Synthesis of polymer-supported chiral lithium amide bases and application in asymmetric deprotonation of prochiral cyclic ketones

Ma, Lili; Williard, Paul G.

doi:10.1016/j.tetasy.2006.11.011

Cited by 14 publications

(2 citation statements)

References 41 publications

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“…Despite these fascinating properties, there have been very few studies on the development of asymmetric organobase catalysts [31,39,89], compared with the dramatic progress in polymer-supported chiral lithium amide based asymmetric transformations [90]. It can be expected that new effective polymer-supported chiral superbase reagents will be discovered in the near future.…”

Section: Discussionmentioning

confidence: 99%

Polymer‐Supported Organosuperbases

Kotsuki

2009

Superbases for Organic Synthesis

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Section: Discussionmentioning

confidence: 99%

Polymer‐Supported Organosuperbases

Kotsuki

2009

Superbases for Organic Synthesis

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“…Nowadays one of the most important challenges in organic chemistry is the preparation of new chiral molecules in enantiomerically pure forms, evaluating different ways to carry out the hydrogenation of prochiral molecules and better yet to obtain materials which can be a potential chiral catalyst . Multiple results about the synthesis of new enantiomerically pure materials that provides satisfactory results, and show high yields and enantioselectivity, have been reported. One disadvantage of the homogeneous synthesis is the difficulty to isolate the obtained product, since it is necessary to use chromatographic columns, extractions with different solvents or using specialized equipment such as HPLC.…”

Section: Introductionmentioning

confidence: 99%

Stereoselective Reducing Complexes Supported in Solid Phase: Preparation and Reactivity Study

et al. 2019

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Twelve new chiral chelating resins have been prepared using solid phase organic synthesis with the Merrifield and Wang resins and the bidentate amine 1,2‐ethylenediamine, followed by the coupling of asymmetric ketones such as 1‐phenyletanone, 4‐methyl‐2‐pentanone 4‐nitroacetophenone and 4‐methoxyacetophenone to form prochiral imines. The enantioselective reduction with borane and (R)‐(+)‐2‐Methyl‐CBS‐oxazaborolidine leads to the chiral resins with yields greater than 86%. We used these chiral resins to prepare 24 reducing complexes with alkali tetrahydroborates in a very simple way giving yields greater than 87%. Finally, we achieved a preliminary enantioselective reduction of acetophenone employing the Merrifield's chiral chelating resins obtaining the corresponding S alcohol in a 70:30 ratio with the R analog alcohol.

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Asymmetric Transformations by Deprotonation Using Chiral Lithium Amides

Simpkins

Weller

2012

Organic Reactions

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Lithium dialkylamides, especially lithium diisopropylamide (LDA), are valuable bases in organic synthesis but it is only since 1980 that their chiral counterparts have found application in reactions that can be broadly defined as asymmetric deprotonations. This chapter provides a comprehensive overview of all selective deprotonation processes mediated by chiral lithium amides, including desymmetrizations, kinetic resolutions, and other applications such as regioselective enolizations of chiral substrates. The chapter covers the entire substrate scope of chiral lithium amide deprotonation reactions, which includes rearrangement of epoxides to allylic alcohols, enolizations of carbonyl compounds (principally, but not exclusively, cyclic ketones), and metalations of organometallics (especially tricarbonyl(η 6 ‐arene)chromium(0) complexes) and miscellaneous phosphorous‐ or sulfur‐containing compounds. It is possible to perform some benchmark reactions under “catalytic conditions,” i.e., using substoichiometic quantities of chiral lithium amide, particularly epoxide rearrangements. The capability of deprotonations, mediated by chiral lithium amides, to deliver non‐racemic intermediates with acceptable selectivity for target synthesis is amply illustrated by the examples included in the review. In particular, the desymmetrization of conformationally biased prochiral cyclic ketones has become a well‐established strategy for organic synthesis, and has seen significant application in target‐oriented synthesis.

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Synthesis of polymer-supported chiral lithium amide bases and application in asymmetric deprotonation of prochiral cyclic ketones

Cited by 14 publications

References 41 publications

Polymer‐Supported Organosuperbases

Polymer‐Supported Organosuperbases

Stereoselective Reducing Complexes Supported in Solid Phase: Preparation and Reactivity Study

Asymmetric Transformations by Deprotonation Using Chiral Lithium Amides

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