Novel Intramolecular Reactivity of Oximes:  Synthesis of Cyclic and Spiro-Fused Imines

Savarin, Cécile; Grisé, Christiane M.; Murry, Jerry A.; Reamer, Robert A.; Hughes, David L.

doi:10.1021/ol0630043

Cited by 33 publications

(9 citation statements)

References 27 publications

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“…NMR spectroscopic analysis of the crude product obtained after addition of PhMgBr and aqueous work‐up revealed a mixture of the N,O‐hemiaminal 17 and acyclic ketone 18 , which were both unstable, but were characterized by 1 H and 13 C NMR spectroscopic analysis. After a few hours storage, a further compound was detected that turned out to be imine 19 29. The formation of 19 could be accelerated by addition of an acid or silica gel, to the extent that is was obtained as the main product.…”

Section: Resultsmentioning

confidence: 99%

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Addition of Organometallic Reagents to Chiral N‐Methoxylactams: Enantioselective Syntheses of Pyrrolidines and Piperidines

Jäkel

Schnitzer

et al. 2013

Chemistry A European J

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Enantioselective iridium-catalyzed allylic substitutions were used to prepare N-allyl hydroxamic acid derivatives that were suitable for ring-closing metathesis, giving N-methoxylactams. Reactions of these derivatives with Grignard or organolithium compounds gave hemiaminals, which could be reduced diastereoselectively via acyliminium intermediates to give cis-piperidines or cis-pyrrolidines with substituents in the 2,6- or 2,5-positions, respectively. In addition, compounds with a quaternary carbon center could be synthesized by corresponding reactions with potassium cyanide/AcOH. The procedures were applied in the syntheses of alkaloids (-)-209D and (+)-prosophylline.

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Section: Resultsmentioning

confidence: 99%

“…After a few hours storage, a further compound was detected that turned out to be imine 19. [29] The formation of 19 could be accelerated by addition of an acid or silica gel, to the extent that is was obtained as the main product. Accordingly, the crude product from the addition of the Grignard reagent had to be immediately reduced.…”

Section: Introductionmentioning

confidence: 99%

Addition of Organometallic Reagents to Chiral N‐Methoxylactams: Enantioselective Syntheses of Pyrrolidines and Piperidines

Jäkel

Schnitzer

et al. 2013

Chemistry A European J

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“…The signs of angles of opti cal rotation for hydrogenation products 5 and 10 (see Table 1) were determined on a Spectropolyarimetr PU 09 instrument. Methyl 5 hydroxyimino 5 phenylpentanoate (3) 25 . Hydr oxylamine hydrate hydrochloride (6.67 g, 96 mmol) and AcONa (7.87 g, 96 mmol) were placed into a round bottom flask equipped with a reflux condenser and a magnetic stirring bar, followed by addition of MeOH (40 mL) and H 2 O (20 mL).…”

Section: Methodsmentioning

confidence: 99%

Stereocontrolled approach to δ-amino acids by asymmetric hydrogenation of 5-acetylaminopent-4-enoic acid derivatives

et al. 2010

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Asymmetric hydrogenation of the C=C bond in 5 acetylamino 5 phenylpent 4 enoic acid methyl ester or N,N dimethylamide catalyzed by rhodium complexes with chiral bisphosphine ligands (1 mol.% of the catalyst, 20 atm. of H 2 , MeOH, 50 °C) gives the corresponding saturat ed derivatives with enantioselectivity up to 40% ee.Key words: asymmetric hydrogenation, rhodium complexes, bisphosphine chiral ligands, nonracemic 5 acetylamino 5 phenylpentanoic acid.Amino acids and their derivatives are important natu ral objects and are widely used in the synthesis of various pharmacologically active compounds and ligands for asymmetric catalysis. 1-3 Widespread methods for the syn thesis of chiral amino acids, including asymmetric hydro genation of unsaturated precursors intensively developed in the last years, 4-6 in fact are mainly used for obtaining acids with the amino group in α or β position. Amino acids with more remote amino group, viz., chiral γ and δ amino acids, are significantly less available. It is note worthy that the absolute configuration of one of the sim plest chiral δ amino acids, i.e., levorotating δ aminoca prylic acid, was unambiguously established 7 only in 1965. As a rule, laborious multi step schemes involving stoichi ometric amounts of inconvenient in handling organome tallic reagents and expensive chiral inductors are required for the synthesis of chiral γ and δ amino acids. 8-11 There are also known separate examples of solving the same prob lem by asymmetric hydrogenation of the C=N bond in imino carboxylic acid derivatives with the use of complex catalytic systems. 12 Earlier, we have studied asymmetric catalytic hydro genation of prochiral substrates containing a keto group. 13-16 In the present work, we made an attempt to use similar approach to the synthesis of chiral δ amino acids starting from available δ keto acids. 5 Oxo 5 phenylpentanoic acid (1) has been chosen as the starting compound (Scheme 1), which gave rise to two model sub strates, viz., ω enamides 4 and 9.Reductive N acetylation of the corresponding keto oximes 3 and 8 with finely dispersed iron metal in the presence of Ac 2 O and AcOH is the key step in the synthe sis of both enamides. Earlier, only simple keto oximes containing no other functional groups have been used in this reaction 17-21 with just rare exceptions. 19,21 In the present work, reductive N acetylation, as far as we known, was for the first time accomplished for oximes with an ester and amide functional groups, and the earlier unde scribed enamide 4 was isolated in the crystalline form as an individual E isomer. Its two dimensional 1 H NMR spectrum (500 MHz, the NOESY procedure) contains an intensive cross signal, corresponding to the spatial inter action of the phenyl protons (δ 7.3) with the protons of the methylene group (a broad singlet at δ 2.35). At the same time, the spectrum contains no cross signal responsible for the spatial interaction of the phenyl group with the olefin proton (δ 6.3). Unlike enamide 4, enamide 9 was not isolated in the isomerically ...

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“…After irradiation with 254 nm UV‐light, the azide can decompose and a very reactive intermediate nitrene compound is formed . This nitrene can partake in many chemical reactions, such as CH insertion reactions or cycloadditions, in this case covalently binding the alginic acid onto the PEEK surface …”

Section: The Future Of Dental Implant Coatings—bio‐inspired Solutionsmentioning

confidence: 99%

On the Future Design of Bio‐Inspired Polyetheretherketone Dental Implants

Knaus

Schaffarczyk

Cölfen

2019

Macromolecular Bioscience

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Polyetheretherketone (PEEK) is a promising implant material because of its excellent mechanical characteristics. Although this polymer is a standard material in spinal applications, PEEK is not in use in the manufacturing of dental implants, where titanium is still the most‐used material. This may be caused by its relative bio‐inertness. By the use of various surface modification techniques, efforts have been made to enhance its osseointegrative characteristics to enable the polymer to be used in dentistry. In this feature paper, the state‐of‐the‐art for dental implants is given and different surface modification techniques of PEEK are discussed. The focus will lie on a covalently attached surface layer mimicking natural bone. The usage of such covalently anchored biomimetic composite materials combines many advantageous properties: A biocompatible organic matrix and a mineral component provide the cells with a surrounding close to natural bone. Bone‐related cells may not recognize the implant as a foreign body and therefore, may heal and integrate faster and more firmly. Because neither metal‐based nor ceramics are ideal material candidates for a dental implant, the combination of PEEK and a covalently anchored mineralized biopolymer layer may be the start of the desired evolution in dental surgery.

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Novel Intramolecular Reactivity of Oximes: Synthesis of Cyclic and Spiro-Fused Imines

Cited by 33 publications

References 27 publications

Addition of Organometallic Reagents to Chiral N‐Methoxylactams: Enantioselective Syntheses of Pyrrolidines and Piperidines

Addition of Organometallic Reagents to Chiral N‐Methoxylactams: Enantioselective Syntheses of Pyrrolidines and Piperidines

Stereocontrolled approach to δ-amino acids by asymmetric hydrogenation of 5-acetylaminopent-4-enoic acid derivatives

On the Future Design of Bio‐Inspired Polyetheretherketone Dental Implants

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