Construction of Acyclic Vicinal Tertiary and Quaternary Carbon Stereocenters via a Pd‐Catalyzed Allylic Alkylation of Stereodefined Polysubstituted Ketene Aminals

Huang, Jianqiang; Marek, Ilan

doi:10.1002/ejoc.201901741

Cited by 12 publications

(2 citation statements)

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“…By utilising E ‐silyl enol ethers ( E )‐ 438 in place of E ‐allyl enol carbonates ( E )‐ 434 , Marek showed that the palladium‐catalysed AAA reaction of oxazolidinone ( E )‐ 438 with substituted allylic electrophile 352 gave almost no diastereoselectivity in the formation of 439 (1.8 : 1 dr), albeit with excellent enantioselectivity for the two diastereoisomers (95 % and 97 % ee, respectively) (A, Scheme 91). [128] Therefore, the authors developed the palladium‐catalysed diastereoselective allylic alkylation of geometrically and enantiomerically pure silyl enol ethers 440 with allylic electrophiles 441 in the presence of chiral ligand ( R )‐ L48 for palladium (B, Scheme 91). Specifically, 442 a was formed with >95 : <2 : 2 : 1 dr of the four possible diastereoisomers, showing a marked improvement when compared with the analogous AAA reaction of achiral silyl enol ether ( E )‐ 438 (1.8 : 1 dr).…”

Section: The Aaa Reaction Of Amidesmentioning

confidence: 99%

The Catalytic Asymmetric Allylic Alkylation of Acyclic Enolates for the Construction of Quaternary and Tetrasubstituted Stereogenic Centres

Griffiths,

Franckevičius

2024

Chemistry A European J

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To facilitate the discovery and development of new pharmaceuticals, the demand for novel stereofunctionalised building blocks has never been greater. Whilst molecules bearing quaternary and tetrasubstituted stereogenic centres are ideally suited to explore untapped areas of chemical space, the asymmetric construction of sterically congested carbon centres remains a longstanding challenge in organic synthesis. The enantioselective assembly of acyclic stereogenic centres is even more demanding due to the need to restrict a much wider range of geometries and conformations of the intermediates involved. In this context, the catalytic asymmetric allylic alkylation (AAA) of acyclic prochiral nucleophiles, namely enolates, has become an indispensable tool to access a range of linear α‐quaternary and α‐tetrasubstituted carbonyl compounds. However, unlike the AAA of cyclic enolates with a fixed enolate geometry, to achieve high levels of stereocontrol in the AAA of acyclic enolates, the stereoselectivity of enolisation must be considered. The aim of this review is to offer a comprehensive discussion of catalytic AAA reactions of acyclic prochiral enolates and their analogues to generate congested quaternary and tetrasubstituted chiral centres using metal, non‐metal and dual catalysis, with particular focus given to the control of enolate geometry and its impact on the stereochemical outcome of the reaction.

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Section: The Aaa Reaction Of Amidesmentioning

confidence: 99%

The Catalytic Asymmetric Allylic Alkylation of Acyclic Enolates for the Construction of Quaternary and Tetrasubstituted Stereogenic Centres

Griffiths,

Franckevičius

2024

Chemistry A European J

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“…Transition metal catalysis has played a dominant role in achieving a high level of enantiocontrol through π-allyl metal complexes derived from allylic substrates . Therein, a variety of soft and prochiral nucleophiles have been identified for the allylations, including enolates and enamines, as well as their precursors such as β-ketoesters, esters, amides, ketones, nitriles, and aldehydes that features acidic α-hydrogens. Aromatic rings, such as phenols and indoles, have also been utilized via asymmetric dearomative allylation processes .…”

Section: Introductionmentioning

confidence: 99%

Quaternary Stereocenters via Catalytic Enantioconvergent Allylation of Epoxides

Shen,

Xu,

Yang

et al. 2023

J. Am. Chem. Soc.

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The development of catalytic and enantioselective transformations for the synthesis of all-carbon quaternary stereocenters has long been recognized as a significant challenge in organic synthesis. While considerable progress has been made in asymmetric allylations, their potential to functionalize the commonly used synthon, epoxide, remains largely underexplored. Here we demonstrate the first highly regio- and enantioselective allylation of epoxides that delivers a range of quaternary stereocenters in the face of potentially problematic elimination and protonation reactions. The reaction proceeds via a radical approach under mild conditions and benefits from the use of earth-abundant titanium with a highly sophisticated salen ligand, which facilitates remarkable enantiocontrol and suppresses undesired side reactions. The resulting allylation products are multifunctional building blocks that can be elaborated chemo- and stereoselectively to a broad array of stereodefined structural motifs.

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