Issue 19, 2019

Evaluating aryl esters as bench-stable C(1)-ammonium enolate precursors in catalytic, enantioselective Michael addition–lactonisations

Abstract

An evaluation of a range of aryl, alkyl and vinyl esters as prospective C(1)-ammonium enolate precursors in enantioselective Michael addition–lactonisation processes with (E)-trifluoromethylenones using isothiourea catalysis is reported. Electron deficient aryl esters are required for reactivity, with 2,4,6-trichlorophenyl esters providing optimal product yields. Catalyst screening showed that tetramisole was the most effective isothiourea catalyst, giving the desired dihydropyranone product in excellent yield and stereoselectivity (up to 90 : 10 dr and 98 : 2 er). The scope and limitations of this process have been evaluated, with a range of diester products being generated after ring-opening with MeOH to give stereodefined dihydropyranones with excellent stereocontrol (10 examples, typically ∼90 : 10 dr and >95 : 5 er).

Graphical abstract: Evaluating aryl esters as bench-stable C(1)-ammonium enolate precursors in catalytic, enantioselective Michael addition–lactonisations

Supplementary files

Article information

Article type
Paper
Submitted
26 Mar 2019
Accepted
08 Apr 2019
First published
11 Apr 2019

Org. Biomol. Chem., 2019,17, 4747-4752

Evaluating aryl esters as bench-stable C(1)-ammonium enolate precursors in catalytic, enantioselective Michael addition–lactonisations

C. M. Young, J. E. Taylor and A. D. Smith, Org. Biomol. Chem., 2019, 17, 4747 DOI: 10.1039/C9OB00703B

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