Iridium-catalyzed enantioselective direct vinylogous allylic alkylation of coumarins

“…In this context, the first iridium-catalyzed enantioselective vinylogous allylic alkylation of coumarins has been recently reported almost contemporarily and independently by the groups of Mukherjee and Yin in 2018 ( Scheme 197 ). In particular, using easily accessible linear allylic carbonates 773 , as allylic electrophiles (eq 1), Mukherjee and co-workers 510 found that [Ir(cod)Cl] 2 complexed with chiral ligand L27 effectively promoted the vinylogous allylic alkylation of 4-methylcoumarins 772 , in an exclusively branched-selective manner (>20:1 branched vs linear), affording the corresponding γ-adducts 774 in generally high yields (up to 98%) with an excellent level of enantioselectivity (up to 98%). Similarly, the catalytic asymmetric, vinylogous allylic alkylation of 4-methylcoumarins 772 and differently shaped, α,β-unsaturated lactones of type 776 was achieved by Yin et al 511 using allylic carbonates of type 775 and suitable ligands such as L27 or L28 to be complexed with [Ir(COD)Cl] 2 ( Scheme 197 , eqs 2 and 3).…”

Section: Vinylogous Esters and Lactonesmentioning

confidence: 99%

New Developments of the Principle of Vinylogy as Applied to π-Extended Enolate-Type Donor Systems

et al. 2020

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The principle of vinylogy states that the electronic effects of a functional group in a molecule are possibly transmitted to a distal position through interposed conjugated multiple bonds. As an emblematic case, the nucleophilic character of a π-extended enolate-type chain system may be relayed from the legitimate α-site to the vinylogous γ, ε, ..., ω remote carbon sites along the chain, provided that suitable HOMO-raising strategies are adopted to transform the unsaturated pronucleophilic precursors into the reactive polyenolate species. On the other hand, when “unnatural” carbonyl ipso -sites are activated as nucleophiles (umpolung), vinylogation extends the nucleophilic character to “unnatural” β, δ, ... remote sites. Merging the principle of vinylogy with activation modalities and concepts such as iminium ion/enamine organocatalysis, NHC-organocatalysis, cooperative organo/metal catalysis, bifunctional organocatalysis, dicyanoalkylidene activation, and organocascade reactions represents an impressive step forward for all vinylogous transformations. This review article celebrates this evolutionary progress, by collecting, comparing, and critically describing the achievements made over the nine year period 2010–2018, in the generation of vinylogous enolate-type donor substrates and their use in chemical synthesis.

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“…With our interest in Ir-catalyzed AAS reactions, we envisaged that the reaction of vinyl azide with an in situ generated electrophilic π-allyl–Ir complex could lead to an overall α-allylic alkylation of α-unsubstituted secondary acetamides (Scheme C).…”

mentioning

confidence: 99%

Iridium-Catalyzed Enantioselective α-Allylic Alkylation of Amides Using Vinyl Azide as Amide Enolate Surrogate

Chakrabarty

Mukherjee

2020

Org. Lett.

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Among the unstabilized enolates used as nucleophiles in iridium-catalyzed asymmetric allylic alkylation reactions, amide enolates are the least explored. Vinyl azides are now employed as amide enolate surrogates in Ir-catalyzed asymmetric allylic alkylation with branched allylic alcohols as the allylic electrophile. Competing reaction pathways are suppressed through the systematic tuning of the steric and electronic properties of vinyl azide to effect the α-allylic alkylation of secondary acetamides with high atom economy, exclusive branched selectivity, and mostly excellent enantioselectivity.

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Iridium-catalyzed enantioselective direct vinylogous allylic alkylation of coumarins

Cited by 35 publications

References 70 publications

Enantioselective Synthesis of Functionalized Tetrahydropyridines through Iridium-Catalyzed Formal [5+1] Annulation

Enantioselective Synthesis of Functionalized Tetrahydropyridines through Iridium-Catalyzed Formal [5+1] Annulation

New Developments of the Principle of Vinylogy as Applied to π-Extended Enolate-Type Donor Systems

Iridium-Catalyzed Enantioselective α-Allylic Alkylation of Amides Using Vinyl Azide as Amide Enolate Surrogate

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