A Systematic Investigation of Quaternary Ammonium Ions As Asymmetric Phase-transfer Catalysts. Synthesis of Catalyst Libraries and Evaluation of Catalyst Activity
Overview
Affiliations
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 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 on the basis of the effective positive potential of the ammonium ion.
Asymmetric phase-transfer catalysis.
Lee H, Maruoka K Nat Rev Chem. 2024; 8(11):851-869.
PMID: 39385042 DOI: 10.1038/s41570-024-00642-x.
Enantioselective Phase-Transfer-Catalyzed Synthesis of Spirocyclic Azetidine Oxindoles.
Boddy A, Sahay A, Rivers E, White A, Spivey A, Bull J Org Lett. 2024; 26(10):2079-2084.
PMID: 38447584 PMC: 10949229. DOI: 10.1021/acs.orglett.4c00358.
Synthesis and Catalytic Activity of Bifunctional Phase-Transfer Organocatalysts Based on Camphor.
Ciber L, Pozgan F, Brodnik H, Stefane B, Svete J, Waser M Molecules. 2023; 28(3).
PMID: 36771181 PMC: 9921693. DOI: 10.3390/molecules28031515.
Trialkylammonium salt degradation: implications for methylation and cross-coupling.
Washington J, Assante M, Yan C, McKinney D, Juba V, Leach A Chem Sci. 2021; 12(20):6949-6963.
PMID: 34123322 PMC: 8153232. DOI: 10.1039/d1sc00757b.
Bencivenni G, Salazar Illera D, Moccia M, Houk K, Izzo J, Novacek J Chemistry. 2021; 27(44):11352-11366.
PMID: 33963788 PMC: 8453964. DOI: 10.1002/chem.202100908.