Conquering three-carbon axial chirality of allenes

Ye, Juntao; Ma, Shengming

doi:10.1039/c4qo00208c

Cited by 283 publications

(83 citation statements)

References 108 publications

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“…[6][7][8] With this broad range of chiral starting materials at hand it was a matter of time since the development of methodologies taking advantage of the axial-to-central chirality transfer offered by allenes for the synthesis of chiral molecules would arise. Thus, a number of metal-free enantioselective synthesis based on chiral allenes have been developed in the last few years.9,10 However, the number of metal-catalysed reactions of chiral allenes is scarce.…”

Section: Metal-catalysed Reactions Involving Chirality Transfer From mentioning

confidence: 99%

Chirality transfer in metal-catalysed intermolecular addition reactions involving allenes

2016

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Allene chemistry in the presence of transition metal complexes is nowadays a very important topic that underpins many challenges and advances in organic synthesis. The amount of research articles covering new transformations of allenes is vast and the development of enantioselective reactions involving allenes has flourished in the last 10-15 years. In this review we cover three important topics in allene chemistry that we feel are timely appropriate for this special issue celebrating the work of Prof Trost: the metal-catalysed reactions involving chirality transfer from chiral allenes to products; the analysis of the possible racemization processes that have been observed in the interaction of some metals with allenes; and the chirality transfer using racemic allenes in reactions catalysed by metal complexes bearing chiral ligands to produce enantioriched products. We have focussed the review on intermolecular addition reactions as they are still much less explored than the intramolecular version.

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Section: Metal-catalysed Reactions Involving Chirality Transfer From mentioning

confidence: 99%

Chirality transfer in metal-catalysed intermolecular addition reactions involving allenes

2016

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“…(a)].F used indole 6, which is acommon structural motif in pharmaceutical agents and organic light-emitting materials,c an be effectively prepared by intramolecular cyclization of 3a [Eq. [17] Based on the aforementioned results and previous reports, [2,5,6] aplausible mechanism was proposed (for details, see Scheme S1 in the Supporting Information). [14] As eries of experiments were conducted to gain insight into the reaction mechanism.…”

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confidence: 81%

Manganese(I)‐Catalyzed Regioselective C−H Allenylation: Direct Access to 2‐Allenylindoles

et al. 2017

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A Mn -catalyzed regioselective C-H allenylation is reported that allows a broad range of 2-allenylindoles to be synthesized regioselectively on a gram scale under simple conditions. Notably, a highly efficient chirality transfer was observed (up to 93 % ee) in this transformation. This procedure was further found to allow, for the first time, the direct preparation of ketones by Mn -catalyzed C-H activation. Mechanistic investigations revealed that the precoordination of the oxygen atom to the manganese center as well as the congested tertiary carbon atom in the propargylic carbonates play a crucial role.

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“…9 As predicted by van’t Hoff in 1875, 1 the orthogonal relationship between the adjacent π systems within the allene structure gives rise to the possibility of axial chirality, which has inspired the development of methods that enable the enantioselective synthesis of allenes. 10–12 Traditional approaches have typically involved the stereospecific transformation of chiral propargylic precursors, such as [3,3] 13,14 and [2,3] 15 sigma-tropic rearrangements, S N 2′ displacements, 16–22 and reductive transposition. 23 Strategies using stoichiometric chiral reagents have also been developed, 24 as well as those employing kinetic resolution of preformed racemic allenes.…”

Section: Introductionmentioning

confidence: 99%

“…43 Thus, path A (red) provides a direct and convenient method for accessing enantioenriched α -allenols that complements existing procedures. 10–12 …”

Section: Introductionmentioning

confidence: 99%

Enantioselective Synthesis of Allenes by Catalytic Traceless Petasis Reactions

et al. 2017

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Allenes are useful functional groups in synthesis as a result of their inherent chemical properties and established reactivity patterns. One property of chemical bonding renders 1,3-substituted allenes chiral, making them attractive targets for asymmetric synthesis. While there are many enantioselective methods to synthesize chiral allenes from chiral starting materials, fewer methods exist to directly synthesize enantioenriched chiral allenes from achiral precursors. We report here an asymmetric boronate addition to sulfonyl hydrazones catalyzed by chiral biphenols to access enantioenriched allenes in a traceless Petasis reaction. The resulting Mannich product from nucleophilic addition eliminates sulfinic acid, yielding a propargylic diazene that performs an alkyne walk to afford the allene. Two enantioselective approaches have been developed; alkynyl boronates add to glycolaldehyde imine to afford allylic hydroxyl allenes, and allyl boronates add to alkynyl imines to form 1,3-alkenyl allenes. In both cases, the products are obtained in high yields and enantioselectivities.

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Conquering three-carbon axial chirality of allenes

Cited by 283 publications

References 108 publications

Chirality transfer in metal-catalysed intermolecular addition reactions involving allenes

Chirality transfer in metal-catalysed intermolecular addition reactions involving allenes

Manganese(I)‐Catalyzed Regioselective C−H Allenylation: Direct Access to 2‐Allenylindoles

Enantioselective Synthesis of Allenes by Catalytic Traceless Petasis Reactions

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