Identification of a highly effective asymmetric phase-transfer catalyst derived from α-methylnaphthylamine

Lygo, Barry; Allbutt, Bryan; James, Sarah

doi:10.1016/s0040-4039(03)01352-2

Cited by 98 publications

(44 citation statements)

References 20 publications

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“…The first notable advances were from independent studies by Lygo 23 and Corey, 24 in which the incorporation of a 9-anthracenylmethyl moiety as the nitrogen substituent markedly improved the enantioselectivity (Chart 1). Analogously, Park and Jew developed a tri-fluorinated N - benzyl quaternary ammonium catalysts 25a and dimeric, meta-bridged cinchoninium catalysts.…”

Section: Introductionmentioning

confidence: 99%

A Systematic Investigation of Quaternary Ammonium Ions as Asymmetric Phase-Transfer Catalysts. Synthesis of Catalyst Libraries and Evaluation of Catalyst Activity

2011

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Despite over three decades of research into asymmetric phase transfer catalysis (APTC), a fundamental understanding of the factors that affect the rate and stereoselectivity of this important process are still obscure. This paper describes the initial stages of a long-term program aimed at elucidating the physical organic foundations of APTC employing a chemoinformatic analysis of the alkylation of a protected glycine imine with a libraries of enantiomerically enriched quaternary ammonium ions. The synthesis of the quaternary ammonium ions follows a diversity oriented approach wherein the tandem inter[4+2]/intra[3+2] cycloaddition of nitroalkenes serves as the key transformation. A two part synthetic strategy comprised of: (1) preparation of enantioenriched scaffolds and (2) development of parallel synthesis procedures is described. The strategy allows for the facile introduction of four variable groups in the vicinity of a stereogenic quaternary ammonium ion. The quaternary ammonium ions exhibited a wide range of activity and to a lesser degree enantioselectivity. Catalyst activity and selectivity are rationalized in a qualitative way based on the effective positive potential of the ammonium ion.

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Section: Introductionmentioning

confidence: 99%

A Systematic Investigation of Quaternary Ammonium Ions as Asymmetric Phase-Transfer Catalysts. Synthesis of Catalyst Libraries and Evaluation of Catalyst Activity

2011

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“…In the second report, 35b a model was generated for the same reaction while using different catalyst scaffolds developed by Lygo and coworkers. 36 The contributions of steric and electrostatic interactions to the variation in enantioselectivity were found to be roughly equivalent but the implications of electrostatic or electrostatic interactions were not discussed in detail in these reports, which are considered to be the predominate forces responsible for the ion-pair interaction strength. 37 Despite these important contributions, ambiguity is still present as to the dependence of electrostatic interactions on the observed enantioselectivity.…”

Section: Introductionmentioning

confidence: 95%

A Systematic Investigation of Quaternary Ammonium Ions as Asymmetric Phase-Transfer Catalysts. Application of Quantitative Structure Activity/Selectivity Relationships

2011

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While the synthetic utility of asymmetric phase transfer catalysis continues to expand, the number of proven catalyst types and design criteria remains limited. At the origin of this scarcity is a lack in understanding of how catalyst structural features affect the rate and enantioselectivity of phase transfer catalyzed reactions. Described in this paper is the development of quantitative structure-activity relationships (QSAR) and -selectivity relationships (QSSR) for the alkylation of a protected glycine imine with libraries of quaternary ammonium ion catalysts. Catalyst descriptors including ammonium ion accessibility, interfacial adsorption affinity, and partition coefficient were found to correlate meaningfully with catalyst activity. The physical nature of the descriptors was rationalized through differing contributions of the interfacial and extraction mechanisms to the reaction under study. The variation in the observed enantioselectivity was rationalized employing a comparative molecular field analysis (CoMFA) using both the steric and electrostatic fields of the catalysts. A qualitative analysis of the developed model reveals preferred regions for catalyst binding to afford both configurations of the alkylated product.

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“…In this case, the formation comprised either a conjugate addition of hydroxyl amine 195 followed by intramolecular cyclization to give 196, or a conjugate addition of HO 2 − to 140, intramolecular epoxide formation and a terminating epoxide opening/ring closure to obtain 198. Whereas, Córdova employed proline derivative 151 to receive the cyclic product in good yields and very good to excellent ee, Jørgensen and colleagues utilized 142 and a Lygo-type chiral ammonium salt 199 as a phase-transfer catalyst to obtain 198 in good yields and with near-perfect enantiomeric excess [67].…”

Section: Organocatalytic Domino Michael Reactions/electrophilic Trappingmentioning

confidence: 99%

Domino Reactions Involving Catalytic Enantioselective Conjugate Additions

Tietze

Düfert

2010

Catalytic Asymmetric Conjugate Reactions

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Identification of a highly effective asymmetric phase-transfer catalyst derived from α-methylnaphthylamine

Cited by 98 publications

References 20 publications

A Systematic Investigation of Quaternary Ammonium Ions as Asymmetric Phase-Transfer Catalysts. Synthesis of Catalyst Libraries and Evaluation of Catalyst Activity

A Systematic Investigation of Quaternary Ammonium Ions as Asymmetric Phase-Transfer Catalysts. Synthesis of Catalyst Libraries and Evaluation of Catalyst Activity

A Systematic Investigation of Quaternary Ammonium Ions as Asymmetric Phase-Transfer Catalysts. Application of Quantitative Structure Activity/Selectivity Relationships

Domino Reactions Involving Catalytic Enantioselective Conjugate Additions

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