Enantiopure Monoprotected <i>cis</i>‐1,2‐Diaminocyclohexane: One‐Step Preparation and Application in Asymmetric Organocatalysis

Berkessel, Albrecht; Ong, Mike; Nachi, M.; Neudörfl, Jörg‐M.

doi:10.1002/cctc.201000104

Cited by 34 publications

(35 citation statements)

References 46 publications

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“…Our own work in this area has focused on the simplification of the salalen ligand structure and, at the same time, increasing catalyst stability and performance . In 2013, we reported that switching from trans ‐DACH to cis ‐DACH as a building block largely increased the catalyst's stability against oxidative degradation under the reaction conditions . We observed that ligands as simple as cis ‐ 2 a and cis ‐ 2 b (Figure ), at loadings as low as 1 mol %, were able to effect, for example, the epoxidation of 1‐octene in 82 % yield with 95 % ee .…”

Section: Figuresupporting

confidence: 53%

Titanium cis‐1,2‐Diaminocyclohexane Salalen Catalysts of Outstanding Activity and Enantioselectivity for the Asymmetric Epoxidation of Nonconjugated Terminal Olefins with Hydrogen Peroxide

et al. 2016

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We report a new and readily accessible class of titanium salalen complexes derived from cis‐1,2‐diaminocyclohexane (cis‐DACH) and fluorinated salicylic aldehyde derivatives. With aqueous hydrogen peroxide as the oxidant, these complexes catalyze the epoxidation of terminal, nonconjugated olefins in high yields with high enantioselectivities. We furthermore discovered that the addition of certain acidic or basic co‐catalysts significantly accelerated the epoxidation. For example, in the presence of 1 mol % Ti catalyst and 1 mol % pentafluorobenzoic acid, 1‐octene epoxidation (95 % ee) was completed at room temperature within 8 h. The catalytic process was compatible with many functional groups (e.g., ethers, esters, halides, nitriles, and nitro groups), whereas free hydroxy groups appeared to slow down the reaction to some extent. Catalyst recycling was possible.

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Section: Figuresupporting

confidence: 53%

Titanium cis‐1,2‐Diaminocyclohexane Salalen Catalysts of Outstanding Activity and Enantioselectivity for the Asymmetric Epoxidation of Nonconjugated Terminal Olefins with Hydrogen Peroxide

et al. 2016

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“…For instance, compound 342 (10 mol%) combined with TFA in water has a good performance (76-90% yield, 94-98% de, and 90-99% ee) in the reaction between α-hydroxyacetone (58a) or cyclic ketones such as 52c, 61, and 140b and aromatic aldehydes, yielding aldol products mainly as syn-isomers, while with cyclic ketones, the corresponding anti-aldols were achieved as major products [405]. The sulfonamide derivative of 1,2-diaminocyclohexane (343, 5 mol%) was used in the aldol reaction between cyclohexanone (52c) and p-nitrobenzaldehyde (53a) in an aqueous THF at 25 • C, affording the aldol product as anti-isomers with 86% yield and 97% ee [406]. Compound 344 (5 mol%) was tested in the aldol reaction between cyclic ketones such as 52c and 63, under similar reaction conditions, and was found to lead to mainly anti-aldols as main product in good yields and high diastereo-and enantioselectivities (25-99%, 66-99% de, and 76-99% ee).…”

Section: Ketones As Source Of Nucleophilementioning

confidence: 99%

Organocatalyzed Aldol Reactions

Guillena¹

2013

Modern Methods in Stereoselective Aldol Reactions

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The use of catalytic enantioselective methods to perform an aldol reaction provides a direct entry for the synthesis of chiral compounds and is probably the most attractive way to achieve this goal with high control of the chemo-, regio-, diastereo-, and enantioselectivity. The application of biochemical methods based on enzyme aldolases or antibodies, which are discussed in other chapters, avoid the use of preformed enolates or their equivalents for enhancing the global atom efficiency of the process [1] for which the narrow substrate scope is a major drawback. The discovery of methodologies to carry out the enantioselective direct aldol reaction [2] has eluded the production of stoichiometric by-products increasing the substrate scope. This task could be accomplished by using small molecules as catalysts, such as metal complexes (which are covered along this book) and organic molecules, also known as organocatalysts [3]. The growth of this last research area and the direct aldol reaction are closely linked [4], with the report on the use of (S)-proline as catalyst for the intermolecular aldol [5] definitely being the push for the development of the organocatalytic methods as a competitive methodology for the synthesis of chiral compounds.In a strict sense, an organocatalyzed reaction is a process in which all the involved reagents and catalysis are purely organic compounds of low-molecular weight, excluding boron-and silicon-containing derivatives. However, in some cases, the presence of a silyl group only plays a steric role and therefore can also be considered as an organocatalyzed process. Also, if the organocatalyst involved in a reaction is immobilized in a polymer, a dendrimer, or even an inorganic material that serves only as a support to facilitate its recovery [6], it could still be considered as an organocatalyst, although those types of derivatives have been scarcely used in the natural product synthesis and therefore will be excluded from this chapter. Therefore, a comprehensive overview of the direct aldol reaction [7], emphasizing the reactivity, scope, selectivity, and limitations of the methodology and giving several examples of their application to the synthesis of biologically active compounds, is discussed in this chapter.

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“…Compounds used herein were purchased from Aldrich, Alfa-Aesar, or TCI and were used as received. Catalysts 6a–6d , 18 6h , 19 6i 20 and isothiocyanate 2b , 3c 2c 3c were prepared according to literature procedures.…”

Section: Methodsmentioning

confidence: 99%

Organocatalytic enantioselective tandem aldol-cyclization reaction of α-isothiocyanato imides and activated carbonyl compounds

Guang

Zhao

2011

Tetrahedron: Asymmetry

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The organocatalytic enantioselective tandem aldol-cyclization reactions of α-isothiocyanato imides and activated carbonyl compounds, such as isatins, an α-ketolactone and a 1,2-dione, have been studied with cinchona alkaloid-derived thiourea-catalysts. This methodology provided an easy way to access enantiomerically enriched spirobicyclic thiocarbamates with high yields and good to excellent stereoselectivity, which have been demonstrated to be useful precursors for the synthesis of biologically active molecules.

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Enantiopure Monoprotected cis‐1,2‐Diaminocyclohexane: One‐Step Preparation and Application in Asymmetric Organocatalysis

Cited by 34 publications

References 46 publications

Titanium cis‐1,2‐Diaminocyclohexane Salalen Catalysts of Outstanding Activity and Enantioselectivity for the Asymmetric Epoxidation of Nonconjugated Terminal Olefins with Hydrogen Peroxide

Titanium cis‐1,2‐Diaminocyclohexane Salalen Catalysts of Outstanding Activity and Enantioselectivity for the Asymmetric Epoxidation of Nonconjugated Terminal Olefins with Hydrogen Peroxide

Organocatalyzed Aldol Reactions

Organocatalytic enantioselective tandem aldol-cyclization reaction of α-isothiocyanato imides and activated carbonyl compounds

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