Enantioselective Protonation of the Lithium Transient Enolate of2‐Methyltetralone with 2‐Sulfinyl Alcohols

Abstract

A new catalytic cycle for the enantioselective protonation of cyclic ketone enolates with sulfinyl alcohols has been developed. An enol trifluoroacetate that can be easily obtained from the corresponding ketone is used for the first time as an enolate precursor of a cyclic ketone enolate. In this method, the achiral alcohol plays two roles: it is involved, as is usual in catalytic asymmetric protonation reactions, in the turnover of the chiral proton source and also in the generation of a

Enantioselective Protonation of Alkenyl Trifluoroacetates Catalyzed by Chiral Tin Methoxide

“…Alkenyl esters have been shown to be superior substrates for the enantioselective protonation employing a cinchona alkaloid as the chiral catalyst 3r. 10 We attempted the asymmetric protonation of a 2‐methyl‐1‐tetralone‐derived alkenyl trifluoroacetate and, as a consequence, obtained the targeted ketone in a satisfactory yield with improved enantiomeric excess in the reaction for 1 h (Scheme ).…”

From Overstoichiometric to Substoichiometric Enantioselective Protonation with 2‐Sulfinyl Alcohols: A View in Perspective

“…23 The method was designed to circumvent the limitations related to the preformed enolate approach, especially the reversibility of the proton transfer step as shown by the fact that a 2.5-fold excess of protic compounds (chiral + achiral) versus enolate was needed to take the reaction to completion. Since only 0.4 equiv.…”