Magnesium amide base-mediated enantioselective deprotonation processes

Henderson, Kenneth W.; Kerr, William J.; Moir, Jennifer H.

doi:10.1016/s0040-4020(02)00364-2

Cited by 50 publications

(23 citation statements)

References 71 publications

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“…Alkaline earth metal silyl amides are one of the most commonly used classes of polar organometallic reagents in organic synthesis including catalytic transformations, enolization reactions, hydroamination reactions and carbon dioxide fixation [2,26,29,[45][46][47][48][49][50][51]. The alkaline earth metal silyl amides serve as versatile reagents in organic synthesis, while the heavier congeners have provided a long sought access to a range of heavy alkaline earth metal derivatives [2,12].…”

Section: Secondary Silylated Aminesmentioning

confidence: 99%

Advances in alkaline earth-nitrogen chemistry

Torvisco

O'Brien

Ruhlandt‐Senge

2011

Coordination Chemistry Reviews

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Section: Secondary Silylated Aminesmentioning

confidence: 99%

Advances in alkaline earth-nitrogen chemistry

Torvisco

O'Brien

Ruhlandt‐Senge

2011

Coordination Chemistry Reviews

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“…2 As can be seen from Table 1, a good 88% conversion to silyl enol ether (S)-6a was observed using 0.5 equivalents HMPA as an additive and, upon analysis, an enantiomeric ratio (e.r.) 2 As can be seen from Table 1, a good 88% conversion to silyl enol ether (S)-6a was observed using 0.5 equivalents HMPA as an additive and, upon analysis, an enantiomeric ratio (e.r.)…”

Section: Figurementioning

confidence: 80%

“…of 84:16 was displayed. 2 However, in this instance significantly different reactivity is observed using the heteroleptic complex (R)-4, where reaction in the absence of any additive still gave a reasonable 61% conversion to silyl enol ether 6a. ), yet which required double the quantity of chiral ligand.…”

Section: Figurementioning

confidence: 83%

“…These results are promising when compared to those obtained using the magnesium bisamide base (R)-1, which previously gave similar results (82% conversion, 91:9 e.r. 2,9 Having established that base (R)-4 was indeed capable of performing enantioselective deprotonation reactions, the effect of temperature on the selectivity of the base was then investigated. 9 We were also pleased to note that the more environmentally benign additive DMPU could replace the known mutagen HMPA, in turn, furnishing a slight increase in selectivity (86:14 er).…”

Section: Figurementioning

confidence: 99%

“…Enantiomerically pure magnesium bisamides (R 2 N) 2 Mg have recently been shown to be excellent reagents for use in enantioselective deprotonation reactions, 2 providing a complementary system to their well-established lithiumcounterparts. 3 Our previous studies have concentrated on the use of homoleptic magnesium complexes, where the metal binds to a pair of identical chiral amide anions.…”

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confidence: 99%

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Novel Enantiomerically PureHeteroleptic Magnesium Complexes for Use in Enantioselective DeprotonationReactions

Carswell¹,

Hayes²,

Henderson³

et al. 2003

Synlett

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Two classes of heteroleptic magnesium complexes, alkylmagnesium amides RMgNR 2 and aryloxymagnesium amides ROMgNR 2 , have been prepared and subsequently shown to be efficient bases in the enantioselective deprotonation of substituted cyclic ketones. When compared with their magnesium bisamide counterparts, significantly different reactivity and selectivity profiles, including an unexpected reversal in enantioselectivity, has been observed with the new reagents.

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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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Magnesium amide base-mediated enantioselective deprotonation processes

Cited by 50 publications

References 71 publications

Advances in alkaline earth-nitrogen chemistry

Advances in alkaline earth-nitrogen chemistry

Novel Enantiomerically PureHeteroleptic Magnesium Complexes for Use in Enantioselective DeprotonationReactions

Asymmetric Transformations by Deprotonation Using Chiral Lithium Amides

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