Zhao F, Shu C, Young CM, Carpenter‐Warren C, Slawin AMZ, Smith AD. Enantioselective Synthesis of α-Aryl-β
2 -Amino-Esters by Cooperative Isothiourea and Brønsted Acid Catalysis.
Angew Chem Int Ed Engl 2021;
60:11892-11900. [PMID:
33646631 PMCID:
PMC8252622 DOI:
10.1002/anie.202016220]
[Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2020] [Indexed: 01/07/2023]
Abstract
The synthesis of α-aryl-β2 -amino esters through enantioselective aminomethylation of an arylacetic acid ester in high yields and enantioselectivity via cooperative isothiourea and Brønsted acid catalysis is demonstrated. The scope and limitations of this process are explored (25 examples, up to 94 % yield and 96:4 er), with applications to the synthesis of (S)-Venlafaxine⋅HCl and (S)-Nakinadine B. Mechanistic studies are consistent with a C(1)-ammonium enolate pathway being followed rather than an alternative dynamic kinetic resolution process. Control studies indicate that (i) a linear effect between catalyst and product er is observed; (ii) an acyl ammonium ion can be used as a precatalyst; (iii) reversible isothiourea addition to an in situ generated iminium ion leads to an off-cycle intermediate that can be used as a productive precatalyst.
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