Polymergebundene Cinchonaalkaloide als Katalysatoren in der <i>Michael</i> Reaktion

Hermann, Kurt; Wynberg, Hans

doi:10.1002/hlca.19770600713

Cited by 56 publications

(16 citation statements)

References 12 publications

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“…Immobilization of quinine alkaloids onto polymers (styrenedivinylbenzene or acrylonitrile) allows asymmetric conjugate addition of MVK to indanone derivatives, although the selectivity is dramatically diminished. [143,144] More recently, Wu et al have reported the use of cinchona alkaloids 230 for the Michael addition of several vinyl ketones to keto-esters with good yields and enantioselectivities at room temperature (however the configuration of the stereogenic center is not reported) (Scheme 62). [145] The phenanthryl group allows an increase in selectivity.…”

Section: Non-covalent Interaction: Brønsted Basementioning

confidence: 99%

“…[142] In addition, the spatial arrangement of the tertiary amine and the hydroxy group are reported to be responsible for the selectivity,with aspecial emphasis on the hydroxy group since its acetylation causes astrong decrease in the reactivity and selectivity.T he immobilization of quinine alkaloids on polymers (styrene-divinylbenzene or acrylonitrile) allows asymmetric conjugate addition of 12 to indanone derivatives,a lthough the selectivity is dramatically diminished. [143,144] More recently,W ue tal. reported the use of cinchona alkaloids 230 for the Michael addition of several vinyl ketones to ketoesters with good yields and enantioselectivities at room temperature (however,the configuration of the stereogenic center was not reported;S cheme 62).…”

Section: Reviewsmentioning

confidence: 99%

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Enantioselective Access to Robinson Annulation Products and Michael Adducts as Precursors

2017

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The Robinson annulation is a reaction that has been useful for numerous syntheses since its discovery in 1935, especially in the field of steroid synthesis. The products are usually obtained after three consecutive steps: the formation of an enolate (or derivative), a conjugate addition, and an aldol reaction. Over the years, several methodological improvements have been made for each individual step or alternative routes have been devised to access the Robinson annulation products. The first part of this Review outlines the most relevant developments towards the formation of monocarbonyl-derived Robinson annulation products (MRA products, MRAPs) and activated monocarbonyl-derived Robinson annulation products (AMRA products, AMRAPs). The following sections are then devoted to the diastereoselective and enantioselective synthesis of these products, while the last section describes the enantiomeric resolution of racemic mixtures.

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Section: Non-covalent Interaction: Brønsted Basementioning

confidence: 99%

Section: Reviewsmentioning

confidence: 99%

Enantioselective Access to Robinson Annulation Products and Michael Adducts as Precursors

2017

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“…Quinine (6), quinidine (7), and eucupine (8) were from commercial sources, and 0-acetylquinine (9) 9 and quinine methiodide (10) l o were synthesized according t o known procedures. Seven different catalysts were tested.…”

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confidence: 99%

Asymmetric induction in the Michael reaction

Hermann¹,

Wynberg²

1979

J. Org. Chem.

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177

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to the flask, and the assembly was immersed in an oil bath heated to 100 "C. The slurry was stirred at 100 "C for 48 h and then allowed to cool to room temperature. The reaction was quenched by addition of deuterium oxides (5 mL) and worked up in the usual manner. NMR integration of a VPC2* collected sample of the product (4a) showed no evidence for deuterium incorporation.Reduction of a Mixture of 2a and 3a with LiAlH4 in DME-dlo. A 0.35-g (2.1 mmol) sample of monochlorides 2a and 3a (75:25), 0.441 g (11.6 mmol) ol'LiAIH4, and 5 mL of DME-dlo (Merch, Sharp and Dohme Canada) were placed in a 25-mL flask equipped with a reflux condenser and a drying tube. The flask was immersed in an oil bath heated to 100 "C. The slurry was stirred at 100 "C for 50 h, cooled, quenched with water, and worked up in the usual manner. An NMR of the crude product (4a) showed no evidence of deuterium incorporation.R e g i s t r y No.--la, :, J. Am. Chem. SOC., 84,2252 (1962).Reaction of the bromide with lithium may be occurring by way of a radical mechanism which allows for inversion of the intermediate radical and hydrogen incorporation from the ethereal solvent.A 13 ft X 0.25 in. column packed with 20% DEGS on 80-100 mesh Chromosorb W at an oven temperature of 160 OC was used for VPC analyses.An 8 ft X 0.75 in. column packed with 20% DEGS on 45-60 mesh Chromosorb W at an oven temperature of 160 OC with a Helium flow rate of 600 mL/min was used for preparative VPC separations.

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“…Again, Wynberg was the first who used polymer-bound cinchona alkaloid catalysts in Michael reactions: quinine and its derivatives were immobilized by ether and ester linkages of the secondary alcohol or a quinoline alkoxy group to styrenedivinylbenzene copolymers. In the model reaction of carboxylate 5a to give indanone derivative 8a enantiomeric excesses with these catalysts did not exceed 53% [15]. Kobayashi and coworkers used the vinyl moiety of quinine for copolymerization with acrylonitrile; however, with maximum 57% ee for 8a they could not significantly improve Wynberg's results [16].…”

Section: Polymer-bound Alkaloidsmentioning

confidence: 95%