Cooperative benzylic–oxyallylic stabilized cations: regioselective construction of α-quaternary centers in ketone-derived compounds

Dange, Nitin S.; Stepherson, Jacob R.; Ayala, Caitlan E.; Fronczek, Frank R.; Kartika, Rendy

doi:10.1039/c5sc01914a

Cited by 26 publications

(5 citation statements)

References 64 publications

(19 reference statements)

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“…The highly reactive cations are generated under weakly basic conditions and trapped by neutral heteroatoms and soft π-nucleophiles. Kartika and co-workers reported regioselective nucleophilic additions to unsymmetrical oxyallyl cations under mild Brønsted acid catalysis in 2015. − …”

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confidence: 99%

Origins of Stereoselectivity in Chiral Aminoalcohol Catalysis of Oxyallyl Cation–Indole Reactions

Lam

et al. 2017

Org. Lett.

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The enantioselective coupling of indoles with racemic α-tosyloxy ketones mediated by a chiral amino alcohol catalyst is studied with density functional theory (DFT) calculations. The addition of indole to an oxyallyl cation intrinsically favors the (S,S) and (R,R) stereoisomeric products through electrostatic interactions in the transition state. Our model shows that the enantioselectivity is controlled by the cyclohexane moiety of the catalyst; selectivity diminishes upon removal of the cyclohexane ring. Substitution to enhance the enantioselectivity of this reaction is proposed.

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confidence: 99%

Origins of Stereoselectivity in Chiral Aminoalcohol Catalysis of Oxyallyl Cation–Indole Reactions

Lam

et al. 2017

Org. Lett.

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“…Later, Tang reported the reaction of α-chlorocyclohexanone with 2-naphthol . Finally, Kartika reported that 6-membered aryl-substituted α-hydroxy methylenol ethers were readily converted to the corresponding oxyallyl cations and regioselectively trapped by indoles . While each method is powerful in its own right, the classes of arenes employed (indoles/naphthols) were limited, and the number of actual examples involving cyclohexanones was small (<6 examples).…”

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confidence: 99%

Catalytic, Interrupted Formal Homo-Nazarov Cyclization with (Hetero)arenes: Access to α-(Hetero)aryl Cyclohexanones

Williams

Shenje

2016

J. Org. Chem.

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The first examples of a Lewis-acid catalyzed (hetero)arene interrupted, formal homo-Nazarov cyclization have been disclosed. Using SnCl4 as the catalyst, alkenyl cyclopropyl ketones undergo ring-opening cyclization to form six-membered cyclic oxyallyl cations. Subsequent intermolecular Friedel-Crafts-type arylation with various electron-rich arenes and heteroarenes provides functionalized α-(hetero)arylated cyclohexanones, a scaffold present in many natural products and bioactive compounds, in yields up to 88% and diastereomeric ratios up to 12:1. Regiospecific arylation occurs at the α-carbon of the oxyallyl cation due to polarization caused by the ester group.

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“…Carbon nucleophiles, including arenes, heteroarenes, alkenes and alkynes, add readily to cyclic oxyallyl cation species. This chemistry forms the basis for “interrupted” versions of the oxy -Nazarov cyclization, , and has also been developed in conjunction with a simple ionization event. − To test the feasibility of a interrupted halo -Nazarov strategy, we chose to examine aldehyde 1a , which bears an electron-rich aryl group well-suited for intramolecular capture of the type 5 haloallyl cation intermediate, with irreversible formation of a new C–C bond and all-carbon quaternary center.…”

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confidence: 99%

Cationic Cascade for Building Complex Polycyclic Molecules from Simple Precursors: Diastereoselective Installation of Three Contiguous Stereogenic Centers in a One-Pot Process

Alachouzos

Frontier

2018

J. Am. Chem. Soc.

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An expedient strategy for the synthesis of polycyclic small molecules is described. The method first joins together two achiral building blocks (an enyne and an aldehyde or a ketone) using an alkynyl halo-Prins protocol. Then, in the same reaction vessel, acidic conditions initiate a cationic cascade that includes a stereospecific halo-Nazarov electrocyclization and a diastereoselective Friedel–Crafts allylation. The entire sequence forms three carbon–carbon bonds and a carbon–halogen bond, generating halocyclopentene adducts in one pot from simple precursors. The process occurs with excellent diastereocontrol, providing highly functionalized polycycles containing three tertiary or quaternary stereogenic centers in a linear array. It is even possible to install three contiguous all-carbon quaternary centers using this method.

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Cooperative benzylic–oxyallylic stabilized cations: regioselective construction of α-quaternary centers in ketone-derived compounds

Abstract: Herein we describe a direct capture of benzylic–oxyallylic stabilized carbocations with high value nucleophiles towards regioselective construction of α-quaternary centers.

Cited by 26 publications

References 64 publications

Origins of Stereoselectivity in Chiral Aminoalcohol Catalysis of Oxyallyl Cation–Indole Reactions

Origins of Stereoselectivity in Chiral Aminoalcohol Catalysis of Oxyallyl Cation–Indole Reactions

Catalytic, Interrupted Formal Homo-Nazarov Cyclization with (Hetero)arenes: Access to α-(Hetero)aryl Cyclohexanones

Cationic Cascade for Building Complex Polycyclic Molecules from Simple Precursors: Diastereoselective Installation of Three Contiguous Stereogenic Centers in a One-Pot Process

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