Synergistic Kinetic Resolution and Asymmetric Propargyl Claisen Rearrangement for the Synthesis of Chiral Allenes

Liu, Yangbin; Liu, Xiaohua; Hu, Haipeng; Guo, Jing; Xia, Yong; Lin, Lili; Feng, Xiaoming

doi:10.1002/ange.201511776

Cited by 39 publications

(11 citation statements)

References 33 publications

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“…21,22 Thus, treatment of 25 with: (i) ethanol/DBU converts 25 to the chiral ester 27 (95%, 96:4 er), (ii) aqueous ammonia affords the chiral amide ( S )- 28 (85%, 97:3 er), 27 or (iii) aqueous sodium hydroxide forms the known chiral carboxylic acid 28 ( S )- 29 (91%, 96:4 er). 29 Treatment of 25 with phenylmagnesium bromide gives after aqueous workup the stable α-hydroxyphosphonate as a mixture of diastereomers. Treatment of the latter with aqueous base liberates the known chiral phenyl ketone 30 ( S )- 30 (78% overall yield).…”

Section: Resultsmentioning

confidence: 99%

Phosphonate-Directed Catalytic Asymmetric Hydroboration: Delivery of Boron to the More Substituted Carbon, Leading to Chiral Tertiary Benzylic Boronic Esters

Chakrabarty

Takacs

2018

ACS Catal.

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Phosphonate-directed catalytic asymmetric hydroboration (CAHB) of β-aryl/heteroaryl methylidenes and trisubstituted alkenes by pinacolborane enables facile access to functionalized, chiral tertiary benzylic boronic esters. Hydroboration is catalyzed by a chiral rhodium catalyst prepared in situ from a Rh(I)-precursor in combination with a simple TADDOL-derived chiral cyclic monophosphite in a 1:1 ratio. The regio- and stereochemistry arises from the combined effects of the relative disposition of the directing group to the alkene, the alkene substitution pattern, and the necessity of an aryl substituent attached to the alkene. A range of aryl and heteroaryl substituents can be accommodated, and for several chiral substrates, the reactions are efficiently catalyst-controlled enabling the choice of diastereomeric products as desired. Stereospecific transformations of the chiral boronic ester afford chiral phosphonates bearing a quaternary carbon stereocenter. The synthetic utility of the products is further demonstrated by α-oxidation of the phosphonate leading to hydroxy- and oxo-phosphonates; the latter readily undergo elimination/substitution reactions to unmask the phosphonate functionality with the formation of aldehydes, alcohols, esters, amides, acids and ketones.

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Section: Resultsmentioning

confidence: 99%

Phosphonate-Directed Catalytic Asymmetric Hydroboration: Delivery of Boron to the More Substituted Carbon, Leading to Chiral Tertiary Benzylic Boronic Esters

Chakrabarty

Takacs

2018

ACS Catal.

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“…1). Over the past decades, substantial efforts have been devoted to the construction of axially chiral allenes, however, the strategies to prepare chiral exocyclic allenes are still rare [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31] . Traditional methods to access chiral exocyclic allenes are mainly focused on the nucleophilic substitution of enantioenriched propargylic derivatives through central-to-axial chirality transfer 32,33 .…”

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confidence: 99%

Copper(I)-catalyzed diastereo- and enantio-selective construction of optically pure exocyclic allenes

Tan

Wang

et al. 2020

Nat Commun

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Among about 150 identified allenic natural products, the exocyclic allenes constitute a major subclass. Substantial efforts are devoted to the construction of axially chiral allenes, however, the strategies to prepare chiral exocyclic allenes are still rare. Herein, we show an efficient strategy for the asymmetric synthesis of chiral exocyclic allenes with the simultaneous control of axial and central chirality through copper(I)-catalyzed asymmetric intramolecular reductive coupling of 1,3-enynes to cyclohexadienones. This tandem reaction exhibits good functional group compatibility and the corresponding optically pure exocyclic allenes bearing cis-hydrobenzofuran, cis-hydroindole, and cis-hydroindene frameworks, are obtained with high yields (up to 99% yield), excellent diastereoselectivities (generally >20:1 dr) and enantioselectivities (mostly >99% ee). Furthermore, a gram-scale experiment and several synthetic transformations of the chiral exocyclic allenes are also presented.

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“…Classic approaches typically involve (kinetic) resolution of racemic allenes 4,5 or chirality transfer from optically pure propargylic precursors [6][7][8][9][10] . Recent years have witnessed a tremendous development on metal-catalyzed enantioselective synthesis of chiral allenes [11][12][13][14][15][16] , such as nucleophilic addition to 1,3-enynes [17][18][19] , enantioselective functionalization of racemic allenes [20][21][22] , β-hydride elimination from enol triflates 23 , rearrangement of propargylic compounds [24][25][26][27] , coupling of terminal alkynes with diazo compounds [28][29][30][31] , and enantioselective addition of terminal alkynes to aldehydes 32 . In addition, several asymmetric organocatalytic protocols have also been reported, such as nucleophilic addition to activated enynes 33,34 , isomerization of alkynes 35,36 , phase-transfer-catalyzed alleno-Mannich reaction 37,38 , alkynylogous Mukaiyama aldol reactions 39 , and chiral ion-pair catalysis involving a formal propargylic carbocation from racemic propargylic alcohols 40 .…”

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confidence: 99%

Catalytic asymmetric synthesis of chiral trisubstituted heteroaromatic allenes from 1,3-enynes

Sang

Zhang

et al. 2018

Commun Chem

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Chiral allene and N-heteroaryl motifs are present in an ever-growing list of biologically active natural products and synthetic drugs. Although significant progress has been made in asymmetric syntheses of chiral allenes, general and practical protocols for enantioselective syntheses of chiral N-heteroaryl-substituted allenes from readily available starting materials still remain rare. Here we report a highly enantioselective synthesis of quinolinyl-substituted chiral allenes through a copper-catalyzed asymmetric allenylation of quinoline N-oxides with readily available 1,3-enynes. A variety of 1,3-enynes react with quinoline N-oxides, affording the corresponding quinolinyl-substituted allenes in high yields (up to 95%) and high enantioselectivities (up to 99% ee). This transformation tolerates a variety of functional groups, such as chloro, bromo, trifluoromethyl ether, tertiary amine, siloxy, carboxylic ester, imide, pyridine, and thiophene moieties. DFT calculations suggest a pathway involving an intramolecular nucleophilic addition of an allenyl copper intermediate with a coordinated quinoline N-oxide through a five-membered, rather than seven-membered, transition state.

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Synergistic Kinetic Resolution and Asymmetric Propargyl Claisen Rearrangement for the Synthesis of Chiral Allenes

Cited by 39 publications

References 33 publications

Phosphonate-Directed Catalytic Asymmetric Hydroboration: Delivery of Boron to the More Substituted Carbon, Leading to Chiral Tertiary Benzylic Boronic Esters

Phosphonate-Directed Catalytic Asymmetric Hydroboration: Delivery of Boron to the More Substituted Carbon, Leading to Chiral Tertiary Benzylic Boronic Esters

Copper(I)-catalyzed diastereo- and enantio-selective construction of optically pure exocyclic allenes

Catalytic asymmetric synthesis of chiral trisubstituted heteroaromatic allenes from 1,3-enynes

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