Organocatalytic Asymmetric Synthesis Using Proline and Related Molecules. Part 2.

Kotsuki, Hiyoshizo; Ikishima, Hideaki; Okuyama, Atsushi

doi:10.3987/rev-07-621

Cited by 90 publications

(12 citation statements)

References 370 publications

(46 reference statements)

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“…Such compounds are well-known organocatalysts. 29,34 The screening of different organocatalysts (Table 1) showed promising results in the reaction at room temperature. A comparative reaction without a catalyst resulted in 45% conversion after 96 h (entry 1).…”

Section: Resultsmentioning

confidence: 99%

Enantioselective Friedel–Crafts reaction of indoles with trifluoroacetaldehyde catalyzed by Cinchona alkaloids

2011

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The first direct asymmetric synthetic preparation of trifluoro-1-(indol-3-yl)ethanols (TFIEs) is described by an enantioselective organocatalytic method from indoles and inexpensive trifluoroacetaldehyde methyl hemiacetal. The reaction is catalyzed by hydroquinine to produce TFIEs in an almost quantitative yield and with enantioselectivities up to 75% at room temperature. The enantioselectivity is strongly dependent on the concentration of substrates and catalyst due to the competitive noncatalyzed reaction.

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Section: Resultsmentioning

confidence: 99%

Enantioselective Friedel–Crafts reaction of indoles with trifluoroacetaldehyde catalyzed by Cinchona alkaloids

2011

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“…[41][42][43][44][45] In particular, proline is a remarkable candidate for the asymmetric reactions. [46][47][48][49][50] Amino acid with a carbonyl and an amino group can behave both as an acid and a base to facilitate chemical reactions. Jiang et al reported the synthesis of cyclic carbonates from CO 2 and epoxides catalyzed by amino acids.…”

Section: Introductionmentioning

confidence: 99%

Proline-Catalyzed Synthesis of 5-Aryl-2-oxazolidinones from Carbon Dioxide and Aziridines Under Solvent-Free Conditions

Dou

Yang

2011

Synthetic Communications

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Natural a-amino acids were proven to be ecofriendly and recyclable catalysts for the carboxylation of aziridines with CO 2 without utilization of any organic solvents or additives. Notably, a series of 5-aryl-2-oxazolidinones were obtained in good yield together with excellent chemo-and regioselectivity under mild conditions using proline as the catalyst. Notably, the catalyst could be recycled more than five times after a simple separation procedure without appreciable loss of catalytic activity. This process represents a promising strategy for homogeneous catalyst recycling.

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“…The use of proline derivatives as organocatalysts13 and as key building blocks of many pharmaceuticals and natural products14 ensures its status as a privileged structural motif. Chiral 2,3-dehydroproline (3-pyrroline) products commonly originate from natural 3-hydroxy proline,15 a neglected family of chiral proline products emerged as an ideal target for our new methodology.…”

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confidence: 99%

Stereospecific Ring Expansion of Chiral Vinyl Aziridines

et al. 2011

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In this report, it is demonstrated that chiral vinyl aziridines can be stereospecifically ring expanded. This synthetic approach allows controlled access to chiral 2,5-cis or 2,5-trans-3-pyrroline products from starting materials with the appropriate aziridine geometry. Twenty three ring expansion examples, most of which feature a stereospecific cyclization, are presented.A cursory review of the structural motifs of the top 200 top selling drugs 1 reveals that around 90% contain at least one nitrogen atom and approximately 65% are decorated with a heterocycle. Not surprisingly, the majority of these heterocycles are nitrogenous, with pyrrolidines a commonly occurring heterocyclic scaffold. Given the success of chiral pyrrolidines as important pharmaceutical building blocks it follows that a range of practical synthetic methods are needed 2 to provide access to any targeted structural and stereochemical pyrrolidine pattern.We have chosen to tackle the challenge of developing useful pyrrolidine forming methods by revisiting the ring expansion of vinyl aziridines, first reported by Atkinson. 3 Surprisinigly, despite the potential usefulness of converting a vinylaziridine into a 3-pyrroline, there had only been a single study focused on using metal catalysts to aid the rearrangement prior to our contribution to this field. 4 Oshima and coworkers found that tosylated dieneaziridines could be ring expanded in the presence of a palladium catalyst to the 3-pyrrolines. Both the N-tosyl group and the diene moiety were reported to be essential for the success of this rearrangement. Simple non-dienic vinyl aziridines did not ring expand, furnishing instead a complex mixture of products. In our recent report, we demonstrated that this significant substrate limitation could be solved using Cu(hfacac) 2 as a catalyst. 5 The substrate scope of this new transformation, which we demonstrated for a range of tosyl (Ts) and N-phthalimide (NPhth) protected vinyl aziridines, was shown to be quite broad. In this report we expand these investigations further and focus our attention on stereospecific vinyl aziridine ring expansions and application of this new methods towards accessing chiral pyrroline products.njardars@email.arizona.edu. Supporting Information Available Full experimental details for all new compounds reported in this article including X-ray data for compounds 15d, 15j, 15l, 21d and 21f are available free of charge via the Internet at http://pubs.acs.org. In order to maximize the synthetic potential of our method for preparing chiral pyrroline products, it is essential that reliable, asymmetric, convergent, and scalable routes be available to access the requisite starting materials (chiral vinyl aziridines). 6 The union of an imine and suitably activated nucleophile quickly emerged as the optimal approach (Scheme 1). The imine based retrosynthetic analysis is highlighted for chiral pyrroline 3, which we envisioned would originate from the copper catalyzed ring expansion of a trans-or cis-vinyl aziridine (4 and ...

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Organocatalytic Asymmetric Synthesis Using Proline and Related Molecules. Part 2.

Cited by 90 publications

References 370 publications

Enantioselective Friedel–Crafts reaction of indoles with trifluoroacetaldehyde catalyzed by Cinchona alkaloids

Enantioselective Friedel–Crafts reaction of indoles with trifluoroacetaldehyde catalyzed by Cinchona alkaloids

Proline-Catalyzed Synthesis of 5-Aryl-2-oxazolidinones from Carbon Dioxide and Aziridines Under Solvent-Free Conditions

Stereospecific Ring Expansion of Chiral Vinyl Aziridines

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