A Catalytic Method for the Enantioselective Synthesis of α‐Quaternary Ketones, α‐Ketoesters and Aldehydes

Abstract

A practical method for the efficient and enantioselective preparation of versatile ketones and aldehydes that contain an α-quaternary stereocenter is described. Reactions utilize simple carboxylic acid or ester starting materials, a monodentate chiral phosphine, and afford a variety of aryl, alkenyl, alkynyl, and alkylsubstituted ketone and aldehyde products in 25-94 % yield and 90 : 10 to > 99 : 1 enantiomeric ratio. Reactions proceed by acyl substitution with in situ formed chiral allylic nucleophiles, and display selectivity and conversion dependence on a protic additive. The utility of the approach is demonstrated through several product transformations.

Recent progress in the catalytic enantioselective reactions of 1,1-diborylalkanes

“…Of note, the use of a protic additive CD 3 OD is beneficial, for it can facilitate the decomposition of the (L)Cu-O 2 COMe species to enhance the catalyst turnover and suppress a competitive but less enantioselective transmetalation (Scheme 26). 28 In the above-discussed reactions, only one of the two boryls is kept after the reactions. However, in view of the abundant transformations of boryl, an enantioselective reaction which could retain both of the two boryls would be more appealing.…”

“…Of note, the use of a protic additive CD 3 OD is beneficial, for it can facilitate the decomposition of the (L)Cu–O 2 COMe species to enhance the catalyst turnover and suppress a competitive but less enantioselective transmetalation (Scheme 26). 28…”