective α-hydroxymethylation of aldehydes employing the α,α-diarylprolinol trimethylsilyl ether class of organocatalysts are described. This process has proven efficient for access to β-hydroxycarboxylic acids and δ-hydroxy-α,β-unsaturated esters from aldehydes in generally good yields, excellent enantioselectivity, and compatibility with a broad range of functional groups in the aldehyde. The goal of these studies was to identify the critical reaction variables that influence the yield and enantioselectivity of the α-hydroxymethylation process such as catalyst structure, pH of the medium, purity of the reactants and reagents particularly with respect to the presence of acidic impurities, and the nature of the buffer, along with the standard variables including solvent, time, temperature and mixing efficiency. The previously identified intermediate lactol has been further characterized and its reactivity examined. These studies have led to identification of the most critical variables translating directly into improved substrate scope, reproducibility, enantioselectivity, and yields.
Boeckman, Robert K.,Biegasiewicz, Kyle F.,Tusch, Douglas J.,Miller, John R.
p. 4030 - 4045
(2015/05/05)

Novel catalysts for the enantioselective Henry reaction
Two novel catalytic systems based on the CuII complexes with N-(3,5-dibromo-2-hydroxybenzyl)- and N-(2-hydroxy-3-nitrobenzyl)-(S)-α,α-diphenylprolinols were developed. These systems catalyze the condensation of 4-nitrobenzaldehyde with nitromethane to produce S-nitroaldol with maximum enantiomeric excess of >90% (99% yield). The reactions of nitromethane with aliphatic aldehydes give the corresponding products in the yields above 80% and ee > 90%.
Veselovsky,Stepanov
p. 422 - 425
(2015/02/02)

Catalytic asymmetric aldol-type reaction of zinc enolate equivalent of amides
Treatment of phenyl isocyanate with bis(iodozincio)methane gave a zinciomethylenated product, which acts as an amide-enoate equivalent. It did not react with an aldehyde efficiently, but gave the corresponding adduct in good yield in the presence of an aminoalcohol. Use of a catalytic amount of chiral aminoalcohol led the process to the catalytic asymmetric Aldol-type reaction.
Haraguchi, Ryosuke,Matsubara, Seijiro
supporting information
p. 3378 - 3380
(2013/07/26)

Dual catalyst system for asymmetric alternating copolymerization of carbon dioxide and cyclohexene oxide with chiral aluminum complexes: Lewis base as catalyst activator and lewis acid as monomer activator
Optically active aluminum complexes such as Schiff base, binuclear β-ketoiminate, and bisprolinol complexes were found to promote asymmetric alternating copolymerizations of carbon dioxide and cyclohexene oxide. The aluminum Schiff base complexes-tetraethylammonium acetate afforded isotactic poly(cyclohexene carbonate)s with low enantioselectivities. Lewis bases having two coordinating sites were utilized to enhance activity and selectivity based on the binuclear structure of the aluminum β-ketoiminate clarified by X-ray crystallography. [2gAlMe]2-bulky bisimidazole produced the alternating copolymer with high enantioselectivity (62% ee). The polymerization is considered to preferentially proceed at more crowded, enantioselective site owing to coordination of bulky Lewis bases to aluminums in less enantioselective sites. 32AlMe-2-picoline also exhibited a high enantioselectivity (67% ee). Methylaluminum bis(2,6-di-tert-butyl-4-methylphenoxide) was applied to perform faster and more enantioselective copolymerizations at low temperature (82% ee). The asymmetric copolymerizations were found to be significantly dependent on size of epoxide, temperature, and kind/amount of activators.
Nishioka, Kiyoshi,Goto, Hidetoshi,Sugimoto, Hiroshi
p. 8172 - 8192
(2013/01/15)

Highly enantioselective synthesis of chiral allenes by sequential creation of stereogenic center and chirality transfer in a single pot operation
Chiral allenes are readily accessed in a single pot operation in the reaction of terminal alkynes, aldehydes, chiral secondary amines, and zinc halides in good yields (up to 77% yield) and excellent enantioselectivities (up to 99% ee) in toluene at 120 °C. The reaction proceeds through initial formation of chiral propargylamine intermediates with creation of a new stereogenic center and subsequent chirality transfer via an intramolecular hydride shift to produce chiral allenes with high enantiomeric purities.
Periasamy, Mariappan,Sanjeevakumar, Nalluri,Dalai, Manasi,Gurubrahamam, Ramani,Reddy, Polimera Obula
supporting information; experimental part
p. 2932 - 2935
(2012/08/28)

Chiral aminophosphines as catalysts for enantioselective double-michael indoline syntheses
The bisphosphine-catalyzed double-Michael addition of dinucleophiles to electron-deficient acetylenes is an efficient process for the synthesis of many nitrogencontaining heterocycles. Because the resulting heterocycles contain at least one stereogenic center, this double-Michael reaction would be even more useful if an asymmetric variant of the reaction were to be developed. Aminophosphines can also facilitate the double-Michael reaction and chiral amines are more readily available in Nature and synthetically; therefore, in this study we prepared several new chiral aminophosphines. When employed in the asymmetric double-Michael reaction between ortho-tosylamidophenyl malonate and 3-butyn-2-one, the chiral aminophosphines produced indolines in excellent yields with moderate asymmetric induction.
Khong, San N.,Kwon, Ohyun
scheme or table
p. 5626 - 5650
(2012/07/03)

Highly enantioselective henry reactions in water catalyzed by a copper tertiary amine complex and applied in the synthesis of (S)-N-trans-feruloyl octopamine
It's in the water! A new copper tertiary amine complex was prepared and applied in asymmetric Henry reactions in water and in the short synthesis of (S)-N-trans-feruloyl octopamine. This catalytic system provided an approach to the enantioselective Henry reaction of aldehydes with hydroxyl substituents (see graphic).
Lai, Guoyin,Guo, Fengfeng,Zheng, Yueqin,Fang, Yang,Song, Haigang,Xu, Kun,Wang, Sujing,Zha, Zhenggen,Wang, Zhiyong
supporting information; scheme or table
p. 1114 - 1117
(2011/03/21)

A simple synthesis of (S)-α,α-diaryl-2-pyrrolidinemethanols
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Wang, Ping-An,Liu, Wen - Min,Sun, Xiao-Li
experimental part
p. 477 - 483
(2011/12/03)

A concise synthesis of (S)-2-(fluorodiphenylmethyl)pyrrolidine: A novel organocatalyst for the stereoselective epoxidation of α,β-unsaturated aldehydes
A concise synthesis of (S)-2-(fluorodiphenylmethyl)pyrrolidine from cheap, commercially available starting materials is described. Pertinent features of this synthetic route include ease of synthesis, facile purification steps, and an operationally simple deoxy?fluorination step to install the C-F bond. Georg Thieme Verlag Stuttgart · New York.
Sparr, Christof,Tanzer, Eva-Maria,Bachmann, Julia,Gilmour, Ryan
experimental part
p. 1394 - 1397
(2010/07/02)

Synthesis and crystal structure of the chiral β-amino alcohol (S)-α,α-diphenyl-2-pyrrolidine methanol
Optically pure (S)-α,α-diphenyl-2-pyrrolidine methanol was prepared from L-proline via protection of the amino group, reaction with the Grignard reagents and deprotection of the amino-protected groups in 54.4% yield. The synthetic conditions to prepare (S)-α,α-diphenyl-2- pyrrolidinemethanol were optimised. Single crystal X-ray diffraction analysis revealed that the molecular structure of the compound was enantiomerically pure. The crystals are orthorhombic, space group P2(1)2(1)2(1), with unit cell parameters a = 8.9000(18) A, b = 9.2405(18) A, c = 16.671(3) A, V = 1371.1(5) A3, Dx = 1.227 g cm -3, Z =4, T = 113(2)K, F(000) = 628, R1 = 0.0335 and wR2 = 0.0707. The absolute structure parameter was -1.6(17).
Zhang, Yu-Mei,Liu, Peng,Zhang, Hong-Li
experimental part
p. 610 - 612
(2011/03/18)

Enantioselective michael addition to α,β-Unsaturated aldehydes: Combinatorial catalyst preparation and screening, reaction optimization and mechanistic studies
Shortcut to chiral catalysts: An efficient combinatorial strategy based on back reaction screening by ESI-MS allows rapid evaluation of organocatalysis for the asymmetric Michael addition to α,β-unsaturated aldehydes (see scheme). An unexpected nonlinear effect has been observed in this reaction, resulting from a double nucleophilic-electrophilic activation mechanism involving two catalyst molecules "Chemical Equation Presented"
Fleischer, Ivana,Pfaltz, Andreas
supporting information; experimental part
p. 95 - 99
(2010/03/26)

Asymmetric reduction of ketimines with trichlorosilane employing an imidazole derived organocatalyst
Organocatalysts for the asymmetric reduction of ketimines are presented that function well at low catalyst loadings providing chiral amines in good yield and enantioselectivity, the latter appearing to be independent of the ketimine substrate geometry.
Gautier, Franois-Moana,Jones, Simon,Martin, Stephen J.
supporting information; experimental part
p. 229 - 231
(2009/03/11)

A direct and versatile access to α,α-disubstituted 2-pyrrolidinylmethanols by SmI2-mediated reductive coupling
(Chemical Equation Presented) Various α,α-disubstituted 2-pyrrolidinylmethanols are efficiently prepared in a single step from ketones using a SmI2-mediated cross-coupling with 1-pyrroline N-oxide. The N-hydroxy-α,α-diphenylprolinol is also easily prepared and resolved.
Burchak, Olga N.,Philouze, Christian,Chavant, Pierre Yves,Py, Sandrine
supporting information; experimental part
p. 3021 - 3023
(2009/04/18)

First enantioselective reductive amination of α-fluoroenones
From α-fluoroenones 2, a synthesis of (E) ketone oxime O-alkyl ethers 5 is reported with good to excellent yields. Then the first enantioselective reduction of these ketimines, via oxazaborolidine, is described with moderate to good enantiomeric excesses, leading to valuable chiral fluoroallylic amines 1.
Dutheuil, Guillaume,Bailly, Laetitia,Couve-Bonnaire, Samuel,Pannecoucke, Xavier
p. 34 - 39
(2008/03/13)

Design and evaluation of inclusion resolutions, based on readily available host compounds
Resolution of enantiomers through selective crystallisation of diastereomeric inclusion compounds can extend the scope of traditional racemate resolution beyond salt forming compounds. To assess the practical value of this approach the literature was carefully screened and promising results were checked. Also an extensive range of new inclusion hosts suitable for resolution processes, derived from simple hydroxy- and amino acids were prepared and tested. Several techniques, including the Dutch Resolution approach utilizing mixtures of resolving agents, were applied. Over 70 potential resolving agents were tested in combinations with 34 racemates (over 100 racemates if literature results are included). Reproducibility of literature results was found to be problematic. Also the number of successful new resolutions found was very limited: only two efficient resolutions out of 1200 combinations of racemate and resolving agent tested in over 10.000 experiments! Crystal studies of representative combinations of resolving agents and inclusion compounds revealed some of the causes for the low rate of success in inclusion resolution. Compared to diastereomeric salts, the absence of strong electrostatic interactions substantially reduces the probability of forming crystals including both components. Molecular structure features allowing formation of intricate intramolecular and intermolecular H-bond networks were found to be responsible for inclusion crystal formation, and for the quality of the ensuing resolution through selective diastereomer crystallisation, in the successful cases. Whereas diastereomeric salt resolution continues to be of scientific and industrial interest, inclusion resolution should be viewed as of very limited scope; useful in specific instances, but lacking the wide applicability of classical resolution. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005.
Mueller, Simona,Afraz, Marcel Cyrus,De Gelder, Rene,Ariaans, Gerry J. A.,Kaptein, Bernard,Broxterman, Quirinus B.,Bruggink, Alle
p. 1082 - 1096
(2007/10/03)

Asymmetric alternating copolymerization of cyclohexene oxide and CO2 with dimeric zinc complexes
Dimeric zinc complex 2a [= Et2Zn2(1a)2] has been synthesized by the reaction of Et2Zn and (S)-diphenyl(pyrrolidin-2-yl)methanol (1a-H). X-ray crystallography revealed that the alkoxide ligand replaced one of the two ethyl groups of Et2Zn and formed a five-membered chelate ring through a Zn - N dative bond. Two zinc centers were bridged by oxygen atoms to form a Zn2O2 four-membered ring with a syn relationship between the two ethyl groups on the zinc centers. Dimeric zinc complex 2a was an active catalyst for asymmetric alternating copolymerization of cyclohexene oxide and CO2. An MALDI-TOF mass spectrum of the obtained copolymer showed that the copolymerization was initiated by the insertion of CO2 into Zn - alkoxide to give [(S)-diphenyl(pyrroridin-2-ly)methoxy] - [C(=O)O - (1,2-cyclohexylene) - O]n -H (copolymer I), including chiral ligand 1a as an initiating group. Complex 3a-OEt (= EtZn(1a)2ZnOEt), in which an ethoxy group replaced one of the two ethyl groups in 2a, also polymerized cyclohexene oxide and CO2 with higher catalytic activity and enantioselectivity than 2a and afforded EtO - [C(=O)O - (1,2- cyclohexylene) - O]n - H (= copolymer III), including an ethoxy group as an initiating group. Throughout the studies, dimeric zinc species are indicated to be the active species for the copolymerization. It is also depicted that the substituent on the aryl moiety in diaryl(pyrrolidin-2-yl)methanol 2b - e influenced the polymerization activity.
Nakano, Koji,Nozaki, Kyoko,Hiyama, Tamejiro
p. 5501 - 5510
(2007/10/03)

Highly π-facial stereoselective aldol reaction of (S)-proline-derived amide enolate with benzaldehydes
The asymmetric aldol reaction of the (S)-proline-derived bicyclic amide enolate 1 with benzaldehydes selectively affords the two diastereomeric aldol adducts (3S,3′R,8S)-3a and (3S,3′S,8S)-3a, of four possible diastereomers, in good yield. The high control of π-facial stereoselectivity at the endocyclic C-3 stereocenter is due to perfect shielding by the pseudo-axial phenyl ring at the C-1 position. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003.
Adam, Waldemar,Zhang, Aimin
p. 587 - 591
(2007/10/03)

Diastereospecific synthesis of (S,S)-2-substituted-4,4-diphenyl-3,1-oxazabicyclo[3.3.0]octanes
(S,S)-2-substituted-4,4-diphenyl-3,1-oxazabicyclo[3.3.0]octanes were synthesized from aldehydes and (S)-2-(hydroxy-diphenylmethyl)pyrrolidine, which was obtained from L-proline. The stereospecificity of the condensation reaction was discussed. The stereo-structure of each product in the condensation was found to be in agreement with the product of a similar reaction of (S)-phenylglycinol with an aldehyde. The method was found to be useful for the synthesis of cis 3,1-oxazabicyclo[3.3.0]octane derivatives.
Zuo, Gang,Zhang, Qihan,Xu, Jiaxi
p. 42 - 45
(2007/10/03)

Asymmetric carbonyl reduction with borane catalyzed by chiral phosphinamides derived from L-amino acid
Two types of chiral phosphinamide catalysts 3a-d and 4a-c were prepared from L-phenylalanine and L-proline, respectively. Their applications in the asymmetric borane reduction of prochiral ketones were investigated. The chiral secondary alcohols were obtained with excellent chemical yields and moderate to high enantiomeric excesses.
Li, Kangying,Zhou, Zhenghong,Wang, Lixin,Chen, Qifa,Zhao, Guofeng,Zhou, Qilin,Tang, Chuchi
p. 95 - 100
(2007/10/03)

Towards more chemically robust polymer-supported chiral catalysts: α,α-diphenyl-L-prolinol based catalysts for the reduction of prochiral ketones with borane
α,α-Diphenyl-L-prolinol derivatives with para-bromo substituants in either one or both of the phenyl rings are easily bound to crosslinked polystyrene beads containing phenylboronic acid residues by Suzuki couplings. By using extended reaction periods boronic acid residues that do not take part in the couplings are simply lost by hydrolysis. The polymer-supported (PS) α,α-diphenyl-L-prolinols were used to catalyse reductions of several prochiral ketones with borane in tetrahydrofuran at 22 °C. The expected secondary alcohols were obtained in high chemical yields and ees were generally in the range 79-97 %. One PS catalyst was recycled 14 times without loss of stereochemical performance.
Kell, Roger J.,Hodge, Philip,Snedden, Peter,Watson, David
p. 3238 - 3243
(2007/10/03)

Comparison of solid-phase and solution-phase chiral auxiliaries in the alkylation/iodolactonization sequence to γ-butyrolactones
Five prolinol-based chiral auxilaries have been compared for the stereoselective synthesis of γ-butyrolactones via the sequence of N-acylation, Cα-allylation, and iodolactonization under both solution-phase and solid-phase conditions. Comparisons of stereoselectivity of both the Cα-allylation and iodolactonization processes indicate that incorporation of a non-C2-symmetric auxiliary as a polymer cross-link gives results superior to those obtained either in solution or with other non-C2-symmetric auxiliaries and comparable to those observed using a polymer-supported pseudo-C2-symmetric auxiliary.
Price, Michael D.,Kurth, Mark J.,Schore, Neil E.
p. 7769 - 7773
(2007/10/03)

Oxazaborolidines as functional monomers: Ketone reduction using polymer-supported Corey, Bakshi, and Shibata catalysts
The first two polymer-supported versions of the Corey, Bakshi, and Shibata (CBS) catalyst have been prepared. Functional monomers based structurally upon the original B-methylated catalyst have been used to prepare catalytic polymers containing the CBS moiety bound both in a pendant fashion and in the form of a cross-link. Enantioselective reductions of two prochiral ketones have been carried out using the original catalyst in the solution phase as well as the two solid-state systems. While the pendant-bound system shows reduced stereoselectivity, the cross-linked version affords enantioselectivities almost identical to those of the solution-phase model.
Price, Michael D.,Sui, Jennifer K.,Kurth, Mark J.,Schore, Neil E.
p. 8086 - 8089
(2007/10/03)

Towards more chemically robust polymer-supported chiral catalysts for the reactions of aldehydes with dialkylzincs.
N-Methyl-alpha,alpha-diphenyl-L-prolinol derivatives with para-bromo substituents in one or both of the phenyl rings are easily bound to crosslinked polystyrene beads containing phenylboronic acid residues using Suzuki reactions. When the products were used as catalysts for the reactions of aldehydes with diethylzinc in toluene at 20 degrees C, the alcohols were produced in chemical yields >90% and with ees of upto 94%. The better of the two supported catalysts gave ees only 0-9% lower than those obtained with the corresponding soluble catalyst. One of the supported catalysts was recycled successfully nine times.
Kell, Roger J,Hodge, Philip,Nisar, Mohammad,Watson, David
p. 1803 - 1807
(2007/10/03)

Lanthanide Lewis acid-mediated enantioselective conjugate radical additions
(figure presented) Lanthanide triflates along with proline-derived ligands have been found to be efficient catalysts for enantioselective conjugate addition of nucleophilic radicals to enoates. N-Acyl oxazolidinones, when used as achiral additives, gave meaningful enhancements in the ees for the product.
Sibi, Mukund P.,Manyem, Shankar
p. 2929 - 2932
(2007/10/03)

Asymmetric synthesis of (M)-2-hydroxymethyl-1-(2-hydroxy-4,6-dimethylphenyl)naphthalene via a configurationally unstable biaryl lactone: [2-naphthalenemethanol, 1-(2-hydroxy-4,6-dimethylphenyl)-, (R)-]
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Bringmann, Gerhard,Breuning, Matthias,Henschel, Petra,Hinrichs, Jürgen,Greenen, Peter M.,Curran, Dennis P.
p. 72 - 72
(2017/10/06)

New methods of resolution and purification of racemic and diastereomeric amino alcohol derivatives using boric acid and chiral 1,1′-bi-2-naphthol
Resolution of the racemic amino alcohol derivatives 1-6 is readily achieved to obtain enantiomerically enriched compounds using chiral 1,1′-bi-2-naphthol and boric acid in solvents such as CH3-CN, THF, and MeOH. Purification of the diastereomer
Periasamy,Kumar,Sivakumar,Rao,Ramanathan,Venkatraman
p. 3828 - 3833
(2007/10/03)

(S)-tetrahydro-1-methyl-3,3-diphenyl-1H,3H-pyrrolo-[1,2-c][1,3,2]oxazaborole-borane complex
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Xavier, Lyndon C.,Mohan, Julie J.,Mathre, David J.,Thompson, Andrew S.,Carroll, James D.,Corley, Edward G.,Desmond, Richard
p. 50 - 50
(2017/09/12)

A triphosgene-based synthesis of (S)-αα-diphenyl-2-pyrrolidinemethanol
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Kaufman, Teodoro S.,Ponzo, Viviana L.,Zinczuk, Juan
p. 487 - 490
(2007/10/03)

A New Route to Oxazolidinones
The oxazolidinones 5 and 7 have been prepared by coupling Grignard reagents with N-alkoxycarbonyl-α-amino esters.Hydrolysis of oxazolidinones 5 afforded β-amino alcohols with good yield and enantiomeric excess.
Delaunay, Dominique,Corre, Maurice Le
p. 3041 - 3042
(2007/10/02)

Convenient method for the synthesis of chiral α,α-diphenyl-2-pyrrolidinemethanol
A simplified, convenient synthesis of chiral α,α-diphenyl-2-pyrrolidine-methanol involving one step N-and O-protection of S-proline using ethylchloroformate followed by Grignard addition-alkaline hydrolysis (KOH/CH3OH) is described.
Kanth, J. V. Bhaskar,Periasamy, Mariappan
p. 5127 - 5132
(2007/10/02)

A Practical Enantioselective Synthesis of α,α-Diaryl-2-pyrrolidinemethanol. Preparation and Chemistry of the Corresponding Oxazaborolidines
A practical two-step enantioselective synthesis of α,α-diaryl-2-pyrrolidinemethanols (1) from proline, based on the addition of aryl Grignard reagents to proline-N-carboxanhydride (3), is reported.An investigation into the chemistry of the corresponding B-alkyl- and B-aryloxazaborolidines (2) led to the development of a reliable procedure for their preparation.
Mathre, David J.,Jones, Todd K.,Xavier, Lyndon C.,Blacklock, Thomas J.,Reamer, Robert A.,et al.
p. 751 - 762
(2007/10/02)

Enantioselective reduction of ketones
Chiral 1,3,2-oxazaborolidines and tetrahydro-1,3,2-oxazaborines are effective catalysts for the borane reduction of prochiral ketones to optically active alcohols.
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(2008/06/13)

Process for the preparation of the (-)-antipode of (E)-1-cyclohexyl-4, 4-dimethyl-3-hydroxy-2-(1,2,4-triazol-1-yl)-pent-1-ene
A process for the preparation of the (-)-antipode of (E)-1-cyclohexyl-4,4-dimethyl-3-hydroxy-2-(1,2,4-triazol-1-yl)-pent-1-ene of the formula STR1 which comprises reacting the (E)-isomer of 1-cyclohexyl-4,4-dimethyl-2-(1,2,4-triazol-1-yl)-pent-1-en-3-one of the formula STR2 (a) with boron hydride in the presence of an optically active proline derivative of the formula STR3 in which, R1 is alkyl, phenyl or benzyl, or (b) with a complex borohydride in the presence of an acid addition salt of the optically active proline derivative, in the presence of a diluent at a temperature between about -70° C. and +60° C. The proline derivatives are also new and are produced from S-proline esters. The end product is a known plant growth regulant.
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(2008/06/13)

LARGE SCALE PREPARATION OF VERSATILE CHIRAL AUXILIARIES DERIVED FROM (S)-PROLINE
The synthesis of a variety of enantiomerically pure chiral auxiliaries based on (S)-proline and bearing sterically demanding side chains at the pyrrolidine moiety, such as the secondary amines (S)-3,5 and 7 and the hydrazines (S)-6, is described on a molar scale.As key step, the Grignard or RLi addition to the N-benzylated proline ester (S)-1 is used.
Enders, Dieter,Kipphardt, Helmut,Gerdes, Peter,Brena-Valle, Leonardo J.,Bhushan, Vidya
p. 691 - 704
(2007/10/02)

An Efficient and Catalytically Enantioselective Route to (S)-(-)-Phenyloxirane
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Corey, E.J.,Shibata, Saizo,Bakshi, Raman K.
p. 2861 - 2863
(2007/10/02)

Enantioselective Carbon-Carbon Bond Formation by Chiral Organotitanium Compounds; Methyltitanium (S)-N-Acylpyrrolidinyl-methoxide Diisopropoxides
New chiral compounds, (S)-N-acylpyrrolidinylmethanols (1b-f and 1h), were synthesized and chiral methyltitanium diisopropoxides (2a-h) were prepared from 1a-h.Enantioselective carbon-carbon bond formation between aromatic carbaldehydes and 2a-h was achieved in yields of 90-97 percent and 10.5-54.1 percent ee.The chiral auxiliaries (1a-h) were recovered in almost quantitative yields without any loss of optical purity.Keywords: (S)-N-acylpyrrolidinylmethanol; carbon-carbon bond formation; enantioselective reaction; methyltitanium diisopropoxide; (R)-1-(1-naphthyl)ethanol; (R)-1-phenylethanol; (S)-prolinol
Takahashi, Hiroshi,Kawabata, Akihiro,Higashiyama, Kimio
p. 1604 - 1607
(2007/10/02)

A Stable and Easily Prepared Catalyst for the Enantioselective Reduction of Ketones. Applications to Multistep Synthesis
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Corey, E. J.,Bakshi, Raman K.,Shibata, Saizo,Chen Chung-Pin,Singh, Vinod K.
p. 7925 - 7926
(2007/10/02)