A cyclisation reaction of methyl (4R)-3-(2-diazo-3-oxobutanoyl)thiazolidine-4-carboxylate which proceeds with retention of configuration, probably via a planar ester enolate intermediate possessing axial chirality

Beagley, B.; Betts, Michael J.; Pritchard, Robin G.; Schofield, Anthony; Stoodley, Richard J.; Vohra, Shaheen

doi:10.1039/c39910000924

Cited by 28 publications

(14 citation statements)

References 7 publications

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“…195,196 Chirality transfer from a transient axially chiral enolate was described by Stoodley during the cyclization of the enolate derived from 1,3-thiazolidine-4-carboxylate 229 onto an internal electrophile (Scheme 83). 197 The complete retention of configuration can be explained by the enantioselective formation of axially chiral enolate 231 from the favored conformer of the substrate in which 1,3-allylic strain is minimized. 198 The fast addition of the enolate to the electrophilic diazo function avoids the enolate racemization.…”

Section: V1 Transient Axial Chirality In Enolate Intermediatesmentioning

confidence: 99%

Axial-to-central chirality transfer in cyclization processes

et al. 2013

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Substrates, bearing axial chirality, can cyclize intra- or inter-molecularly with concomitant transfer of axial-to-central chirality to produce at least one stereocenter. In order to satisfy a strict definition of axial-to-central chirality transfer, the initial axial chirality must be lost during the cyclization process. Highly functionalized enantiopure carbocycles and heterocycles were prepared using this strategy. The transformations of configurationally stable substrates take place with high regio- and stereo-selectivity. Selected examples involving allenes, biaryls, arylamides and transient axially chiral short-lived species are discussed. Special attention is focused on the mechanistic rationale of the chirality transfer.

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Section: V1 Transient Axial Chirality In Enolate Intermediatesmentioning

confidence: 99%

Axial-to-central chirality transfer in cyclization processes

et al. 2013

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“…This phenomenon has been described as “memory of chirality”. − For example, in Scheme b, reactant D (with point chirality) enolizes to chiral conformer E . When E cyclizes, its conformational chirality is captured as an sp 3 stereogenic center in product F . − In this early example, the authors ascribed the selectivity to “hidden axial chirality.” Notably, in these examples, the stereogenic center in the reactant preorganizes the system such that as the intermediate evolves, one atropisomer is generated preferentially. In this study, we describe how a reactant with fixed chirality and a rigid, curved backbone ( G , Scheme c) evolves into a reactive intermediate with transient helical chirality ( H ), enabling efficient chirality transfer in the halo - Nazarov cyclization.…”

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confidence: 99%

Stereochemical Relay through a Cationic Intermediate: Helical Preorganization Dictates Direction of Conrotation in the halo-Nazarov Cyclization

2020

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A stereocontrolled halo-Prins/halo-Nazarov cyclization protocol is reported, where chiral information from a secondary alcohol is relayed through several intermediates yielding halocyclopentene products diastereoselectively. An enantiopure product is obtained when a nonracemic secondary alcohol is used. Experimental and computational studies are described, enabling the design and synthesis of systems that ionize and cyclize with >95% chirality transfer through a mechanism involving the creation and preservation of transient helical chirality in a pentadienyl cation intermediate. First, a diastereoselective alkynyl Prins cyclization is executed to synthesize a conformationally distorted dihydropyran intermediate with a curved backbone and high reactivity. This chiral precursor adopts a specific helical alignment early in the subsequent cationic ionization/halo-Nazarov cyclization process, dictating the direction of conrotation in the electrocyclization. Notably, despite the ablation of an sp3 stereogenic center during ionization, the low halo-Nazarov barrier enables efficient capture of a cationic intermediate with dynamic conformational chirality. The ionization and electrocyclization thus occur with “memory of chirality”.

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“…Concurrent with Fuji's early studies on MOC, Stoodley and co-workers isolated the bicyclic side product 50 with complete retention of configuration as they attempted to transform 48 into 49 (Scheme 11). 19…”

Section: Other Cyclization Reactions Involving Axially Chiral Enolatementioning

confidence: 99%

Memory of Chirality: An Emerging Strategy for Asymmetric Synthesis

Zhao¹,

Hsu²,

Carlier³

2004

Synthesis

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Memory of chirality' (MOC) is an intriguing strategy for asymmetric synthesis because it appears to do the impossible: the sole chiral center of a molecule directs the stereochemical course of a reaction even though that center is destroyed in the key reactive intermediate. This review describes the critical role of transient conformational chirality in these processes, and defines the three essential requirements for success in an MOC method. The growing application of MOC to asymmetric synthesis methodology is discussed, with extensive coverage of enolate, radical, photochemical and carbocation reactions.

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A cyclisation reaction of methyl (4R)-3-(2-diazo-3-oxobutanoyl)thiazolidine-4-carboxylate which proceeds with retention of configuration, probably via a planar ester enolate intermediate possessing axial chirality

Cited by 28 publications

References 7 publications

Axial-to-central chirality transfer in cyclization processes

Axial-to-central chirality transfer in cyclization processes

Stereochemical Relay through a Cationic Intermediate: Helical Preorganization Dictates Direction of Conrotation in the halo-Nazarov Cyclization

Memory of Chirality: An Emerging Strategy for Asymmetric Synthesis

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